详解java生成json字符串的方法

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：

apple

orange

name Michael
age 30

baby [Lucy, Lily]

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