简介

本文用示例介绍SpringMVC如何获取路径中的参数。也就是： Content-Type为x-www-form-urlencoded。

代码

Controller

BasicController.java

package com.example.demo.controller;

import com.example.demo.entity.User;
import org.springframework.web.bind.annotation.*;

import java.util.Arrays;
import java.util.List;

// localhost:8080/basic/no_annotation/string1
@RequestMapping("/basic")
@RestController
public class BasicController {
    @RequestMapping("/1")
    public String test1(int intVal, Long longVal, String myStr) {
        System.out.println("intVal  : " + intVal);
        System.out.println("longVal : " + longVal);
        System.out.println("myStr   : " + myStr);
        return "Hello world";
    }

    @RequestMapping("/2")
    public User test2(@RequestParam Integer intVal,
                      @RequestParam(value = "my_str", required = false) String[] myStr,
                      @RequestParam String[] password,
                      @RequestParam List<Integer> scoreArray,
                      @RequestParam Integer age,
                      User user) {
        System.out.println("intVal     : " + intVal);
        System.out.println("age        : " + age);
        System.out.println("myStr      : " + Arrays.asList(myStr));
        System.out.println("password   : " + Arrays.asList(password));
        System.out.println("scoreArray : " + scoreArray);

        return user;
    }

    @RequestMapping("/3")
    public User test3(@RequestBody User user) {
        return user;
    }
}

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;
}

测试

测试1：基本类型为空导致错误

http://localhost:8080/basic/1

后端打印

java.lang.IllegalStateException: Optional int parameter 'intVal' is present but cannot be translated into a null value due to being declared as a primitive type. Consider declaring it as object wrapper for the corresponding primitive type.

前端结果

测试2：正常操作

其实也不正常，最好不要用基本类型接收。

http://localhost:8080/basic/1?intVal=2&myStr=hehe

后端

intVal  : 2
longVal : null
myStr   : hehe

前端

测试3：正常操作

http://localhost:8080/basic/2?intVal=2&my_str=Tony,Stark&name=Jarvis&age=21&password=ab,cd&scoreArray=99,98&phoneNum=12

后端

intVal     : 2
age        : 21
myStr      : [Tony, Stark]
password   : [ab, cd]
scoreArray : [99, 98]

前端

结论

如果一个参数，实体类与接口参数都有，则都会赋值。
若实体类中有数组/List 成员，也会对它直接赋值。
若实体类含有实体类，无法赋值。因为参数中没有与实体类相同名字的key，此时就要用form-data或者json了。（或者x-www-urlencoded也有写类参数的方法，目前不知道）

测试4：@RequestParam缺少参数访问（失败）

http://localhost:8080/basic/2?intVal=2&my_str=Tony,Stark&name=Jarvis&age=21&password=ab,cd&phoneNum=12

后端

2020-07-04 18:00:37.222  WARN 15844 --- [nio-8080-exec-8] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.web.bind.MissingServletRequestParameterException: Required List parameter 'scoreArray' is not present]

前端

测试5：用@RequestBody接收（失败）

http://localhost:8080/basic/3?intVal=2&my_str=Tony,Stark&name=Jarvis&age=21&password=ab,cd&scoreArray=99,98&phoneNum=12

后端

2020-07-04 14:02:55.954  WARN 15844 --- [nio-8080-exec-3] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.http.converter.HttpMessageNotReadableException: Required request body is missing: public com.example.demo.entity.User com.example.demo.controller.BasicController.test3(com.example.demo.entity.User)]

前端