org.springframework.context.annotation

Annotation Type PropertySource

@Target(value=TYPE)
@Retention(value=RUNTIME)
@Documented
public @interface PropertySource

Annotation providing a convenient and declarative mechanism for adding a PropertySource to Spring's Environment. To be used in conjunction with @Configuration classes.

Example usage

Given a file app.properties containing the key/value pair testbean.name=myTestBean, the following @Configuration class uses @PropertySource to contribute app.properties to the Environment's set of PropertySources.

 @Configuration
 @PropertySource("classpath:/com/myco/app.properties")
 public class AppConfig {
     @Autowired
     Environment env;

     @Bean
     public TestBean testBean() {
         TestBean testBean = new TestBean();
         testBean.setName(env.getProperty("testbean.name"));
         return testBean;
     }
 }

Notice that the Environment object is @Autowired into the configuration class and then used when populating the TestBean object. Given the configuration above, a call to testBean.getName() will return "myTestBean".

Resolving ${...} placeholders in <bean> and @Value annotations

In order to resolve ${...} placeholders in <bean> definitions or @Value annotations using properties from a PropertySource, one must register a PropertySourcesPlaceholderConfigurer. This happens automatically when using <context:property-placeholder> in XML, but must be explicitly registered using a static @Bean method when using @Configuration classes. See the "Working with externalized values" section of @Configuration Javadoc and "a note on BeanFactoryPostProcessor-returning @Bean methods" of @Bean Javadoc for details and examples.

Resolving ${...} placeholders within @PropertySource resource locations

Any ${...} placeholders present in a @PropertySource resource location will be resolved against the set of property sources already registered against the environment. For example:

 @Configuration
 @PropertySource("classpath:/com/${my.placeholder:default/path}/app.properties")
 public class AppConfig {
     @Autowired
     Environment env;

     @Bean
     public TestBean testBean() {
         TestBean testBean = new TestBean();
         testBean.setName(env.getProperty("testbean.name"));
         return testBean;
     }
 }

Assuming that "my.placeholder" is present in one of the property sources already registered, e.g. system properties or environment variables, the placeholder will be resolved to the corresponding value. If not, then "default/path" will be used as a default. Expressing a default value (delimited by colon ":") is optional. If no default is specified and a property cannot be resolved, an IllegalArgumentException will be thrown.

A note on property overriding with @PropertySource

In cases where a given property key exists in more than one .properties file, the last @PropertySource annotation processed will 'win' and override. For example, given two properties files a.properties and b.properties, consider the following two configuration classes that reference them with @PropertySource annotations:

 @Configuration
 @PropertySource("classpath:/com/myco/a.properties")
 public class ConfigA { }

 @Configuration
 @PropertySource("classpath:/com/myco/b.properties")
 public class ConfigB { }
 

The override ordering depends on the order in which these classes are registered with the application context.

 AnnotationConfigApplicationContext ctx =
     new AnnotationConfigApplicationContext();
 ctx.register(ConfigA.class);
 ctx.register(ConfigB.class);
 ctx.refresh();
 

In the scenario above, the properties in b.properties will override any duplicates that exist in a.properties, because ConfigB was registered last.

In certain situations, it may not be possible or practical to tightly control property source ordering when using @ProperySource annotations. For example, if the @Configuration classes above were registered via component-scanning, the ordering is difficult to predict. In such cases - and if overriding is important - it is recommended that the user fall back to using the programmatic PropertySource API. See ConfigurableEnvironment and MutablePropertySources Javadoc for details.

Since:

3.1

Author:

Chris Beams

See Also:

Configuration, PropertySource, ConfigurableEnvironment.getPropertySources(), MutablePropertySources

Required Element Summary

Required Elements

Modifier and Type	Required Element and Description
String[]	value Indicate the resource location(s) of the properties file to be loaded.

Optional Element Summary

Optional Elements

Modifier and Type	Optional Element and Description
String	name Indicate the name of this property source.

Element Detail

value

public abstract String[] value

Indicate the resource location(s) of the properties file to be loaded. For example, "classpath:/com/myco/app.properties" or "file:/path/to/file".

Resource location wildcards (e.g. **/*.properties) are not permitted; each location must evaluate to exactly one .properties resource.

${...} placeholders will be resolved against any/all property sources already registered with the Environment. See above for examples.

Each location will be added to the enclosing Environment as its own property source, and in the order declared.

name

public abstract String name

Indicate the name of this property source. If omitted, a name will be generated based on the description of the underlying resource.

See Also:

PropertySource.getName(), Resource.getDescription()

Default:

""