java生成json字符串的方法

转http://www.cnblogs.com/zhujiabin/p/5498555.html

例1：将map对象添加一次元素（包括字符串对、数组），转换成json对象一次。

代码：

package com.json;

//这是使用org.json的程序：

import java.util.HashMap;

import java.util.Map;

import org.json.JSONException;

import org.json.JSONObject;

public class jsontest {

public static void main(String[] args) throws JSONException {

String json = "{'name':'reiz'}";

JSONObject jsonObj = new JSONObject(json);

String name = jsonObj.getString("name");

System.out.println(jsonObj);

jsonObj.put("initial", name.substring(0, 1).toUpperCase());

String[] likes = new String[] { "JavaScript", "Skiing", "Apple Pie" };

jsonObj.put("likes", likes);

System.out.println(jsonObj);

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);

}

}

运行结果：

{"name":"reiz"}{"initial":"R","likes":["JavaScript","Skiing","Apple Pie"],"name":"reiz"}{"ingredients":{"apples":"3kg","pastry":"2.4kg","bestEaten":"outdoors","sugar":"1kg"},"initial":"R","likes":["JavaScript","Skiing","Apple Pie"],"name":"reiz"}

（需要用到的包可在官网下载：http://www.json.org/java/index.html）

例2：list转换成json的三种参数形式。

import java.util.ArrayList;import java.util.List; import net.sf.json.JSONArray;import net.sf.json.JSONObject;publicclass listToJson {publicstaticvoid main(String[] args) { boolean[] boolArray = new boolean[]{true,false,true};JSONArray jsonArray1 = JSONArray.fromObject( boolArray );System.out.println( jsonArray1 );// prints [true,false,true] List list = new ArrayList();list.add("first" );list.add("second" );JSONArray jsonArray2 = JSONArray.fromObject( list );System.out.println( jsonArray2 );// prints ["first","second"] JSONArray jsonArray3 = JSONArray.fromObject("['json','is','easy']" );System.out.println( jsonArray3 );// prints ["json","is","easy"] }}

运行结果：

[true,false,true]["first","second"]["json","is","easy"]

例3：json转换成list和map。

package com.json; import java.util.Collection;import java.util.Map;import java.util.Map.Entry; import net.sf.json.JSONArray;import net.sf.json.JSONObject; publicclass jsonToListandMap {publicstaticvoid main(String[] args) {// TODO Auto-generated method stub String listStr = "[\"apple\",\"orange\"]"; Collection<String> strlist = JSONArray.toCollection(JSONArray.fromObject(listStr)); for (String str : strlist) { System.out.println(str); } String mapStr = "{\"age\":30,\"name\":\"Michael\",\"baby\":[\"Lucy\",\"Lily\"]}"; Map<String, Object> map = (Map) JSONObject.toBean(JSONObject .fromObject(mapStr), Map.class);for (Entry<String, Object> entry : map.entrySet()) { System.out.println(entry.getKey() +"" + entry.getValue()); } } }

运行结果：

appleorangename Michaelage30baby [Lucy, Lily]