/*
* 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.sling.launchpad.webapp;
import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.GenericServlet;
import javax.servlet.Servlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.HttpServletResponse;
import org.apache.sling.launchpad.base.shared.Launcher;
import org.apache.sling.launchpad.base.shared.Loader;
import org.apache.sling.launchpad.base.shared.Notifiable;
import org.apache.sling.launchpad.base.shared.SharedConstants;
import org.apache.sling.launchpad.base.shared.Util;
/**
* The <code>SlingServlet</code> is the externally visible Web Application
* launcher for Sling. Please refer to the full description <i>The Sling
* Launchpad</i> on the Sling Wiki for a full description of this class.
* <p>
* Logging goes to ServletContext.log methods.
* <p>
* This class goes into the secondary artifact with the classifier <i>webapp</i>
* to be used as the main servlet to be registered in the servlet container.
*
* @see <a href="http://cwiki.apache.org/SLING/the-sling-launchpad.html">The
* Sling Launchpad</a>
*/
@SuppressWarnings("serial")
public class SlingServlet extends GenericServlet implements Notifiable {
/**
* The number times Sling will be tried to be started before giving up
* (value is 20). This number is chosen deliberately as generally Sling
* should start up smoothly. Whether any bundles within Sling start or not
* is not counted here.
*/
private static final int MAX_START_FAILURES = 20;
/**
* The name of the system property which may be set to define the default
* prefix for the sling.home value generated from the Sling servlet context
* path.
*
* @see #toSlingHome(String)
*/
private static final String SLING_HOME_PREFIX = "sling.home.prefix";
/**
* The default value to be used as the prefix for the sling.home value
* generated from the Sling servlet context path if the
* {@link #SLING_HOME_PREFIX sling.home.prefix} system property is not set.
*
* @see #toSlingHome(String)
*/
private static final String SLING_HOME_PREFIX_DEFAULT = "sling/";
private Map<String, String> properties;
private String slingHome;
private Loader loader;
private Servlet sling;
/**
* Field managed by the {@link #startSling(String)} method to indicate
* whether Sling is in the process of being started.
*/
private Thread startingSling;
/**
* Counter to count the number of failed startups. After this number
* expires, the SlingServlet will not try to start Sling any more.
*/
private int startFailureCounter = 0;
// ---------- GenericServlet
/**
* Launches the SLing framework if the sling.home setting can be derived
* from the configuration or the SerlvetContext. Otherwise Sling is not
* started yet and will be started when the first request comes in.
*/
@Override
public void init() {
this.properties = collectInitParameters();
this.slingHome = getSlingHome(null);
if (this.slingHome != null) {
startSling();
} else {
log("Apache Sling cannot be started yet, because sling.home is not defined yet");
}
log("Servlet " + getServletName() + " initialized");
}
@Override
public String getServletInfo() {
if (sling != null) {
return sling.getServletInfo();
}
return "Sling Launchpad Proxy";
}
/**
* If Sling has already been started, the request is forwarded to the
* started Sling framework. Otherwise the Sling framework is started unless
* there were too many startup failures.
* <p>
* If the request is not forwarded to Sling, this method returns a 404/NOT
* FOUND if the startup failure counter has exceeded or 503/SERVICE
* UNAVAILABLE if the Sling framework is starting up.
* <p>
* If a request causes the framework to start, it is immediately terminated
* with said response status and framework is started in a separate thread.
*/
@Override
public void service(ServletRequest req, ServletResponse res)
throws ServletException, IOException {
// delegate the request to the registered delegatee servlet
Servlet delegatee = sling;
if (delegatee != null) {
// check for problematic application servers like WebSphere
// where path info and servlet path is set wrong SLING-2410
final HttpServletRequest request = (HttpServletRequest) req;
if ( request.getPathInfo() == null && request.getServletPath() != null
&& request.getServletPath().endsWith(".jsp") ) {
req = new HttpServletRequestWrapper(request) {
@Override
public String getPathInfo() {
return request.getServletPath();
}
@Override
public String getServletPath() {
return "";
}
};
}
delegatee.service(req, res);
} else if (startFailureCounter > MAX_START_FAILURES) {
// too many startup retries, fail for ever
((HttpServletResponse) res).sendError(HttpServletResponse.SC_NOT_FOUND);
} else {
startSling(req);
((HttpServletResponse) res).sendError(
HttpServletResponse.SC_SERVICE_UNAVAILABLE,
"Apache Sling is currently starting up, please try again");
}
}
/**
* Stop the Sling framework when the web application is being stopped
*/
@Override
public void destroy() {
if (sling != null) {
sling.destroy();
}
// clear fields
slingHome = null;
loader = null;
sling = null;
}
// ---------- Notifiable interface
/**
* The framework has been stopped by calling the <code>Bundle.stop()</code>
* on the system bundle. This actually terminates the Sling Standalone
* application.
