dubbo filter 扩展 以及 重写 dubbo ExceptionFilter

dubbo 自身提供了filter 的扩展，用于入参，出参，规范返回参数 都是非常实用的，本文就以重写dubbo 自身的ExceptionFilter 为例 详细说明 dubbo 的filter功能

我们的项目中很多情况下都会抛出一些自定义异常来替代返回错误码，但是在dubbo服务中往往不能达到理想的效果，因为dubbo 的ExceptionFilter过滤器会将我们的异常信息进行包装，我们重写一下ExceptioFilter 就可以轻松的实现我们的效果

1. 将ExceptionFilter copy 到我们的项目改名为DubboExceptionFilter或者新建一个Filter 继承com.alibaba.dubbo.rpc.Filter

import com.alibaba.dubbo.common.Constants;
import com.alibaba.dubbo.common.extension.Activate;
import com.alibaba.dubbo.common.logger.Logger;
import com.alibaba.dubbo.common.logger.LoggerFactory;
import com.alibaba.dubbo.common.utils.ReflectUtils;
import com.alibaba.dubbo.common.utils.StringUtils;
import com.alibaba.dubbo.rpc.Filter;
import com.alibaba.dubbo.rpc.Invocation;
import com.alibaba.dubbo.rpc.Invoker;
import com.alibaba.dubbo.rpc.Result;
import com.alibaba.dubbo.rpc.RpcContext;
import com.alibaba.dubbo.rpc.RpcException;
import com.alibaba.dubbo.rpc.RpcResult;
import com.alibaba.dubbo.rpc.service.GenericService;

import java.lang.reflect.Method;

@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;
                    }
                    if (className.startsWith("com.dliberty")) {
                        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. 在此处加上一段代码来过滤我们项目中的异常以免被dubbo 重新封装为 RpcException

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
   

image.png

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