JSONObject,JSONArray,Map,String之间转换

转自:https://blog.csdn.net/superit401/article/details/51727739

1.String转JSONObject

（1）.String jsonMessage = "{"语文":"88","数学":"78","计算机":"99"}";

JSONObject  myJson = JSONObject.fromObject(jsonMessage);

（2）.用阿里巴巴的fastjson的jar包

String str = "{"baid":null,"32d3:":"null",433:"0x32",032:"ju9fw"}";
com.alibaba.fastjson.JSONObject jm = com.alibaba.fastjson.JSON.parseObject(str);

2.String转JSONArray

String jsonMessage = "[{'num':'成绩', '外语':88, '历史':65, '地理':99, 'object':{'aaa':'1111','bbb':'2222','cccc':'3333'}}," +
          "{'num':'兴趣', '外语':28, '历史':45, '地理':19, 'object':{'aaa':'11a11','bbb':'2222','cccc':'3333'}}," +
          "{'num':'爱好', '外语':48, '历史':62, '地理':39, 'object':{'aaa':'11c11','bbb':'2222','cccc':'3333'}}]";
 JSONArray myJsonArray = JSONArray.fromObject(jsonMessage);
 System.out.println(myJsonArray);

3.String转Map

(1)

String jsonMessage = "{"语文":"88","数学":"78","计算机":"99"}";

JSONObject  myJson = JSONObject.fromObject(jsonMessage);

Map m = myJson; 

（2）用阿里巴巴的fastjson的jar包

String str = "{"baid":null,"32d3:":"null",433:"0x32",032:"ju9fw"}";
Map mapTypes = com.alibaba.fastjson.JSON.parseObject(str);

(3) (需要引入jackjson的core、databind、annotations三个jar包  )

String json = "{"PayPal key2":"PayPal value2","PayPal key1":"PayPal value1","PayPal key3":"PayPalvalue3"}";  

ObjectMapper mapper = new ObjectMapper();    
 Map<String,Object> m = mapper.readValue(json, Map.class);  

(4)(特殊格式的String)

String a ="{se=2016, format=xml, at=en co=3}";

a =  a.substring(1, a.length()-1);
Map docType = new HashMap();  
Java.util.StringTokenizer items;  
for(StringTokenizer entrys = new StringTokenizer(a, ", ");entrys.hasMoreTokens();   
docType.put(items.nextToken(), items.hasMoreTokens() ? ((Object) (items.nextToken())) : null)){  
     items = new StringTokenizer(entrys.nextToken(), "=");  
   }

4.JSONObject、JSONArray，Map转String

JSONObject——String：

System.out.println(myJsonObject);//可直接输出JSONObject的内容

myJsonObject.toString();

阿里巴巴fastjson：

String str = JSON.toJSONString(obj,SerializerFeature.BrowserCompatible);

JSONArray——String：

System.out.println(myJsonArray);//可直接输出myJsonArray的内容

myJsonArray.toString();

Map——String:

System.out.println(map);//可直接输出map的内容

map.toString();

5.JSONObject转JSONArray

6.JSONObject转Map

JSONObject  myJson = JSONObject.fromObject(jsonString);

Map m = myJson; 

7.JSONArray转JSONObject

  for(int i=0 ; i < myJsonArray.length() ;i++)
   {
    //获取每一个JsonObject对象
    JSONObject myjObject = myJsonArray.getJSONObject(i);

}

8.JSONArray转Map

9.Map转JSONObject

JSONObject json = JSONObject.fromObject( map );   

或

String jsonString = JSON.toJSONString(map,SerializerFeature.WriteMapNullValue,SerializerFeature.WriteNullStringAsEmpty);

JSONObject jm = JSON.parseObject(str);

(此为alibaba的fastjson)

10.Map转JSONArray

   JSONArray.fromObject(map);

11.List转JSONArray
JSONArray jsonArray2 = JSONArray.fromObject( list );      

12.JSONArray转List

List<Map<String,Object>> mapListJson = (List)jsonArray;

或

public static List<Map<String, Object>> jsonArrayToList(JSONArray ja){  
        return JSONArray.toJavaObject(ja, List.class);  
    } 

13.String转数组

String string = "a,b,c";
String [] stringArr= string.split(",");  //注意分隔符是需要转译滴...
如果是"abc"这种字符串,就直接
String string = "abc" ;
char [] stringArr = string.toCharArray(); //注意返回值是char数组
如果要返回byte数组就直接使用getBytes方法就ok了~~
String string = "abc" ;
byte [] stringArr = string.getBytes();

数组转String

char[] data={a,b,c}; 
String s=new String(data); 

14.java实体类的List转String

JSON与String关系比较近，而JSON的子类JSONArray又和List关系比较近，故把JSONArray做中介过渡：

import com.alibaba.fastjson.JSONArray;

public String list2str(List<?> list){
JSONArray jsonArray = (JSONArray) JSONArray.toJSON(list);   //List转JSONArray
System.out.println(jsonArray.toString());
return jsonArray.toJSONString();    //JSONArray比较容易转String
}

15.Array、List、Set之间转换：

String[] arr = new String[]{"Tom", "Bob", "Jane"};
//Array转List
List<String> arr2list = Arrays.asList(arr);
//Array转Set
Set<String> arr2set = new HashSet<String>(Arrays.asList(arr));
//List转Array
Object[] list2arr = arr2list.toArray();
//List转Set
Set<String> list2set = new HashSet<>(arr2list);
//Set转Array
Object[] set2arr = list2set.toArray();
//Set转List
List<String> set2list = new ArrayList<>(arr2set);
List<String> list = new ArrayList<String>(new HashSet<String>());//