Solved

Java, JSON and reflection

Posted on 2008-10-09
7
1,654 Views
Last Modified: 2013-12-22
Hy all

I playing a little with Java and Reflection.

So the Idea is to transform a Java object in a JSON object.

For now seems that works if I have a class just with public fields. But if I have package fields, they aren't collectable like this. How to get them?

Note: I will say thanks if you get me a Lib doing this, but I prefer to do it myself.


package oleber.json.simple;
 
import java.lang.reflect.Field;
import java.util.Collection;
import java.util.Map;
 
public class JSONable implements IJSONable {
 
	@Override
	public JSONObject toJSON() {
		try {
			JSONObject objJSON = new JSONObject();
			JSONObject objValues = new JSONObject();
			JSONObject objTypes = new JSONObject();
 
			objJSON.put("values", objValues);
			objJSON.put("types", objTypes);
 
			for ( Field field : getClass().getFields() ) {
				if ( field.getType() == byte.class ) {
					objValues.put(field.getName(), field.getByte(this));
				} else if ( field.getType() == char.class ) {
					objValues.put(field.getName(), field.getChar(this));
				} else if ( field.getType() == short.class ) {
					objValues.put(field.getName(), field.getShort(this));
				} else if ( field.getType() == int.class ) {
					objValues.put(field.getName(), field.getInt(this));
				} else if ( field.getType() == long.class ) {
					objValues.put(field.getName(), field.getLong(this));
				} else if ( field.getType() == float.class ) {
					objValues.put(field.getName(), field.getFloat(this));
				} else if ( field.getType() == double.class ) {
					objValues.put(field.getName(), field.getDouble(this));
				} else if ( field.getType() == boolean.class ) {
					objValues.put(field.getName(), field.getBoolean(this));
				} else if ( field.getType() == String.class ) {
					objValues.put(field.getName(), field.get(this));
				} else {
					Object value = field.get(this);
					if ( value == null ) {
						objValues.put(field.getName(), null);
					} else if ( value instanceof String || value instanceof IJSONable) {
						objValues.put(field.getName(), value);
						objTypes.put(field.getName(), value.getClass().toString());
					} else if ( value instanceof Collection ) {
						JSONArray array = new JSONArray( ( Collection<?> ) value );
						objValues.put(field.getName(), array);
						objTypes.put(field.getName(), value.getClass().toString());
					} else if ( value instanceof Map ) {
						JSONObject object = new JSONObject( ( Map<String,?> ) value );
						objValues.put(field.getName(), object);
						objTypes.put(field.getName(), value.getClass().toString());
					}
				}
			}
			return objJSON;
		} catch ( Exception e ) {
			e.printStackTrace();
			return null;
		}
	}
 
	@Override
	public JSONable toJSON(JSONObject obj) {
		return null;
	}
 
	@Override
	public String toString() {
		return toJSON().toString();
	}
}

Open in new window

0
Comment
Question by:oleber
  • 5
  • 2
7 Comments
 
LVL 6

Expert Comment

by:manuel_m
ID: 22676503
Try the following. This will return an array of all fields of the class, including package, private, protected and public fields.
for ( Field field : getClass().getDeclaredFields() ) {

Open in new window

0
 
LVL 6

Expert Comment

by:manuel_m
ID: 22676527
hmm. ignore it. with this code snippet you get the fields but you can't access them from another package.
With field.isAccessible() you can check the accessibility of the field. If this field has default access only, you will get an error:
java.lang.IllegalAccessException: Class reflectiontest.Main can not access a member of class com.xxx.test.Test with modifiers ""
        at sun.reflect.Reflection.ensureMemberAccess(Reflection.java:65)
0
 
LVL 10

Author Comment

by:oleber
ID: 22676562
that is my problem ;)


But you serialize a class, Where is the secret?
0
Netscaler Common Configuration How To guides

If you use NetScaler you will want to see these guides. The NetScaler How To Guides show administrators how to get NetScaler up and configured by providing instructions for common scenarios and some not so common ones.

 
LVL 6

Expert Comment

by:manuel_m
ID: 22676639
Do you know the structure of the classes?

Can't you access the package variables from the get methods?
0
 
LVL 10

Author Comment

by:oleber
ID: 22676690
I'm trying to do this generic. Basically every child class from this would be able of convert itself to JSON.
0
 
LVL 6

Expert Comment

by:manuel_m
ID: 22676735
0
 
LVL 6

Accepted Solution

by:
manuel_m earned 500 total points
ID: 22676748
0

Featured Post

Microsoft Certification Exam 74-409

Veeam® is happy to provide the Microsoft community with a study guide prepared by MVP and MCT, Orin Thomas. This guide will take you through each of the exam objectives, helping you to prepare for and pass the examination.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

For customizing the look of your lightweight component and making it look opaque like it was made of plastic.  This tip assumes your component to be of rectangular shape and completely opaque.   (CODE)
Java Flight Recorder and Java Mission Control together create a complete tool chain to continuously collect low level and detailed runtime information enabling after-the-fact incident analysis. Java Flight Recorder is a profiling and event collectio…
Viewers learn about the third conditional statement “else if” and use it in an example program. Then additional information about conditional statements is provided, covering the topic thoroughly. Viewers learn about the third conditional statement …
This tutorial covers a step-by-step guide to install VisualVM launcher in eclipse.

770 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question