springboot2.0-统一处理返回结果和异常情况

版权声明：转发请注明，谢谢配合 https://blog.csdn.net/qq_31289187/article/details/82980714

一、统一处理返回结果和异常处理的原因：

1、在springboot项目里我们希望接口返回的数据包含至少三个属性：

a、code：请求接口的返回码，成功或者异常等返回编码，例如定义请求成功，code = "0000",查询结果为null，code = "0001";

b、msg：请求接口的描述，也就是对返回编码的描述，"0000"：就表示请求成功，"0001"：表示结果为null；

c、data：请求接口成功，返回的结果。

{
    "data": {
        "id": 1,
        "studentId": "13240115",
        "name": "Tiger",
        "age": 25,
        "famillyAddress": "北京",
        "createdDate": "2018-10-08T05:45:49.000+0000",
        "updatedDate": "2018-10-09T03:15:33.000+0000"
    },
    "code": "0000",
    "msg": "请求成功"
}

2、在springboot项目里我们希望请求结果失败之后，通过返回码和返回描述来告诉前端接口请求异常。

{
    "code": "0001",
    "msg": "学号不存在"
}

二、案例

1、建一张学生信息表，包含学生的学号、姓名、年龄、家庭住址等

CREATE TABLE student_info (
  id bigint(20) NOT NULL AUTO_INCREMENT COMMENT '自增',
  student_id varchar(20) NOT NULL COMMENT '学号',
  name varchar(64) NOT NULL COMMENT '姓名',
  age int(2) NOT NULL COMMENT '年龄',
  familly_address varchar(256) NOT NULL COMMENT '家庭地址',
  created_date datetime NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',
  updated_date datetime NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '更新时间',
  PRIMARY KEY (student_id),
  KEY id (id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4

2、pom.xml

<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-data-redis</artifactId>
		</dependency>

		<dependency>
			<groupId>org.mybatis.spring.boot</groupId>
			<artifactId>mybatis-spring-boot-starter</artifactId>
			<version>1.3.1</version>
		</dependency>

		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<version>5.1.46</version>
		</dependency>

		<dependency>
			<groupId>com.alibaba</groupId>
			<artifactId>druid</artifactId>
			<version>1.1.9</version>
		</dependency>

		<dependency>
			<groupId>org.projectlombok</groupId>
			<artifactId>lombok</artifactId>
			<version>1.16.22</version>
		</dependency>

		<dependency>
			<groupId>com.alibaba</groupId>
			<artifactId>fastjson</artifactId>
			<version>1.2.43</version>
		</dependency>


		<dependency>
			<groupId>com.squareup.okhttp3</groupId>
			<artifactId>okhttp</artifactId>
			<version>3.9.1</version>
		</dependency>

		<dependency>
			<groupId>org.glassfish</groupId>
			<artifactId>javax.json</artifactId>
			<version>1.0.4</version>
		</dependency>

		<dependency>
			<groupId>org.apache.tomcat.embed</groupId>
			<artifactId>tomcat-embed-jasper</artifactId>
		</dependency>

	</dependencies>

3、案例中使用redis进行缓存，可以不需要

Windows环境安装redis以及缓存应用

4、创建实体类：StudentInfo

package com.dl.cn.message.bean;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.io.Serializable;
import java.util.Date;

/**
 * Created by Tiger on 2018/10/8.
 */
@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class StudentInfo implements Serializable{

    private static final long serialVersionUID = 2597547944454691103L;

    private Long id;
    private String studentId;
    private String name;
    private Integer age;
    private String famillyAddress;
    private Date createdDate;
    private Date updatedDate;
}

5、创建Mapper：StudentInfoMapper

package com.dl.cn.message.mapper;

import com.dl.cn.message.bean.StudentInfo;
import org.apache.ibatis.annotations.*;

/**
 * Created by Tiger on 2018/10/8.
 */
@Mapper
public interface StudentInfoMapper {
    @Insert("insert into student_info(student_id,name,age,familly_address)" +
            " values(#{studentId},#{name},#{age},#{famillyAddress})")
    /**
     * 通过bean保存实体类是，建议不要通过@Param注解，负责实体类的属性都在@Param中找
     * */
    void saveStudentInfo(StudentInfo studentInfo);


    @Select("select * from student_info where student_id = #{studentId}")
    StudentInfo findByStudentId(@Param("studentId") String studentId);


    @Update("update student_info set familly_address = #{famillyAddress},updated_date = now() ")
    void updateFamillyAddress(@Param("studentId") String studentId,@Param("famillyAddress") String famillyAddress);
}

6、创建service：StudentInfoService

package com.dl.cn.message.service;

import com.dl.cn.message.bean.StudentInfo;
import com.dl.cn.message.mapper.StudentInfoMapper;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.CacheConfig;
import org.springframework.cache.annotation.CacheEvict;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;

/**
 * Created by Tiger on 2018/10/8.
 */
@Service
@CacheConfig(cacheNames = "studentInfo")
@Slf4j
public class StudentInfoService {

