Json or toString without nulls - using reflection to omit null object fields from toString or toJson

JsonNoNulls.java

/*
 * Copyright (C) 2014 Matthew Roberts
 * MIT License, http://opensource.org/licenses/MIT
 */
package org.matthewroberts;

import java.io.Serializable;
import java.lang.reflect.Field;

/**
 *
 * This is an example of using reflection to build a JSON-formatted String
 * at runtime which omits any null values. You can use something similar 
 * to override a toString method. I've used a JSON format as an example 
 * because there are many cases where you may not want to expose null 
 * values. There are many frameworks that handle this sort of thing for 
 * you, but in this case we're just using good old fashioned Java. 
 *
 * @author mroberts
 * 
 */
public class JsonNoNulls implements Serializable {

	private static final long serialVersionUID = 1L;

	private String firstName, lastName, email;

	public String getFirstName() {
		return firstName;
	}

	public void setFirstName(String firstName) {
		this.firstName = firstName;
	}

	public String getLastName() {
		return lastName;
	}

	public void setLastName(String lastName) {
		this.lastName = lastName;
	}

	public String getEmail() {
		return email;
	}

	public void setEmail(String email) {
		this.email = email;
	}

	/**
	 * Returns a Json-formatted String, omitting null values.
	 * 
	 * @return returns a Json-formatted String
	 */
	public String toJsonNotNull() {

		Class<?> clazz = null;
		StringBuilder stringBuilder = new StringBuilder();

		try {
			clazz = Class.forName(this.getClass().getName());
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}

		Field[] classFields = clazz.getDeclaredFields();

		stringBuilder.append("{");

		for (int i = 0; i < classFields.length; i++) {

			Field field = classFields[i];

			try {

				if (field.get(this) != null
						&& !field.getName().equals("serialVersionUID")) {
					stringBuilder.append("\"" + field.getName() + "\":\""
							+ field.get(this) + "\",");
				}
			} catch (IllegalArgumentException e) {
				e.printStackTrace();
			} catch (IllegalAccessException e) {
				e.printStackTrace();
			}
		}

		stringBuilder.setLength(stringBuilder.length() - 1);
		stringBuilder.append("}");

		return stringBuilder.toString();
	}
}

JsonNoNullsTest.java

/*
 * Copyright (C) 2014 Matthew Roberts
 * MIT License, http://opensource.org/licenses/MIT
 */
package org.matthewroberts;

import junit.framework.TestCase;

import org.junit.Test;

public class JsonNoNullsTest extends TestCase {

	@Test
	public void testObjectFieldsNotNull() {

		TestObject testObj = new TestObject();

		testObj.setFirstName("Matthew");
		testObj.setLastName("Roberts");

		String testJsonNotNull = testObj.toJsonNotNull();

		assertTrue(testObj.getFirstName().equals("Matthew"));
		assertTrue(testObj.getLastName().equals("Roberts"));
		assertTrue(testObj.getEmail() == null);
		assertTrue(testJsonNotNull.contains("firstName"));
		assertTrue(testJsonNotNull.contains("lastName"));
		assertTrue(!testJsonNotNull.contains("email"));
	}
}