src/main/java/org/apache/sling/servlets/get/impl/helpers/HeadServletResponse.java

/*
 * 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.helpers;

import java.io.PrintWriter;
import java.io.Writer;

import javax.servlet.ServletOutputStream;
import javax.servlet.WriteListener;

import org.apache.sling.api.SlingHttpServletResponse;
import org.apache.sling.api.wrappers.SlingHttpServletResponseWrapper;

/**
 * The <code>HeadServletResponse</code> is a Sling response wrapper which
 * ensures that nothing will ever be written by return null writers or output
 * streams.
 */

public 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) {
		}

		@Override
		public boolean isReady() {
			return true;
		}

		@Override
		public void setWriteListener(WriteListener writeListener) {
		}
	}

	/**
	 * 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() {
		}
	}
}