JSON与javabean对象互换

 

http://code.google.com/p/google-gson/

 

http://json-lib.sourceforge.net/index.html

 

json-lib使用了ezmorph进行对象之间的转换，已经实现了基本类型的转换支持。基本使用上手较快。

需要下面JAR 包

• jakarta commons-lang 2.4
• jakarta commons-beanutils 1.7.0
• jakarta commons-collections 3.2
• jakarta commons-logging 1.1.1

 

boolean[] boolArray = new boolean[]{true,false,true};   
JSONArray jsonArray = JSONArray.fromObject( boolArray );   
System.out.println( jsonArray );   
// prints [true,false,true]  

 

List list = new ArrayList();   
list.add( "first" );   
list.add( "second" );   
JSONArray jsonArray = JSONArray.fromObject( list );   
System.out.println( jsonArray );   
// prints ["first","second"]  

 

 

JSONArray jsonArray = JSONArray.fromObject( "['json','is','easy']" );   
System.out.println( jsonArray );   
// prints ["json","is","easy"]  

 

From Beans & Maps to JSON

Map map = new HashMap();   
map.put( "name", "json" );   
map.put( "bool", Boolean.TRUE );   
map.put( "int", new Integer(1) );   
map.put( "arr", new String[]{"a","b"} );   
map.put( "func", "function(i){ return this.arr[i]; }" );   
  
JSONObject jsonObject = JSONObject.fromObject( map );   
System.out.println( jsonObject );   
// prints ["name":"json","bool":true,"int":1,"arr":["a","b"],"func":function(i){ return this.arr[i]; }]  

 

class MyBean{   
   private String name = "json";   
   private int pojoId = 1;   
   private char[] options = new char[]{'a','f'};   
   private String func1 = "function(i){ return this.options[i]; }";   
   private JSONFunction func2 = new JSONFunction(new String[]{"i"},"return this.options[i];");   
  
   // getters & setters   
   ...   
}   
  
JSONObject jsonObject = JSONObject.fromObject( new MyBean() );   
System.out.println( jsonObject );   
/* prints  
  {"name":"json","pojoId":1,"options":["a","f"],  
  "func1":function(i){ return this.options[i];},  
  "func2":function(i){ return this.options[i];}}  

 

 

From JSON to Beans

 

String json = "{name=\"json\",bool:true,int:1,double:2.2,func:function(a){ return a; },array:[1,2]}";   
JSONObject jsonObject = JSONObject.fromObject( json );   
Object bean = JSONObject.toBean( jsonObject );   
assertEquals( jsonObject.get( "name" ), PropertyUtils.getProperty( bean, "name" ) );   
assertEquals( jsonObject.get( "bool" ), PropertyUtils.getProperty( bean, "bool" ) );   
assertEquals( jsonObject.get( "int" ), PropertyUtils.getProperty( bean, "int" ) );   
assertEquals( jsonObject.get( "double" ), PropertyUtils.getProperty( bean, "double" ) );   
assertEquals( jsonObject.get( "func" ), PropertyUtils.getProperty( bean, "func" ) );   
List expected = JSONArray.toList( jsonObject.getJSONArray( "array" ) );   
Assertions.assertListEquals( expected, (List) PropertyUtils.getProperty( bean, "array" ) );  

 

String json = "{bool:true,integer:1,string:\"json\"}";   
JSONObject jsonObject = JSONObject.fromObject( json );   
BeanA bean = (BeanA) JSONObject.toBean( jsonObject, BeanA.class );   
assertEquals( jsonObject.get( "bool" ), Boolean.valueOf( bean.isBool() ) );   
assertEquals( jsonObject.get( "integer" ), new Integer( bean.getInteger() ) );   
assertEquals( jsonObject.get( "string" ), bean.getString() );  

 

 

gson 提供了一个JSON <-->JavaBean相互转换的框架，采用了java中的reflect，同时类型转换要求比较严格， 如果是图方便最好还是用json-lib。第一眼就没看出来怎么用，后来才发现：

 

Gson是google自己写的一个Java对象与JSON相互转化的工具包．它轻巧简便，易于使用，而且有很完备的文档可供查询，不用多说，当然是开源喽．

List<List<Map<String, String>>>类型的java对象obj转化为json的格式，你可以这么写 Gson gson = new Gson;
         String json = gson.toJson(obj, new TypeToken<List<List<Map<String, String>>>(){}.getType());// to Json
         List<List<Map<String, String>>> obj2 = gson.from(obj, new TypeToken<List<List<Map<String, String>>>(){}.getType());// from json

 

 

Gson这个类是其中的关键，它负责来进行转化java对象和json．将对象转化为json的格式，使用方法toJson（），这个方法有几个不同的用 法．对于比较简单的对象，比如一个数组，或者一个list，你可以只将要转化的java对象作为参数，可以如果你的对象的格式蛮复杂，那么，你就需要另一 个参数来描述一个java对象的结构，这另一个参数可以是Type或者是Class，它的建立方法也很简单