LazyResponseOutputStream.java

/**
 * $Id: LazyResponseOutputStream.java 105077 2012-02-24 22:54:29Z ottenhoff@longsight.com $
 * $URL: https://source.sakaiproject.org/svn/entitybroker/trunk/utils/src/java/org/sakaiproject/entitybroker/util/http/LazyResponseOutputStream.java $
 * LazyOutputStream.java - entity-broker - Aug 15, 2008 7:52:58 PM - azeckoski
 **************************************************************************
 * Copyright (c) 2008, 2009 The Sakai Foundation
 *
 * Licensed under the Educational Community 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.opensource.org/licenses/ECL-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.sakaiproject.entitybroker.util.http;

import java.io.IOException;
import java.io.OutputStream;

import javax.servlet.http.HttpServletResponse;

/**
 * This will get the response to get an outputstream from but will not actually get it from the response
 * until someone attempts to use the outputstream<br/>
 * This is horrible but required because of the way Sakai tool forwarding works<br/>
 * 
 * @author Aaron Zeckoski (azeckoski @ gmail.com)
 */
public class LazyResponseOutputStream extends OutputStream {

    /**
     * the output stream that will be used once it is first called
     */
    private OutputStream stream = null;
    private HttpServletResponse response = null;
    private OutputStream getStream() {
        if (stream == null) {
            try {
                stream = response.getOutputStream();
            } catch (IOException e) {
                throw new RuntimeException("LazyResponseOutputStream failed getting response output stream from HttpServletResponse", e);
            }
        }
        return stream;
    }

    /**
     * @param response the response that will be used to get the outputstream,
     * this will die if someone has tried to get the writer out of this
     */
    public LazyResponseOutputStream(HttpServletResponse response) {
        if (response == null) {
            throw new IllegalArgumentException("response cannot be null");
        }
        this.response = response;
    }
    @Override
    public void write(byte[] b) throws IOException {
        getStream().write(b);
    }
    @Override
    public void write(byte[] b, int off, int len) throws IOException {
        getStream().write(b, off, len);
    }
    @Override
    public void write(int b) throws IOException {
        getStream().write(b);
    }
    @Override
    public void close() throws IOException {
        getStream().close();
    }
    @Override
    public void flush() throws IOException {
        getStream().flush();
    }
    @Override
    public boolean equals(Object obj) {
        if (stream == null) {
            return super.equals(obj);
        } else {
            return getStream().equals(obj);
        }
    }
    @Override
    public int hashCode() {
        if (stream == null) {
            return super.hashCode();
        } else {
            return getStream().hashCode();
        }
    }
    @Override
    public String toString() {
        // make sure the toString does not actually open up the lazy stream
        if (stream == null) {
            return super.toString() + ":LazyStreamNotOpenYet";
        } else {
            return getStream().toString();
        }
    }

}