java的json使用需要用到6个工具包，

json-lib-2.3-jdk15.jar | Jakarta commons-lang 2.5 | Jakarta commons-beanutils 1.8.0 | Jakarta commons-collections 3.2.1 | Jakarta commons-logging 1.1.1 | ezmorph 1.0.6

其中json-lib-2.3-jdk15.jar为主包，其它5个为依赖包：

下面分别介绍，json格式与其他数据格式的转换

1. 数组与List转JSON

说明：使用JSONArray.fromObject()方法

1）数组

private static void arrayToJson() {
    String[] arr = {"123", "abc", "3edd", "feh"};
    JSONArray jsonArr = JSONArray.fromObject(arr);
    System.out.println(jsonArr.toString());
}

output:
["123","abc","3edd","feh"]

2）List

private static void listToJson() {
    List<People> peoples = new ArrayList<People>();
    People p1 = new People("小明", "男");
    People p2 = new People("小桃", "女");
    peoples.add(p1);
    peoples.add(p2);
    JSONArray jsonArr = JSONArray.fromObject(peoples);
    System.out.println(jsonArr.toString());
}

output:
[{"name":"小明","sex":"男"},{"name":"小桃","sex":"女"}]

People类

public class People {
	private String name;
	private String sex;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getSex() {
		return sex;
	}

	public void setSex(String sex) {
		this.sex = sex;
	}

	public People(String name, String sex) {
		this.name = name;
		this.sex = sex;
	}
}

附：注意要重写变量的set和get方法。

2. 对象和map转json

说明：使用JSONObject.fromObject()方法

1）对象

private static void objectToJson() {
    People p1 = new People("小明", "男");
    JSONObject jsonObj = JSONObject.fromObject(p1);
    System.out.println(jsonObj.toString());
}

output:
{"name":"小明","sex":"男"}

2）Map

private static void mapToJson() {
    Map<String, String> map = new HashMap<String, String>();
    map.put("随遇而安", "孟非的人生经历");
    map.put("浪潮之巅", "讲诉互联网公司的兴衰与变革");
    JSONObject jsonObj = JSONObject.fromObject(map);
    System.out.println(jsonObj.toString());
}

output:
{"随遇而安":"孟非的人生经历","浪潮之巅":"讲诉互联网公司的兴衰与变革"

3. 将json字符串转换为对象

说明：使用JSONObject.toBean()方法

private static void jsonToObj() {
    String jsonStr = "{\"name\":\"小明\",\"sex\":\"男\"}";
    JSONObject jsonObj = JSONObject.fromObject(jsonStr);
    People p = (People)JSONObject.toBean(jsonObj, People.class);
    System.out.println("name: "+p.getName()+"/sex: "+p.getSex());
}

output:
name: 小明/sex: 男

附：运行时我这边出现：java.lang.NoSuchMethodException: json.People.<init>()错误

原因是没有People()构造方法，即必须加一个空的构造方法

4. json字符串的解析

虽然json字符串直接可以映射到具体的对象，但也可以直接解析出json格式，再封装成一个对象

在People加上一个变量：friends,  类型为List<People>，为其增加set，get方法

private static void parseJsonStr() {
		People p1 = new People("小明", "男");
		List<People> friends = new ArrayList<People>();
		People f1 = new People("小朱", "男");
		People f2 = new People("小桃", "女");
		friends.add(f1);
		friends.add(f2);
		p1.setFriends(friends);
		JSONObject jsonObj = JSONObject.fromObject(p1);
		System.out.println(jsonObj.toString());

		String jsonStr = jsonObj.toString();
		JSONObject obj = JSONObject.fromObject(jsonStr);
		People p = (People)JSONObject.toBean(obj, People.class);
		System.out.println("name: "+p.getName()+"/sex: "+p.getSex()+"/friends: "+p.getFriends());

	}

说明：上面的一种方式是直接通过toBean方法，转换为people对象，

当然还可以直接解析，如下：

private static void parseJsonStr() {
		String jsonStr = "{\"friends\":[{\"friends\":[],\"name\":\"小朱\",\"sex\":\"男\"},{\"friends\":[],\"name\":\"小桃\",\"sex\":\"女\"}],\"name\":\"小明\",\"sex\":\"男\"}";
		JSONObject obj = JSONObject.fromObject(jsonStr);

		People p = new People();
		p.setName(obj.getString("name"));
		p.setSex(obj.getString("sex"));

		JSONArray jsonArr = obj.getJSONArray("friends");
		List<People> friends = new ArrayList<People>();

		for(int i=0;i<jsonArr.size();i++) {
			People f = new People();
			f.setName(jsonArr.getJSONObject(i).getString("name"));
			f.setSex(jsonArr.getJSONObject(i).getString("sex"));
			friends.add(f);
		}
		p.setFriends(friends);
		System.out.println("name: "+p.getName()+"/sex: "+p.getSex()+"/friends: "+JSONArray.fromObject(p.getFriends()).toString());
	}