短链接--异常码的设计和使用

####异常码的设计和使用

​ 为了更快的确定异常原因，从而快速定位出错地点并解决异常。可以使用异常码，每个异常码都对应一个特定的错误。本项目参考阿里巴巴开发手册，将出错原因大体上分为3类：用户端出错，服务器端出错以及远端第三方组件出错，分别用大写英文字母A、B、C标识，每个类别下使用6位数字来表示出错原因，因而总共可以表示30万种错误。每个大类中根据内容详细程度不同，分为3个级别，级别越高内容越详细。

异常码设计

public Interface IErrorCode{
    String code;
    String message;
}

基础异常码

/**
 * 基础错误码定义
 */
public enum BaseErrorCode implements IErrorCode {

    // ========== 一级宏观错误码 客户端错误 ==========
    CLIENT_ERROR("A000001", "用户端错误"),

    // ========== 二级宏观错误码 用户注册错误 ==========
    USER_REGISTER_ERROR("A000100", "用户注册错误"),
    USER_NAME_VERIFY_ERROR("A000110", "用户名校验失败"),
    USER_NAME_EXIST_ERROR("A000111", "用户名已存在"),
    USER_NAME_SENSITIVE_ERROR("A000112", "用户名包含敏感词"),
    USER_NAME_SPECIAL_CHARACTER_ERROR("A000113", "用户名包含特殊字符"),
    PASSWORD_VERIFY_ERROR("A000120", "密码校验失败"),
    PASSWORD_SHORT_ERROR("A000121", "密码长度不够"),
    PHONE_VERIFY_ERROR("A000151", "手机格式校验失败"),

    // ========== 二级宏观错误码 系统请求缺少幂等Token ==========
    IDEMPOTENT_TOKEN_NULL_ERROR("A000200", "幂等Token为空"),
    IDEMPOTENT_TOKEN_DELETE_ERROR("A000201", "幂等Token已被使用或失效"),

    // ========== 一级宏观错误码 系统执行出错 ==========
    SERVICE_ERROR("B000001", "系统执行出错"),
    // ========== 二级宏观错误码 系统执行超时 ==========
    SERVICE_TIMEOUT_ERROR("B000100", "系统执行超时"),

    // ========== 一级宏观错误码 调用第三方服务出错 ==========
    REMOTE_ERROR("C000001", "调用第三方服务出错");

    private final String code;

    private final String message;

    BaseErrorCode(String code, String message) {
        this.code = code;
        this.message = message;
    }

    @Override
    public String code() {
        return code;
    }

    @Override
    public String message() {
        return message;
    }
}

异常的设计和使用

​ 根据异常码的分类，因此产生的异常也分为3类.

异常类设计

import com.nageoffer.shortlink.admin.common.convention.errorcode.IErrorCode;
import lombok.Getter;
import org.springframework.util.StringUtils;

import java.util.Optional;

/**
 * 抽象项目中三类异常体系，客户端异常、服务端异常以及远程服务调用异常
 *
 * @see ClientException
 * @see ServiceException
 * @see RemoteException
 */
@Getter
public abstract class AbstractException extends RuntimeException {

    public final String errorCode;

    public final String errorMessage;

    public AbstractException(String message, Throwable throwable, IErrorCode errorCode) {
        super(message, throwable);
        this.errorCode = errorCode.code();
        this.errorMessage = Optional.ofNullable(StringUtils.hasLength(message) ? message : null).orElse(errorCode.message());
    }
}

import com.nageoffer.shortlink.admin.common.convention.errorcode.BaseErrorCode;
import com.nageoffer.shortlink.admin.common.convention.errorcode.IErrorCode;

/**
 * 客户端异常
 */
public class ClientException extends AbstractException {

    public ClientException(IErrorCode errorCode) {
        this(null, null, errorCode);
    }

    public ClientException(String message) {
        this(message, null, BaseErrorCode.CLIENT_ERROR);
    }

    public ClientException(String message, IErrorCode errorCode) {
        this(message, null, errorCode);
    }

    public ClientException(String message, Throwable throwable, IErrorCode errorCode) {
        super(message, throwable, errorCode);
    }

    @Override
    public String toString() {
        return "ClientException{" +
                "code='" + errorCode + "'," +
                "message='" + errorMessage + "'" +
                '}';
    }
}

import com.nageoffer.shortlink.admin.common.convention.errorcode.BaseErrorCode;
import com.nageoffer.shortlink.admin.common.convention.errorcode.IErrorCode;

/**
 * 远程服务调用异常
 */
public class RemoteException extends AbstractException {

    public RemoteException(String message) {
        this(message, null, BaseErrorCode.REMOTE_ERROR);
    }

    public RemoteException(String message, IErrorCode errorCode) {
        this(message, null, errorCode);
    }

    public RemoteException(String message, Throwable throwable, IErrorCode errorCode) {
        super(message, throwable, errorCode);
    }

