https://github.com/spring-projects/spring-framework: Spring Context (Spring IO)
  • Juergen Hoeller 
/*
 * Copyright 2002-2012 the original author or authors.
 *
 * Licensed 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.springframework.remoting.rmi;

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLStreamHandler;
import java.rmi.Naming;
import java.rmi.NotBoundException;
import java.rmi.Remote;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.rmi.server.RMIClientSocketFactory;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;

import org.springframework.aop.support.AopUtils;
import org.springframework.lang.Nullable;
import org.springframework.remoting.RemoteConnectFailureException;
import org.springframework.remoting.RemoteInvocationFailureException;
import org.springframework.remoting.RemoteLookupFailureException;
import org.springframework.remoting.support.RemoteInvocationBasedAccessor;
import org.springframework.remoting.support.RemoteInvocationUtils;


MethodInterceptor for accessing conventional RMI services or RMI invokers. The service URL must be a valid RMI URL (e.g. "rmi://localhost:1099/myservice"). 
RMI invokers work at the RmiInvocationHandler level, needing only one stub for any service. Service interfaces do not have to extend java.rmi.Remote or throw java.rmi.RemoteException. Spring's unchecked RemoteAccessException will be thrown on remote invocation failure. Of course, in and out parameters have to be serializable. 
With conventional RMI services, this invoker is typically used with the RMI
service interface. Alternatively, this invoker can also proxy a remote RMI service
with a matching non-RMI business interface, i.e. an interface that mirrors the RMI
service methods but does not declare RemoteExceptions. In the latter case,
RemoteExceptions thrown by the RMI stub will automatically get converted to
Spring's unchecked RemoteAccessException.

Author:Juergen Hoeller
See Also:
Since:29.09.2003
/**
 * {@link org.aopalliance.intercept.MethodInterceptor} for accessing conventional
 * RMI services or RMI invokers. The service URL must be a valid RMI URL
 * (e.g. "rmi://localhost:1099/myservice").
 *
 * <p>RMI invokers work at the RmiInvocationHandler level, needing only one stub for
 * any service. Service interfaces do not have to extend {@code java.rmi.Remote}
 * or throw {@code java.rmi.RemoteException}. Spring's unchecked
 * RemoteAccessException will be thrown on remote invocation failure.
 * Of course, in and out parameters have to be serializable.
 *
 * <p>With conventional RMI services, this invoker is typically used with the RMI
 * service interface. Alternatively, this invoker can also proxy a remote RMI service
 * with a matching non-RMI business interface, i.e. an interface that mirrors the RMI
 * service methods but does not declare RemoteExceptions. In the latter case,
 * RemoteExceptions thrown by the RMI stub will automatically get converted to
 * Spring's unchecked RemoteAccessException.
 *
 * @author Juergen Hoeller
 * @since 29.09.2003
 * @see RmiServiceExporter
 * @see RmiProxyFactoryBean
 * @see RmiInvocationHandler
 * @see org.springframework.remoting.RemoteAccessException
 * @see java.rmi.RemoteException
 * @see java.rmi.Remote
 */
public class RmiClientInterceptor extends RemoteInvocationBasedAccessor
		implements MethodInterceptor {

	private boolean lookupStubOnStartup = true;

	private boolean cacheStub = true;

	private boolean refreshStubOnConnectFailure = false;

	private RMIClientSocketFactory registryClientSocketFactory;

	private Remote cachedStub;

	private final Object stubMonitor = new Object();


	
Set whether to look up the RMI stub on startup. Default is "true".

Can be turned off to allow for late start of the RMI server.
In this case, the RMI stub will be fetched on first access.

See Also:
  • setCacheStub
/**
	 * Set whether to look up the RMI stub on startup. Default is "true".
	 * <p>Can be turned off to allow for late start of the RMI server.
	 * In this case, the RMI stub will be fetched on first access.
	 * @see #setCacheStub
	 */
	public void setLookupStubOnStartup(boolean lookupStubOnStartup) {
		this.lookupStubOnStartup = lookupStubOnStartup;
	}

	
Set whether to cache the RMI stub once it has been located.
Default is "true".

Can be turned off to allow for hot restart of the RMI server.
In this case, the RMI stub will be fetched for each invocation.

See Also:
  • setLookupStubOnStartup
/**
	 * Set whether to cache the RMI stub once it has been located.
	 * Default is "true".
	 * <p>Can be turned off to allow for hot restart of the RMI server.
	 * In this case, the RMI stub will be fetched for each invocation.
	 * @see #setLookupStubOnStartup
	 */
	public void setCacheStub(boolean cacheStub) {
		this.cacheStub = cacheStub;
	}

	
Set whether to refresh the RMI stub on connect failure.
Default is "false".

