Externalized Configuration
Spring Boot lets you externalize your configuration so that you can work with the same application code in different environments. You can use a variety of external configuration sources including Java properties files, YAML files, environment variables, and command-line arguments.
Property values can be injected directly into your beans by using the @Value
annotation, accessed through Spring’s Environment
abstraction, or be bound to structured objects through @ConfigurationProperties
.
Spring Boot uses a very particular PropertySource
order that is designed to allow sensible overriding of values.
Later property sources can override the values defined in earlier ones.
Sources are considered in the following order:
-
Default properties (specified by setting
SpringApplication.setDefaultProperties
). -
@PropertySource
annotations on your@Configuration
classes. Please note that such property sources are not added to theEnvironment
until the application context is being refreshed. This is too late to configure certain properties such aslogging.*
andspring.main.*
which are read before refresh begins. -
Config data (such as
application.properties
files). -
A
RandomValuePropertySource
that has properties only inrandom.*
. -
OS environment variables.
-
Java System properties (
System.getProperties()
). -
JNDI attributes from
java:comp/env
. -
ServletContext
init parameters. -
ServletConfig
init parameters. -
Properties from
SPRING_APPLICATION_JSON
(inline JSON embedded in an environment variable or system property). -
Command line arguments.
-
properties
attribute on your tests. Available on@SpringBootTest
and the test annotations for testing a particular slice of your application. -
@DynamicPropertySource
annotations in your tests. -
@TestPropertySource
annotations on your tests. -
Devtools global settings properties in the
$HOME/.config/spring-boot
directory when devtools is active.
Config data files are considered in the following order:
-
Application properties packaged inside your jar (
application.properties
and YAML variants). -
Profile-specific application properties packaged inside your jar (
application-{profile}.properties
and YAML variants). -
Application properties outside of your packaged jar (
application.properties
and YAML variants). -
Profile-specific application properties outside of your packaged jar (
application-{profile}.properties
and YAML variants).
It is recommended to stick with one format for your entire application.
If you have configuration files with both .properties and YAML format in the same location, .properties takes precedence.
|
If you use environment variables rather than system properties, most operating systems disallow period-separated key names, but you can use underscores instead (for example, SPRING_CONFIG_NAME instead of spring.config.name ).
See Binding From Environment Variables for details.
|
If your application runs in a servlet container or application server, then JNDI properties (in java:comp/env ) or servlet context initialization parameters can be used instead of, or as well as, environment variables or system properties.
|
To provide a concrete example, suppose you develop a @Component
that uses a name
property, as shown in the following example:
-
Java
-
Kotlin
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component
public class MyBean {
@Value("${name}")
private String name;
// ...
}
import org.springframework.beans.factory.annotation.Value
import org.springframework.stereotype.Component
@Component
class MyBean {
@Value("\${name}")
private val name: String? = null
// ...
}
On your application classpath (for example, inside your jar) you can have an application.properties
file that provides a sensible default property value for name
.
When running in a new environment, an application.properties
file can be provided outside of your jar that overrides the name
.
For one-off testing, you can launch with a specific command line switch (for example, java -jar app.jar --name="Spring"
).
The env and configprops endpoints can be useful in determining why a property has a particular value.
You can use these two endpoints to diagnose unexpected property values.
See the Production ready features section for details.
|
Accessing Command Line Properties
By default, SpringApplication
converts any command line option arguments (that is, arguments starting with --
, such as --server.port=9000
) to a property
and adds them to the Spring Environment
.
As mentioned previously, command line properties always take precedence over file-based property sources.
If you do not want command line properties to be added to the Environment
, you can disable them by using SpringApplication.setAddCommandLineProperties(false)
.
JSON Application Properties
Environment variables and system properties often have restrictions that mean some property names cannot be used. To help with this, Spring Boot allows you to encode a block of properties into a single JSON structure.
When your application starts, any spring.application.json
or SPRING_APPLICATION_JSON
properties will be parsed and added to the Environment
.
For example, the SPRING_APPLICATION_JSON
property can be supplied on the command line in a UN*X shell as an environment variable:
$ SPRING_APPLICATION_JSON='{"my":{"name":"test"}}' java -jar myapp.jar
In the preceding example, you end up with my.name=test
in the Spring Environment
.
The same JSON can also be provided as a system property:
$ java -Dspring.application.json='{"my":{"name":"test"}}' -jar myapp.jar
Or you could supply the JSON by using a command line argument:
$ java -jar myapp.jar --spring.application.json='{"my":{"name":"test"}}'
If you are deploying to a classic Application Server, you could also use a JNDI variable named java:comp/env/spring.application.json
.
Although null values from the JSON will be added to the resulting property source, the PropertySourcesPropertyResolver treats null properties as missing values.
This means that the JSON cannot override properties from lower order property sources with a null value.
|
External Application Properties
Spring Boot will automatically find and load application.properties
and application.yaml
files from the following locations when your application starts:
-
From the classpath
-
The classpath root
-
The classpath
/config
package
-
-
From the current directory
-
The current directory
-
The
config/
subdirectory in the current directory -
Immediate child directories of the
config/
subdirectory
-
The list is ordered by precedence (with values from lower items overriding earlier ones).
Documents from the loaded files are added as PropertySources
to the Spring Environment
.
If you do not like application
as the configuration file name, you can switch to another file name by specifying a spring.config.name
environment property.
For example, to look for myproject.properties
and myproject.yaml
files you can run your application as follows:
$ java -jar myproject.jar --spring.config.name=myproject
You can also refer to an explicit location by using the spring.config.location
environment property.
This property accepts a comma-separated list of one or more locations to check.
The following example shows how to specify two distinct files:
$ java -jar myproject.jar --spring.config.location=\
optional:classpath:/default.properties,\
optional:classpath:/override.properties
Use the prefix optional: if the locations are optional and you do not mind if they do not exist.
|
spring.config.name , spring.config.location , and spring.config.additional-location are used very early to determine which files have to be loaded.
They must be defined as an environment property (typically an OS environment variable, a system property, or a command-line argument).
|
If spring.config.location
contains directories (as opposed to files), they should end in /
.
At runtime they will be appended with the names generated from spring.config.name
before being loaded.
Files specified in spring.config.location
are imported directly.
Both directory and file location values are also expanded to check for profile-specific files.
For example, if you have a spring.config.location of classpath:myconfig.properties , you will also find appropriate classpath:myconfig-<profile>.properties files are loaded.
|
In most situations, each spring.config.location
item you add will reference a single file or directory.
Locations are processed in the order that they are defined and later ones can override the values of earlier ones.
