java-在Spring Boot中处理异常的正确方法

我在阅读Spring文档时发现,从ResponseEntityExceptionHandler创建子类是处理异常的好方法.但是,我尝试以不同的方式处理异常,因为我需要将BusinessException与TechnicalException区别.

创建了一个名为BusinessFault的Bean,其中封装了异常详细信息：

BusinessFault.java

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonInclude.Include;
import com.fasterxml.jackson.annotation.JsonProperty;

@JsonInclude(value = Include.NON_NULL)
public class BusinessFault {

    @JsonProperty(value = "category")
    private final String CATEGORY = "Business Failure";
    protected String type;
    protected String code;
    protected String reason;
    protected String description;
    protected String instruction;

    public BusinessFault(String type, String code, String reason) {
        this.type = type;
        this.code = code;
        this.reason = reason;
    }

    public BusinessFault(String type, String code, String reason, String description, String instruction) {
        this.type = type;
        this.code = code;
        this.reason = reason;
        this.description = description;
        this.instruction = instruction;
    }

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    public String getReason() {
        return reason;
    }

    public void setReason(String reason) {
        this.reason = reason;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public String getInstruction() {
        return instruction;
    }

    public void setInstruction(String instruction) {
        this.instruction = instruction;
    }

    public String getCATEGORY() {
        return CATEGORY;
    }
}

创建了一个BusinessException类,该类通过通过其构造函数传递的详细信息创建一个BusinessFault bean来完成工作：

BusinessException.java

import com.rest.restwebservices.exception.fault.BusinessFault;

public abstract class BusinessException extends RuntimeException {

    private BusinessFault businessFault;

    public BusinessException(String type, String code, String reason) {
        this.businessFault = new BusinessFault(type, code, reason);
    }

    public BusinessException(String type, String code, String reason, String description, String instruction) {
        this.businessFault = new BusinessFault(type, code, reason, description, instruction);
    }

    public BusinessException(BusinessFault businessFault) {
        this.businessFault = businessFault;
    }

    public BusinessFault getBusinessFault() {
        return businessFault;
    }

    public void setBusinessFault(BusinessFault businessFault) {
        this.businessFault = businessFault;
    }
}

创建了一个特定的UserNotFoundException类,该类从BusinessException类扩展：

UserNotFoundException.java

import com.rest.restwebservices.exception.fault.BusinessFault;
import com.rest.restwebservices.exception.map.ExceptionMap;

public class UserNotFoundException extends BusinessException {

    public UserNotFoundException(BusinessFault businessFault) {
        super(businessFault);
    }

    public UserNotFoundException(String reason) {
        super(ExceptionMap.USERNOTFOUND.getType(), ExceptionMap.USERNOTFOUND.getCode(), reason);
    }

    public UserNotFoundException(String reason, String description, String instruction) {
        super(ExceptionMap.USERNOTFOUND.getType(), ExceptionMap.USERNOTFOUND.getCode(), reason, description,
                instruction);
    }
}

创建了一个BusinessExceptionHandler,但是它不是@ResponseEntityExceptionHandler的子类,它仅具有@ControllerAdvice批注和处理所有引发的BusinessException的方法：

BusinessExceptionHandler.java

import javax.servlet.http.HttpServletRequest;

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;

import com.rest.restwebservices.controller.UserController;
import com.rest.restwebservices.exception.BusinessException;
import com.rest.restwebservices.exception.fault.BusinessFault;

@ControllerAdvice(basePackageClasses = UserController.class)
public class BusinessExceptionHandler {

    @ExceptionHandler(BusinessException.class)
    @ResponseBody
    public ResponseEntity<BusinessFault> genericHandler(HttpServletRequest request, BusinessException ex) {
        return new ResponseEntity<BusinessFault>(ex.getBusinessFault(), HttpStatus.OK);
    }
}

服务层可以引发UserNotFoundException：

@Service
public class UserService {

    @Autowired
    private UserRepository userRepository;

    public User findById(Long id) {
        User user = userRepository.findOne(id);
        if (user == null)
            throw new UserNotFoundException("The ID " + id + " doesn't behave to any user!");

        return user;
    }
}

工作正常.但是我想知道这是否是处理异常的不良做法？

解决方法:

我对您的异常处理有点问题.原则上,捕获运行时异常,对其进行处理并将其发送给客户端绝对是可以的,这可能是使用REST服务并将错误响应作为JSON对象获取的人.如果您能告诉他他做错了什么,他可以做些什么,那就太好了！当然,它会增加一些复杂性,但是使用该API可能很容易且舒适.

但是,请考虑与您的代码一起使用的后端开发人员.尤其是UserService中的公共用户findById(Long id)方法是晦涩的.这样做的原因是您使BusinessException(特别是UserNotFoundException)处于未选中状态.

如果我加入了您的(后端)团队,并且打算使用该服务编写一些业务逻辑,那么我将非常确定我对该方法的期望：我传递了一个用户ID,如果有,则返回一个User对象.找到,否则返回null.这就是为什么我会写这样的代码

User user = userService.findById("42A");
if (user == null) {
  // create a User or return an error or null or whatever
} else {
  // proceed
}

但是,我永远不会知道,第一个条件永远不会为真,因为您永远不会返回null.我怎么知道我必须捕获一个异常？

编译器告诉我抓住它了吗？不,因为未选中.

我会调查一下您的源代码吗？一定不行！您的情况非常简单. UserNotFoundException可能会在几百行代码中的另一个类的另一个方法中引发.有时,无论如何,我还是看不到它,因为UserService只是依赖项中的已编译类.

我可以阅读JavaDoc吗？哈哈哈假设有50％的时间我不愿意,而另外50％的您却忘记记录了.

因此,开发人员必须等到他的代码被使用(无论是由客户端还是在单元测试中)后,才能看到它无法按预期工作,从而迫使他重新设计到目前为止的代码.而且,如果您的整个API是这样设计的,那么未经检查的异常就会无处不在,这可能会非常烦人,既浪费时间和金钱,又很容易避免.

标签：spring-rest,spring-boot,spring-restcontroller,spring,java
来源： https://codeday.me/bug/20191109/2010731.html