Can be turned on to allow for hot restart of the RMI server.
If a cached RMI stub throws an RMI exception that indicates a
remote connect failure, a fresh proxy will be fetched and the
invocation will be retried.

See Also:
/**
	 * Set whether to refresh the RMI stub on connect failure.
	 * Default is "false".
	 * <p>Can be turned on to allow for hot restart of the RMI server.
	 * If a cached RMI stub throws an RMI exception that indicates a
	 * remote connect failure, a fresh proxy will be fetched and the
	 * invocation will be retried.
	 * @see java.rmi.ConnectException
	 * @see java.rmi.ConnectIOException
	 * @see java.rmi.NoSuchObjectException
	 */
	public void setRefreshStubOnConnectFailure(boolean refreshStubOnConnectFailure) {
		this.refreshStubOnConnectFailure = refreshStubOnConnectFailure;
	}

	
Set a custom RMI client socket factory to use for accessing the RMI registry.

See Also:
/**
	 * Set a custom RMI client socket factory to use for accessing the RMI registry.
	 * @see java.rmi.server.RMIClientSocketFactory
	 * @see java.rmi.registry.LocateRegistry#getRegistry(String, int, RMIClientSocketFactory)
	 */
	public void setRegistryClientSocketFactory(RMIClientSocketFactory registryClientSocketFactory) {
		this.registryClientSocketFactory = registryClientSocketFactory;
	}


	@Override
	public void afterPropertiesSet() {
		super.afterPropertiesSet();
		prepare();
	}

	
Fetches RMI stub on startup, if necessary.

Throws:
  • RemoteLookupFailureException – if RMI stub creation failed
See Also:
/**
	 * Fetches RMI stub on startup, if necessary.
	 * @throws RemoteLookupFailureException if RMI stub creation failed
	 * @see #setLookupStubOnStartup
	 * @see #lookupStub
	 */
	public void prepare() throws RemoteLookupFailureException {
		// Cache RMI stub on initialization?
		if (this.lookupStubOnStartup) {
			Remote remoteObj = lookupStub();
			if (logger.isDebugEnabled()) {
				if (remoteObj instanceof RmiInvocationHandler) {
					logger.debug("RMI stub [" + getServiceUrl() + "] is an RMI invoker");
				}
				else if (getServiceInterface() != null) {
					boolean isImpl = getServiceInterface().isInstance(remoteObj);
					logger.debug("Using service interface [" + getServiceInterface().getName() +
						"] for RMI stub [" + getServiceUrl() + "] - " +
						(!isImpl ? "not " : "") + "directly implemented");
				}
			}
			if (this.cacheStub) {
				this.cachedStub = remoteObj;
			}
		}
	}

	
Create the RMI stub, typically by looking it up.

Called on interceptor initialization if "cacheStub" is "true"; else called for each invocation by getStub(). 
The default implementation looks up the service URL via java.rmi.Naming. This can be overridden in subclasses. 
Throws:
See Also:
Returns:the RMI stub to store in this interceptor
/**
	 * Create the RMI stub, typically by looking it up.
	 * <p>Called on interceptor initialization if "cacheStub" is "true";
	 * else called for each invocation by {@link #getStub()}.
	 * <p>The default implementation looks up the service URL via
	 * {@code java.rmi.Naming}. This can be overridden in subclasses.
	 * @return the RMI stub to store in this interceptor
	 * @throws RemoteLookupFailureException if RMI stub creation failed
	 * @see #setCacheStub
	 * @see java.rmi.Naming#lookup
	 */
	protected Remote lookupStub() throws RemoteLookupFailureException {
		try {
			Remote stub = null;
			if (this.registryClientSocketFactory != null) {
				// RMIClientSocketFactory specified for registry access.
				// Unfortunately, due to RMI API limitations, this means
				// that we need to parse the RMI URL ourselves and perform
				// straight LocateRegistry.getRegistry/Registry.lookup calls.
				URL url = new URL(null, getServiceUrl(), new DummyURLStreamHandler());
				String protocol = url.getProtocol();
				if (protocol != null && !"rmi".equals(protocol)) {
					throw new MalformedURLException("Invalid URL scheme '" + protocol + "'");
				}
				String host = url.getHost();
				int port = url.getPort();
				String name = url.getPath();
				if (name != null && name.startsWith("/")) {
					name = name.substring(1);
				}
				Registry registry = LocateRegistry.getRegistry(host, port, this.registryClientSocketFactory);
				stub = registry.lookup(name);
			}
			else {
				// Can proceed with standard RMI lookup API...
				stub = Naming.lookup(getServiceUrl());
			}
			if (logger.isDebugEnabled()) {
				logger.debug("Located RMI stub with URL [" + getServiceUrl() + "]");
			}
			return stub;
		}
		catch (MalformedURLException ex) {
			throw new RemoteLookupFailureException("Service URL [" + getServiceUrl() + "] is invalid", ex);
		}
		catch (NotBoundException ex) {
			throw new RemoteLookupFailureException(
					"Could not find RMI service [" + getServiceUrl() + "] in RMI registry", ex);
		}
		catch (RemoteException ex) {
			throw new RemoteLookupFailureException("Lookup of RMI stub failed", ex);
		}
	}

	
Return the RMI stub to use. Called for each invocation.

