/*
* Copyright 2002-2008 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.remoting.RemoteConnectFailureException;
import org.springframework.remoting.RemoteInvocationFailureException;
import org.springframework.remoting.RemoteLookupFailureException;
import org.springframework.remoting.support.RemoteInvocationBasedAccessor;
import org.springframework.remoting.support.RemoteInvocationUtils;
/**
* {@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</code>
* or throw <code>java.rmi.RemoteException</code>. 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".
* <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".
* <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".
* <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 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 #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.
* <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</code>. 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.
* <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 <code>doInvoke</code>.
* 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
*/
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.
* <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.
* <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
*/
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.
* @param invocation the AOP method invocation
* @return the invocation result, if any
* @throws Throwable in case of invocation failure
* @see #invoke
*/
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.
* @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
*/
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 {@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
*/
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
* <code>java.net.URL</code> 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();
}
}
}
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