SpringBoot-统一异常处理

作者: 我可能是个假开发 | 来源:发表于2017-08-17 16:30 被阅读1528次

    SpringBoot-统一异常处理

    一、什么是异常处理

    异常(exception) 是程序运行过程中发生的事件, 该事件可以中断程序指令的正常执行流程.

    1当Java程序运行时出现问题时,系统会自动检测到该错误,并立即生成一个与该错误对应的异常对象
    2:然后把该异常对象提交给JAVA虚拟机
    3:JAVA虚拟机会自动寻找相应的处理代码来处理这个异常,如果没有找到,则程序终止
    4:程序员可以自己编写代码来扑捉可能出现的异常,并编写代码来处理相应的异常.
    

    二、为什么要统一异常处理

    例:需求:

    获取某女生的年龄并判断:
    小于10,返回“应该在上小学”;
    大于10且小于16,返回“可能在上初中”;
    

    需求:把System.out.println(bindingResult.getFieldError().getDefaultMessage());信息输出到网页

    版本一:

    GirlController:

    @RestController
    public class GirlController {
    
        /**
         * getLogger方法中的参数与类名对应
         */
        private final static Logger logger = LoggerFactory.getLogger(GirlController.class);
    
        @Autowired
        private GirlRepository girlRepository;
    
        @Autowired
        private GirlService girlService;
    
    
        //添加一个女生
        @PostMapping(value="/girls")
        public Girl girlAdd(@Valid Girl girl, BindingResult bindingResult) {
            if (bindingResult.hasErrors()) {
                System.out.println(bindingResult.getFieldError().getDefaultMessage());
                return null;
            }
            girl.setCupSize(girl.getCupSize());
            girl.setAge(girl.getAge());
    
            return girlRepository.save(girl);
        }
    }
    

    Girl:

    @Entity //该注解表示该类在数据库中有对应的表 不用创建该表
    public class Girl {
    
        @Id
        @GeneratedValue
        private Integer id;
    
        @NotBlank(message = "这个字段必传")
        private String cupSize;
    
        /**
         * 给年龄加上限制:年龄必须大于18岁
         * value:值
         * message:提示信息
         */
        @Min(value =18,message = "年龄必须大于18岁")
        private Integer age;
    
        @NotNull(message = "金额必传")
        private Double money;
    
        public Girl() {
        }
    
        @Override
        public String toString() {
            return "Girl{" +
                    "id=" + id +
                    ", cupSize='" + cupSize + '\'' +
                    ", age=" + age +
                    '}';
        }
    
        public Double getMoney() {
            return money;
        }
    
        public void setMoney(Double money) {
            this.money = money;
        }
    
        public Integer getId() {
            return id;
        }
    
        public void setId(Integer id) {
            this.id = id;
        }
    
        public String getCupSize() {
            return cupSize;
        }
    
        public void setCupSize(String cupSize) {
            this.cupSize = cupSize;
        }
    
        public Integer getAge() {
            return age;
        }
    
        public void setAge(Integer age) {
            this.age = age;
        }
    }
    
    1.jpg 2.jpg

    目前,金额必传是打印在控制台上的,现在需要打印在网页上:

    修改方法:

    版本二:

    @PostMapping(value="/girls")
    public Object girlAdd(@Valid Girl girl, BindingResult bindingResult) {
        if (bindingResult.hasErrors()) {
            return bindingResult.getFieldError().getDefaultMessage();
        }
        girl.setCupSize(girl.getCupSize());
        girl.setAge(girl.getAge());
    
        return girlRepository.save(girl);
    }
    

    结果:

    3.jpg 4.jpg

    问题:返回的格式不统一,对返回的格式作统一(失败和成功):

    {
        "code":1,
        "msg":"金额必传",
        "data":null
    }
    {
        "code":0
        "msg":"成功",
        "data":{
            "id":20,
            "cupSize":"B",
            "age":25,
            "money":1.2
        }
    }
    

    版本三:

    Result:

    /**
     * Created by HCX on 2017/8/17.
     * http请求返回的最外层对象
     */
    public class Result<T> {
    
        //错误码
        private Integer code;
    
        //提示信息
        private String msg;
    
        //具体的内容
        private T data;
    
        public Integer getCode() {
            return code;
        }
    
        public void setCode(Integer code) {
            this.code = code;
        }
    
        public String getMsg() {
            return msg;
        }
    
        public void setMsg(String msg) {
            this.msg = msg;
        }
    
        public T getData() {
            return data;
        }
    
        public void setData(T data) {
            this.data = data;
        }
    }
    

    GirlController:

    @RestController
    public class GirlController {
    
        /**
         * getLogger方法中的参数与类名对应
         */
        private final static Logger logger = LoggerFactory.getLogger(GirlController.class);
    
