Spring Framework example source code file (JndiRmiClientInterceptor.java)

This example Spring Framework source code file (JndiRmiClientInterceptor.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Spring Framework tags/keywords

corba, could, jndi, naming, namingexception, object, object, reflection, remote, remote, remoteexception, remotelookupfailureexception, remotelookupfailureexception, rmi, rmi, rmiinvocationhandler, throwable

The Spring Framework JndiRmiClientInterceptor.java source code

/*
 * Copyright 2002-2007 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.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.rmi.Remote;
import java.rmi.RemoteException;

import javax.naming.NamingException;
import javax.rmi.PortableRemoteObject;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.omg.CORBA.OBJECT_NOT_EXIST;
import org.omg.CORBA.SystemException;

import org.springframework.aop.support.AopUtils;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.jndi.JndiObjectLocator;
import org.springframework.remoting.RemoteAccessException;
import org.springframework.remoting.RemoteConnectFailureException;
import org.springframework.remoting.RemoteInvocationFailureException;
import org.springframework.remoting.RemoteLookupFailureException;
import org.springframework.remoting.support.DefaultRemoteInvocationFactory;
import org.springframework.remoting.support.RemoteInvocation;
import org.springframework.remoting.support.RemoteInvocationFactory;
import org.springframework.util.ReflectionUtils;

/**
 * {@link org.aopalliance.intercept.MethodInterceptor} for accessing RMI services from JNDI.
 * Typically used for RMI-IIOP (CORBA), but can also be used for EJB home objects
 * (for example, a Stateful Session Bean home). In contrast to a plain JNDI lookup,
 * this accessor also performs narrowing through PortableRemoteObject.
 *
 * <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.
 *
 * <p>The JNDI environment can be specified as "jndiEnvironment" property,
 * or be configured in a <code>jndi.properties file or as system properties.
 * For example:
 *
 * <pre class="code"><property name="jndiEnvironment">
 * 	 <props>
 *		 <prop key="java.naming.factory.initial">com.sun.jndi.cosnaming.CNCtxFactory</prop>
 *		 <prop key="java.naming.provider.url">iiop://localhost:1050</prop>
 *	 </props>
 * </property></pre>
 *
 * @author Juergen Hoeller
 * @since 1.1
 * @see #setJndiTemplate
 * @see #setJndiEnvironment
 * @see #setJndiName
 * @see JndiRmiServiceExporter
 * @see JndiRmiProxyFactoryBean
 * @see org.springframework.remoting.RemoteAccessException
 * @see java.rmi.RemoteException
 * @see java.rmi.Remote
 * @see javax.rmi.PortableRemoteObject#narrow
 */
public class JndiRmiClientInterceptor extends JndiObjectLocator
    implements MethodInterceptor, InitializingBean {

	private Class serviceInterface;

	private RemoteInvocationFactory remoteInvocationFactory = new DefaultRemoteInvocationFactory();

	private boolean lookupStubOnStartup = true;

	private boolean cacheStub = true;

	private boolean refreshStubOnConnectFailure = false;

	private Remote cachedStub;

	private final Object stubMonitor = new Object();


	/**
	 * Set the interface of the service to access.
	 * The interface must be suitable for the particular service and remoting tool.
	 * <p>Typically required to be able to create a suitable service proxy,
	 * but can also be optional if the lookup returns a typed stub.
	 */
	public void setServiceInterface(Class serviceInterface) {
		if (serviceInterface != null && !serviceInterface.isInterface()) {
			throw new IllegalArgumentException("'serviceInterface' must be an interface");
		}
		this.serviceInterface = serviceInterface;
	}

	/**
	 * Return the interface of the service to access.
	 */
	public Class getServiceInterface() {
		return this.serviceInterface;
	}

	/**
	 * Set the RemoteInvocationFactory to use for this accessor.
	 * Default is a {@link DefaultRemoteInvocationFactory}.
	 * <p>A custom invocation factory can add further context information
	 * to the invocation, for example user credentials.
	 */
	public void setRemoteInvocationFactory(RemoteInvocationFactory remoteInvocationFactory) {
		this.remoteInvocationFactory = remoteInvocationFactory;
	}

	/**
	 * Return the RemoteInvocationFactory used by this accessor.
	 */
	public RemoteInvocationFactory getRemoteInvocationFactory() {
		return this.remoteInvocationFactory;
	}

	/**
	 * 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;
	}


	public void afterPropertiesSet() throws NamingException {
		super.afterPropertiesSet();
		prepare();
	}

