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* to you under the Apache License, Version 2.0 (the
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* http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.cayenne.remote.service;
import java.io.ByteArrayOutputStream;
import java.io.PrintWriter;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import org.apache.cayenne.CayenneRuntimeException;
import org.apache.cayenne.DataChannel;
import org.apache.cayenne.access.ClientServerChannel;
import org.apache.cayenne.access.DataDomain;
import org.apache.cayenne.conf.Configuration;
import org.apache.cayenne.conf.DefaultConfiguration;
import org.apache.cayenne.remote.ClientMessage;
import org.apache.cayenne.remote.RemoteService;
import org.apache.cayenne.remote.RemoteSession;
import org.apache.cayenne.util.Util;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* A generic implementation of an RemoteService. Subclasses can be customized to work with
* different remoting mechanisms, such as Hessian or JAXRPC.
*
* @since 1.2
* @author Andrus Adamchik
*/
public abstract class BaseRemoteService implements RemoteService {
public static final String EVENT_BRIDGE_FACTORY_PROPERTY = "cayenne.RemoteService.EventBridge.factory";
// keep logger non-static so that it could be garbage collected with this instance..
private final Log logObj = LogFactory.getLog(BaseRemoteService.class);
protected DataDomain domain;
protected String eventBridgeFactoryName;
protected Map eventBridgeParameters;
public String getEventBridgeFactoryName() {
return eventBridgeFactoryName;
}
public Map getEventBridgeParameters() {
return eventBridgeParameters != null ? Collections
.unmodifiableMap(eventBridgeParameters) : Collections.EMPTY_MAP;
}
/**
* A method that sets up a service, initializing Cayenne stack. Should be invoked by
* subclasses from their appropriate service lifecycle methods.
*/
protected void initService(Map properties) throws CayenneRuntimeException {
// start Cayenne service
logObj.debug(this.getClass().getName() + " is starting");
initCayenneStack(properties);
initEventBridgeParameters(properties);
logObj.debug(getClass().getName() + " started");
}
/**
* Shuts down this service. Should be invoked by subclasses from their appropriate
* service lifecycle methods.
*/
protected void destroyService() {
logObj.debug(getClass().getName() + " destroyed");
}
/**
* Returns a DataChannel that is a parent of all session DataChannels.
*/
public DataChannel getRootChannel() {
return domain;
}
/**
* Creates a new ServerSession with a dedicated DataChannel.
*/
protected abstract ServerSession createServerSession();
/**
* Creates a new ServerSession based on a shared DataChannel.
*
* @param name shared session name used to lookup a shared DataChannel.
*/
protected abstract ServerSession createServerSession(String name);
/**
* Returns a ServerSession object that represents Cayenne-related state associated
* with the current session. If ServerSession hasn't been previously saved, returns
* null.
*/
protected abstract ServerSession getServerSession();
public RemoteSession establishSession() {
logObj.debug("Session requested by client");
RemoteSession session = createServerSession().getSession();
logObj.debug("Established client session: " + session);
return session;
}
public RemoteSession establishSharedSession(String name) {
logObj.debug("Shared session requested by client. Group name: " + name);
if (name == null) {
throw new CayenneRuntimeException("Invalid null shared session name");
}
return createServerSession(name).getSession();
}
public Object processMessage(ClientMessage message) throws Throwable {
if (message == null) {
throw new IllegalArgumentException("Null client message.");
}
ServerSession handler = getServerSession();
if (handler == null) {
throw new MissingSessionException("No session associated with request.");
}
logObj.debug("processMessage, sessionId: " + handler.getSession().getSessionId());
// intercept and log exceptions
try {
return DispatchHelper.dispatch(handler.getChannel(), message);
}
catch (Throwable th) {
th = Util.unwindException(th);
logObj.info("error processing message", th);
// This exception will probably be propagated to the client.
// Recast the exception to a serializable form.
ByteArrayOutputStream causeMessageStream = new ByteArrayOutputStream();
PrintWriter causeMessage = new PrintWriter(causeMessageStream);
String exceptionText = th.getLocalizedMessage();
if (exceptionText != null) {
causeMessage.print(exceptionText);
causeMessage.print(System.getProperty("line.separator"));
}
th.printStackTrace(causeMessage);
Exception cause = new Exception(causeMessageStream.toString());
StringBuffer wrapperMessage = new StringBuffer();
wrapperMessage.append("Exception processing message ")
.append(message.getClass().getName())
.append(" of type ").append(message.toString());
throw new CayenneRuntimeException(wrapperMessage.toString(), cause);
}
}
protected RemoteSession createRemoteSession(
String sessionId,
String name,
boolean enableEvents) {
RemoteSession session = (enableEvents) ? new RemoteSession(
sessionId,
eventBridgeFactoryName,
eventBridgeParameters) : new RemoteSession(sessionId);
session.setName(name);
return session;
}
/**
* Creates a server-side channel that will handle all client requests. For shared
* sessions the same channel instance is reused for the entire group of clients. For
* dedicated sessions, one channel per client is created. <p/> This implementation
* returns {@link ClientServerChannel} instance wrapping a DataContext. Subclasses may
* override the method to customize channel creation. For instance they may wrap
* channel in the custom interceptors to handle transactions or security.
*/
protected DataChannel createChannel() {
return new ClientServerChannel(domain);
}
/**
* Sets up Cayenne stack.
*/
protected void initCayenneStack(Map properties) {
Configuration cayenneConfig = new DefaultConfiguration(
Configuration.DEFAULT_DOMAIN_FILE);
try {
cayenneConfig.initialize();
cayenneConfig.didInitialize();
}
catch (Exception ex) {
throw new CayenneRuntimeException("Error starting Cayenne", ex);
}
// TODO (Andrus 10/15/2005) this assumes that mapping has a single domain...
// do something about multiple domains
this.domain = cayenneConfig.getDomain();
}
/**
* Initializes EventBridge parameters for remote clients peer-to-peer communications.
*/
protected void initEventBridgeParameters(Map properties) {
String eventBridgeFactoryName = (String) properties
.get(BaseRemoteService.EVENT_BRIDGE_FACTORY_PROPERTY);
if (eventBridgeFactoryName != null) {
Map eventBridgeParameters = new HashMap(properties);
eventBridgeParameters.remove(BaseRemoteService.EVENT_BRIDGE_FACTORY_PROPERTY);
this.eventBridgeFactoryName = eventBridgeFactoryName;
this.eventBridgeParameters = eventBridgeParameters;
}
}
}