SpringBoot--通过JSON传递请求参数--方法/实例

逃离我推掉我的手 2023-10-02 21:18 10阅读 0赞

原文网址：[SpringBoot--通过JSON传递请求参数--方法/实例\_IT利刃出鞘的博客-CSDN博客][SpringBoot--_JSON_--_IT_-CSDN]

## 简介 ##

本文用示例介绍SpringMVC如何通过JSON格式传递入参。

JSON格式使用post方式来请求，即：对应的注解为：@PostMapping。

@PostMapping注解的方法可以接收**1个@RequestBody标记的参数和多个没有@RequestBody标记的参数**。

## **代码** ##

### **Entity** ###

User.java

package com.example.demo.entity;
    
    import lombok.Data;
    import java.util.List;
    
    @Data
    public class User {
        private String name;
        private Integer age;
        private String[] password;
        private List<Integer> scoreArray;
    }

Account.java

package com.example.demo.entity;
    
    import lombok.Data;
    import java.io.Serializable;
    
    @Data
    public class Account implements Serializable {
        private String phoneNum;
        private String[] emails;
    }

### **Controller** ###

package com.example.demo.controller;
    
    import com.example.demo.entity.User;
    import org.springframework.web.bind.annotation.RestController;
    import org.springframework.web.bind.annotation.RequestBody;
    import org.springframework.web.bind.annotation.PostMapping;
    import org.springframework.web.bind.annotation.RequestParam;
    import org.springframework.web.bind.annotation.ResponseBody;
    
    import java.util.Arrays;
    import java.util.List;
    
    @RequestMapping("/json")
    @RestController
    public class JsonController {
        @PostMapping("/1")
        public User setUserNoAnnotation(User user, List<String> password, Integer[] scoreArray) {
            printUser(user);
            return user;
        }
    
        @RequestMapping("/2")
        public User setUserAnnotation(@RequestBody User user) {
            printUser(user);
            return user;
        }
    
        @RequestMapping("/3")
        public User setUserAnnotation1(@RequestBody User user, @RequestParam List<String> password, Integer[] scoreArray) {
            System.out.println(password);
            if (scoreArray != null) {
                System.out.println(Arrays.asList(scoreArray));
            } else {
                System.out.println("scoreArray = null");
            }
            System.out.println();
            printUser(user);
    
            return user;
        }
    
        @RequestMapping("/4")
        public User setUserAnnotation2(@RequestBody User user, @RequestBody List<String> password, @RequestBody Integer[] scoreArray) {
            if (password != null) {
                System.out.println(password);
            } else {
                System.out.println("password = null");
            }
    
            if (scoreArray != null) {
                System.out.println(Arrays.asList(scoreArray));
            } else {
                System.out.println("scoreArray = null");
            }
            System.out.println();
            printUser(user);
            return user;
        }
    
        private void printUser(User user){
            System.out.println("name            : " + user.getName());
            System.out.println("password        : " + Arrays.asList(user.getPassword()));
            System.out.println("scoreArray      : " + user.getScoreArray());
            System.out.println("acount.phoneNum : " + user.getAccount().getPhoneNum());
            System.out.println("account.emails  : " + Arrays.asList(user.getAccount().getEmails()));
        }
    }

## 测试 ##

为方便测试，我用了[knife4j][]。

**测试前提**

json的body

{
        "name": "Jarvis",
        "password": [
            "ab",
            "cd"
        ],
        "scoreArray": [
            99,
            98
        ],
        "account": {
            "phoneNum": "123",
            "emails": [
                "123@qq.com",
                "456@163.com"
            ]
        }
    }

### 正确的用法 ###

#### **1个RequestBody** ####

### ![6957d7624a1c4989bc406d88116a18a4.png][] ###

#### 0个@RequestBody，多个无@RequestBody ####

![bb6e1447cd474c268e9338c631241770.png][]

#### 1个@RequestBody，多个无@RequestBody ####

![313bc6f7b0454801bc1569159e0e74e5.png][]

## 错误的用法（会报错） ##

#### **多个@RequestBody** ####

![b3d3d0691eb244b69d96e6eae67b489b.png][]

后端报错信息

2022-09-20 22:04:45.857  WARN 3340 --- [nio-8080-exec-1] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.http.converter.HttpMessageNotReadableException: I/O error while reading input message; nested exception is java.io.IOException: Stream closed]

**错误原因**

每个方法只能有一个@RequestBody。使用@RequestBody把请求转化为特定的Object（在最后会关闭相应的流），所以在同一个方法中第二次使用@RequestBody是没用的，因为流已经关闭。

You cannot use it this way as only one @RequestBody per method is allowed. Using @RequestBody Spring converts incoming request body into the specified object (what closes the stream representing body at the end) so attempting to use @RequestBody second time in the same method makes no sense as stream has been already closed.

#### 不带@RequestBody参数类型是List ####

![f1197cc916774ef4ba4206038c3fc8f9.png][]

后端错误信息

2022-09-20 23:19:11.044 ERROR 3340 --- [nio-8080-exec-2] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.IllegalStateException: No primary or default constructor found for interface java.util.List] with root cause
    
    java.lang.NoSuchMethodException: java.util.List.<init>()
    	at java.lang.Class.getConstructor0(Class.java:3082) ~[na:1.8.0_201]
    	at java.lang.Class.getDeclaredConstructor(Class.java:2178) ~[na:1.8.0_201]
    	...（其他信息）

**错误原因**

不支持非@RequstBody的参数是List类型。（数组类型可以）。

[SpringBoot--_JSON_--_IT_-CSDN]: https://knife.blog.csdn.net/article/details/126955477
[knife4j]: https://knife.blog.csdn.net/article/details/120753090
[6957d7624a1c4989bc406d88116a18a4.png]: https://img-blog.csdnimg.cn/6957d7624a1c4989bc406d88116a18a4.png
[bb6e1447cd474c268e9338c631241770.png]: https://img-blog.csdnimg.cn/bb6e1447cd474c268e9338c631241770.png
[313bc6f7b0454801bc1569159e0e74e5.png]: https://img-blog.csdnimg.cn/313bc6f7b0454801bc1569159e0e74e5.png
[b3d3d0691eb244b69d96e6eae67b489b.png]: https://img-blog.csdnimg.cn/b3d3d0691eb244b69d96e6eae67b489b.png
[f1197cc916774ef4ba4206038c3fc8f9.png]: https://img-blog.csdnimg.cn/f1197cc916774ef4ba4206038c3fc8f9.png