Dubbo捕获异常，处理异常的机制

dubbo版本2.7.4-release

1.测试代码

1.1 声明接口

public interface DemoService {
    int testException();
}

1.2 接口实现

public class DemoServiceImpl implements DemoService {
    private static final Logger logger = LoggerFactory.getLogger(DemoServiceImpl.class);
    @Override
    public int testException() {
         int a = 1/0;
         return a;
    }

}

1.3 provider启动类

public class Application {
    public static void main(String[] args) throws Exception {
        ServiceConfig<DemoServiceImpl> service = new ServiceConfig<>();
        service.setApplication(new ApplicationConfig("dubbo-demo-api-provider"));
        service.setRegistry(new RegistryConfig("zookeeper://127.0.0.1:2181"));
        service.setInterface(DemoService.class);
        service.setRef(new DemoServiceImpl());
        service.export();
        System.in.read();
    }
}

1.3 consumer测试类

public class Application {
    public static void main(String[] args) throws IOException {
        ReferenceConfig<DemoService> reference = new ReferenceConfig<>();
        reference.setApplication(new ApplicationConfig("dubbo-demo-api-consumer"));
        reference.setRegistry(new RegistryConfig("zookeeper://127.0.0.1:2181"));
        reference.setInterface(DemoService.class);
        reference.setTimeout(100000);
        DemoService service = reference.get();
        int i = service.testException();
        System.out.println(message);
    }
}

1.4 运行1.3结果

2 .反编译代理类,查看异常捕获方式；

org.apache.dubbo.common.bytecode.Wrapper1

package org.apache.dubbo.common.bytecode;

import java.lang.reflect.InvocationTargetException;
import java.util.Map;
import org.apache.dubbo.common.bytecode.ClassGenerator;
import org.apache.dubbo.common.bytecode.NoSuchMethodException;
import org.apache.dubbo.common.bytecode.NoSuchPropertyException;
import org.apache.dubbo.common.bytecode.Wrapper;
import org.apache.dubbo.demo.provider.DemoServiceImpl;

public class Wrapper1
extends Wrapper
implements ClassGenerator.DC {
     .....

    public Object invokeMethod(Object object, String string, Class[] arrclass, Object[] arrobject) throws InvocationTargetException {
        DemoServiceImpl demoServiceImpl;
        try {
            demoServiceImpl = (DemoServiceImpl)object;
        }
        catch (Throwable throwable) {
            throw new IllegalArgumentException(throwable);
        }
        try {
            if ("sayHello".equals(string) && arrclass.length == 1) {
                return demoServiceImpl.sayHello((String)arrobject[0]);
            }
            if ("testException".equals(string) && arrclass.length == 0) {
                return new Integer(demoServiceImpl.testException());
            }
        }
        catch (Throwable throwable) {
        //将java.lang.ArithmeticException异常封装成InvocationTargetException继续往上抛
            throw new InvocationTargetException(throwable);
        }
        throw new NoSuchMethodException(new StringBuffer().append("Not found method \"").append(string).append("\" in class org.apache.dubbo.demo.provider.DemoServiceImpl.").toString());
    }
}

 

3.provider返回包含异常结果

public abstract class AbstractProxyInvoker<T> implements Invoker<T> {
    Logger logger = LoggerFactory.getLogger(AbstractProxyInvoker.class);
    ......
 

    @Override
    public Result invoke(Invocation invocation) throws RpcException {
        try {
            Object value = doInvoke(proxy, invocation.getMethodName(), invocation.getParameterTypes(), invocation.getArguments());
            CompletableFuture<Object> future = wrapWithFuture(value, invocation);
            AsyncRpcResult asyncRpcResult = new AsyncRpcResult(invocation);
            future.whenComplete((obj, t) -> {
                AppResponse result = new AppResponse();
                if (t != null) {
                    if (t instanceof CompletionException) {
                        result.setException(t.getCause());
                    } else {
                        result.setException(t);
                    }
                } else {
                    result.setValue(obj);
                }
                asyncRpcResult.complete(result);
            });
            return asyncRpcResult;
        } catch (InvocationTargetException e) {
            if (RpcContext.getContext().isAsyncStarted() && !RpcContext.getContext().stopAsync()) {
                logger.error("Provider async started, but got an exception from the original method, cannot write the exception back to consumer because an async result may have returned the new thread.", e);
            }
 //异常封装到DefaultAsyncResult，返回给consumer
            return AsyncRpcResult.newDefaultAsyncResult(null, e.getTargetException(), invocation);
        } catch (Throwable e) {
            throw new RpcException("Failed to invoke remote proxy method " + invocation.getMethodName() + " to " + getUrl() + ", cause: " + e.getMessage(), e);
        }
    }

  


}

4.consumer如何处理异常

org.apache.dubbo.rpc.AppResponse#recreate

public class AppResponse extends AbstractResult implements Serializable {
    ........

    @Override
    public Object recreate() throws Throwable {
        if (exception != null) {
            // fix issue#619
            try {
                // get Throwable class
                Class clazz = exception.getClass();
                while (!clazz.getName().equals(Throwable.class.getName())) {
                    clazz = clazz.getSuperclass();
                }
                // get stackTrace value
                Field stackTraceField = clazz.getDeclaredField("stackTrace");
                stackTraceField.setAccessible(true);
                Object stackTrace = stackTraceField.get(exception);
                if (stackTrace == null) {
                    exception.setStackTrace(new StackTraceElement[0]);
                }
            } catch (Exception e) {
                // ignore
            }
//这里抛出服务端返回的异常
            throw exception;
        }
        return result;
    }

}

这里麻烦点的就是如何反编译代理类

可参考这个：

http://dubbo.apache.org/zh-cn/docs/source_code_guide/service-invoking-process.html

2.1节服务调试