	/**
	 * Fetches the 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("JNDI RMI object [" + getJndiName() + "] is an RMI invoker");
				}
				else if (getServiceInterface() != null) {
					boolean isImpl = getServiceInterface().isInstance(remoteObj);
					logger.debug("Using service interface [" + getServiceInterface().getName() +
					    "] for JNDI RMI object [" + getJndiName() + "] - " +
					    (!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 retrieves the service from the
	 * JNDI environment. 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 #lookup
	 */
	protected Remote lookupStub() throws RemoteLookupFailureException {
		try {
			Object stub = lookup();
			if (getServiceInterface() != null && Remote.class.isAssignableFrom(getServiceInterface())) {
				try {
					stub = PortableRemoteObject.narrow(stub, getServiceInterface());
				}
				catch (ClassCastException ex) {
					throw new RemoteLookupFailureException(
							"Could not narrow RMI stub to service interface [" + getServiceInterface().getName() + "]", ex);
				}
			}
			if (!(stub instanceof Remote)) {
				throw new RemoteLookupFailureException("Located RMI stub of class [" + stub.getClass().getName() +
						"], with JNDI name [" + getJndiName() + "], does not implement interface [java.rmi.Remote]");
			}
			return (Remote) stub;
		}
		catch (NamingException ex) {
			throw new RemoteLookupFailureException("JNDI lookup for RMI service [" + getJndiName() + "] 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 NamingException if stub creation failed
	 * @throws RemoteLookupFailureException if RMI stub creation failed
	 */
	protected Remote getStub() throws NamingException, 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 {@link #doInvoke}.
	 * If configured to refresh on connect failure, it will call
	 * {@link #refreshAndRetry} on corresponding RMI exceptions.
	 * @see #getStub
	 * @see #doInvoke
	 * @see #refreshAndRetry
	 * @see java.rmi.ConnectException
	 * @see java.rmi.ConnectIOException
	 * @see java.rmi.NoSuchObjectException
	 */
	public Object invoke(MethodInvocation invocation) throws Throwable {
		Remote stub = null;
		try {
			stub = getStub();
		}
		catch (NamingException ex) {
			throw new RemoteLookupFailureException("JNDI lookup for RMI service [" + getJndiName() + "] failed", ex);
		}
		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;
			}
		}
		catch (SystemException 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);
	}

	/**
	 * Determine whether the given CORBA exception indicates a connect failure.
	 * <p>The default implementation checks for CORBA's
	 * {@link org.omg.CORBA.OBJECT_NOT_EXIST} exception.
	 * @param ex the RMI exception to check
	 * @return whether the exception should be treated as connect failure
	 */
	protected boolean isConnectFailure(SystemException ex) {
		return (ex instanceof OBJECT_NOT_EXIST);
	}

	/**
	 * 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 failed too.
	 */
	private Object handleRemoteConnectFailure(MethodInvocation invocation, Exception ex) throws Throwable {
		if (this.refreshStubOnConnectFailure) {
			if (logger.isDebugEnabled()) {
				logger.debug("Could not connect to RMI service [" + getJndiName() + "] - retrying", ex);
			}
			else if (logger.isWarnEnabled()) {
				logger.warn("Could not connect to RMI service [" + getJndiName() + "] - retrying");
			}
			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 convertRmiAccessException(ex, invocation.getMethod());
			}
			catch (SystemException ex) {
				throw convertCorbaAccessException(ex, invocation.getMethod());
			}
			catch (InvocationTargetException ex) {
				throw ex.getTargetException();
			}
			catch (Throwable ex) {
				throw new RemoteInvocationFailureException("Invocation of method [" + invocation.getMethod() +
						"] failed in RMI service [" + getJndiName() + "]", ex);
			}
		}
		else {
			// traditional RMI stub
			try {
				return RmiClientInterceptorUtils.doInvoke(invocation, stub);
			}
			catch (InvocationTargetException ex) {
				Throwable targetEx = ex.getTargetException();
				if (targetEx instanceof RemoteException) {
					throw convertRmiAccessException((RemoteException) targetEx, invocation.getMethod());
				}
				else if (targetEx instanceof SystemException) {
					throw convertCorbaAccessException((SystemException) targetEx, invocation.getMethod());
				}
				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 [" + getJndiName() + "]";
		}

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

	/**
	 * Create a new RemoteInvocation object for the given AOP method invocation.
	 * <p>The default implementation delegates to the configured
	 * {@link #setRemoteInvocationFactory RemoteInvocationFactory}.
	 * This can be overridden in subclasses in order to provide custom RemoteInvocation
	 * subclasses, containing additional invocation parameters (e.g. user credentials).
	 * <p>Note that it is preferable to build a custom RemoteInvocationFactory
	 * as a reusable strategy, instead of overriding this method.
	 * @param methodInvocation the current AOP method invocation
	 * @return the RemoteInvocation object
	 * @see RemoteInvocationFactory#createRemoteInvocation
	 */
	protected RemoteInvocation createRemoteInvocation(MethodInvocation methodInvocation) {
		return getRemoteInvocationFactory().createRemoteInvocation(methodInvocation);
	}

	/**
	 * Convert the given RMI RemoteException that happened during remote access
	 * to Spring's RemoteAccessException if the method signature does not declare
	 * RemoteException. Else, return the original RemoteException.
	 * @param method the invoked method
	 * @param ex the RemoteException that happened
	 * @return the exception to be thrown to the caller
	 */
	private Exception convertRmiAccessException(RemoteException ex, Method method) {
		return RmiClientInterceptorUtils.convertRmiAccessException(method, ex, isConnectFailure(ex), getJndiName());
	}

	/**
	 * Convert the given CORBA SystemException that happened during remote access
	 * to Spring's RemoteAccessException if the method signature does not declare
	 * RemoteException. Else, return the SystemException wrapped in a RemoteException.
	 * @param method the invoked method
	 * @param ex the RemoteException that happened
	 * @return the exception to be thrown to the caller
	 */
	private Exception convertCorbaAccessException(SystemException ex, Method method) {
		if (ReflectionUtils.declaresException(method, RemoteException.class)) {
			// A traditional RMI service: wrap CORBA exceptions in standard RemoteExceptions.
			return new RemoteException("Failed to access CORBA service [" + getJndiName() + "]", ex);
		}
		else {
			if (isConnectFailure(ex)) {
				return new RemoteConnectFailureException("Could not connect to CORBA service [" + getJndiName() + "]", ex);
			}
			else {
				return new RemoteAccessException("Could not access CORBA service [" + getJndiName() + "]", ex);
			}
		}
	}

}