        @Autowired
        private GirlRepository girlRepository;
    
        @Autowired
        private GirlService girlService;
    
        //添加一个女生
        @PostMapping(value="/girls")
        public Result<Girl> girlAdd(@Valid Girl girl, BindingResult bindingResult) {
            if(bindingResult.hasErrors()){
                Result result = new Result();
                result.setCode(1);
                result.setMsg(bindingResult.getFieldError().getDefaultMessage());
                result.setData(null);
                return result;
            }
            girl.setCupSize(girl.getCupSize());
            girl.setAge(girl.getAge());
            Result result = new Result();
            result.setCode(0);
            result.setMsg("成功");
            result.setData(girlRepository.save(girl));
            return result;
        }
    }
    

    运行结果:

    5.jpg 6.jpg

    可见代码重复了,进行优化:版本四

    定义返回结果的工具类ResultUtil:

    public class ResultUtil {
    
        public static Result success(Object object){
            Result result = new Result();
            result.setCode(0);
            result.setMsg("成功");
            result.setData(object);
            return result;
        }
    
        public static Result success(){
            return success(null);
        }
    
        public static Result error(Integer code,String msg){
            Result result = new Result();
            result.setCode(code);
            result.setMsg(msg);
            return result;
        }
    }
    

    GirlController:

    @RestController
    public class GirlController {
    
        /**
         * getLogger方法中的参数与类名对应
         */
        private final static Logger logger = LoggerFactory.getLogger(GirlController.class);
    
        @Autowired
        private GirlRepository girlRepository;
    
        @Autowired
        private GirlService girlService;
    
        
        //添加一个女生
        @PostMapping(value="/girls")
        public Result<Girl> girlAdd(@Valid Girl girl, BindingResult bindingResult) {
            if(bindingResult.hasErrors()){
                return ResultUtil.error(1,bindingResult.getFieldError().getDefaultMessage());
            }
            girl.setCupSize(girl.getCupSize());
            girl.setAge(girl.getAge());
            return ResultUtil.success(girlRepository.save(girl));
        }
    }
    

    三、案例

    需求:获取某女生的年龄并判断,小于10,返回“应该在上小学”;大于10且小于16,返回“可能在上初中”

    GirlController:

    @RestController
    public class GirlController {
    
        /**
         * getLogger方法中的参数与类名对应
         */
        private final static Logger logger = LoggerFactory.getLogger(GirlController.class);
    
        @Autowired
        private GirlRepository girlRepository;
    
        @Autowired
        private GirlService girlService;
    
        @GetMapping(value = "girls/getAge/{id}")
        public void getAge(@PathVariable("id") Integer id) throws Exception{
            girlService.getAge(id);
        }
    }
    

    GirlService:

    @Service
    public class GirlService {
    
        @Autowired
        private GirlRepository girlRepository;
    
        public void getAge(Integer id) throws Exception{
            Girl girl = girlRepository.findOne(id);
            Integer age = girl.getAge();
            if(age<10){
                //返回“你可能在上小学” code=100
                throw new Exception("你可能在上小学");
            }else if(age>10 && age<16){
                //返回“你可能在上初中” code=101
                throw new Exception("你可能在上初中");
            }
        }
    }
    

    ExceptionHandle:

    @ControllerAdvice
    public class ExceptionHandle {
    
        /**
         *  @ExceptionHandler(value = Exception.class):声明要捕获的异常类
         * @return
         */
        @ExceptionHandler(value = Exception.class)
        @ResponseBody
        public Result handle(Exception e){
            return ResultUtil.error(100,e.getMessage());
        }
    }
    

    此时,已经按照我们所期望的格式返回了:

    7.jpg

    问题:返回的错误码都是一样的,但是在实际问题中,我们希望定位的错误更准确,希望不同的错误可以返回不同的错误码,所以可以自定义一个Exception:

    GirlException:

    public class GirlException extends RuntimeException{
        /**
         * 注意要继承自RuntimeException,底层RuntimeException继承了Exception,
         * spring框架只对抛出的异常是RuntimeException才会进行事务回滚,
         * 如果是抛出的是Exception,是不会进行事物回滚的
         */
        private Integer code;
    
        public GirlException(Integer code,String message) {
            //父类的构造方法本身会传message进去
            super(message);
            this.code = code;
        }
    
        public Integer getCode() {
            return code;
        }
    
        public void setCode(Integer code) {
            this.code = code;
        }
    }
    

    ExceptionHandle:

