Spring Java Config | How to fetch IndexedArgumentsValue from BeanDefinition - spring

Question

Consider the following example :
Config Class
#Configuration
public class MyTestConfig {
#Value("${const.arg.a}") String constArgA;
#Value("${const.arg.b}") String constArgB;
#Bean
public static PropertyPlaceholderConfigurer properties(){
SystemPropertyPlaceholderConfigurer propertyConfigurer = new SystemPropertyPlaceholderConfigurer();
propertyConfigurer.setLocation( "test.properties" );
propertyConfigurer.setPropertyPrefixValue("TEST");
propertyConfigurer.setIgnoreUnresolvablePlaceholders( true );
return propertyConfigurer;
}
#Bean
public SpringTest springTest(){
return new SpringTest(constArgA, constArgB);
}
}
Bean
public class SpringTest {
private String constArgA;
private String constArgB;
public SpringTest(String constArgA, String constArgB){
this.constArgA = constArgA;
this.constArgB = constArgB;
System.out.println("constArgA " + constArgA);
System.out.println("constArgB " + constArgB);
}
public void sayHello(){
System.out.println("Hello, I hope this works");
System.out.println("constArgA " + constArgA);
System.out.println("constArgB " + constArgB);
}
}
SystemPropertyPlaceholderConfigurer is a extension of the PropertyPlaceholderConfigurer in which we try to manipulate some of the Bean Constructor arguments.
For my use case I need to access the constructor arguments but I see a empty list if I obtain a BeanDefinition from ConfigurableListableBeanFactory .
To be precise all of the following for the Bean 'SpringTest' are empty :
beanDefinition.getPropertyValues();
beanDefinition.getConstructorArgumentValues().getIndexedArgumentValues();
beanDefinition.getConstructorArgumentValues().getGenericArgumentValues();
I expect to receive constArgA and constArgB in the ConstructorArgumentValues.
Now if I replace Java Based Config with a Xml Based Config as follows :
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd">
<bean
class="com.abc.SystemPropertyPlaceholderConfigurer">
<property name="location">
<value>test.properties</value>
</property>
<property name="propertyPrefixValue">
<value>TEST</value>
</property>
</bean>
<bean id="springTest" class="com.abc.SpringTest" >
<constructor-arg index="0" type="java.lang.String" value="${const.arg.a}" />
<constructor-arg index="1" type="java.lang.String" value="${const.arg.b}" />
</bean>
</beans>
Now if I try to access my BeanDefinition I get the 2 constructor arguments in :
beanDefinition.getConstructorArgumentValues().getIndexedArgumentValues()
Can you please help me to understand what is the difference in these 2 configuration ways and if I want to use a Java Based Config , how do I access the constructor arguments on my beans ? I basically need to inject my properties from a property file as constructor arguments and need to perform some processing on it through my implementation of PropertyPlaceholderConfigurer.

Answer 1

In #configuration class, I usually do it like this
#Configuration
#PropertySource("classpath:/test.properties")
public class MyTestConfig {
#Resource
private Environment env;
#Bean
public SpringTest springTest(){
return new SpringTest(env.getRequiredProperty("const.arg.a"), env.getRequiredProperty("const.arg.b"));
}
}