Registering properties in Spring
Starting with Spring 3.1, the new
Environment and
PropertySource abstractions simplify working with properties. The default Spring Environment now contains two property sources: the System properties and the JVM properties, with the System properties having precedence.
(1) Registering Properties via the XML namespace:
<context:property-placeholder location="classpath:config/${env:local}/**/*.properties" ignore-unresolvable="true"/>
(2) Registering Properties via Java Annotation:(2)
@PropertySource("classpath:config/${env:local}/environment.properties")
Spring 3.1 introduces the new @PropertySource annotation, as a convenient mechanism of adding property sources to the environment. But as opposed to using XML namespace element, the Java @PropertySource annotation does not automatically register a PropertySourcesPlaceholderConfigurer with Spring.
Instead, the bean must be explicitly defined in the configuration to get the property resolution mechanism working.
@Bean
public static PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer() {
return new PropertySourcesPlaceholderConfigurer();
}
Note: Resource location wildcards (e.g. **/*.properties) are not permitted; each location must evaluate to exactly one .properties resource. So if you want to use wildcards in your propertySource, don't use Method 2).
(3) Registering Properties via Java configuration:
static @Bean public PropertySourcesPlaceholderConfigurer myPropertySourcesPlaceholderConfigurer() throws IOException {
String envVar = System.getenv("env");
if (envVar == null)
envVar = "local";
PropertySourcesPlaceholderConfigurer p = new PropertySourcesPlaceholderConfigurer();
p.setLocations(new PathMatchingResourcePatternResolver()
.getResources("classpath*:config/"+envVar+"/*.properties"));
p.setIgnoreUnresolvablePlaceholders(true);
return p;
}
Using properties in Spring
Both the older PropertyPlaceholderConfigurer and the new PropertySourcesPlaceholderConfigurer added in Spring 3.1 resolve ${…} placeholders within bean definition property values and @Value annotations.
For example, to inject a property using the @Value annotation:
@Value( "${jdbc.url}" )
private String jdbcUrl;
Using properties in Spring XML configuration:
<bean id="dataSource">
<property name="url" value="${jdbc.url}" />
</bean>
And lastly, obtaining properties via the new Environment APIs:
@Autowired
private Environment env;
...
dataSource.setUrl(env.getProperty("jdbc.url"));
