Spring中使用JSR303请求约束判空的实现

1. 适用场景

有时候我们在表单里提交一系列参数, 到后台封装成一个对象, 要对对象的属性做各种字段值的约束; 这时候, 当然可以if-else一个一个的判断, 有更简洁的做法, 就是使用 JSR303+spring的validation:

2. 使用方法步骤(分3步)

• 实体类加字段约束注解
• Controller类中@Valid标注启用(@Validated也兼容@Valid)
• BindingResult获取报错信息

2.1 实体类加字段约束注解

如我们要收集前端表单的字段数据到Person实体中:

对需要约束的字段进行注解标注;

示例:

2.1.1 Person.java

package com.niewj.demo.model;
import lombok.Data;
import org.hibernate.validator.constraints.Length;
import org.hibernate.validator.constraints.URL;
import javax.validation.constraints.*;
import java.util.List;

@Data
public class Person {
  @Length(min = 4, max = 10)
  @NotNull(message = "name不能为空")
  private String name;

  @Min(0)
  @Max(40)
  @NotNull(message = "age不能为空")
  private Integer age;

  @NotBlank
  @NotBlank
  @URL(message = "logo必须是URL格式")
  private String logo;

  @NotEmpty(message = "hobbies不能为空")
  private List<String> hobbies;

  @Email
  @NotNull(message = "email不能为空!")
  private String mail;
}

@NotNull 约束字段不可为空;

@NotEmpty 约束集合/map等不能为空不能为0元素

@Email 约束是 email格式

@URL 约束必须是url的格式

message属性可以修改默认错误说明

2.2 Controller类中@Valid标注启用(@Validated兼容@Valid)

2.2.1 HelloController.java

package com.niewj.demo.controller;

import com.google.gson.Gson;
import com.niewj.demo.common.Result;
import com.niewj.demo.model.Person;
import com.niewj.demo.service.TestService1;
import org.springframework.stereotype.Controller;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.*;

import javax.annotation.Resource;
import javax.validation.Valid;
import java.util.HashMap;
import java.util.Map;

/**
 * test
 *
 * @author niewj
 * @since 2020/11/16 15:22
 */
@Controller
public class HelloController {

  /**
   * @param person
   * @param bindingResult
   * @return
   */
  @PostMapping("/test")
  @ResponseBody
  public Result doSth(@Valid @RequestBody Person person, BindingResult bindingResult) {
    Map<String, String> map = new HashMap<>();
    if (bindingResult.hasErrors()) {
      bindingResult.getFieldErrors().stream().forEach(fe-> map.put(fe.getField(), fe.getDefaultMessage()));
      System.out.println(bindingResult.getFieldError().getDefaultMessage());
      return Result.withErrorParamData(map);
    }

    return Result.withSuccessData(person);
  }
}

@RequestBody可以将body中的请求流信息(Request.getInputStream)通过HttpMessageConverter自动转换为目标java类型:

• 如果前端 Content-Type为application/json, 就使用 JSON消息转换器 帮你转为JSON对象;
• 如果前端 Content-Type为application/xml, 就使用 XML消息转换器 帮你转为xml;
• 如果前端 Content-Type为text/plain, 就是用 String消息转换器 帮你转成 String; (只有类型为String时才可以转换)

2.2.2 Result.java:

package com.niewj.demo.common;

import lombok.Data;

import java.io.Serializable;
import java.util.Map;

/**
 * 返回结果模板封装
 *
 * @author niewj
 * @since 2020/12/17 18:05
 */
@Data
public class Result<T> implements Serializable {
  private int code;
  private String msg;
  private T data;

  public Result(int code, String msg, T data) {
    this(code, msg);
    this.data = data;
  }

  public Result(int code, String msg) {
    this.msg = msg;
    this.code = code;
  }

  public static <T> Result<T> withData(ResponseEnum responseCode, T data) {
    Result<T> re = new Result(responseCode.getCode(), responseCode.getMsg());
    re.data = data;
    return re;
  }

  public static Result<String> withSuccessNoData() {
    Result re = new Result(ResponseEnum.SUCCESS.getCode(), ResponseEnum.SUCCESS.getMsg());
    re.data = "";
    return re;
  }

  public static <T> Result<T> withSuccessData(T data) {
    Result re = new Result(ResponseEnum.SUCCESS.getCode(), ResponseEnum.SUCCESS.getMsg());
    re.data = data;
    return re;
  }

  public static Result<Map<String, String>> withErrorParamData(Map<String, String> data) {
    Result re = new Result(ResponseEnum.BAD_REQUEST.getCode(), ResponseEnum.BAD_REQUEST.getMsg());
    re.data = data;
    return re;
  }
}

2.2.3 ResponseEnum.java

package com.niewj.demo.common;

/**
 * 通用响应码
 */
public enum ResponseEnum {

  SUCCESS(200, "成功"),
  BAD_REQUEST(400, "请求参数不合规");

  /**
   * 错误码
   */
  private Integer code;
  /**
   * 错误信息
   */
  private String msg;

  ResponseEnum(Integer code, String msg) {
    this.code = code;
    this.msg = msg;
  }

  public String getMsg() {
    return msg;
  }

  public Integer getCode() {
    return code;
  }
}

2.3 BindingResult获取报错信息

• BindingResult用来收集约束字段的错误信息, 可通过 bindingResult.hasErrors()的 true来过滤错误信息;
• bindingResult.getFieldErrors() 会返回 List<FieldError>;
• FieldError 得到字段名: getField(); 得到错误信息: getDefaultMessage()

3. 调用测试:

http://localhost:8888/test

3.1 请求用例1: 字段为空

header: Content-Type: application/json

{
  "name": "1"
}

响应:

{
  "code": 400,
  "msg": "请求参数不合规",
  "data": {
    "mail": "email不能为空!",
    "hobbies": "hobbies不能为空",
    "name": "长度需要在4和10之间",
    "logo": "不能为空",
    "age": "age不能为空"
  }
}

3.2 请求用例2: list无元素/email/url格式不对

header: Content-Type: application/json

{
  "name": "1234",
  "hobbies": [],
  "mail": "niewj",
  "logo": "niewj.com"
}

响应:

{
  "code": 400,
  "msg": "请求参数不合规",
  "data": {
    "mail": "不是一个合法的电子邮件地址",
    "hobbies": "hobbies不能为空",
    "logo": "logo必须是URL格式",
    "age": "age不能为空"
  }
}

3.3 请求用例3: 完整字段信息

header: Content-Type: application/json

{
  "name": "1234",
  "hobbies": ["running"],
  "mail": "hi@niewj.com",
  "logo": "http://niewj.com",
  "age": 40
}

响应:

{
  "code": 200,
  "msg": "成功",
  "data": {
    "name": "1234",
    "age": 40,
    "logo": "http://niewj.com",
    "hobbies": [
      "running"
    ],
    "mail": "hi@niewj.com"
  }
}

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