前后端通过Json传数据，并将Json转化成实体类

傷城~ 2022-01-22 08:57 558阅读 0赞

> 今天尝试着用thymeleaf写马上就要使用的计算机基础知识大赛的比赛系统，然后卡在如何将多个对象通过form表单发送给后端，最后没有找到比较好的办法，只能使用js将需要发送的数据转化成Json然后使用ajax发送请求。然后在后台在将数据转化成实体类

###### 首先我们的实体类如下: ######

package com.njupt.sacc.cbkc.problem.entity;
    
    public class ProblemResult { 
    
        private Integer id;
        private Integer uid;
        private Integer pid;
        private String result;
    
        public Integer getId() { 
            return id;
        }
    
        public void setId(Integer id) { 
            this.id = id;
        }
    
        public Integer getUid() { 
            return uid;
        }
    
        public void setUid(Integer uid) { 
            this.uid = uid;
        }
    
        public Integer getPid() { 
            return pid;
        }
    
        public void setPid(Integer pid) { 
            this.pid = pid;
        }
    
        public String getResult() { 
            return result;
        }
    
        public void setResult(String result) { 
            this.result = result;
        }
    
        @Override
        public String toString() { 
            return "ProblemResult{" +
                    "id=" + id +
                    ", uid=" + uid +
                    ", pid=" + pid +
                    ", result='" + result + '\'' +
                    '}';
        }
    }

###### 然后我们的目标就是前端向后端发送多个ProblemResult对象，然后在进行处理，首先我们看前端的实现方案（此时后端向前端发送的是一个List）： ######

<!DOCTYPE html>
    <html lang="en" xmlns:th="http://www.w3.org/1999/xhtml">
    
    <head>
        <meta charset="UTF-8">
        <title>Title</title>
        <script src="http://apps.bdimg.com/libs/jquery/2.1.4/jquery.min.js"></script>
    
    </head>
    <body>
    <hr>
    <div th:each="problem : ${problems}">
        <span th:text="${problem.id}"></span>
        <form th:object="${problem}" th:if="${problem.isSingle == 1}">
            <input type="radio" th:name="${problem.id}" th:text="${problem.aOption}" value="a">
            <input type="radio" th:name="${problem.id}" th:text="${problem.bOption}" value="b">
            <input type="radio" th:name="${problem.id}" th:text="${problem.cOption}" value="c">
            <input type="radio" th:name="${problem.id}" th:text="${problem.dOption}" value="d">
        </form>
        <form th:object="${problem}" th:if="${problem.isSingle == 0}">
            <input type="checkbox" th:name="${problem.id}" th:text="${problem.aOption}" value="a">
            <input type="checkbox" th:name="${problem.id}" th:text="${problem.bOption}" value="b">
            <input type="checkbox" th:name="${problem.id}" th:text="${problem.cOption}" value="c">
            <input type="checkbox" th:name="${problem.id}" th:text="${problem.dOption}" value="d">
        </form>
        <hr>
    </div>
    <button name="save" onclick="loadXMLDoc(name)">保存</button>
    <button name="push" onclick="loadXMLDoc(name)">提交</button>
    
    <script type="text/javascript">
        //将答案转化成Json格式
        //name用来判断是保存操作还是提交操作
        function f(name) { 
            var json = [];
            //[[$[count]]]为thymeleaf中js获取值的方法
            var count = [[${ count}]];
            for (var i = 1; i <= count; i++) { 
                var type = document.getElementsByName(i).item(0).getAttribute("type");
                //js获取单选框的值
                if (type == "radio") { 
                    var radio = document.getElementsByName(i);
                    var result = "";
                    for (var j = 0; j < radio.length; j++) { 
                        if (radio[j].checked) { 
                            result = radio[j].value;
                            break;
                        }
                    }
                } else { //js获取多选框的值
                    var checkbox = document.getElementsByName(i);
                    var result = "";
                    for (var j = 0; j < checkbox.length; j++) { 
                        if (checkbox[j].checked)
                            result = result + checkbox[j].value;
                    }
                }
                var row = { "pid": i, "result": result};
                json.push(row);
            }
            return { "type":name,"data":json};
        }
        //发送ajax请求
        function loadXMLDoc(name) { 
            var xmlhttp;
            if (window.XMLHttpRequest) { 
                // IE7+, Firefox, Chrome, Opera, Safari 浏览器执行代码
                xmlhttp = new XMLHttpRequest();
            } else { 
                // IE6, IE5 浏览器执行代码
                xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
            }
            xmlhttp.onreadystatechange = function () { 
                if (xmlhttp.readyState == 4 && xmlhttp.status == 200) { 
                    console.log("successful");
                }
            };
            xmlhttp.open("POST", "/test", true);
            xmlhttp.setRequestHeader("Content-Type", "application/json");
            var data = f(name);
            xmlhttp.send(JSON.stringify(data));
        }
    </script>
    </body>
    </html>

###### 传送的数据示例大致如下: ######

{ 
    	"submit":[
    		{ "pid":1,"result":"a"},
    		{ "pid":2,"result":"ab"},
    		{ "pid":3,"result":""},
    		{ "pid":4,"result":"abcd"},
    		{ "pid":5,"result":"a"},
    		{ "pid":6,"result":"d"},
    		{ "pid":7,"result":"b"},
    		{ "pid":8,"result":"c"}
    	],
    	"type":"save"
    }

###### 之后我们看后端如何获取数据并将数据转化成实体类： ######

@RequestMapping("/test")
        public String submit(@RequestBody JSONObject jsonObject){ 
            //通过key获取前端发送的json的数组
            JSONArray problemResults = jsonObject.getJSONArray("data");
            //通过key获取前端发送的json中的type字段
            String submitType = String.valueOf(jsonObject.get("type"));
            List<ProblemResult> list = new ArrayList<>();
            //通过遍历将json数据中的数据转化成实体类
            for (Object problemResult : problemResults) { 
                //会用JSONObject包中的函数将字符串转化成实体类
                ProblemResult result = (ProblemResult) JSONObject.toJavaObject((JSONObject) problemResult, ProblemResult.class);
                list.add(result);
            }
            return "index";
        }

> 经过上面的操作，我们就成功的完成了前端向后端发送多个对象，整体思想大概就是先把需要传的所有对象看成一个数组，然后传到后端之后再对json数据进行解析，然后获取数据中的json字符串，然后通过json库中的函数将json字符串转化成实体类，全部完成

##### 参考博文： #####

> 阿里巴巴的JSONObject对象转换 [https://blog.csdn.net/a990914093/article/details/81217581][https_blog.csdn.net_a990914093_article_details_81217581]  
> JSONObject如何转换成实体类型  
> [https://blog.csdn.net/m0\_38129335/article/details/80047034][https_blog.csdn.net_m0_38129335_article_details_80047034]  
> json数据与实体类之间的相互转换  
> [https://blog.csdn.net/nandao158/article/details/71122851][https_blog.csdn.net_nandao158_article_details_71122851]

[https_blog.csdn.net_a990914093_article_details_81217581]: https://blog.csdn.net/a990914093/article/details/81217581
[https_blog.csdn.net_m0_38129335_article_details_80047034]: https://blog.csdn.net/m0_38129335/article/details/80047034
[https_blog.csdn.net_nandao158_article_details_71122851]: https://blog.csdn.net/nandao158/article/details/71122851