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;
public
class listToJson {
public
static
void 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; public
class jsonToListandMap {
public
static
void 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 Michaelage
30baby [Lucy, Lily]