    @Autowired
    StudentInfoMapper studentInfoMapper;

    /**
     * 保存学生信息
     * @param studentInfo
     * */
    public void saveStudentInfo(StudentInfo studentInfo){
        studentInfoMapper.saveStudentInfo(studentInfo);
    }

    /**
     * 根据学号查学生信息
     * @param studentId
     * @return
     * */
    @Cacheable(key = "#studentId",unless = "#result == null")
    public StudentInfo findByStudentId(String studentId){
        log.info("查找信息:{}",studentId);
        return studentInfoMapper.findByStudentId(studentId);
    }

    /**
     * 根据学号更新家庭地址
     * @param studentId
     * @param famillyAddress
     * */
    //删除对应key的缓存
    @CacheEvict(key = "#studentId")
    public void updateFamillyAddress(String studentId,String famillyAddress){
        studentInfoMapper.updateFamillyAddress(studentId,famillyAddress);
    }
}

7、创建统一返回结果类：Response

package com.dl.cn.message.response;

import com.fasterxml.jackson.databind.annotation.JsonSerialize;
import lombok.Getter;
import lombok.Setter;

import java.io.Serializable;

/**
 * 请求返回类
 * Created by Tiger on 2018/10/9.
 */
@Getter
@Setter
@JsonSerialize(include= JsonSerialize.Inclusion.NON_NULL)
public class Response<T> implements Serializable {

    private static final long serialVersionUID = -4505655308965878999L;

    //请求成功返回码为：0000
    private static final String successCode = "0000";
    //返回数据
    private T data;
    //返回码
    private String code;
    //返回描述
    private String msg;

    public Response(){
        this.code = successCode;
        this.msg = "请求成功";
    }

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

8、创建异常编码和描述类：ErrorCodeAndMsg

package com.dl.cn.message.enums;

/**
 * Created by Tiger on 2018/10/9.
 */
public enum  ErrorCodeAndMsg {

    Student_number_does_not_exist("0001","学号不存在"),
    Insufficient_student_number("0002","学号长度不足"),
    Student_number_is_empty("0003","学号为空"),
    Network_error("9999","网络错误，待会重试"),
    ;

    private String code;
    private String msg;

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

    public String getCode() {
        return code;
    }
    public void setCode(String code) {
        this.code = code;
    }
    public String getMsg() {
        return msg;
    }
    public void setMsg(String msg) {
        this.msg = msg;
    }
}

9、创建统一异常处理类：StudentException

package com.dl.cn.message.exception;

import com.dl.cn.message.enums.ErrorCodeAndMsg;

import java.io.Serializable;

/**
 * 统一异常捕获类
 * Created by Tiger on 2018/10/9.
 */
public class StudentException extends RuntimeException{

    private static final long serialVersionUID = -6370612186038915645L;

    private final ErrorCodeAndMsg response;

    public StudentException(ErrorCodeAndMsg response) {
        this.response = response;
    }
    public ErrorCodeAndMsg getResponse() {
        return response;
    }
}

10、创建异常处理的全局配置类：ExceptionHandler

package com.dl.cn.message.exception;

import com.dl.cn.message.enums.ErrorCodeAndMsg;
import com.dl.cn.message.response.Response;
import lombok.extern.slf4j.Slf4j;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.servlet.http.HttpServletRequest;

/**
 * Created by Tiger on 2018/10/9.
 */
@ControllerAdvice
@Slf4j
public class ExceptionHandler {
    @org.springframework.web.bind.annotation.ExceptionHandler(StudentException.class)
    @ResponseBody
    public Response handleStudentException(HttpServletRequest request, StudentException ex) {
        Response response;
        log.error("StudentException code:{},msg:{}",ex.getResponse().getCode(),ex.getResponse().getMsg());
        response = new Response(ex.getResponse().getCode(),ex.getResponse().getMsg());
        return response;
    }
    @org.springframework.web.bind.annotation.ExceptionHandler(Exception.class)
    @ResponseBody
    public Response handleException(HttpServletRequest request, Exception ex) {
        Response response;
        log.error("exception error:{}",ex);
        response = new Response(ErrorCodeAndMsg.Network_error.getCode(),
                ErrorCodeAndMsg.Network_error.getMsg());
        return response;
    }
}

11、创建controler类：StudentInofController

package com.dl.cn.message.controller;

import com.dl.cn.message.enums.ErrorCodeAndMsg;
import com.dl.cn.message.exception.StudentException;
import com.dl.cn.message.response.Response;
import com.dl.cn.message.service.StudentInfoService;
import com.dl.cn.message.bean.StudentInfo;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

/**
 * Created by Tiger on 2018/10/8.
 */
@RestController
@RequestMapping("/student")
@Slf4j
public class StudentInofController {
    @Autowired
    StudentInfoService studentInfoService;

