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：。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:1 userId is:112 element 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: 1 userId: 112 123,haha 456,hehe
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附：
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") );
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。介绍。