TwelveMonkeys/twelvemonkeys-servlet/src/main/java/com/twelvemonkeys/servlet/ServletResponseStreamDelegate.java

/*
 * Copyright (c) 2008, Harald Kuhr
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name "TwelveMonkeys" nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package com.twelvemonkeys.servlet;

import javax.servlet.ServletOutputStream;
import javax.servlet.ServletResponse;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.OutputStream;

/**
 * A delegate for handling stream support in wrapped servlet responses.
 *
 * @author <a href="mailto:harald.kuhr@gmail.com">Harald Kuhr</a>
 * @author last modified by $Author: haku $
 * @version $Id: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-servlet/src/main/java/com/twelvemonkeys/servlet/ServletResponseStreamDelegate.java#2 $
 */
public class ServletResponseStreamDelegate {
    private Object mOut = null;
    protected final ServletResponse mResponse;

    public ServletResponseStreamDelegate(ServletResponse pResponse) {
        if (pResponse == null) {
            throw new IllegalArgumentException("response == null");
        }
        mResponse = pResponse;
    }

    // NOTE: Intentionally NOT threadsafe, as one request/response should be
    // handled by one thread ONLY.
    public final ServletOutputStream getOutputStream() throws IOException {
        if (mOut == null) {
            OutputStream out = createOutputStream();
            mOut = out instanceof ServletOutputStream ? out : new OutputStreamAdapter(out);
        }
        else if (mOut instanceof PrintWriter) {
            throw new IllegalStateException("getWriter() allready called.");
        }

        return (ServletOutputStream) mOut;
    }

    // NOTE: Intentionally NOT threadsafe, as one request/response should be
    // handled by one thread ONLY.
    public final PrintWriter getWriter() throws IOException {
        if (mOut == null) {
            // NOTE: getCharacterEncoding may should not return null
            OutputStream out = createOutputStream();
            String charEncoding = mResponse.getCharacterEncoding();
            mOut = new PrintWriter(charEncoding != null ? new OutputStreamWriter(out, charEncoding) : new OutputStreamWriter(out));
        }
        else if (mOut instanceof ServletOutputStream) {
            throw new IllegalStateException("getOutputStream() allready called.");
        }

        return (PrintWriter) mOut;
    }

    /**
     * Returns the {@code OutputStream}.
     * Override this method to provide a decoreated outputstream.
     * This method is guaranteed to be invoked only once for a request/response.
     * <P/>
     * This implementation simply returns the output stream from the wrapped
     * response.
     *
     * @return the {@code OutputStream} to use for the response
     * @throws IOException if an I/O exception occurs
     */
    protected OutputStream createOutputStream() throws IOException {
        return mResponse.getOutputStream();
    }

    public void flushBuffer() throws IOException {
        if (mOut instanceof ServletOutputStream) {
            ((ServletOutputStream) mOut).flush();
        }
        else if (mOut != null) {
            ((PrintWriter) mOut).flush();
        }
    }

    public void resetBuffer() {
        // TODO: Is this okay? Probably not... :-)
        mOut = null;
    }
}