DK's Notes
zdk
2022-08-12
目录

Dubbo的服务异常处理

Table of Contents generated with DocToc (opens new window)

# Dubbo异常处理

# 起因

按我们非rpt式的写法，在provider的serviceImpl中，抛出一个业务异常BusinessException(继承RuntimeException)，但是我们会发现，在consumer端接收到的异常信息只是RuntimeException，只是message是我们自己的信息，其他的都只是一个普通的RuntimeException，这里就开始疑惑，为什么Dubbo服务端不能识别我们自定义的异常类型呢？

# 源码 org.apache.dubbo.rpc.filter.ExceptionFilter

@Activate(group = CommonConstants.PROVIDER)
public class ExceptionFilter implements Filter, Filter.Listener {
    private Logger logger = LoggerFactory.getLogger(ExceptionFilter.class);

    @Override
    public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
        return invoker.invoke(invocation);
    }

    @Override
    public void onResponse(Result appResponse, Invoker<?> invoker, Invocation invocation) {
        //响应入口开始
        
        if (appResponse.hasException() && GenericService.class != invoker.getInterface()) {
            //上面的语句的意思是  如果有异常 且没有实现GenericService这个接口则进入下一步 否则不执行任何操作
            try {
                Throwable exception = appResponse.getException();

                // directly throw if it's checked exception
                // 如果不是 运行时异常 或者 受检查异常  直接返回
                if (!(exception instanceof RuntimeException) && (exception instanceof Exception)) {
                    return;
                }
                // directly throw if the exception appears in the signature
                // 如果调用的这个方法上面  有throws xxException 签名 直接抛出这个签名的异常
                try {
                    Method method = invoker.getInterface().getMethod(invocation.getMethodName(), invocation.getParameterTypes());
                    Class<?>[] exceptionClassses = method.getExceptionTypes();
                    for (Class<?> exceptionClass : exceptionClassses) {
                        if (exception.getClass().equals(exceptionClass)) {
                            return;
                        }
                    }
                } catch (NoSuchMethodException e) {
                    return;
                }

                // for the exception not found in method's signature, print ERROR message in server's log.
                logger.error("Got unchecked and undeclared exception which called by " + RpcContext.getContext().getRemoteHost() + ". service: " + invoker.getInterface().getName() + ", method: " + invocation.getMethodName() + ", exception: " + exception.getClass().getName() + ": " + exception.getMessage(), exception);

                // directly throw if exception class and interface class are in the same jar file.
                // 这里是如果异常类和接口类在同一个jar包中，直接抛出
                String serviceFile = ReflectUtils.getCodeBase(invoker.getInterface());
                String exceptionFile = ReflectUtils.getCodeBase(exception.getClass());
                if (serviceFile == null || exceptionFile == null || serviceFile.equals(exceptionFile)) {
                    return;
                }
                // directly throw if it's JDK exception
                // 如果这个异常是jdk的异常  直接抛出
                String className = exception.getClass().getName();
                if (className.startsWith("java.") || className.startsWith("javax.")) {
                    return;
                }
                // directly throw if it's dubbo exception
                // 如果是Dubbo自定义的这个RpcException 直接抛出
                if (exception instanceof RpcException) {
                    return;
                }

                // otherwise, wrap with RuntimeException and throw back to the client
                // 都不是以上几种情况的时候 只把message保留  然后封装为一个RuntimeException抛出
                appResponse.setException(new RuntimeException(StringUtils.toString(exception)));
            } catch (Throwable e) {
                logger.warn("Fail to ExceptionFilter when called by " + RpcContext.getContext().getRemoteHost() + ". service: " + invoker.getInterface().getName() + ", method: " + invocation.getMethodName() + ", exception: " + e.getClass().getName() + ": " + e.getMessage(), e);
            }
        }
    }

    @Override
    public void onError(Throwable e, Invoker<?> invoker, Invocation invocation) {
        logger.error("Got unchecked and undeclared exception which called by " + RpcContext.getContext().getRemoteHost() + ". service: " + invoker.getInterface().getName() + ", method: " + invocation.getMethodName() + ", exception: " + e.getClass().getName() + ": " + e.getMessage(), e);
    }

    // For test purpose
    public void setLogger(Logger logger) {
        this.logger = logger;
    }
}
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# 能正常抛出的情况总结