    /**
     * 保存学生信息
     * @param studentId
     * @param name
     * @param age
     * @param famillyAddress
     * */
    @PostMapping("/save")
    public void saveStudentInfo(@RequestParam("student_id") String studentId,
                                @RequestParam("name") String name,
                                @RequestParam("age") Integer age,
                                @RequestParam("familly_address") String famillyAddress){
        StudentInfo studentInfo = StudentInfo.builder()
                .studentId(studentId)
                .name(name)
                .age(age)
                .famillyAddress(famillyAddress)
                .build();
        studentInfoService.saveStudentInfo(studentInfo);
    }

    /**
     * 根据学号查学生信息
     * @param studentId
     * @return
     * */
    @PostMapping("/findByStudentId")
    public Response findByStudentId(@RequestParam("student_id") String studentId){
        try{
            log.info("Get student information based on student number:{}",studentId);
            if(studentId == null){
                throw new StudentException(ErrorCodeAndMsg.Student_number_is_empty);
            }
            //学号固定为8位
            if(studentId.length() != 8){
                throw new StudentException(ErrorCodeAndMsg.Insufficient_student_number);
            }
            StudentInfo studentInfo = studentInfoService.findByStudentId(studentId);
            if(studentInfo == null){
                throw new StudentException(ErrorCodeAndMsg.Student_number_does_not_exist);
            }
            return new Response(studentInfo);
        }catch (Exception e){
            if(e instanceof StudentException){
                throw e;
            }else {
                log.error("findByStudentId error:",e);
                throw new StudentException(ErrorCodeAndMsg.Network_error);
            }
        }
    }

    @PostMapping("/updateFamillyAddress")
    public Response updateFamillyAddress(@RequestParam("student_id") String studentId,
                                     @RequestParam("familly_address") String famillyAddress){
        studentInfoService.updateFamillyAddress(studentId,famillyAddress);
        Response response = new Response();
        System.out.println(response.toString());
        return response;
    }


}

12、application.properties配置

#redis
spring.redis.host=127.0.0.1
spring.redis.port=6379
spring.redis.password=tiger

#mybatis
#开启mybatis驼峰命名，这样可以将mysql中带有下划线的映射成驼峰命名的字段
mybatis.configuration.map-underscore-to-camel-case=true

#datasource
spring.datasource.url=jdbc:mysql://127.0.0.1:3306/tiger?useUnicode=true&characterEncoding=UTF-8&zeroDateTimeBehavior=convertToNull&autoReconnect=true&generateSimpleParameterMetadata=true
spring.datasource.username=tiger
spring.datasource.password=tiger
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
spring.datasource.max-idle=10
spring.datasource.max-wait=60000
spring.datasource.min-idle=5
spring.datasource.initial-size=5
spring.datasource.validationQuery=select 'x'

三、说明

1、controller层使用注解@RestController，这样返回结果就是json格式，而@Controller返回结果是字符串

2、throw 异常

如果exception类型是自定义的异常StudentException，直接抛出，如果是其它异常统一抛出网络错误

try{

}catch (Exception e){
            if(e instanceof StudentException){
                throw e;
            }else {
                log.error("findByStudentId error:",e);
                throw new StudentException(ErrorCodeAndMsg.Network_error);
       }
}

3、在返回结果类添加了注解@JsonSerialize(include= JsonSerialize.Inclusion.NON_NULL)

是因为更新或者删除操作，一般没有返回值，我只需要知道是否更新成功或者删除成功就OK了，如果不加这个注解

我们返回的结果中data为null！！！

{
    "data": null,
    "code": "0000",
    "msg": "请求成功"
}

加上注解再更新数据，返回结果：

{
    "code": "0000",
    "msg": "请求成功"
}

因此这个注解的作用就是：返回结果中有null值，干掉它！

四、测试结果

mysql数据库中有一条学号为13240115的数据：

1、student_id = "13240115"时

{
    "data": {
        "id": 1,
        "studentId": "13240115",
        "name": "Tiger",
        "age": 25,
        "famillyAddress": "北京",
        "createdDate": "2018-10-08T05:45:49.000+0000",
        "updatedDate": "2018-10-09T05:36:36.000+0000"
    },
    "code": "0000",
    "msg": "请求成功"
}

2、student_id = "13240114"时

{
    "code": "0001",
    "msg": "学号不存在"
}

3、student_id = "1324011"，不足8位时

{
    "code": "0002",
    "msg": "学号长度不足"
}

4、student_id = "13240115"，然后在接口中加上一行代码，System.out.println(1/0);

返回结果：

{
    "code": "9999",
    "msg": "网络错误，待会重试"
}

控制台日志：

java.lang.ArithmeticException: / by zero
	at com.dl.cn.message.controller.StudentInofController.findByStudentId(StudentInofController.java:54) ~[classes/:na]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_161]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_161]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_161]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_161]
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209) [spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) [spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]

通过测试，发现这个小案例满足刚开始我们提出的需求，一定还有很多其它问题，暂时没有发现，我会及时修改，不知道有人是否看我的博客？我只是想把自己的学习成果总结记录下来。人可以成长为芳草，也可以长成杂莠！！！