JSONObject 解析json

String message = new String(delivery.getBody());//得到交付的消息System.out.println(" [x] 订单 '" + message + "'");JSONObject jsonObject = JSONObject.fromObject(message);Map<String,Object> mapJson = JSONObject.fromObject(jsonObject);

这几天一直在做Java解析Json数据的一个项目，因为初识json，所以很多东西都是有着懵懂的认识。这里写下我解析时遇到的问题和收获。
   我解析json时用到的是json-lib包。下载地址：http://json-lib.sourceforge.net。用这个包时，还要用到其他几个支持包：commons-lang.jar、commons-logging.jar，commons-beanutils.jar、xom-1.0-2005-01-05.jar、ezmorph-1.0.1.jar，以上包都可在http://json-lib.sourceforge.net下载。
 
  先给出2个简单的例子。
1.java2json
样例：
public class testJson{ public static void main(String[] args) {    String json = "{\"name\":\"reiz\"}";    JSONObject jsonObj = JSONObject.fromObject(json);    String name = jsonObj.getString("name");         jsonObj.put("initial", name.substring(0, 1).toUpperCase());
    String[] likes = new String[] { "JavaScript", "Skiing", "Apple Pie" };    jsonObj.put("likes", likes);
    Map<String, String> ingredients = new HashMap<String, String>();    ingredients.put("apples", "3kg");    ingredients.put("sugar", "1kg");    ingredients.put("pastry", "2.4kg");    ingredients.put("bestEaten", "outdoors");    jsonObj.put("ingredients",ingredients);         System.out.println(jsonObj);     }
} 
输出结果：
{"name":"reiz","initial":"R","likes":["JavaScript","Skiing","Apple Pie"],"ingredients":{"apples":"3kg","pastry":"2.4kg","bestEaten":"outdoors","sugar":"1kg"}}
java2json的资料网上很多，此不具体研究。
 
2.javafromjson
例子：
public class testJson{ public static void main(String[] args) {  String json = "{x:'1',y:'2',userId:'112',element:[{id:'123',name:'haha'},{id:'456',name:'hehe'}]}";     JSONObject obj = JSONObject.fromObject(json);   String x = obj.getString("x");   String userid = obj.getString("userId");   System.out.println("x is:" + x);   System.out.println("userId is:" + userid);     // 数组array结果：[{"id":"123","name":"haha"},{"id":"456","name":"hehe"}]   JSONArray jsonArray = obj.getJSONArray("element");   for (int i = 0; i < jsonArray.size(); i++) {    System.out.println("element " + i + " :" + jsonArray.get(i));   } }}    
输出：
x is:1userId is:112element 0 :{"id":"123","name":"haha"}element 1 :{"id":"456","name":"hehe"}
从上例可以看出，若取某一数组，可用json.get(i)取出。若想继续取出数组中第i个元素内的某一个值，如取出数组第一个元素中id的值，可用(JSONObject)json.get(0).getInt("id")取出,为了看出细节，我们设取第二个元素中name的值，代码如下：
     JSONObject obj2 = JSONObject.fromObject(array.get(1));     System.out.println(obj2.getString("name"));
   输出结果为 hehe
   可以看出一般步骤为：将要目标字符串转为JSON对象（JSONObject.fromObject()方法），再根据相应方法取出该对象中需要的值。
    如果我们要将json反序列化为javabean呢？
    String jsonStr = "{x:1,\"userId\":\"112\",element:[{id:'123',name:'haha'},{id:'456',name:'hehe'}]}";   Map<String,Class<?>> m  = new HashMap<String,Class<?>>();   m.put("x", Integer.class);   m.put("userId", String.class);   m.put("element",Element.class);    Jsontobean myBean  = (Jsontobean)JSONObject.toBean( JSONObject.fromObject(jsonStr), Jsontobean.class, m );   System.out.println("x: " + myBean.getX());   System.out.println("userId: " + myBean.getUserId());    for(Element e : myBean.getElement()){     System.out.println(e.getId() +"," + e.getName());   }
 
public class Jsontobean {    private int x = 1;    private String userId = "112";    private List<Element> element;    public int getX() {        return x;    }    public void setX(int x) {        this.x = x;    }    public String getUserId() {        return userId;    }    public void setUserId(String userId) {        this.userId = userId;    }    public List<Element> getElement() {        return element;    }    public void setElement(List<Element> element) {        this.element = element;    }  }
 
public class Element {    private int id;    private String name;    private Element source;    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    } public void setSource(Element source) {  this.source = source; } public Element getSource() {  return source; }    public String toString(){         return "" + id + "," + name;    }}
输出：
x: 1userId: 112123,haha456,hehe
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附：jsontojava对象
1)JSONObject to DynaBean
所谓动态bean即是java运行的时候根据情况创建的，而不是程序员已经写好了的Bean。JsonLib会自动根据Json格式数据创建字段，然后创建一个包含这些字段的Object。代码片段：
String str = "{'string':'JSON', 'integer': 1, 'double': 2.0, 'boolean': true}";   
JSONObject jsonObject = (JSONObject) JSONSerializer.toJSON( str );   
DynaBean bean = (DynaBean) JSONSerializer.toJava( jsonObject );   
assertEquals( "JSON", bean.get("string") );         
assertEquals( new Integer(1), bean.get("integer") );         
assertEquals( new Double(2.0), bean.get("double") );         
assertEquals( Boolean.TRUE, bean.get("boolean") );      
2)JSONObject to JavaBean
JSONLIB在转换的时候会自动查找关系，比如子类和父类例如JSON数据源    String s = "{'shopList':[{name:'重量',property:'p1'},{name:'尺寸',property:'p2'}, {name:'显卡 类型',property:'p3'},{name:'硬盘容量',property:'p4'},{name:'处理器 ',property:'p5'},{name:'内存',property:'p6'},{name:'型号',property:'p7'}, {name:'货号',property:'p8'},{name:'品牌',property:'p9'}]}";   存入Map   map.put("shopList", Shop.class);   ShopList shopList = (ShopList) JSONObject.toBean(JSONObject.fromObject(s), ShopList.class, map);JSONObject.toBean()方法的三个参数分别表示数据源对应的JSON对象，转化后的对象ShopList和数据源map。这种方法和动态转换的区别在于，动态转换仅仅只是转为Object，而静态转换是转换为已经定义过的实体类，会自动映射。JSONObject.toBean()的参数介绍。
 
  这里，衷心谢谢各位给予我的帮助。