org.apache.hadoop.ipc.RemoteException.java Source code

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Here is the source code for org.apache.hadoop.ipc.RemoteException.java

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/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.ipc;

import java.io.IOException;
import java.lang.reflect.Constructor;

import org.apache.hadoop.ipc.protobuf.RpcHeaderProtos.RpcResponseHeaderProto.RpcErrorCodeProto;
import org.xml.sax.Attributes;

public class RemoteException extends IOException {
    /** this value should not be defined in RpcHeader.proto so that protobuf will return a null */
    private static final int UNSPECIFIED_ERROR = -1;
    /** For java.io.Serializable */
    private static final long serialVersionUID = 1L;
    private final int errorCode;

    private final String className;

    /**
     * @param className wrapped exception, may be null
     * @param msg may be null
     */
    public RemoteException(String className, String msg) {
        this(className, msg, null);
    }

    /**
     * @param className wrapped exception, may be null
     * @param msg may be null
     * @param erCode may be null
     */
    public RemoteException(String className, String msg, RpcErrorCodeProto erCode) {
        super(msg);
        this.className = className;
        if (erCode != null)
            errorCode = erCode.getNumber();
        else
            errorCode = UNSPECIFIED_ERROR;
    }

    /**
     * @return the class name for the wrapped exception; may be null if none was given.
     */
    public String getClassName() {
        return className;
    }

    /**
     * @return may be null if the code was newer than our protobuf definitions or none was given.
     */
    public RpcErrorCodeProto getErrorCode() {
        return RpcErrorCodeProto.valueOf(errorCode);
    }

    /**
     * If this remote exception wraps up one of the lookupTypes
     * then return this exception.
     * <p>
     * Unwraps any IOException.
     * 
     * @param lookupTypes the desired exception class. may be null.
     * @return IOException, which is either the lookupClass exception or this.
     */
    public IOException unwrapRemoteException(Class<?>... lookupTypes) {
        if (lookupTypes == null)
            return this;
        for (Class<?> lookupClass : lookupTypes) {
            if (!lookupClass.getName().equals(getClassName()))
                continue;
            try {
                return instantiateException(lookupClass.asSubclass(IOException.class));
            } catch (Exception e) {
                // cannot instantiate lookupClass, just return this
                return this;
            }
        }
        // wrapped up exception is not in lookupTypes, just return this
        return this;
    }

    /**
     * Instantiate and return the exception wrapped up by this remote exception.
     * 
     * <p> This unwraps any <code>Throwable</code> that has a constructor taking
     * a <code>String</code> as a parameter.
     * Otherwise it returns this.
     * 
     * @return <code>Throwable
     */
    public IOException unwrapRemoteException() {
        try {
            Class<?> realClass = Class.forName(getClassName());
            return instantiateException(realClass.asSubclass(IOException.class));
        } catch (Exception e) {
            // cannot instantiate the original exception, just return this
        }
        return this;
    }

    private IOException instantiateException(Class<? extends IOException> cls) throws Exception {
        Constructor<? extends IOException> cn = cls.getConstructor(String.class);
        cn.setAccessible(true);
        IOException ex = cn.newInstance(this.getMessage());
        ex.initCause(this);
        return ex;
    }

    /**
     * Create RemoteException from attributes
     * @param attrs may not be null
     */
    public static RemoteException valueOf(Attributes attrs) {
        return new RemoteException(attrs.getValue("class"), attrs.getValue("message"));
    }

    @Override
    public String toString() {
        return getClass().getName() + "(" + className + "): " + getMessage();
    }
}