前端传json对象（包含json数组在里面）的时候，后台为Java，用SSM时候如何接收

前端JS代码 如下：

var url = "web";
var postdata = {
"history":[
                          {
                             "time":"2017-10-18 10:10:10", //time 字段：时间
                            "option":"human" //option 字段：用户human，机器machine
                           },
                          {
                            "time":"2017-10-19 99:99:99",
                            "option":"machine"
                           }
                         ],
               "openid":"abcdefghijklmn",  
               "type":"家庭"
              };
$.ajax({
type:"POST",

url:url,

//JSON.stringify()，将postdata对象转换成字符串形式
data:{"postdata":JSON.stringify(postdata)}, //调用ajax的时候，data属性必须这样写。必须
dataType:"json",
success:function(data){

}
}

});

Java代码如下

//@RequestParam("postdata") 这句话是关键，跟前端的 data:{"postdata":JSON.stringify(postdata)} 对应，属性名要一致

@RequestMapping("/addQuestionIntelligence")
public @ResponseBody ResponseResult addQuestionIntelligence(@RequestParam("postdata") String postdata, HttpServletRequest request,HttpSession session)throws Exception{

org.json.JSONObject json = new org.json.JSONObject(postdata);

}

【前端向后端传 

问题背景：
我要在一个表单里同时一次性提交多名乘客的个人信息到SpringMVC，前端HTML和SpringMVC Controller里该如何处理？

    第1种方法：表单提交，以字段数组接收；
    第2种方法：表单提交，以BeanListModel接收；
    第3种方法：将Json对象序列化成Json字符串提交，以List接收；
    第4种方法：将表单对象序列化成Json字符串提交，以List接收；
    第4种方法其实是第3种方法的升级，就是将表单转成Json对象，再转成Json字符串提交；
    然而，第4种方法还不支持含有多选控件表单的提交，故应该还有第5种加强版的方法。

以上4种方法都共用同一个User实体类，代码如下：

    public class User {
     
        private Integer id;
        private String name;
        private String pwd;
     
        @Override
        public String toString() {
            return "User{" +
                    "id=" + id +
                    ", name='" + name + '\'' +
                    ", pwd='" + pwd + '\'' +
                    '}';
        }
        // .......后面还有getter、setter方法，省略了
     }

第1种方法：表单提交，以字段数组接收
HTML代码如下：

    <form action="/user/submitUserList_1" method="post">
            ID:<input type="text" name="id"><br/>
            Username:<input type="text" name="name"><br/>
            Password:<input type="text" name="pwd"><br/><br/>
     
            ID:<input type="text" name="id"><br/>
            Username:<input type="text" name="name"><br/>
            Password:<input type="text" name="pwd"><br/><br/>
            <input type="submit" value="submit">
        </form>

Java代码如下：

    @RequestMapping(value = "/submitUserList_1", method ={RequestMethod.POST})
        @ResponseBody
        public String submitUserList_1(HttpServletResponse response,Integer[] id, String[] name, String[] pwd)
                                throws Exception{
            String result = "";
            if(id == null || id.length <= 0){ return "No any ID.中文"; }
            List<User> userList = new ArrayList<User>();
            for (int i = 0; i < id.length; i++ ) {
                User user = new User();
                user.setId(id[i]);
                user.setName(name[i]);
                user.setPwd(pwd[i]);
                userList.add(user);
            }
            result = this.showUserList(userList);
            return result;
        }

第2种方法：表单提交，以BeanListModel接收
HTML代码如下：

    <form action="/user/submitUserList_2" method="post">
            ID:<input type="text" name="users[0].id"><br/>
            Username:<input type="text" name="users[0].name"><br/>
            Password:<input type="text" name="users[0].pwd"><br/><br/>
     
            ID:<input type="text" name="users[2].id"><br/>
            Username:<input type="text" name="users[2].name"><br/>
            Password:<input type="text" name="users[2].pwd"><br/><br/>
            <input type="submit" value="Submit">
        </form>

Java代码：
除了刚才公用的User类，还要封装一个User的容器类UserModel：

    public class UserModel {
        private List<User> users;
     
        public List<User> getUsers() {
            return users;
        }
     
        public void setUsers(List<User> users) {
            this.users = users;
        }
     
        public UserModel(List<User> users) {
            super();
            this.users = users;
        }
     
        public UserModel() {
            super();
        }
     
    }

SpringMVC Controller方法：

    @RequestMapping(value = "/submitUserList_2", method ={RequestMethod.POST})
        @ResponseBody
        public String submitUserList_2(UserModel users)
                throws Exception{
            String result = "";
            List<User> userList = users.getUsers();
            if(userList == null || userList.size() <= 0){ return "No any ID.中文"; }
            result = this.showUserList(userList);
            return result;
        }