If you have a complex location setup, and you use profile-specific configuration files, you may need to provide further hints so that Spring Boot knows how they should be grouped.
A location group is a collection of locations that are all considered at the same level.
For example, you might want to group all classpath locations, then all external locations.
Items within a location group should be separated with ;
.
See the example in the Profile Specific Files section for more details.
Locations configured by using spring.config.location
replace the default locations.
For example, if spring.config.location
is configured with the value optional:classpath:/custom-config/,optional:file:./custom-config/
, the complete set of locations considered is:
-
optional:classpath:custom-config/
-
optional:file:./custom-config/
If you prefer to add additional locations, rather than replacing them, you can use spring.config.additional-location
.
Properties loaded from additional locations can override those in the default locations.
For example, if spring.config.additional-location
is configured with the value optional:classpath:/custom-config/,optional:file:./custom-config/
, the complete set of locations considered is:
-
optional:classpath:/;optional:classpath:/config/
-
optional:file:./;optional:file:./config/;optional:file:./config/*/
-
optional:classpath:custom-config/
-
optional:file:./custom-config/
This search ordering lets you specify default values in one configuration file and then selectively override those values in another.
You can provide default values for your application in application.properties
(or whatever other basename you choose with spring.config.name
) in one of the default locations.
These default values can then be overridden at runtime with a different file located in one of the custom locations.
Optional Locations
By default, when a specified config data location does not exist, Spring Boot will throw a ConfigDataLocationNotFoundException
and your application will not start.
If you want to specify a location, but you do not mind if it does not always exist, you can use the optional:
prefix.
You can use this prefix with the spring.config.location
and spring.config.additional-location
properties, as well as with spring.config.import
declarations.
For example, a spring.config.import
value of optional:file:./myconfig.properties
allows your application to start, even if the myconfig.properties
file is missing.
If you want to ignore all ConfigDataLocationNotFoundExceptions
and always continue to start your application, you can use the spring.config.on-not-found
property.
Set the value to ignore
using SpringApplication.setDefaultProperties(…)
or with a system/environment variable.
Wildcard Locations
If a config file location includes the *
character for the last path segment, it is considered a wildcard location.
Wildcards are expanded when the config is loaded so that immediate subdirectories are also checked.
Wildcard locations are particularly useful in an environment such as Kubernetes when there are multiple sources of config properties.
For example, if you have some Redis configuration and some MySQL configuration, you might want to keep those two pieces of configuration separate, while requiring that both those are present in an application.properties
file.
This might result in two separate application.properties
files mounted at different locations such as /config/redis/application.properties
and /config/mysql/application.properties
.
In such a case, having a wildcard location of config/*/
, will result in both files being processed.
By default, Spring Boot includes config/*/
in the default search locations.
It means that all subdirectories of the /config
directory outside of your jar will be searched.
You can use wildcard locations yourself with the spring.config.location
and spring.config.additional-location
properties.
A wildcard location must contain only one * and end with */ for search locations that are directories or */<filename> for search locations that are files.
Locations with wildcards are sorted alphabetically based on the absolute path of the file names.
|
Wildcard locations only work with external directories.
You cannot use a wildcard in a classpath: location.
|
Profile Specific Files
As well as application
property files, Spring Boot will also attempt to load profile-specific files using the naming convention application-{profile}
.
For example, if your application activates a profile named prod
and uses YAML files, then both application.yaml
and application-prod.yaml
will be considered.
Profile-specific properties are loaded from the same locations as standard application.properties
, with profile-specific files always overriding the non-specific ones.
If several profiles are specified, a last-wins strategy applies.
For example, if profiles prod,live
are specified by the spring.profiles.active
property, values in application-prod.properties
can be overridden by those in application-live.properties
.
The last-wins strategy applies at the location group level.
A For example, continuing our /cfg application-live.properties /ext application-live.properties application-prod.properties When we have a
When we have
|
The Environment
has a set of default profiles (by default, [default]
) that are used if no active profiles are set.
In other words, if no profiles are explicitly activated, then properties from application-default
are considered.
Properties files are only ever loaded once. If you have already directly imported a profile specific property files then it will not be imported a second time. |
Importing Additional Data
Application properties may import further config data from other locations using the spring.config.import
property.
Imports are processed as they are discovered, and are treated as additional documents inserted immediately below the one that declares the import.
For example, you might have the following in your classpath application.properties
file:
-
Properties
-
YAML
spring.application.name=myapp
spring.config.import=optional:file:./dev.properties
spring:
application:
name: "myapp"
config:
import: "optional:file:./dev.properties"
This will trigger the import of a dev.properties
file in current directory (if such a file exists).
Values from the imported dev.properties
will take precedence over the file that triggered the import.
In the above example, the dev.properties
could redefine spring.application.name
to a different value.
An import will only be imported once no matter how many times it is declared. The order an import is defined inside a single document within the properties/yaml file does not matter. For instance, the two examples below produce the same result:
-
Properties
-
YAML
spring.config.import=my.properties
my.property=value
spring:
config:
import: "my.properties"
my:
property: "value"
-
Properties
-
YAML
my.property=value
spring.config.import=my.properties
my:
property: "value"
spring:
config:
import: "my.properties"
In both of the above examples, the values from the my.properties
file will take precedence over the file that triggered its import.
Several locations can be specified under a single spring.config.import
key.
Locations will be processed in the order that they are defined, with later imports taking precedence.
When appropriate, Profile-specific variants are also considered for import.
The example above would import both my.properties as well as any my-<profile>.properties variants.
|
Spring Boot includes pluggable API that allows various different location addresses to be supported. By default you can import Java Properties, YAML and configuration trees. Third-party jars can offer support for additional technologies (there is no requirement for files to be local). For example, you can imagine config data being from external stores such as Consul, Apache ZooKeeper or Netflix Archaius. If you want to support your own locations, see the |
Importing Extensionless Files
Some cloud platforms cannot add a file extension to volume mounted files. To import these extensionless files, you need to give Spring Boot a hint so that it knows how to load them. You can do this by putting an extension hint in square brackets.
For example, suppose you have a /etc/config/myconfig
file that you wish to import as yaml.
You can import it from your application.properties
using the following:
-
Properties
-
YAML
spring.config.import=file:/etc/config/myconfig[.yaml]
spring:
config:
import: "file:/etc/config/myconfig[.yaml]"
Using Configuration Trees
When running applications on a cloud platform (such as Kubernetes) you often need to read config values that the platform supplies. It is not uncommon to use environment variables for such purposes, but this can have drawbacks, especially if the value is supposed to be kept secret.
As an alternative to environment variables, many cloud platforms now allow you to map configuration into mounted data volumes.
