1、依赖的包
根据：http://json-lib.sourceforge.net/ 可见json-lib使用需要依赖一下包：
下载地址：http://download.csdn.net/download/zfxinli/2117292 或百度盘：http://pan.baidu.com/s/1hq5kGQC
非常有用的参考：
（1）json在线转换器：http://json.parser.online.fr/
（2）json介绍：http://www.json.org/json-zh.html
2、普通JavaBean
（1）基本JavaBean
public class User { private String username; private String password; public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } }
（2）转化成JSONArray
User user = new User(); user.setUsername("lp"); user.setPassword("1234"); JSONArray json = JSONArray.fromObject(user); System.out.println(json); //结果：[{"password":"1234","username":"lp"}]
（3）转化成JSONObject
User user = new User(); user.setUsername("lp"); user.setPassword("1234"); JSONObject json = JSONObject.fromObject(user); System.out.println(json); //结果;{"password":"1234","username":"lp"}
3、List<User>
（1）转化成JSONArray
List<User>users = new ArrayList<>(); User user = new User(); user.setUsername("lp"); user.setPassword("1234"); User userSecond = new User(); userSecond.setUsername("ch"); userSecond.setPassword("4567"); users.add(user); users.add(userSecond); JSONArray json = JSONArray.fromObject(users); System.out.println(json); //结果：[{"password":"1234","username":"lp"},{"password":"4567","username":"ch"}]
（2）转化成JSONObject
不可以直接通过JSONObject jsonObj = JSONObject.fromObject(users);进行
可以通过如下方式：
JSONObject json = new JSONObject(); json.put("users", users); json.put("userSecond", userSecond); System.out.println(json); //结果：{"users":[{"password":"1234","username":"lp"},{"password":"4567","username":"ch"}],"userSecond":{"password":"4567","username":"ch"}}
4、Map
（1）转化成JSONArray
Map<String, Object>map = new HashMap<String, Object>(); map.put("users", users); map.put("user", user); JSONArray json = JSONArray.fromObject(map); System.out.println(json); //结果：[{"users":[{"password":"1234","username":"lp"},{"password":"4567","username":"ch"}],"user":{"password":"1234","username":"lp"}}]
（2）转化成JSONObject
Map<String, Object>map = new HashMap<String, Object>(); map.put("users", users); map.put("user", user); JSONObject json = JSONObject.fromObject(map); System.out.println(json); //结果：{"users":[{"password":"1234","username":"lp"},{"password":"4567","username":"ch"}],"user":{"password":"1234","username":"lp"}}