第3种方法：将Json对象序列化成Json字符串提交，以List接收
HTML代码：

    <head>
        <title>submitUserList_3</title>
        <meta http-equiv="content-type" content="text/html; charset=utf-8">
        <script language="JavaScript" src="/js/jquery.min.js" ></script>
        <script language="JavaScript" src="/js/jquery.json.min.js" ></script>
        <script type="text/javascript" language="JavaScript">
            function submitUserList_3() {alert("ok");
                var customerArray = new Array();
                customerArray.push({id: "1", name: "李四", pwd: "123"});
                customerArray.push({id: "2", name: "张三", pwd: "332"});
                $.ajax({
                    url: "/user/submitUserList_3",
                    type: "POST",
                    contentType : 'application/json;charset=utf-8', //设置请求头信息
                    dataType:"json",
                    //data: JSON.stringify(customerArray),    //将Json对象序列化成Json字符串，JSON.stringify()原生态方法
                    data: $.toJSON(customerArray),            //将Json对象序列化成Json字符串，toJSON()需要引用jquery.json.min.js
                    success: function(data){
                        alert(data);
                    },
                    error: function(res){
                        alert(res.responseText);
                    }
                });
            }
        </script>
    </head>
     
    <body>
        <h1>submitUserList_3</h1>
        <input id="submit" type="button" value="Submit" onclick="submitUserList_3();">
    </body>

Java代码：

    @RequestMapping(value = "/submitUserList_3", method ={RequestMethod.POST})
        @ResponseBody
        public String submitUserList_3(@RequestBody List<User> users)
                throws Exception{
            String result = "";
            if(users == null || users.size() <= 0){ return "No any ID.中文"; }
            result = this.showUserList(users);
            return result;
        }

第4种方法：将表单对象序列化成Json字符串提交，以List接收
HTML代码：

    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
            "http://www.w3.org/TR/html4/loose.dtd">
    <html>
    <head>
        <title>submitUserList_4</title>
        <meta http-equiv="content-type" content="text/html; charset=utf-8">
        <script language="JavaScript" src="/js/jquery.min.js" ></script>
        <script type="text/javascript" language="JavaScript">
            //将表单序列化成json格式的数据(但不适用于含有控件的表单，例如复选框、多选的select)
            (function($){
                $.fn.serializeJson = function(){
                    var jsonData1 = {};
                    var serializeArray = this.serializeArray();
                    // 先转换成{"id": ["12","14"], "name": ["aaa","bbb"], "pwd":["pwd1","pwd2"]}这种形式
                    $(serializeArray).each(function () {
                        if (jsonData1[this.name]) {
                            if ($.isArray(jsonData1[this.name])) {
                                jsonData1[this.name].push(this.value);
                            } else {
                                jsonData1[this.name] = [jsonData1[this.name], this.value];
                            }
                        } else {
                            jsonData1[this.name] = this.value;
                        }
                    });
                    // 再转成[{"id": "12", "name": "aaa", "pwd":"pwd1"},{"id": "14", "name": "bb", "pwd":"pwd2"}]的形式
                    var vCount = 0;
                    // 计算json内部的数组最大长度
                    for(var item in jsonData1){
                        var tmp = $.isArray(jsonData1[item]) ? jsonData1[item].length : 1;
                        vCount = (tmp > vCount) ? tmp : vCount;
                    }
     
                    if(vCount > 1) {
                        var jsonData2 = new Array();
                        for(var i = 0; i < vCount; i++){
                            var jsonObj = {};
                            for(var item in jsonData1) {
                                jsonObj[item] = jsonData1[item][i];
                            }
                            jsonData2.push(jsonObj);
                        }
                        return JSON.stringify(jsonData2);
                    }else{
                        return "[" + JSON.stringify(jsonData1) + "]";
                    }
                };
            })(jQuery);
     
            function submitUserList_4() {alert("ok");
                var jsonStr = $("#form1").serializeJson();
                //console.log("jsonStr:\r\n" + jsonStr);
                //alert(jsonStr);
                $.ajax({
                    url: "/user/submitUserList_4",
                    type: "POST",
                    contentType : 'application/json;charset=utf-8', //设置请求头信息
                    dataType:"json",
                    data: jsonStr,
                    success: function(data){
                        alert(data);
                    },
                    error: function(res){
                        alert(res.responseText);
                    }
                });
            }
        </script>
    </head>
     
    <body>
        <h1>submitUserList_4</h1>
        <form id="form1">
            ID:<input type="text" name="id"><br/>
            Username:<input type="text" name="name"><br/>
            Password:<input type="text" name="pwd"><br/><br/>
     
            ID:<input type="text" name="id"><br/>
            Username:<input type="text" name="name"><br/>
            Password:<input type="text" name="pwd"><br/><br/>
            <input type="button" value="submit" onclick="submitUserList_4();">
        </form>
    </body>
    </html>

Java代码：

    @RequestMapping(value = "/submitUserList_4", method ={RequestMethod.POST})
        @ResponseBody
        public String submitUserList_4(@RequestBody List<User> users)
                throws Exception{
            String result = "";
            if(users == null || users.size() <= 0){ return "No any ID.中文"; }
            result = this.showUserList(users);
            return result;
        }

总结：
第1、2种方法其实都有一个共同的BUG：假如提交三条记录时，前面两条记录的某些字段不填值的话，在SpringMVC里接收不准确了。而且，每2种方法在HMTL中需要给name属性添加[下标]，如果下标有跨度的话（比如第一组控件下标是0,第二组下标是2），那么SpringMVC里其实的是0到2三个对象的，默认下标是1的那个对象全为null值。
第3、4种方法最实用。