SpringBoot通过JSON传递请求参数的实例详解

IT利刃出鞘 2022-11-25 我要评论

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

0个@RequestBody，多个无@RequestBody

1个@RequestBody，多个无@RequestBody

错误的用法（会报错）

多个@RequestBody

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

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）