    @Override
    public String toString() {
        return "RemoteException{" +
                "code='" + errorCode + "'," +
                "message='" + errorMessage + "'" +
                '}';
    }
}

import com.nageoffer.shortlink.admin.common.convention.errorcode.BaseErrorCode;
import com.nageoffer.shortlink.admin.common.convention.errorcode.IErrorCode;

import java.util.Optional;

/**
 * 服务端异常
 */
public class ServiceException extends AbstractException {

    public ServiceException(String message) {
        this(message, null, BaseErrorCode.SERVICE_ERROR);
    }

    public ServiceException(IErrorCode errorCode) {
        this(null, errorCode);
    }

    public ServiceException(String message, IErrorCode errorCode) {
        this(message, null, errorCode);
    }

    public ServiceException(String message, Throwable throwable, IErrorCode errorCode) {
        super(Optional.ofNullable(message).orElse(errorCode.message()), throwable, errorCode);
    }

    @Override
    public String toString() {
        return "ServiceException{" +
                "code='" + errorCode + "'," +
                "message='" + errorMessage + "'" +
                '}';
    }
}

​ 在处理异常上，设置全局异常拦截器，统一处理产生的所有异常

import cn.hutool.core.collection.CollectionUtil;
import cn.hutool.core.util.StrUtil;
import com.nageoffer.shortlink.admin.common.convention.errorcode.BaseErrorCode;
import com.nageoffer.shortlink.admin.common.convention.exception.AbstractException;
import com.nageoffer.shortlink.admin.common.convention.result.Result;
import com.nageoffer.shortlink.admin.common.convention.result.Results;
import jakarta.servlet.http.HttpServletRequest;
import lombok.SneakyThrows;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;
import org.springframework.util.StringUtils;
import org.springframework.validation.BindingResult;
import org.springframework.validation.FieldError;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;

import java.util.Optional;

/**
 * 全局异常处理器
 *
 */
@Component
@Slf4j
@RestControllerAdvice
public class GlobalExceptionHandler {

    /**
     * 拦截参数验证异常
     */
    @SneakyThrows
    @ExceptionHandler(value = MethodArgumentNotValidException.class)
    public Result validExceptionHandler(HttpServletRequest request, MethodArgumentNotValidException ex) {
        BindingResult bindingResult = ex.getBindingResult();
        FieldError firstFieldError = CollectionUtil.getFirst(bindingResult.getFieldErrors());
        String exceptionStr = Optional.ofNullable(firstFieldError)
                .map(FieldError::getDefaultMessage)
                .orElse(StrUtil.EMPTY);
        log.error("[{}] {} [ex] {}", request.getMethod(), getUrl(request), exceptionStr);
        return Results.failure(BaseErrorCode.CLIENT_ERROR.code(), exceptionStr);
    }

    /**
     * 拦截应用内抛出的异常
     */
    @ExceptionHandler(value = {AbstractException.class})
    public Result abstractException(HttpServletRequest request, AbstractException ex) {
        if (ex.getCause() != null) {
            log.error("[{}] {} [ex] {}", request.getMethod(), request.getRequestURL().toString(), ex.toString(), ex.getCause());
            return Results.failure(ex);
        }
        log.error("[{}] {} [ex] {}", request.getMethod(), request.getRequestURL().toString(), ex.toString());
        return Results.failure(ex);
    }

    /**
     * 拦截未捕获异常
     */
    @ExceptionHandler(value = Throwable.class)
    public Result defaultErrorHandler(HttpServletRequest request, Throwable throwable) {
        log.error("[{}] {} ", request.getMethod(), getUrl(request), throwable);
        return Results.failure();
    }

    private String getUrl(HttpServletRequest request) {
        if (StringUtils.isEmpty(request.getQueryString())) {
            return request.getRequestURL().toString();
        }
        return request.getRequestURL().toString() + "?" + request.getQueryString();
    }
}

@SneakyThrows注解：可作用于方法和构造函数上，可以帮助捕获异常，简化代码，比如

public void utf8ToString(byte[] bytes) {
       try {
      return new String(bytes, "UTF-8");
    } catch (Exception e) {
      throw Lombok.sneakyThrow(e);
    }
}    

使用该注解后，可以使代码更加简洁。该注解位于Lombok中

@SneakyThrows
   public void utf8ToString(byte[] bytes) {
       return new String(bytes, "UTF-8");
   }

通过本节需要掌握

1. 异常码的设计和使用
2. 异常类的设计和使用
3. 全局异常处理器的设计
4. @SneakyThrows注解的使用