The default implementation returns the stub created on initialization, if any. Else, it invokes lookupStub to get a new stub for each invocation. This can be overridden in subclasses, for example in order to cache a stub for a given amount of time before recreating it, or to test the stub whether it is still alive. 
Throws:
See Also:
Returns:the RMI stub to use for an invocation
/**
	 * Return the RMI stub to use. Called for each invocation.
	 * <p>The default implementation returns the stub created on initialization,
	 * if any. Else, it invokes {@link #lookupStub} to get a new stub for
	 * each invocation. This can be overridden in subclasses, for example in
	 * order to cache a stub for a given amount of time before recreating it,
	 * or to test the stub whether it is still alive.
	 * @return the RMI stub to use for an invocation
	 * @throws RemoteLookupFailureException if RMI stub creation failed
	 * @see #lookupStub
	 */
	protected Remote getStub() throws RemoteLookupFailureException {
		if (!this.cacheStub || (this.lookupStubOnStartup && !this.refreshStubOnConnectFailure)) {
			return (this.cachedStub != null ? this.cachedStub : lookupStub());
		}
		else {
			synchronized (this.stubMonitor) {
				if (this.cachedStub == null) {
					this.cachedStub = lookupStub();
				}
				return this.cachedStub;
			}
		}
	}


	
Fetches an RMI stub and delegates to doInvoke. If configured to refresh on connect failure, it will call refreshAndRetry on corresponding RMI exceptions. 
See Also:
/**
	 * Fetches an RMI stub and delegates to {@code doInvoke}.
	 * If configured to refresh on connect failure, it will call
	 * {@link #refreshAndRetry} on corresponding RMI exceptions.
	 * @see #getStub
	 * @see #doInvoke(MethodInvocation, Remote)
	 * @see #refreshAndRetry
	 * @see java.rmi.ConnectException
	 * @see java.rmi.ConnectIOException
	 * @see java.rmi.NoSuchObjectException
	 */
	@Override
	public Object invoke(MethodInvocation invocation) throws Throwable {
		Remote stub = getStub();
		try {
			return doInvoke(invocation, stub);
		}
		catch (RemoteConnectFailureException ex) {
			return handleRemoteConnectFailure(invocation, ex);
		}
		catch (RemoteException ex) {
			if (isConnectFailure(ex)) {
				return handleRemoteConnectFailure(invocation, ex);
			}
			else {
				throw ex;
			}
		}
	}

	
Determine whether the given RMI exception indicates a connect failure.

The default implementation delegates to RmiClientInterceptorUtils.isConnectFailure. 
Params:
  • ex – the RMI exception to check
Returns:whether the exception should be treated as connect failure
/**
	 * Determine whether the given RMI exception indicates a connect failure.
	 * <p>The default implementation delegates to
	 * {@link RmiClientInterceptorUtils#isConnectFailure}.
	 * @param ex the RMI exception to check
	 * @return whether the exception should be treated as connect failure
	 */
	protected boolean isConnectFailure(RemoteException ex) {
		return RmiClientInterceptorUtils.isConnectFailure(ex);
	}

	
Refresh the stub and retry the remote invocation if necessary.

If not configured to refresh on connect failure, this method
simply rethrows the original exception.

Params:
  • invocation – the invocation that failed
  • ex – the exception raised on remote invocation
Throws:
  • Throwable – an exception raised by the new invocation,
if it failed as well
See Also:
Returns:the result value of the new invocation, if succeeded
/**
	 * Refresh the stub and retry the remote invocation if necessary.
	 * <p>If not configured to refresh on connect failure, this method
	 * simply rethrows the original exception.
	 * @param invocation the invocation that failed
	 * @param ex the exception raised on remote invocation
	 * @return the result value of the new invocation, if succeeded
	 * @throws Throwable an exception raised by the new invocation,
	 * if it failed as well
	 * @see #setRefreshStubOnConnectFailure
	 * @see #doInvoke
	 */
	@Nullable
	private Object handleRemoteConnectFailure(MethodInvocation invocation, Exception ex) throws Throwable {
		if (this.refreshStubOnConnectFailure) {
			String msg = "Could not connect to RMI service [" + getServiceUrl() + "] - retrying";
			if (logger.isDebugEnabled()) {
				logger.warn(msg, ex);
			}
			else if (logger.isWarnEnabled()) {
				logger.warn(msg);
			}
			return refreshAndRetry(invocation);
		}
		else {
			throw ex;
		}
	}

	
Refresh the RMI stub and retry the given invocation.
Called by invoke on connect failure.