* <p>
* Note, that a new request coming in while the web application is still
* running, will actually cause Sling to restart !
*/
@Override
public void stopped() {
/**
* This method is called if the framework is stopped from within by
* calling stop on the system bundle or if the framework is stopped
* because the VM is going down and the shutdown hook has initated the
* shutdown In any case we ensure the reference to the framework is
* removed and remove the shutdown hook (but don't care if that fails).
*/
log("Apache Sling has been stopped");
// clear the reference to the framework
sling = null;
}
/**
* The framework has been stopped with the intent to be restarted by calling
* either of the <code>Bundle.update</code> methods on the system bundle.
* <p>
* If an <code>InputStream</code> was provided, this has been copied to a
* temporary file, which will be used in place of the existing launcher jar
* file.
*
* @param updateFile The temporary file to replace the existing launcher jar
* file. If <code>null</code> the existing launcher jar will be
* used again.
*/
@Override
public void updated(File updateFile) {
// drop the sling reference to be able to restart
synchronized (this) {
if (startingSling == null) {
sling = null;
}
}
// ensure we have a VM as clean as possible
loader.cleanupVM();
if (updateFile == null) {
log("Restarting Framework and Apache Sling");
startSling((URL) null);
} else {
log("Restarting Framework with update from " + updateFile);
try {
startSling(updateFile.toURI().toURL());
} catch (MalformedURLException mue) {
log("Cannot get URL for file " + updateFile, mue);
} finally {
updateFile.delete();
}
}
}
// --------- internal
/**
* If Sling is not currently starting up, a thread is started to start Sling
* in the background.
*/
private void startSling(final ServletRequest request) {
if (startingSling == null) {
slingHome = getSlingHome((HttpServletRequest) request);
Thread starter = new Thread(new Runnable() {
@Override
public void run() {
startSling();
}
}, "SlingStarter_" + System.currentTimeMillis());
starter.setDaemon(true);
starter.start();
}
}
/**
* Called from the startup thread initiated by a request or from
* {@link #init()} to install the launcher jar and actually start sling.
*/
private void startSling() {
try {
File launchpadHome = getLaunchpadHome(slingHome);
this.loader = new Loader(launchpadHome) {
@Override
protected void info(String msg) {
log(msg);
}
};
} catch (IllegalArgumentException iae) {
startupFailure(null, iae);
return;
}
try {
URL launcherJar = getServletContext().getResource(
SharedConstants.DEFAULT_SLING_LAUNCHER_JAR);
if (launcherJar == null) {
launcherJar = getServletContext().getResource(
"/WEB-INF" + SharedConstants.DEFAULT_SLING_LAUNCHER_JAR);
}
startSling(launcherJar);
} catch (MalformedURLException mue) {
log("Cannot load Apache Sling Launcher JAR "
+ SharedConstants.DEFAULT_SLING_LAUNCHER_JAR, mue);
}
}
/**
* Installs the launcher jar from the given URL (if not <code>null</code>)
* and launches Sling from that launcher.
*/
private void startSling(URL launcherJar) {
synchronized (this) {
if (sling != null) {
log("Apache Sling already started, nothing to do");
return;
} else if (startingSling != null) {
log("Apache Sling being started by Thread " + startingSling);
return;
}
startingSling = Thread.currentThread();
}
if (launcherJar != null) {
try {
log("Checking launcher JAR in " + slingHome);
loader.installLauncherJar(launcherJar);
} catch (IOException ioe) {
startupFailure("Failed installing " + launcherJar, ioe);
return;
}
} else {
log("No Launcher JAR to install");
}
Object object = null;
try {
object = loader.loadLauncher(SharedConstants.DEFAULT_SLING_SERVLET);
} catch (IllegalArgumentException iae) {
startupFailure("Cannot load Launcher Servlet "
+ SharedConstants.DEFAULT_SLING_SERVLET, iae);
return;
}
if (object instanceof Servlet) {
Servlet sling = (Servlet) object;
if (sling instanceof Launcher) {
Launcher slingLauncher = (Launcher) sling;
slingLauncher.setNotifiable(this);
slingLauncher.setCommandLine(properties);
slingLauncher.setSlingHome(slingHome);
}
try {
log("Starting launcher ...");
sling.init(getServletConfig());
this.sling = sling;
this.startFailureCounter = 0;
log("Startup completed");
} catch (ServletException se) {
startupFailure(null, se);
}
}
// reset the starting flag
synchronized (this) {
startingSling = null;
}
}
/**
* Define the sling.home parameter implementing the algorithme defined on
* the wiki page to find the setting according to this algorithm:
* <ol>
* <li>Servlet parameter <code>sling.home</code></li>
* <li>Context <code>sling.home</code></li>
* <li>Derived from ServletContext path</li>
* </ol>
* <p>
* <code>null</code> may be returned by this method if no
* <code>sling.home</code> parameter is set and if the servlet container
* does not provide the Servlet API 2.5
* <code>ServletContext.getContextPath()</code> method and the
* <code>request</code> parameter is <code>null</code>.
