Injecting property value into Spring Bean using annotations

Question

In my Spring app, I have beans configured using annotations, for e.g:

@Repository("personDao")
public class PersonDaoImpl extends AbstractDaoImpl implements PersonDao {
    // .......
}

In the XML file, I have a bean called “PropertyPlaceholderConfigurer” defines as:

<bean id="propertyConfigurer" 
  class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="loc" value="/WEB-INF/app.properties" />
</bean>

Now, from the app.properties I need to inject a property in the above bean. I tried doing the following:

<bean class="com.example.PersonDaoImpl">
    <property name="maxResults" value="${results.max}"/>
</bean>

It's not working, I think the reason behind this is PersonDaoImpl is not a feature in the Spring XML file and is picked up from the classpath using annotations.

So, I tried the below code, but still, I am not able to access the property from PropertyPlaceholderConfigurer.

@Repository("personDao")
public class PersonDaoImpl extends AbstractDaoImpl implements PersonDao {

    @Resource(name = "propertyConfigurer")
    protected void setProperties(PropertyPlaceholderConfigurer ppc) {
    // How to access results.max? 
    }

Can someone suggest how do I access it?

Answer 1

I think you can easily perform this operation in Spring 3 as it provides EL support. Follow the below:

@Value("#{systemProperties.databaseName}")
public void setDatabaseName(String db) { ... }

@Value("#{strategyBean.databaseKeyGenerator}")
public void setKeyGenerator(KeyGenerator keygen) { ... }

Here,

Systemproperties: It is an implicit object.

Strategybean: It is the name of a bean.

Similarly, when you want to access some property from a Properties object, you can use @Value to its fields:

@Value("#{myProperties['github.oauth.clientId']}")
private String githubOauthClientId;

Hope this clears your doubt.