For example, Kubernetes can volume mount both ConfigMaps
and Secrets
.
There are two common volume mount patterns that can be used:
-
A single file contains a complete set of properties (usually written as YAML).
-
Multiple files are written to a directory tree, with the filename becoming the ‘key’ and the contents becoming the ‘value’.
For the first case, you can import the YAML or Properties file directly using spring.config.import
as described above.
For the second case, you need to use the configtree:
prefix so that Spring Boot knows it needs to expose all the files as properties.
As an example, let’s imagine that Kubernetes has mounted the following volume:
etc/
config/
myapp/
username
password
The contents of the username
file would be a config value, and the contents of password
would be a secret.
To import these properties, you can add the following to your application.properties
or application.yaml
file:
-
Properties
-
YAML
spring.config.import=optional:configtree:/etc/config/
spring:
config:
import: "optional:configtree:/etc/config/"
You can then access or inject myapp.username
and myapp.password
properties from the Environment
in the usual way.
The names of the folders and files under the config tree form the property name.
In the above example, to access the properties as username and password , you can set spring.config.import to optional:configtree:/etc/config/myapp .
|
Filenames with dot notation are also correctly mapped.
For example, in the above example, a file named myapp.username in /etc/config would result in a myapp.username property in the Environment .
|
Configuration tree values can be bound to both string String and byte[] types depending on the contents expected.
|
If you have multiple config trees to import from the same parent folder you can use a wildcard shortcut.
Any configtree:
location that ends with /*/
will import all immediate children as config trees.
As with a non-wildcard import, the names of the folders and files under each config tree form the property name.
For example, given the following volume:
etc/
config/
dbconfig/
db/
username
password
mqconfig/
mq/
username
password
You can use configtree:/etc/config/*/
as the import location:
-
Properties
-
YAML
spring.config.import=optional:configtree:/etc/config/*/
spring:
config:
import: "optional:configtree:/etc/config/*/"
This will add db.username
, db.password
, mq.username
and mq.password
properties.
Directories loaded using a wildcard are sorted alphabetically. If you need a different order, then you should list each location as a separate import |
Configuration trees can also be used for Docker secrets.
When a Docker swarm service is granted access to a secret, the secret gets mounted into the container.
For example, if a secret named db.password
is mounted at location /run/secrets/
, you can make db.password
available to the Spring environment using the following:
-
Properties
-
YAML
spring.config.import=optional:configtree:/run/secrets/
spring:
config:
import: "optional:configtree:/run/secrets/"
Property Placeholders
The values in application.properties
and application.yaml
are filtered through the existing Environment
when they are used, so you can refer back to previously defined values (for example, from System properties or environment variables).
The standard ${name}
property-placeholder syntax can be used anywhere within a value.
Property placeholders can also specify a default value using a :
to separate the default value from the property name, for example ${name:default}
.
The use of placeholders with and without defaults is shown in the following example:
-
Properties
-
YAML
app.name=MyApp
app.description=${app.name} is a Spring Boot application written by ${username:Unknown}
app:
name: "MyApp"
description: "${app.name} is a Spring Boot application written by ${username:Unknown}"
Assuming that the username
property has not been set elsewhere, app.description
will have the value MyApp is a Spring Boot application written by Unknown
.
You should always refer to property names in the placeholder using their canonical form (kebab-case using only lowercase letters).
This will allow Spring Boot to use the same logic as it does when relaxed binding For example, |
You can also use this technique to create “short” variants of existing Spring Boot properties. See the Use ‘Short’ Command Line Arguments section in “How-to Guides” for details. |
Working With Multi-Document Files
Spring Boot allows you to split a single physical file into multiple logical documents which are each added independently. Documents are processed in order, from top to bottom. Later documents can override the properties defined in earlier ones.
For application.yaml
files, the standard YAML multi-document syntax is used.
Three consecutive hyphens represent the end of one document, and the start of the next.
For example, the following file has two logical documents:
spring:
application:
name: "MyApp"
---
spring:
application:
name: "MyCloudApp"
config:
activate:
on-cloud-platform: "kubernetes"
For application.properties
files a special #---
or !---
comment is used to mark the document splits:
spring.application.name=MyApp
#---
spring.application.name=MyCloudApp
spring.config.activate.on-cloud-platform=kubernetes
Property file separators must not have any leading whitespace and must have exactly three hyphen characters. The lines immediately before and after the separator must not be same comment prefix. |
Multi-document property files are often used in conjunction with activation properties such as spring.config.activate.on-profile .
See the next section for details.
|
Multi-document property files cannot be loaded by using the @PropertySource or @TestPropertySource annotations.
|
Activation Properties
It is sometimes useful to only activate a given set of properties when certain conditions are met. For example, you might have properties that are only relevant when a specific profile is active.
You can conditionally activate a properties document using spring.config.activate.*
.
The following activation properties are available:
Property | Note |
---|---|
|
A profile expression that must match for the document to be active. |
|
The |
For example, the following specifies that the second document is only active when running on Kubernetes, and only when either the “prod” or “staging” profiles are active:
-
Properties
-
YAML
myprop=always-set
#---
spring.config.activate.on-cloud-platform=kubernetes
spring.config.activate.on-profile=prod | staging
myotherprop=sometimes-set
myprop:
"always-set"
---
spring:
config:
activate:
on-cloud-platform: "kubernetes"
on-profile: "prod | staging"
myotherprop: "sometimes-set"
Encrypting Properties
Spring Boot does not provide any built-in support for encrypting property values, however, it does provide the hook points necessary to modify values contained in the Spring Environment
.
The EnvironmentPostProcessor
interface allows you to manipulate the Environment
before the application starts.
See Customize the Environment or ApplicationContext Before It Starts for details.
If you need a secure way to store credentials and passwords, the Spring Cloud Vault project provides support for storing externalized configuration in HashiCorp Vault.
Working With YAML
YAML is a superset of JSON and, as such, is a convenient format for specifying hierarchical configuration data.
The SpringApplication
class automatically supports YAML as an alternative to properties whenever you have the SnakeYAML library on your classpath.
If you use starters, SnakeYAML is automatically provided by spring-boot-starter .
|
Mapping YAML to Properties
YAML documents need to be converted from their hierarchical format to a flat structure that can be used with the Spring Environment
.
For example, consider the following YAML document:
environments:
dev:
url: "https://dev.example.com"
name: "Developer Setup"
prod:
url: "https://another.example.com"
name: "My Cool App"
In order to access these properties from the Environment
, they would be flattened as follows:
environments.dev.url=https://dev.example.com
environments.dev.name=Developer Setup
environments.prod.url=https://another.example.com
environments.prod.name=My Cool App
Likewise, YAML lists also need to be flattened.