    @ControllerAdvice
    public class ExceptionHandle {
    
        /**
         *  @ExceptionHandler(value = Exception.class):声明要捕获的异常类
         * @return
         */
        @ExceptionHandler(value = Exception.class)
        @ResponseBody
        public Result handle(Exception e){
            if(e instanceof GirlException){
                GirlException girlException = (GirlException)e;
                return ResultUtil.error(girlException.getCode(),girlException.getMessage());
            }else {
                return ResultUtil.error(-1,"未知错误");
            }
        }
    }
    

    GirlService:

    @Service
    public class GirlService {
    
        @Autowired
        private GirlRepository girlRepository;
    
        public void getAge(Integer id) throws Exception{
            Girl girl = girlRepository.findOne(id);
            Integer age = girl.getAge();
            if(age<10){
                //返回“你可能在上小学” code=100
                throw new GirlException(100,"你可能在上小学");
            }else if(age>10 && age<16){
                //返回“你可能在上初中” code=101
                throw new GirlException(101,"你可能在上初中");
            }
        }
    }
    

    GirlController:

    @RestController
    public class GirlController {
    
        /**
         * getLogger方法中的参数与类名对应
         */
        private final static Logger logger = LoggerFactory.getLogger(GirlController.class);
    
        @Autowired
        private GirlRepository girlRepository;
    
        @Autowired
        private GirlService girlService;
    
        @GetMapping(value = "girls/getAge/{id}")
        public void getAge(@PathVariable("id") Integer id) throws Exception{
            girlService.getAge(id);
        }
    }
    

    运行结果:

    8.jpg 9.jpg

    当抛出的是系统异常时,可以通过日志进行记录:

    10.jpg

    ExceptionHandle:

    @ControllerAdvice
    public class ExceptionHandle {
    
        //记录系统异常
        private final static Logger logger = LoggerFactory.getLogger(ExceptionHandle.class);
    
        /**
         *  @ExceptionHandler(value = Exception.class):声明要捕获的异常类
         * @return
         */
        @ExceptionHandler(value = Exception.class)
        @ResponseBody
        public Result handle(Exception e){
            if(e instanceof GirlException){
                GirlException girlException = (GirlException)e;
                return ResultUtil.error(girlException.getCode(),girlException.getMessage());
            }else {
                logger.error("【系统异常】 {}",e);
                return ResultUtil.error(-1,"未知错误");
            }
        }
    }
    

    问题:在自定义异常的错误码和信息时,如果过多,没有统一管理,则会出现重复。使用枚举统一管理code和message:

    ResultEnum:

    public enum ResultEnum {
        UNKNOW_ERROR(-1,"未知错误"),
        SUCCESS(0,"成功"),
        PRIMARY_SCHOOL(100,"你可能在上小学"),
        MIDDLE_SCHOOL(101,"你可能在上初中"),
        ;
    
        private  Integer code;
        private String msg;
    
        ResultEnum(Integer code, String msg) {
            this.code = code;
            this.msg = msg;
        }
    
        public Integer getCode() {
            return code;
        }
    
        public String getMsg() {
            return msg;
        }
    }
    

    GirlException:

    public class GirlException extends RuntimeException{
        /**
         * 注意要继承自RuntimeException,底层RuntimeException继承了Exception,
         * spring框架只对抛出的异常是RuntimeException才会进行事务回滚,
         * 如果是抛出的是Exception,是不会进行事物回滚的
         */
        private Integer code;
    
        public GirlException(ResultEnum resultEnum) {
            //父类的构造方法本身会传message进去
            super(resultEnum.getMsg());
            this.code = resultEnum.getCode();
        }
    
        public Integer getCode() {
            return code;
        }
    
        public void setCode(Integer code) {
            this.code = code;
        }
    }
    

    GirlService:

    @Service
    public class GirlService {
    
        @Autowired
        private GirlRepository girlRepository;
    
        public void getAge(Integer id) throws Exception{
            Girl girl = girlRepository.findOne(id);
            Integer age = girl.getAge();
            if(age<10){
                //返回“你可能在上小学” code=100
                throw new GirlException(ResultEnum.PRIMARY_SCHOOL);
            }else if(age>10 && age<16){
                //返回“你可能在上初中” code=101
                throw new GirlException(ResultEnum.MIDDLE_SCHOOL);
            }
        }
    }
    

    GirlController:

    @RestController
    public class GirlController {
    
        /**
         * getLogger方法中的参数与类名对应
         */
        private final static Logger logger = LoggerFactory.getLogger(GirlController.class);
    
        @Autowired
        private GirlRepository girlRepository;
    
        @Autowired
        private GirlService girlService;
    
        @GetMapping(value = "girls/getAge/{id}")
        public void getAge(@PathVariable("id") Integer id) throws Exception{
            girlService.getAge(id);
        }
    }

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