java/spring printing out bean property values

Question

Hey,

does anybody have a simple way of printing out bean property values ? Without complicated instrospection constructs via getting propertyDescriptors etc. I'm talking about testing and checking that all properties have correct values, during development.

Answer 1

JSR-305: Annotations for Software Defect Detection

Answer 2

Do you want to print out configuration properties which are built by propertyplaceholderconfiguerer or bean properties itself (which may be set manually via xml, has default values...)?

Answer 3

BeanPostProcessor may be able to help you. postProcessBeforeInitialization() method will be called for each bean initialization and you can print values of properties there.

Post processor class:

public class ExampleBeanPostProcessor implements BeanPostProcessor {
    public Object postProcessBeforeInitialization(Object bean, String beanName)
        throws BeansException {
        if (bean instanceof YourBean)
            System.out.println((YourBean) bean).getSomeProp());
        return bean;
    }
    public Object postProcessAfterInitialization(Object bean, String beanName)
        throws BeansException {
        return bean;
    }
}

Declare bean in bean file:

<bean class="ExampleBeanPostProcessor " />

Answer 4

PropertyDescriptors are the way to go, but Spring makes using them a lot easier if you use the BeanWrapper interface.

Here's a stupid test class:

public class Thingy{
    private final String foo = "hey";
    private final int bar = 123;
    private final List<String> grr = Arrays.asList("1", "2", "3");

    public String getFoo(){
        return this.foo;
    }
    public int getBar(){
        return this.bar;
    }
    public List<String> getGrr(){
        return this.grr;
    }
}

And here's a main method to inspect an instance of it:

public static void main(final String[] args) throws Exception{
    final Thingy thingy = new Thingy();
    final BeanWrapper wrapper = new BeanWrapperImpl(thingy);
    for(final PropertyDescriptor descriptor : wrapper.getPropertyDescriptors()){
        System.out.println(descriptor.getName() + ":"
            + descriptor.getReadMethod().invoke(thingy));
    }
}

Output:

bar:123
class:class com.mypackage.Thingy
foo:hey
grr:[1, 2, 3]

Read this for reference:

• Bean manipulation and the BeanWrapper