They are represented as property keys with [index]
dereferencers.
For example, consider the following YAML:
my:
servers:
- "dev.example.com"
- "another.example.com"
The preceding example would be transformed into these properties:
my.servers[0]=dev.example.com
my.servers[1]=another.example.com
Properties that use the [index] notation can be bound to Java List or Set objects using Spring Boot’s Binder class.
For more details see the Type-safe Configuration Properties section below.
|
YAML files cannot be loaded by using the @PropertySource or @TestPropertySource annotations.
So, in the case that you need to load values that way, you need to use a properties file.
|
Directly Loading YAML
Spring Framework provides two convenient classes that can be used to load YAML documents.
The YamlPropertiesFactoryBean
loads YAML as Properties
and the YamlMapFactoryBean
loads YAML as a Map
.
You can also use the YamlPropertySourceLoader
class if you want to load YAML as a Spring PropertySource
.
Configuring Random Values
The RandomValuePropertySource
is useful for injecting random values (for example, into secrets or test cases).
It can produce integers, longs, uuids, or strings, as shown in the following example:
-
Properties
-
YAML
my.secret=${random.value}
my.number=${random.int}
my.bignumber=${random.long}
my.uuid=${random.uuid}
my.number-less-than-ten=${random.int(10)}
my.number-in-range=${random.int[1024,65536]}
my:
secret: "${random.value}"
number: "${random.int}"
bignumber: "${random.long}"
uuid: "${random.uuid}"
number-less-than-ten: "${random.int(10)}"
number-in-range: "${random.int[1024,65536]}"
The random.int*
syntax is OPEN value (,max) CLOSE
where the OPEN,CLOSE
are any character and value,max
are integers.
If max
is provided, then value
is the minimum value and max
is the maximum value (exclusive).
Configuring System Environment Properties
Spring Boot supports setting a prefix for environment properties.
This is useful if the system environment is shared by multiple Spring Boot applications with different configuration requirements.
The prefix for system environment properties can be set directly on SpringApplication
.
For example, if you set the prefix to input
, a property such as remote.timeout
will also be resolved as input.remote.timeout
in the system environment.
Type-safe Configuration Properties
Using the @Value("${property}")
annotation to inject configuration properties can sometimes be cumbersome, especially if you are working with multiple properties or your data is hierarchical in nature.
Spring Boot provides an alternative method of working with properties that lets strongly typed beans govern and validate the configuration of your application.
JavaBean Properties Binding
It is possible to bind a bean declaring standard JavaBean properties as shown in the following example:
-
Java
-
Kotlin
import java.net.InetAddress;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.springframework.boot.context.properties.ConfigurationProperties;
@ConfigurationProperties("my.service")
public class MyProperties {
private boolean enabled;
private InetAddress remoteAddress;
private final Security security = new Security();
// getters / setters...
public boolean isEnabled() {
return this.enabled;
}
public void setEnabled(boolean enabled) {
this.enabled = enabled;
}
public InetAddress getRemoteAddress() {
return this.remoteAddress;
}
public void setRemoteAddress(InetAddress remoteAddress) {
this.remoteAddress = remoteAddress;
}
public Security getSecurity() {
return this.security;
}
public static class Security {
private String username;
private String password;
private List<String> roles = new ArrayList<>(Collections.singleton("USER"));
// getters / setters...
public String getUsername() {
return this.username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return this.password;
}
public void setPassword(String password) {
this.password = password;
}
public List<String> getRoles() {
return this.roles;
}
public void setRoles(List<String> roles) {
this.roles = roles;
}
}
}
import org.springframework.boot.context.properties.ConfigurationProperties
import java.net.InetAddress
@ConfigurationProperties("my.service")
class MyProperties {
var isEnabled = false
var remoteAddress: InetAddress? = null
val security = Security()
class Security {
var username: String? = null
var password: String? = null
var roles: List<String> = ArrayList(setOf("USER"))
}
}
The preceding POJO defines the following properties:
-
my.service.enabled
, with a value offalse
by default. -
my.service.remote-address
, with a type that can be coerced fromString
. -
my.service.security.username
, with a nested "security" object whose name is determined by the name of the property. In particular, the type is not used at all there and could have beenSecurityProperties
. -
my.service.security.password
. -
my.service.security.roles
, with a collection ofString
that defaults toUSER
.
The properties that map to @ConfigurationProperties classes available in Spring Boot, which are configured through properties files, YAML files, environment variables, and other mechanisms, are public API but the accessors (getters/setters) of the class itself are not meant to be used directly.
|
Such arrangement relies on a default empty constructor and getters and setters are usually mandatory, since binding is through standard Java Beans property descriptors, just like in Spring MVC. A setter may be omitted in the following cases:
Some people use Project Lombok to add getters and setters automatically. Make sure that Lombok does not generate any particular constructor for such a type, as it is used automatically by the container to instantiate the object. Finally, only standard Java Bean properties are considered and binding on static properties is not supported. |
Constructor Binding
The example in the previous section can be rewritten in an immutable fashion as shown in the following example:
-
Java
-
Kotlin
import java.net.InetAddress;
import java.util.List;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.bind.DefaultValue;
@ConfigurationProperties("my.service")
public class MyProperties {
// fields...
private final boolean enabled;
private final InetAddress remoteAddress;
private final Security security;
public MyProperties(boolean enabled, InetAddress remoteAddress, Security security) {
this.enabled = enabled;
this.remoteAddress = remoteAddress;
this.security = security;
}
// getters...
public boolean isEnabled() {
return this.enabled;
}
public InetAddress getRemoteAddress() {
return this.remoteAddress;
}
public Security getSecurity() {
return this.security;
}
public static class Security {
// fields...
private final String username;
private final String password;
private final List<String> roles;
public Security(String username, String password, @DefaultValue("USER") List<String> roles) {
this.username = username;
this.password = password;
this.roles = roles;
}
// getters...
public String getUsername() {
return this.username;
}
public String getPassword() {
return this.password;
}
public List<String> getRoles() {
return this.roles;
}
}
}
import org.springframework.boot.context.properties.ConfigurationProperties
import org.springframework.boot.context.properties.bind.DefaultValue
import java.net.InetAddress
@ConfigurationProperties("my.service")
class MyProperties(val enabled: Boolean, val remoteAddress: InetAddress,
val security: Security) {
class Security(val username: String, val password: String,
@param:DefaultValue("USER") val roles: List<String>)
}
In this setup, the presence of a single parameterized constructor implies that constructor binding should be used.
