Java对象与JSON的转换

1、直接将对象转换

将数组转换为JSON：

String[] arr = {"asd","dfgd","asd","234"};

JSONArray jsonarray = JSONArray.fromObject(arr);

System.out.println(jsonarray);

对象转换成JSON：(get和set方法必须有)

UserInfo user = new UserInfo(1001,"张三");

JSONArray jsonArray = JSONArray.fromObject(user);  

System.out.println( jsonArray );    

把Map转换成json， 要使用jsonObject对象：

Map<String, Object> map = new HashMap<String, Object>();

map.put("userId", 1001);

map.put("userName", "张三");

map.put("userSex", "男");

JSONObject jsonObject = JSONObject.fromObject(map);

System.out.println(jsonObject);

把List转换成JSON数据：

List<UserInfo> list = new ArrayList<UserInfo>();

UserInfo user = new UserInfo(1001, "张三");

list.add(user);

list.add(user);

list.add(user);

JSONArray jsonArray = JSONArray.fromObject(list);

System.out.println(jsonArray);

2、自己写方法转换

    //maplist转换为josn数组字符串
    public String listToJsonArrayString(List<Map<String, String>> list){
        StringBuilder jsonBuilder = new StringBuilder();
        String result = null;
        try {
    if(list != null){
        jsonBuilder.append("[");
        Map<String, String> infoMap = new HashMap<String, String>();
    for(int i=0; i<list.size();i++){
    infoMap = list.get(i);
    String string = toJson(infoMap);
    if(string.endsWith("}")){
    jsonBuilder.append(string);
    jsonBuilder.append(",");
    }else{
    jsonBuilder.append(string);
    }
    }
    if(jsonBuilder.toString().endsWith(",")){
    jsonBuilder.deleteCharAt(jsonBuilder.length() - 1); 
}
    jsonBuilder.append("]");
    System.out.println("RoomMember 数组"+jsonBuilder.toString());
               result = jsonBuilder.toString();
    }
    }catch (Exception e) {
    e.printStackTrace();
    result = null;
}finally{
return result;
}
   }
    
    
    //将map生成json字符串(返回{.....}或者"")
   public String toJson(Map<String, String> infoMap){
    String result = null;
    try {
    StringBuilder jsonBuilder = new StringBuilder();
           jsonBuilder.append("{");
        for (Map.Entry<String, String> entry : infoMap.entrySet()) {
        jsonBuilder.append("\"").append(entry.getKey()).append("\":\"") .append(entry.getValue()).append("\",");
    }
      if(!jsonBuilder.toString().equals("{")){//无数据时
      jsonBuilder.deleteCharAt(jsonBuilder.length() - 1);    
      }
     jsonBuilder.append("}");
    // System.out.println("RoomMember json对象"+jsonBuilder.toString());
     result = jsonBuilder.toString();     
} catch (Exception e) {
e.printStackTrace();
result = "";
}finally{
return result;
}
    }