* <p>
* If <code>sling.home</code> can be retrieved, it is returned as an
* absolute path.
*
* @param args The command line arguments
* @return The value to use for sling.home or <code>null</code> if the value
* cannot be retrieved.
*/
private String getSlingHome(HttpServletRequest request) {
String source = null;
// access config and context to be able to log the sling.home source
// 1. servlet config parameter
String slingHome = getServletConfig().getInitParameter(
SharedConstants.SLING_HOME);
if (slingHome != null) {
source = "servlet parameter sling.home";
} else {
// 2. servlet context parameter
slingHome = getServletContext().getInitParameter(
SharedConstants.SLING_HOME);
if (slingHome != null) {
source = "servlet context parameter sling.home";
} else {
// 3. servlet context path (Servlet API 2.5 and later)
try {
String contextPath = getServletContext().getContextPath();
slingHome = toSlingHome(contextPath);
source = "servlet context path";
} catch (NoSuchMethodError nsme) {
// 4.servlet context path (Servlet API 2.4 and earlier)
if (request != null) {
String contextPath = request.getContextPath();
slingHome = toSlingHome(contextPath);
source = "servlet context path (from request)";
} else {
log("ServletContext path not available here, delaying startup until first request");
return null;
}
}
}
}
// substitute any ${...} references and make absolute
slingHome = Util.substVars(slingHome, SharedConstants.SLING_HOME, null, properties);
slingHome = new File(slingHome).getAbsolutePath();
log("Setting sling.home=" + slingHome + " (" + source + ")");
return slingHome;
}
/**
* Define the sling.launchpad parameter implementing the algorithme defined
* on the wiki page to find the setting according to this algorithm:
* <ol>
* <li>Servlet init parameter <code>sling.launchpad</code>. This path is
* resolved against the <code>slingHome</code> folder if relative.</li>
* <li>Servlet context init parameter <code>sling.launchpad</code>. This
* path is resolved against the <code>slingHome</code> folder if relative.</li>
* <li>Default to same as <code>sling.home</code></li>
* </ol>
* <p>
* The absolute path of the returned file is stored as the
* <code>sling.launchpad</code> property in the {@link #properties} map.
*
* @param slingHome The absolute path to the Sling Home folder (aka the
* <code>sling.home</code>.
* @return The absolute <code>File</code> indicating the launchpad folder.
*/
private File getLaunchpadHome(final String slingHome) {
String launchpadHomeParam = properties.get(SharedConstants.SLING_LAUNCHPAD);
if (launchpadHomeParam == null || launchpadHomeParam.length() == 0) {
properties.put(SharedConstants.SLING_LAUNCHPAD, slingHome);
return new File(slingHome);
}
File launchpadHome = new File(launchpadHomeParam);
if (!launchpadHome.isAbsolute()) {
launchpadHome = new File(slingHome, launchpadHomeParam);
}
properties.put(SharedConstants.SLING_LAUNCHPAD,
launchpadHome.getAbsolutePath());
return launchpadHome;
}
/**
* Converts the servlet context path to a path used for the sling.home
* property. The servlet context path is converted to a simple name by
* replacing all slash characters in the path with underscores (or a single
* underscore for the root context path being empty or null). Next the
* result is prefixed with either value of the
* <code>sling.home.prefix</code> system property or the (default prefix)
* <code>sling/</code>.
*
* @param contextPath
* @return
*/
private String toSlingHome(String contextPath) {
String prefix = System.getProperty(SLING_HOME_PREFIX,
SLING_HOME_PREFIX_DEFAULT);
if (!prefix.endsWith("/")) {
prefix = prefix.concat("/");
}
if (contextPath == null || contextPath.length() == 0) {
return prefix + "_";
}
return prefix + contextPath.replace('/', '_');
}
private void startupFailure(String message, Throwable cause) {
// ensure message
if (message == null) {
message = "Failed to start Apache Sling in " + slingHome;
}
// unwrap to get the real cause
while (cause.getCause() != null) {
cause = cause.getCause();
}
// log it now and increase the failure counter
log(message, cause);
startFailureCounter++;
// ensure the startingSling fields is not set
synchronized (this) {
startingSling = null;
}
}
// ---------- Property file variable substition support --------------------
private Map<String, String> collectInitParameters() {
HashMap<String, String> props = new HashMap<String, String>();
for (Enumeration<String> keys = getServletContext().getInitParameterNames(); keys.hasMoreElements();) {
String key = keys.nextElement();
props.put(key, getServletContext().getInitParameter(key));
}
for (Enumeration<String> keys = getServletConfig().getInitParameterNames(); keys.hasMoreElements();) {
String key = keys.nextElement();
props.put(key, getServletConfig().getInitParameter(key));
}
return props;
}
}