  1. 首先，服务类不能实现GenericService接口，否则不会处理异常

    image-20220812172005562

  2. 抛出的异常得是RuntimeException或受检异常 及其子类

    • 自定义异常通常是RuntimeException

    image-20220812172436335

  3. Impl方法上有throws xxException 签名，可以直接抛出

    • 作为生产服务端，不应显式抛出异常给客户的进行处理，所以也不适用

    image-20220812172451910

  4. 调用的接口类和抛出的异常类在同一个jar包中，可以直接抛出

    • 较大的项目一般都会有一些common包，定义好异常类型，使用二方包的方式引用，所以也不适用

    image-20220812172515160

  5. 全类名以java.或javax.开头，可以直接抛出

    • 这个方案不现实，也不符合规范，所以不采用

    image-20220812172529144

  6. 抛出的异常是RpcException及其子类，可以直接抛出

    image-20220812172546687

其他的情况，就只用发现的异常的message封装一个RuntimeException返回

image-20220812172623283

# 处理方案

最好的方案是重写一下这个Filter，加上处理业务异常的逻辑

  1. 将ExceptionFilter copy 到自己的项目改名为DubboExceptionFilter或者新建一个Filter 实现org.apache.dubbo.rpc.Filter接口

    @Activate(group = Constants.PROVIDER)
public class DubboExceptionFilter implements Filter {

    private final Logger logger;

    public DubboExceptionFilter() {
        this(LoggerFactory.getLogger(DubboExceptionFilter.class));
    }

    public DubboExceptionFilter(Logger logger) {
        this.logger = logger;
    }

    @Override
    public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
        try {
            Result result = invoker.invoke(invocation);
            if (result.hasException() && GenericService.class != invoker.getInterface()) {
                try {
                    Throwable exception = result.getException();

                    // directly throw if it's checked exception
                    if (!(exception instanceof RuntimeException) && (exception instanceof Exception)) {
                        return result;
                    }
                    // directly throw if the exception appears in the signature
                    try {
                        Method method = invoker.getInterface().getMethod(invocation.getMethodName(), invocation.getParameterTypes());
                        Class<?>[] exceptionClassses = method.getExceptionTypes();
                        for (Class<?> exceptionClass : exceptionClassses) {
                            if (exception.getClass().equals(exceptionClass)) {
                                return result;
                            }
                        }
                    } catch (NoSuchMethodException e) {
                        return result;
                    }

                    // for the exception not found in method's signature, print ERROR message in server's log.
                    logger.error("Got unchecked and undeclared exception which called by " + RpcContext.getContext().getRemoteHost()
                            + ". service: " + invoker.getInterface().getName() + ", method: " + invocation.getMethodName()
                            + ", exception: " + exception.getClass().getName() + ": " + exception.getMessage(), exception);

                    // directly throw if exception class and interface class are in the same jar file.
                    String serviceFile = ReflectUtils.getCodeBase(invoker.getInterface());
                    String exceptionFile = ReflectUtils.getCodeBase(exception.getClass());
                    if (serviceFile == null || exceptionFile == null || serviceFile.equals(exceptionFile)) {
                        return result;
                    }
                    // directly throw if it's JDK exception
                    String className = exception.getClass().getName();
                    if (className.startsWith("java.") || className.startsWith("javax.")) {
                        return result;
                    }
                    // 在此处指定我们要处理的异常类的包名前缀
                    if (className.startsWith("com.zdk.xx.exception")) {
                        return result;
                    }
                    // directly throw if it's dubbo exception
                    if (exception instanceof RpcException) {
                        return result;
                    }

                    // otherwise, wrap with RuntimeException and throw back to the client
                    return new RpcResult(new RuntimeException(StringUtils.toString(exception)));
                } catch (Throwable e) {
                    logger.warn("Fail to ExceptionFilter when called by " + RpcContext.getContext().getRemoteHost()
                            + ". service: " + invoker.getInterface().getName() + ", method: " + invocation.getMethodName()
                            + ", exception: " + e.getClass().getName() + ": " + e.getMessage(), e);
                    return result;
                }
            }
            return result;
        } catch (RuntimeException e) {
            logger.error("Got unchecked and undeclared exception which called by " + RpcContext.getContext().getRemoteHost()
                    + ". service: " + invoker.getInterface().getName() + ", method: " + invocation.getMethodName()
                    + ", exception: " + e.getClass().getName() + ": " + e.getMessage(), e);
            throw e;
        }
    }
}
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  2. 指定我们要处理的异常类的包名前缀，避免被Dubbo封装为RpcException

    // 在此处指定我们要处理的异常类的包名前缀
if (className.startsWith("com.zdk.xx.exception")) {
    return result;
}
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  3. 在resources目录下添加纯文本文件META-INF/dubbo/com.alibaba.dubbo.rpc.Filter并添加内容

    dubboExceptionFilter=com.dliberty.core.exception.DubboExceptionFilter
    1

    image-20220812173201945

    这里利用的是Dubbo的自定义扩展机制

  4. 修改dubbo 的配置文件，将DubboExceptionFilter加载进去并且去掉自身的ExceptionFilter

    <dubbo:provider filter="dubboExceptionFilter,-exception" ></dubbo:provider>
    1

这样就完成了对业务异常的完美处理了

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#Dubbo
最后更新: 2022/10/04, 8:10:00
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