通过传递字符串的形式获取json中的key与value中的方法

function getJson(key){  
    var jsonObj={"name":"赵云","age":"24","profession":"武将"};  
    //1、使用eval方法      
    var eValue=eval('jsonObj.'+key);  
    alert(eValue);  
    //2、遍历Json串获取其属性  
    for(var item in jsonObj){  
        if(item==key){  //item 表示Json串中的属性，如'name'  
            var jValue=jsonObj[item];//key所对应的value  
            alert(jValue);  
        }  
    }  
    //3、直接获取  
    alert(jsonObj[''+key+'']);  
    //alert(jsonObj['name']); 
}  

var json = [
    {"id":"1","pid":"0","tagName":"red"},
    {"id":"5","pid":"0","tagName":"green"}
];
 
$.each(json, function(idx, obj) {
    alert(obj.tagName);
});

如果出现如下报错

Uncaught TypeError: Cannot use 'in' operator to search for '375' in [{"id":"01","state":null,"pid":"0","icon":null,"iconClose":null,"iconOpen":null,"name":"oos??","open":true,"isParent":true}]

改为标准JSON.parse()或jQuery 的 $.parseJSON 将其转换为JavaScript对象。

$.each(JSON.parse(json), function(idx, obj) {
    alert(obj.tagName);
});

import net.sf.json.JSONObject;
import com.google.gson.Gson;
import com.nenglong.k12.oos.module.po.resource.Exercise;

String res = "{"_index":"k12oos","_type":"exercise","_id":"-0WtGG1FhQSmqIQhKU8pMg","_version":2,"found":true,"_source":{"code":"1009430255","stageId":"go2Leq1wj5y8vuA_5w7Azw","gradeId":"26vYkWDVjhivNno6Kbz7ZM","courseStageId":"PcjbvAQ8h9KaTfZ8q6UZcw","exerciseType":{"name":"张三","id":"-0WtGG1FhQSmqIQhKU8pMg"}}";

JSONObject jsonObject = new JSONObject();
jsonObject = jsonObject.fromObject(res);//将String转为JSON数据
String exerciseStr = jsonObject.getString("_source");//获取key为"_source"的值。

Gson gson = new Gson();
Exercise exercise = gson.fromJson(exerciseStr, Exercise.class);