This means that the binder will find a constructor with the parameters that you wish to have bound.
If your class has multiple constructors, the @ConstructorBinding
annotation can be used to specify which constructor to use for constructor binding.
To opt out of constructor binding for a class with a single parameterized constructor, the constructor must be annotated with @Autowired
or made private
.
Constructor binding can be used with records.
Unless your record has multiple constructors, there is no need to use @ConstructorBinding
.
Nested members of a constructor bound class (such as Security
in the example above) will also be bound through their constructor.
Default values can be specified using @DefaultValue
on constructor parameters and record components.
The conversion service will be applied to coerce the annotation’s String
value to the target type of a missing property.
Referring to the previous example, if no properties are bound to Security
, the MyProperties
instance will contain a null
value for security
.
To make it contain a non-null instance of Security
even when no properties are bound to it (when using Kotlin, this will require the username
and password
parameters of Security
to be declared as nullable as they do not have default values), use an empty @DefaultValue
annotation:
-
Java
-
Kotlin
public MyProperties(boolean enabled, InetAddress remoteAddress, @DefaultValue Security security) {
this.enabled = enabled;
this.remoteAddress = remoteAddress;
this.security = security;
}
class MyProperties(val enabled: Boolean, val remoteAddress: InetAddress,
@DefaultValue val security: Security) {
class Security(val username: String?, val password: String?,
@param:DefaultValue("USER") val roles: List<String>)
}
To use constructor binding the class must be enabled using @EnableConfigurationProperties or configuration property scanning.
You cannot use constructor binding with beans that are created by the regular Spring mechanisms (for example @Component beans, beans created by using @Bean methods or beans loaded by using @Import )
|
To use constructor binding the class must be compiled with -parameters .
This will happen automatically if you use Spring Boot’s Gradle plugin or if you use Maven and spring-boot-starter-parent .
|
The use of java.util.Optional with @ConfigurationProperties is not recommended as it is primarily intended for use as a return type.
As such, it is not well-suited to configuration property injection.
For consistency with properties of other types, if you do declare an Optional property and it has no value, null rather than an empty Optional will be bound.
|
Enabling @ConfigurationProperties-annotated Types
Spring Boot provides infrastructure to bind @ConfigurationProperties
types and register them as beans.
You can either enable configuration properties on a class-by-class basis or enable configuration property scanning that works in a similar manner to component scanning.
Sometimes, classes annotated with @ConfigurationProperties
might not be suitable for scanning, for example, if you’re developing your own auto-configuration or you want to enable them conditionally.
In these cases, specify the list of types to process using the @EnableConfigurationProperties
annotation.
This can be done on any @Configuration
class, as shown in the following example:
-
Java
-
Kotlin
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Configuration;
@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties(SomeProperties.class)
public class MyConfiguration {
}
import org.springframework.boot.context.properties.EnableConfigurationProperties
import org.springframework.context.annotation.Configuration
@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties(SomeProperties::class)
class MyConfiguration
-
Java
-
Kotlin
import org.springframework.boot.context.properties.ConfigurationProperties;
@ConfigurationProperties("some.properties")
public class SomeProperties {
}
import org.springframework.boot.context.properties.ConfigurationProperties
@ConfigurationProperties("some.properties")
class SomeProperties
To use configuration property scanning, add the @ConfigurationPropertiesScan
annotation to your application.
Typically, it is added to the main application class that is annotated with @SpringBootApplication
but it can be added to any @Configuration
class.
By default, scanning will occur from the package of the class that declares the annotation.
If you want to define specific packages to scan, you can do so as shown in the following example:
-
Java
-
Kotlin
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.properties.ConfigurationPropertiesScan;
@SpringBootApplication
@ConfigurationPropertiesScan({ "com.example.app", "com.example.another" })
public class MyApplication {
}
import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.context.properties.ConfigurationPropertiesScan
@SpringBootApplication
@ConfigurationPropertiesScan("com.example.app", "com.example.another")
class MyApplication
When the Assuming that it is in the |
We recommend that @ConfigurationProperties
only deal with the environment and, in particular, does not inject other beans from the context.
For corner cases, setter injection can be used or any of the *Aware
interfaces provided by the framework (such as EnvironmentAware
if you need access to the Environment
).
If you still want to inject other beans using the constructor, the configuration properties bean must be annotated with @Component
and use JavaBean-based property binding.
Using @ConfigurationProperties-annotated Types
This style of configuration works particularly well with the SpringApplication
external YAML configuration, as shown in the following example:
my:
service:
remote-address: 192.168.1.1
security:
username: "admin"
roles:
- "USER"
- "ADMIN"
To work with @ConfigurationProperties
beans, you can inject them in the same way as any other bean, as shown in the following example:
-
Java
-
Kotlin
import org.springframework.stereotype.Service;
@Service
public class MyService {
private final MyProperties properties;
public MyService(MyProperties properties) {
this.properties = properties;
}
public void openConnection() {
Server server = new Server(this.properties.getRemoteAddress());
server.start();
// ...
}
// ...
}
import org.springframework.stereotype.Service
@Service
class MyService(val properties: MyProperties) {
fun openConnection() {
val server = Server(properties.remoteAddress)
server.start()
// ...
}
// ...
}
Using @ConfigurationProperties also lets you generate metadata files that can be used by IDEs to offer auto-completion for your own keys.
See the appendix for details.
|
Third-party Configuration
As well as using @ConfigurationProperties
to annotate a class, you can also use it on public @Bean
methods.
Doing so can be particularly useful when you want to bind properties to third-party components that are outside of your control.
To configure a bean from the Environment
properties, add @ConfigurationProperties
to its bean registration, as shown in the following example:
-
Java
-
Kotlin
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration(proxyBeanMethods = false)
public class ThirdPartyConfiguration {
@Bean
@ConfigurationProperties(prefix = "another")
public AnotherComponent anotherComponent() {
return new AnotherComponent();
}
}
import org.springframework.boot.context.properties.ConfigurationProperties
import org.springframework.context.annotation.Bean
import org.springframework.context.annotation.Configuration
@Configuration(proxyBeanMethods = false)
class ThirdPartyConfiguration {
@Bean
@ConfigurationProperties(prefix = "another")
fun anotherComponent(): AnotherComponent = AnotherComponent()
}
Any JavaBean property defined with the another
prefix is mapped onto that AnotherComponent
bean in manner similar to the preceding SomeProperties
example.
Relaxed Binding
Spring Boot uses some relaxed rules for binding Environment
properties to @ConfigurationProperties
beans, so there does not need to be an exact match between the Environment
property name and the bean property name.
