/*
* 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.servlets.get.impl;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.Writer;
import javax.servlet.RequestDispatcher;
import javax.servlet.Servlet;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.ConfigurationPolicy;
import org.apache.felix.scr.annotations.Properties;
import org.apache.felix.scr.annotations.Property;
import org.apache.felix.scr.annotations.Service;
import org.apache.sling.api.SlingConstants;
import org.apache.sling.api.SlingHttpServletRequest;
import org.apache.sling.api.SlingHttpServletResponse;
import org.apache.sling.api.servlets.SlingSafeMethodsServlet;
import org.apache.sling.api.wrappers.SlingHttpServletRequestWrapper;
import org.apache.sling.api.wrappers.SlingHttpServletResponseWrapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* The <code>DefaultHeadServlet</code> class implements default support for the
* HTTP <i>HEAD</i> request method. It basically wraps the response to provide
* output which does not really write to the client and the forwards to the same
* requested URL (resource actually) acting as if the request was placed with a
* <i>GET</i> method.
*/
@Component(immediate=true, policy=ConfigurationPolicy.IGNORE)
@Service(Servlet.class)
@Properties({
@Property(name="service.description", value="Default HEAD Servlet"),
@Property(name="service.vendor", value="The Apache Software Foundation"),
@Property(name="sling.servlet.resourceTypes", value="sling/servlet/default"),
@Property(name="sling.servlet.prefix", intValue=-1),
@Property(name="sling.servlet.methods", value="HEAD")
})
public class DefaultHeadServlet extends SlingSafeMethodsServlet {
private static final long serialVersionUID = 7416222678552027044L;
/** default log */
private final Logger log = LoggerFactory.getLogger(getClass());
@Override
protected void doHead(SlingHttpServletRequest request,
SlingHttpServletResponse response) throws ServletException,
IOException {
// don't do nothing if the request has already been committed
// or this servlet is called for a servlet include
if (response.isCommitted()) {
// committed response cannot be redirected
log.warn("DefaultHeadServlet: Ignoring request because response is committed");
request.getRequestProgressTracker().log(
"DefaultHeadServlet: Ignoring request because response is committed");
return;
} else if (request.getAttribute(SlingConstants.ATTR_REQUEST_SERVLET) != null) {
// included request will not redirect
log.warn("DefaultHeadServlet: Ignoring request because request is included");
request.getRequestProgressTracker().log(
"DefaultHeadServlet: Ignoring request because request is included");
return;
}
request = new HeadServletRequest(request);
response = new HeadServletResponse(response);
RequestDispatcher dispatcher = request.getRequestDispatcher(request.getResource());
if (dispatcher != null) {
dispatcher.forward(request, response);
}
}
/**
* The <code>HeadServletRequest</code> is a Sling request wrapper which
* simulates a GET request to the included servlets/scripts such that the
* HEAD request acts as if a GET request is being processed without any
* response data being sent back.
*/
private static class HeadServletRequest extends
SlingHttpServletRequestWrapper {
public HeadServletRequest(SlingHttpServletRequest wrappedRequest) {
super(wrappedRequest);
}
@Override
public String getMethod() {
return "GET";
}
}
/**
* The <code>HeadServletResponse</code> is a Sling response wrapper which
* ensures that nothing will ever be written by return null writers or
* output streams.
*/
private static class HeadServletResponse extends
SlingHttpServletResponseWrapper {
private ServletOutputStream stream;
private PrintWriter writer;
public HeadServletResponse(SlingHttpServletResponse wrappedResponse) {
super(wrappedResponse);
}
@Override
public ServletOutputStream getOutputStream() {
if (writer != null) {
throw new IllegalStateException("Writer already obtained");
}
if (stream == null) {
stream = new NullServletOutputStream();
}
return stream;
}
@Override
public PrintWriter getWriter() {
if (stream != null) {
throw new IllegalStateException("OutputStream already obtained");
}
if (writer == null) {
writer = new PrintWriter(new NullWriter());
}
return writer;
}
}
/**
* The <code>NullServletOutputStream</code> is a
* <code>ServletOutputStream</code> which simply does not write out
* anything.
*
* @see HeadServletResponse#getOutputStream()
*/
private static class NullServletOutputStream extends ServletOutputStream {
@Override
public void write(int b) {
}
@Override
public void write(byte[] b) {
}
@Override
public void write(byte[] b, int off, int len) {
}
}
/**
* The <code>NullWriter</code> is a <code>Writer</code> which simply does
* not write out anything.
*
* @see HeadServletResponse#getWriter()
*/
private static class NullWriter extends Writer {
@Override
public void write(char[] cbuf, int off, int len) {
}
@Override
public void write(char[] cbuf) {
}
@Override
public void write(int c) {
}
@Override
public void write(String str) {
}
@Override
public void write(String str, int off, int len) {
}
@Override
public void flush() {
}
@Override
public void close() {
}
}
}