lang/java/ipc/src/main/java/org/apache/avro/ipc/specific/SpecificRequestor.java

/**
 * 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.avro.ipc.specific;

import java.io.IOException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Type;
import java.util.Arrays;

import org.apache.avro.AvroRemoteException;
import org.apache.avro.Protocol;
import org.apache.avro.Schema;
import org.apache.avro.AvroRuntimeException;
import org.apache.avro.io.DatumReader;
import org.apache.avro.io.DatumWriter;
import org.apache.avro.io.Decoder;
import org.apache.avro.io.Encoder;
import org.apache.avro.ipc.Transceiver;
import org.apache.avro.ipc.Requestor;
import org.apache.avro.ipc.Callback;
import org.apache.avro.specific.SpecificData;
import org.apache.avro.specific.SpecificDatumReader;
import org.apache.avro.specific.SpecificDatumWriter;

/** {@link org.apache.avro.ipc.Requestor Requestor} for generated interfaces. */
public class SpecificRequestor extends Requestor implements InvocationHandler {
  SpecificData data;

  public SpecificRequestor(Class<?> iface, Transceiver transceiver)
    throws IOException {
    this(iface, transceiver, new SpecificData(iface.getClassLoader()));
  }

  protected SpecificRequestor(Protocol protocol, Transceiver transceiver)
    throws IOException {
    this(protocol, transceiver, SpecificData.get());
  }

  public SpecificRequestor(Class<?> iface, Transceiver transceiver,
                           SpecificData data)
    throws IOException {
    this(data.getProtocol(iface), transceiver, data);
  }

  public SpecificRequestor(Protocol protocol, Transceiver transceiver,
                           SpecificData data)
    throws IOException {
    super(protocol, transceiver);
    this.data = data;
  }

  public SpecificData getSpecificData() { return data; }

  @Override
  public Object invoke(Object proxy, Method method, Object[] args)
    throws Throwable {
    String name = method.getName();
    if (name.equals("hashCode")) {
      return hashCode();
    }
    else if (name.equals("equals")) {
      Object obj = args[0];
      return (proxy == obj) || (obj != null && Proxy.isProxyClass(obj.getClass())
                                && this.equals(Proxy.getInvocationHandler(obj)));
    }
    else if (name.equals("toString")) {
      String protocol = "unknown";
      String remote = "unknown";
      Class<?>[] interfaces = proxy.getClass().getInterfaces();
      if (interfaces.length > 0) {
        try {
          protocol = Class.forName(interfaces[0].getName()).getSimpleName();
        } catch (ClassNotFoundException e) {
        }

        InvocationHandler handler = Proxy.getInvocationHandler(proxy);
        if (handler instanceof Requestor) {
          try {
            remote = ((Requestor) handler).getTransceiver().getRemoteName();
          } catch (IOException e) {
          }
        }
      }
      return "Proxy[" + protocol + "," + remote + "]";
    }
    else {
      try {
        // Check if this is a callback-based RPC:
        Type[] parameterTypes = method.getParameterTypes();
        if ((parameterTypes.length > 0) &&
            (parameterTypes[parameterTypes.length - 1] instanceof Class) &&
            Callback.class.isAssignableFrom(((Class<?>)parameterTypes[parameterTypes.length - 1]))) {
          // Extract the Callback from the end of of the argument list
          Object[] finalArgs = Arrays.copyOf(args, args.length - 1);
          Callback<?> callback = (Callback<?>)args[args.length - 1];
          request(method.getName(), finalArgs, callback);
          return null;
        }
        else {
          return request(method.getName(), args);
        }
      } catch (Exception e) {
        // Check if this is a declared Exception:
        for (Class<?> exceptionClass : method.getExceptionTypes()) {
          if (exceptionClass.isAssignableFrom(e.getClass())) {
            throw e;
          }
        }

        // Next, check for RuntimeExceptions:
        if (e instanceof RuntimeException) {
          throw e;
        }

        // Not an expected Exception, so wrap it in AvroRemoteException:
        throw new AvroRemoteException(e);
      }
    }
  }

  protected DatumWriter<Object> getDatumWriter(Schema schema) {
    return new SpecificDatumWriter<Object>(schema, data);
  }

  @Deprecated                                     // for compatibility in 1.5
  protected DatumReader<Object> getDatumReader(Schema schema) {
    return getDatumReader(schema, schema);
  }

  protected DatumReader<Object> getDatumReader(Schema writer, Schema reader) {
    return new SpecificDatumReader<Object>(writer, reader, data);
  }

  @Override
  public void writeRequest(Schema schema, Object request, Encoder out)
    throws IOException {
    Object[] args = (Object[])request;
    int i = 0;
    for (Schema.Field param : schema.getFields())
      getDatumWriter(param.schema()).write(args[i++], out);
  }

  @Override
  public Object readResponse(Schema writer, Schema reader, Decoder in)
    throws IOException {
    return getDatumReader(writer, reader).read(null, in);
  }

  @Override
  public Exception readError(Schema writer, Schema reader, Decoder in)
    throws IOException {
    Object value = getDatumReader(writer, reader).read(null, in);
    if (value instanceof Exception)
      return (Exception)value;
    return new AvroRuntimeException(value.toString());
  }

  /** Create a proxy instance whose methods invoke RPCs. */
  public static  <T> T getClient(Class<T> iface, Transceiver transciever)
    throws IOException {
    return getClient(iface, transciever,
                     new SpecificData(iface.getClassLoader()));
  }

  /** Create a proxy instance whose methods invoke RPCs. */
  @SuppressWarnings("unchecked")
  public static  <T> T getClient(Class<T> iface, Transceiver transciever,
                                 SpecificData data)
    throws IOException {
    Protocol protocol = data.getProtocol(iface);
    return (T)Proxy.newProxyInstance
      (data.getClassLoader(),
       new Class[] { iface },
       new SpecificRequestor(protocol, transciever, data));
  }

  /** Create a proxy instance whose methods invoke RPCs. */
  @SuppressWarnings("unchecked")
  public static <T> T getClient(Class<T> iface, SpecificRequestor requestor)
    throws IOException {
    return (T)Proxy.newProxyInstance(requestor.data.getClassLoader(),
                                  new Class[] { iface }, requestor);
  }

  /** Return the remote protocol for a proxy. */
  public static Protocol getRemote(Object proxy) throws IOException {
    return ((Requestor)Proxy.getInvocationHandler(proxy)).getRemote();

  }

}