Common examples where this is useful include dash-separated environment properties (for example, context-path
binds to contextPath
), and capitalized environment properties (for example, PORT
binds to port
).
As an example, consider the following @ConfigurationProperties
class:
-
Java
-
Kotlin
import org.springframework.boot.context.properties.ConfigurationProperties;
@ConfigurationProperties(prefix = "my.main-project.person")
public class MyPersonProperties {
private String firstName;
public String getFirstName() {
return this.firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
}
import org.springframework.boot.context.properties.ConfigurationProperties
@ConfigurationProperties(prefix = "my.main-project.person")
class MyPersonProperties {
var firstName: String? = null
}
With the preceding code, the following properties names can all be used:
Property | Note |
---|---|
|
Kebab case, which is recommended for use in |
|
Standard camel case syntax. |
|
Underscore notation, which is an alternative format for use in |
|
Upper case format, which is recommended when using system environment variables. |
The prefix value for the annotation must be in kebab case (lowercase and separated by - , such as my.main-project.person ).
|
Property Source | Simple | List |
---|---|---|
Properties Files |
Camel case, kebab case, or underscore notation |
Standard list syntax using |
YAML Files |
Camel case, kebab case, or underscore notation |
Standard YAML list syntax or comma-separated values |
Environment Variables |
Upper case format with underscore as the delimiter (see Binding From Environment Variables). |
Numeric values surrounded by underscores (see Binding From Environment Variables) |
System properties |
Camel case, kebab case, or underscore notation |
Standard list syntax using |
We recommend that, when possible, properties are stored in lower-case kebab format, such as my.person.first-name=Rod .
|
Binding Maps
When binding to Map
properties you may need to use a special bracket notation so that the original key
value is preserved.
If the key is not surrounded by []
, any characters that are not alpha-numeric, -
or .
are removed.
For example, consider binding the following properties to a Map<String,String>
:
-
Properties
-
YAML
my.map[/key1]=value1
my.map[/key2]=value2
my.map./key3=value3
my:
map:
"[/key1]": "value1"
"[/key2]": "value2"
"/key3": "value3"
For YAML files, the brackets need to be surrounded by quotes for the keys to be parsed properly. |
The properties above will bind to a Map
with /key1
, /key2
and key3
as the keys in the map.
The slash has been removed from key3
because it was not surrounded by square brackets.
When binding to scalar values, keys with .
in them do not need to be surrounded by []
.
Scalar values include enums and all types in the java.lang
package except for Object
.
Binding a.b=c
to Map<String, String>
will preserve the .
in the key and return a Map with the entry {"a.b"="c"}
.
For any other types you need to use the bracket notation if your key
contains a .
.
For example, binding a.b=c
to Map<String, Object>
will return a Map with the entry {"a"={"b"="c"}}
whereas [a.b]=c
will return a Map with the entry {"a.b"="c"}
.
Binding From Environment Variables
Most operating systems impose strict rules around the names that can be used for environment variables.
For example, Linux shell variables can contain only letters (a
to z
or A
to Z
), numbers (0
to 9
) or the underscore character (_
).
By convention, Unix shell variables will also have their names in UPPERCASE.
Spring Boot’s relaxed binding rules are, as much as possible, designed to be compatible with these naming restrictions.
To convert a property name in the canonical-form to an environment variable name you can follow these rules:
-
Replace dots (
.
) with underscores (_
). -
Remove any dashes (
-
). -
Convert to uppercase.
For example, the configuration property spring.main.log-startup-info
would be an environment variable named SPRING_MAIN_LOGSTARTUPINFO
.
Environment variables can also be used when binding to object lists.
To bind to a List
, the element number should be surrounded with underscores in the variable name.
For example, the configuration property my.service[0].other
would use an environment variable named MY_SERVICE_0_OTHER
.
Merging Complex Types
When lists are configured in more than one place, overriding works by replacing the entire list.
For example, assume a MyPojo
object with name
and description
attributes that are null
by default.
The following example exposes a list of MyPojo
objects from MyProperties
:
-
Java
-
Kotlin
import java.util.ArrayList;
import java.util.List;
import org.springframework.boot.context.properties.ConfigurationProperties;
@ConfigurationProperties("my")
public class MyProperties {
private final List<MyPojo> list = new ArrayList<>();
public List<MyPojo> getList() {
return this.list;
}
}
import org.springframework.boot.context.properties.ConfigurationProperties
@ConfigurationProperties("my")
class MyProperties {
val list: List<MyPojo> = ArrayList()
}
Consider the following configuration:
-
Properties
-
YAML
my.list[0].name=my name
my.list[0].description=my description
#---
spring.config.activate.on-profile=dev
my.list[0].name=my another name
my:
list:
- name: "my name"
description: "my description"
---
spring:
config:
activate:
on-profile: "dev"
my:
list:
- name: "my another name"
If the dev
profile is not active, MyProperties.list
contains one MyPojo
entry, as previously defined.
If the dev
profile is enabled, however, the list
still contains only one entry (with a name of my another name
and a description of null
).
This configuration does not add a second MyPojo
instance to the list, and it does not merge the items.
When a List
is specified in multiple profiles, the one with the highest priority (and only that one) is used.
Consider the following example:
-
Properties
-
YAML
my.list[0].name=my name
my.list[0].description=my description
my.list[1].name=another name
my.list[1].description=another description
#---
spring.config.activate.on-profile=dev
my.list[0].name=my another name
my:
list:
- name: "my name"
description: "my description"
- name: "another name"
description: "another description"
---
spring:
config:
activate:
on-profile: "dev"
my:
list:
- name: "my another name"
In the preceding example, if the dev
profile is active, MyProperties.list
contains one MyPojo
entry (with a name of my another name
and a description of null
).
For YAML, both comma-separated lists and YAML lists can be used for completely overriding the contents of the list.
For Map
properties, you can bind with property values drawn from multiple sources.
However, for the same property in multiple sources, the one with the highest priority is used.
The following example exposes a Map<String, MyPojo>
from MyProperties
:
-
Java
-
Kotlin
import java.util.LinkedHashMap;
import java.util.Map;
import org.springframework.boot.context.properties.ConfigurationProperties;
@ConfigurationProperties("my")
public class MyProperties {
private final Map<String, MyPojo> map = new LinkedHashMap<>();
public Map<String, MyPojo> getMap() {
return this.map;
}
}
import org.springframework.boot.context.properties.ConfigurationProperties
@ConfigurationProperties("my")
class MyProperties {
val map: Map<String, MyPojo> = LinkedHashMap()
}
Consider the following configuration:
-
Properties
-
YAML
my.map.key1.name=my name 1
my.map.key1.description=my description 1
#---
spring.config.activate.on-profile=dev
my.map.key1.name=dev name 1
my.map.key2.name=dev name 2
my.map.key2.description=dev description 2
my:
map:
key1:
name: "my name 1"
description: "my description 1"
---
spring:
config:
activate:
on-profile: "dev"
my:
map:
key1:
name: "dev name 1"
key2:
name: "dev name 2"
description: "dev description 2"
If the dev
profile is not active, MyProperties.map
contains one entry with key key1
(with a name of my name 1
and a description of my description 1
).