Params:
  • invocation – the AOP method invocation
Throws:
See Also:
Returns:the invocation result, if any
/**
	 * Refresh the RMI stub and retry the given invocation.
	 * Called by invoke on connect failure.
	 * @param invocation the AOP method invocation
	 * @return the invocation result, if any
	 * @throws Throwable in case of invocation failure
	 * @see #invoke
	 */
	@Nullable
	protected Object refreshAndRetry(MethodInvocation invocation) throws Throwable {
		Remote freshStub = null;
		synchronized (this.stubMonitor) {
			this.cachedStub = null;
			freshStub = lookupStub();
			if (this.cacheStub) {
				this.cachedStub = freshStub;
			}
		}
		return doInvoke(invocation, freshStub);
	}

	
Perform the given invocation on the given RMI stub.

Params:
  • invocation – the AOP method invocation
  • stub – the RMI stub to invoke
Throws:
Returns:the invocation result, if any
/**
	 * Perform the given invocation on the given RMI stub.
	 * @param invocation the AOP method invocation
	 * @param stub the RMI stub to invoke
	 * @return the invocation result, if any
	 * @throws Throwable in case of invocation failure
	 */
	@Nullable
	protected Object doInvoke(MethodInvocation invocation, Remote stub) throws Throwable {
		if (stub instanceof RmiInvocationHandler) {
			// RMI invoker
			try {
				return doInvoke(invocation, (RmiInvocationHandler) stub);
			}
			catch (RemoteException ex) {
				throw RmiClientInterceptorUtils.convertRmiAccessException(
					invocation.getMethod(), ex, isConnectFailure(ex), getServiceUrl());
			}
			catch (InvocationTargetException ex) {
				Throwable exToThrow = ex.getTargetException();
				RemoteInvocationUtils.fillInClientStackTraceIfPossible(exToThrow);
				throw exToThrow;
			}
			catch (Throwable ex) {
				throw new RemoteInvocationFailureException("Invocation of method [" + invocation.getMethod() +
						"] failed in RMI service [" + getServiceUrl() + "]", ex);
			}
		}
		else {
			// traditional RMI stub
			try {
				return RmiClientInterceptorUtils.invokeRemoteMethod(invocation, stub);
			}
			catch (InvocationTargetException ex) {
				Throwable targetEx = ex.getTargetException();
				if (targetEx instanceof RemoteException) {
					RemoteException rex = (RemoteException) targetEx;
					throw RmiClientInterceptorUtils.convertRmiAccessException(
							invocation.getMethod(), rex, isConnectFailure(rex), getServiceUrl());
				}
				else {
					throw targetEx;
				}
			}
		}
	}

	
Apply the given AOP method invocation to the given RmiInvocationHandler. 
The default implementation delegates to RemoteInvocationBasedAccessor.createRemoteInvocation. 
Params:
  • methodInvocation – the current AOP method invocation
  • invocationHandler – the RmiInvocationHandler to apply the invocation to
Throws:
See Also:
Returns:the invocation result
/**
	 * Apply the given AOP method invocation to the given {@link RmiInvocationHandler}.
	 * <p>The default implementation delegates to {@link #createRemoteInvocation}.
	 * @param methodInvocation the current AOP method invocation
	 * @param invocationHandler the RmiInvocationHandler to apply the invocation to
	 * @return the invocation result
	 * @throws RemoteException in case of communication errors
	 * @throws NoSuchMethodException if the method name could not be resolved
	 * @throws IllegalAccessException if the method could not be accessed
	 * @throws InvocationTargetException if the method invocation resulted in an exception
	 * @see org.springframework.remoting.support.RemoteInvocation
	 */
	@Nullable
	protected Object doInvoke(MethodInvocation methodInvocation, RmiInvocationHandler invocationHandler)
		throws RemoteException, NoSuchMethodException, IllegalAccessException, InvocationTargetException {

		if (AopUtils.isToStringMethod(methodInvocation.getMethod())) {
			return "RMI invoker proxy for service URL [" + getServiceUrl() + "]";
		}

		return invocationHandler.invoke(createRemoteInvocation(methodInvocation));
	}


	
Dummy URLStreamHandler that's just specified to suppress the standard java.net.URL URLStreamHandler lookup, to be able to use the standard URL class for parsing "rmi:..." URLs. 
/**
	 * Dummy URLStreamHandler that's just specified to suppress the standard
	 * {@code java.net.URL} URLStreamHandler lookup, to be able to
	 * use the standard URL class for parsing "rmi:..." URLs.
	 */
	private static class DummyURLStreamHandler extends URLStreamHandler {

		@Override
		protected URLConnection openConnection(URL url) throws IOException {
			throw new UnsupportedOperationException();
		}
	}

}