Dumping a java object's properties

Question

Is there a library that will recursively dump/print an objects properties? I'm looking for something similar to the console.dir() function in Firebug.

I'm aware of the commons-lang ReflectionToStringBuilder but it does not recurse into an object. I.e., if I run the following:

public class ToString {

    public static void main(String [] args) {
        System.out.println(ReflectionToStringBuilder.toString(new Outer(), ToStringStyle.MULTI_LINE_STYLE));
    }

    private static class Outer {
        private int intValue = 5;
        private Inner innerValue = new Inner();
    }

    private static class Inner {
        private String stringValue = "foo";
    }
}

I receive:

ToString$Outer@1b67f74[ intValue=5
innerValue=ToString$Inner@530daa ]

I realize that in my example, I could have overriden the toString() method for Inner but in the real world, I'm dealing with external objects that I can't modify.

Answer 1

You could try XStream.

XStream xstream = new XStream(new Sun14ReflectionProvider(
      FieldDictionary(new ImmutableFieldKeySorter())),
      new DomDriver("utf-8"));
System.out.println(xstream.toXML(new Outer()));

prints out:

<foo.ToString_-Outer>
  <intValue>5</intValue>
  <innerValue>
    <stringValue>foo</stringValue>
  </innerValue>
</foo.ToString_-Outer>

You could also output in JSON

And be careful of circular references ;)

Answer 2

Maybe you could use an XML binding framework like XStream, Digester or JAXB for that.

Answer 3

Scroll down for an example of dumping an object using reflection. http://stackoverflow.com/questions/37628/what-is-reflection-and-why-is-it-useful

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Or go directly to the answer.

Answer 4

You can use ReflectionToStringBuilder with a custom ToStringStyle, for example:

class MyStyle extends ToStringStyle {
private final static ToStringStyle instance = new MyStyle();

public MyStyle() {
 setArrayContentDetail(true);
 setUseShortClassName(true);
 setUseClassName(false);
 setUseIdentityHashCode(false);
 setFieldSeparator(", " + SystemUtils.LINE_SEPARATOR + "  ");
}

public ToStringStyle getInstance() {
 return instance;
};

@Override
public void appendDetail(StringBuffer buffer, String fieldName, Object value) {
 if (!value.getClass().getName().startsWith("java")) {
  buffer.append(ReflectionToStringBuilder.toString(value, instance));
 } else {
  super.appendDetail(buffer, fieldName, value);
 }
}

@Override
public void appendDetail(StringBuffer buffer, String fieldName, Collection value) {
 appendDetail(buffer, fieldName, value.toArray());
}

}

And then you invoke it like:

ReflectionToStringBuilder.toString(value, MyStyle.getInstance());

Beware of circular references though!

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You can also use json-lib (http://json-lib.sourceforge.net) and just do:

JSONObject.fromObject(value);

Answer 5

JSONObject.fromObject(value)

Does not work for Map objects with other keys than String. Maybe JsonConfig can handle this.