If the dev
profile is enabled, however, map
contains two entries with keys key1
(with a name of dev name 1
and a description of my description 1
) and key2
(with a name of dev name 2
and a description of dev description 2
).
The preceding merging rules apply to properties from all property sources, and not just files. |
Properties Conversion
Spring Boot attempts to coerce the external application properties to the right type when it binds to the @ConfigurationProperties
beans.
If you need custom type conversion, you can provide a ConversionService
bean (with a bean named conversionService
) or custom property editors (through a CustomEditorConfigurer
bean) or custom Converters
(with bean definitions annotated as @ConfigurationPropertiesBinding
).
As this bean is requested very early during the application lifecycle, make sure to limit the dependencies that your ConversionService is using.
Typically, any dependency that you require may not be fully initialized at creation time.
You may want to rename your custom ConversionService if it is not required for configuration keys coercion and only rely on custom converters qualified with @ConfigurationPropertiesBinding .
|
Converting Durations
Spring Boot has dedicated support for expressing durations.
If you expose a java.time.Duration
property, the following formats in application properties are available:
-
A regular
long
representation (using milliseconds as the default unit unless a@DurationUnit
has been specified) -
The standard ISO-8601 format used by
java.time.Duration
-
A more readable format where the value and the unit are coupled (
10s
means 10 seconds)
Consider the following example:
-
Java
-
Kotlin
import java.time.Duration;
import java.time.temporal.ChronoUnit;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.convert.DurationUnit;
@ConfigurationProperties("my")
public class MyProperties {
@DurationUnit(ChronoUnit.SECONDS)
private Duration sessionTimeout = Duration.ofSeconds(30);
private Duration readTimeout = Duration.ofMillis(1000);
// getters / setters...
public Duration getSessionTimeout() {
return this.sessionTimeout;
}
public void setSessionTimeout(Duration sessionTimeout) {
this.sessionTimeout = sessionTimeout;
}
public Duration getReadTimeout() {
return this.readTimeout;
}
public void setReadTimeout(Duration readTimeout) {
this.readTimeout = readTimeout;
}
}
import org.springframework.boot.context.properties.ConfigurationProperties
import org.springframework.boot.convert.DurationUnit
import java.time.Duration
import java.time.temporal.ChronoUnit
@ConfigurationProperties("my")
class MyProperties {
@DurationUnit(ChronoUnit.SECONDS)
var sessionTimeout = Duration.ofSeconds(30)
var readTimeout = Duration.ofMillis(1000)
}
To specify a session timeout of 30 seconds, 30
, PT30S
and 30s
are all equivalent.
A read timeout of 500ms can be specified in any of the following form: 500
, PT0.5S
and 500ms
.
You can also use any of the supported units. These are:
-
ns
for nanoseconds -
us
for microseconds -
ms
for milliseconds -
s
for seconds -
m
for minutes -
h
for hours -
d
for days
The default unit is milliseconds and can be overridden using @DurationUnit
as illustrated in the sample above.
If you prefer to use constructor binding, the same properties can be exposed, as shown in the following example:
-
Java
-
Kotlin
import java.time.Duration;
import java.time.temporal.ChronoUnit;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.bind.DefaultValue;
import org.springframework.boot.convert.DurationUnit;
@ConfigurationProperties("my")
public class MyProperties {
// fields...
private final Duration sessionTimeout;
private final Duration readTimeout;
public MyProperties(@DurationUnit(ChronoUnit.SECONDS) @DefaultValue("30s") Duration sessionTimeout,
@DefaultValue("1000ms") Duration readTimeout) {
this.sessionTimeout = sessionTimeout;
this.readTimeout = readTimeout;
}
// getters...
public Duration getSessionTimeout() {
return this.sessionTimeout;
}
public Duration getReadTimeout() {
return this.readTimeout;
}
}
import org.springframework.boot.context.properties.ConfigurationProperties
import org.springframework.boot.context.properties.bind.DefaultValue
import org.springframework.boot.convert.DurationUnit
import java.time.Duration
import java.time.temporal.ChronoUnit
@ConfigurationProperties("my")
class MyProperties(@param:DurationUnit(ChronoUnit.SECONDS) @param:DefaultValue("30s") val sessionTimeout: Duration,
@param:DefaultValue("1000ms") val readTimeout: Duration)
If you are upgrading a Long property, make sure to define the unit (using @DurationUnit ) if it is not milliseconds.
Doing so gives a transparent upgrade path while supporting a much richer format.
|
Converting Periods
In addition to durations, Spring Boot can also work with java.time.Period
type.
The following formats can be used in application properties:
-
An regular
int
representation (using days as the default unit unless a@PeriodUnit
has been specified) -
The standard ISO-8601 format used by
java.time.Period
-
A simpler format where the value and the unit pairs are coupled (
1y3d
means 1 year and 3 days)
The following units are supported with the simple format:
-
y
for years -
m
for months -
w
for weeks -
d
for days
The java.time.Period type never actually stores the number of weeks, it is a shortcut that means “7 days”.
|
Converting Data Sizes
Spring Framework has a DataSize
value type that expresses a size in bytes.
If you expose a DataSize
property, the following formats in application properties are available:
-
A regular
long
representation (using bytes as the default unit unless a@DataSizeUnit
has been specified) -
A more readable format where the value and the unit are coupled (
10MB
means 10 megabytes)
Consider the following example:
-
Java
-
Kotlin
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.convert.DataSizeUnit;
import org.springframework.util.unit.DataSize;
import org.springframework.util.unit.DataUnit;
@ConfigurationProperties("my")
public class MyProperties {
@DataSizeUnit(DataUnit.MEGABYTES)
private DataSize bufferSize = DataSize.ofMegabytes(2);
private DataSize sizeThreshold = DataSize.ofBytes(512);
// getters/setters...
public DataSize getBufferSize() {
return this.bufferSize;
}
public void setBufferSize(DataSize bufferSize) {
this.bufferSize = bufferSize;
}
public DataSize getSizeThreshold() {
return this.sizeThreshold;
}
public void setSizeThreshold(DataSize sizeThreshold) {
this.sizeThreshold = sizeThreshold;
}
}
import org.springframework.boot.context.properties.ConfigurationProperties
import org.springframework.boot.convert.DataSizeUnit
import org.springframework.util.unit.DataSize
import org.springframework.util.unit.DataUnit
@ConfigurationProperties("my")
class MyProperties {
@DataSizeUnit(DataUnit.MEGABYTES)
var bufferSize = DataSize.ofMegabytes(2)
var sizeThreshold = DataSize.ofBytes(512)
}
To specify a buffer size of 10 megabytes, 10
and 10MB
are equivalent.
