当需要把一串字符串转成一个json 数组 ，并遍历其中的内容时。
首先要导入 net.sf.json.JSONArray和net.sf.json.JSONObject 两个jar 包

<dependency>
   <groupId>net.sf.json-lib</groupId>
   <artifactId>json-lib</artifactId>
   <version>2.4</version>
   <classifier>jdk15</classifier>
</dependency>
　　

String str = "[{name:'a',value:'aa'},{name:'b',value:'bb'},{name:'c',value:'cc'},{name:'d',value:'dd'}]" ; // 一个未转化的字符串

JSONArray json = JSONArray.fromObject(str ); // 首先把字符串转成 JSONArray  对象
if(json.size()>0){
  for(int i=0;i<json.size();i++){
    JSONObject job = json.getJSONObject(i);  // 遍历 jsonarray 数组，把每一个对象转成 json 对象
    System.out.println(job.get("name")+"=") ;  // 得到 每个对象中的属性值
  }
}

前端页面json数组转为字符串

var contracts = [
   {id: '1', name: 'yanggb合同1'},
   {id: '2', name: 'yanggb合同2'},
   {id: '3', name: 'yanggb合同3'},
   {id: '4', name: 'yanggb合同4'},
   {id: '5', name: 'yanggb合同5'}
];

JSON.stringify()方法将数组转换为JSON数组字符串
JSON.parse()方法把JSON字符串解析为json对象

$.ajax({
    type: 'post',
    url: 'contract\save',
    data: {contracts: JSON.stringify(contracts)},
    success: function() {
        console.log('保存合同成功！');
    }
});

@PostMapping(value = "/contract/save")
@ResponseBody
public void saveContracts(String contracts) {
    List<Contract> contractList = JSON.parseArray(contracts, Contract.class);
    // 保存操作
}

封装成json数据

function demo(){
  var con = {};
  con["id"] = 0;
  con["name"] = '张三';
  con["job"] = '学生';
  var json = JSON.stringify(con);          
  alert("封装成json数据为："+json);  
}

最终结果为：{"id":0,"name":"张三","job":"学生"}

封装成json数组

function arr(){
  //定义一个数组 
  var cons = new Array(3); 
  for(var i = 0;i<3;i++){
    var con = {};
    con["id"] = 0;
    con["name"] = '张三';
    con["job"] = '学生';
    cons[i] = con;
  }
  var json = JSON.stringify(cons);
  alert("json数组为："+json); 
}
  最终结果为：[{"id":0,"name":"张三","job":"学生"},{"id":0,"name":"张三","job":"学生"},{"id":0,"name":"张三","job":"学生"}]

map转为实体

  <!-- https://mvnrepository.com/artifact/com.alibaba/fastjson -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.70</version>
        </dependency>

 Map<String,Object> map=new HashMap<>();
 map.put("hotId","dfasfaf454af");
 map.put("hotName","小明");
 map.put("hotKey","5464132645");
 map.put("isDelete","1");
 map.put("hotStatus","0");
 String mapString = JSONObject.toJSONString(map);
 Hop hop = JSONObject.parseObject(mapString, Hop.class);
 System.out.println(hop.toString());   

字符串格式：

[
  {
    "cloudState": 0,
    "faceId": "50c3277b-b61d-462a-ad8c-8079e04fcb19",
    "id": 1603445761978,
    "name": "唐工",
    "path": "http://192.168.1.73:8091/FaceRecord/2ff235c0-93c2-4f96-ae4b-b573f3aace6b_50c3277b-b61d-462a-ad8c-8079e04fcb19_唐工_1603445761978.jpg",
    "personId": "2ff235c0-93c2-4f96-ae4b-b573f3aace6b",
    "state": 0,
    "temp": "36.98",
    "time": 1603445761978,
    "type": "face"
  },
  {
    "cloudState": 0,
    "faceId": "50c3277b-b61d-462a-ad8c-8079e04fcb19",
    "id": 1603445759552,
    "name": "唐工",
    "path": "http://192.168.1.73:8091/FaceRecord/2ff235c0-93c2-4f96-ae4b-b573f3aace6b_50c3277b-b61d-462a-ad8c-8079e04fcb19_唐工_1603445759552.jpg",
    "personId": "2ff235c0-93c2-4f96-ae4b-b573f3aace6b",
    "state": 0,
    "temp": "36.81",
    "time": 1603445759552,
    "type": "face"
  },
  {
    "cloudState": 0,
    "faceId": "50c3277b-b61d-462a-ad8c-8079e04fcb19",
    "id": 1603445757134,
    "name": "唐工",
    "path": "http://192.168.1.73:8091/FaceRecord/2ff235c0-93c2-4f96-ae4b-b573f3aace6b_50c3277b-b61d-462a-ad8c-8079e04fcb19_唐工_1603445757134.jpg",
    "personId": "2ff235c0-93c2-4f96-ae4b-b573f3aace6b",
    "state": 0,
    "temp": "35.42",
    "time": 1603445757134,
    "type": "face"
  },
  {
    "cloudState": 0,
    "faceId": "",
    "id": 1603445756765,
    "name": "",
    "path": "http://192.168.1.73:8091/FaceRecord/___1603445756765.jpg",
    "personId": "",
    "state": 0,
    "temp": "36.73",
    "time": 1603445756765,
    "type": "face"
  }
]

//转换成json数组

 //json字符串
            string json = weatherData["data"].ToString();
            textBox1.AppendText(json);
            textBox1.AppendText("\r\n");
            //json字符串转数组
            JArray jo = (JArray)JsonConvert.DeserializeObject(json);

业务需求：

将对象中的picUrl图片地址取出在前端遍历，而picUrl的值是这样的：

json字符串，请求对象是调用别人的接口，所以值的格式不是由我们来决定的，json字符串要取值首先想到的是转成java对象，但是这一堆都是键相同的，显然是没法转对象的，所以想到了jsonArray，之前没怎么操作过，所以记录一下

                    List<SolrImage> li = new ArrayList<>();
                    String picUrl = searchView.getPicUrl();
                    JSONArray jsonArray = JSONArray.parseArray(picUrl);
                    String[] split = picUrl.split(",");
                    for (int j = 0; j < split.length; j++) {
                        JSONObject jsonObject = jsonArray.getJSONObject(j);
                        Object o = jsonObject.get("thumbnail_pic");
                        SolrImage solrImage = new SolrImage();
                        solrImage.setSmUrl(o.toString());
                        li.add(solrImage);
                    }