A size threshold of 256 bytes can be specified as 256
or 256B
.
You can also use any of the supported units. These are:
-
B
for bytes -
KB
for kilobytes -
MB
for megabytes -
GB
for gigabytes -
TB
for terabytes
The default unit is bytes and can be overridden using @DataSizeUnit
as illustrated in the sample above.
If you prefer to use constructor binding, the same properties can be exposed, as shown in the following example:
-
Java
-
Kotlin
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.bind.DefaultValue;
import org.springframework.boot.convert.DataSizeUnit;
import org.springframework.util.unit.DataSize;
import org.springframework.util.unit.DataUnit;
@ConfigurationProperties("my")
public class MyProperties {
// fields...
private final DataSize bufferSize;
private final DataSize sizeThreshold;
public MyProperties(@DataSizeUnit(DataUnit.MEGABYTES) @DefaultValue("2MB") DataSize bufferSize,
@DefaultValue("512B") DataSize sizeThreshold) {
this.bufferSize = bufferSize;
this.sizeThreshold = sizeThreshold;
}
// getters...
public DataSize getBufferSize() {
return this.bufferSize;
}
public DataSize getSizeThreshold() {
return this.sizeThreshold;
}
}
import org.springframework.boot.context.properties.ConfigurationProperties
import org.springframework.boot.context.properties.bind.DefaultValue
import org.springframework.boot.convert.DataSizeUnit
import org.springframework.util.unit.DataSize
import org.springframework.util.unit.DataUnit
@ConfigurationProperties("my")
class MyProperties(@param:DataSizeUnit(DataUnit.MEGABYTES) @param:DefaultValue("2MB") val bufferSize: DataSize,
@param:DefaultValue("512B") val sizeThreshold: DataSize)
If you are upgrading a Long property, make sure to define the unit (using @DataSizeUnit ) if it is not bytes.
Doing so gives a transparent upgrade path while supporting a much richer format.
|
@ConfigurationProperties Validation
Spring Boot attempts to validate @ConfigurationProperties
classes whenever they are annotated with Spring’s @Validated
annotation.
You can use JSR-303 jakarta.validation
constraint annotations directly on your configuration class.
To do so, ensure that a compliant JSR-303 implementation is on your classpath and then add constraint annotations to your fields, as shown in the following example:
-
Java
-
Kotlin
import java.net.InetAddress;
import jakarta.validation.constraints.NotNull;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.validation.annotation.Validated;
@ConfigurationProperties("my.service")
@Validated
public class MyProperties {
@NotNull
private InetAddress remoteAddress;
// getters/setters...
public InetAddress getRemoteAddress() {
return this.remoteAddress;
}
public void setRemoteAddress(InetAddress remoteAddress) {
this.remoteAddress = remoteAddress;
}
}
import jakarta.validation.constraints.NotNull
import org.springframework.boot.context.properties.ConfigurationProperties
import org.springframework.validation.annotation.Validated
import java.net.InetAddress
@ConfigurationProperties("my.service")
@Validated
class MyProperties {
var remoteAddress: @NotNull InetAddress? = null
}
You can also trigger validation by annotating the @Bean method that creates the configuration properties with @Validated .
|
To ensure that validation is always triggered for nested properties, even when no properties are found, the associated field must be annotated with @Valid
.
The following example builds on the preceding MyProperties
example:
-
Java
-
Kotlin
import java.net.InetAddress;
import jakarta.validation.Valid;
import jakarta.validation.constraints.NotEmpty;
import jakarta.validation.constraints.NotNull;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.validation.annotation.Validated;
@ConfigurationProperties("my.service")
@Validated
public class MyProperties {
@NotNull
private InetAddress remoteAddress;
@Valid
private final Security security = new Security();
// getters/setters...
public InetAddress getRemoteAddress() {
return this.remoteAddress;
}
public void setRemoteAddress(InetAddress remoteAddress) {
this.remoteAddress = remoteAddress;
}
public Security getSecurity() {
return this.security;
}
public static class Security {
@NotEmpty
private String username;
// getters/setters...
public String getUsername() {
return this.username;
}
public void setUsername(String username) {
this.username = username;
}
}
}
import jakarta.validation.Valid
import jakarta.validation.constraints.NotEmpty
import jakarta.validation.constraints.NotNull
import org.springframework.boot.context.properties.ConfigurationProperties
import org.springframework.validation.annotation.Validated
import java.net.InetAddress
@ConfigurationProperties("my.service")
@Validated
class MyProperties {
var remoteAddress: @NotNull InetAddress? = null
@Valid
val security = Security()
class Security {
@NotEmpty
var username: String? = null
}
}
You can also add a custom Spring Validator
by creating a bean definition called configurationPropertiesValidator
.
The @Bean
method should be declared static
.
The configuration properties validator is created very early in the application’s lifecycle, and declaring the @Bean
method as static lets the bean be created without having to instantiate the @Configuration
class.
Doing so avoids any problems that may be caused by early instantiation.
The spring-boot-actuator module includes an endpoint that exposes all @ConfigurationProperties beans.
Point your web browser to /actuator/configprops or use the equivalent JMX endpoint.
See the Production ready features section for details.
|
@ConfigurationProperties vs. @Value
The @Value
annotation is a core container feature, and it does not provide the same features as type-safe configuration properties.
The following table summarizes the features that are supported by @ConfigurationProperties
and @Value
:
Feature | @ConfigurationProperties |
@Value |
---|---|---|
Yes |
Limited (see note below) |
|
Yes |
No |
|
|
No |
Yes |
If you do want to use For example, |
If you define a set of configuration keys for your own components, we recommend you group them in a POJO annotated with @ConfigurationProperties
.
Doing so will provide you with structured, type-safe object that you can inject into your own beans.
SpEL
expressions from application property files are not processed at time of parsing these files and populating the environment.
However, it is possible to write a SpEL
expression in @Value
.
If the value of a property from an application property file is a SpEL
expression, it will be evaluated when consumed through @Value
.