/*
* Copyright 2011 <a href="mailto:lincolnbaxter@gmail.com">Lincoln Baxter, III</a>
*
* Licensed 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.ocpsoft.rewrite.transform;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;
import org.ocpsoft.common.util.Streams;
import org.ocpsoft.rewrite.servlet.config.response.ResponseContent;
import org.ocpsoft.rewrite.servlet.config.response.ResponseContentInterceptor;
import org.ocpsoft.rewrite.servlet.config.response.ResponseContentInterceptorChain;
import org.ocpsoft.rewrite.servlet.config.response.ResponseStreamWrapper;
import org.ocpsoft.rewrite.servlet.http.event.HttpServletRewrite;
/**
* This pipeline is responsible to apply the registered {@link Transformer} implementations to the intercepted response
* in the expected order.
* <p>
* TODO An alternate implementation should probably be provided that uses a {@link ResponseStreamWrapper}.
* {@link Transformer} implementations would then need to select between stream wrapping or content interception.
*
* @author Christian Kaltepoth
*/
class PipelineContentInterceptor implements ResponseContentInterceptor
{
private List<Transformer> pipeline = new ArrayList<Transformer>();
public void add(Transformer transformer)
{
pipeline.add(transformer);
}
@Override
public void intercept(HttpServletRewrite event, ResponseContent buffer, ResponseContentInterceptorChain chain)
{
try {
ByteArrayOutputStream output = new ByteArrayOutputStream();
transform(event, new ByteArrayInputStream(buffer.getContents()), output);
buffer.setContents(output.toByteArray());
chain.proceed();
}
catch (IOException e) {
throw new IllegalStateException("Failed to apply transformation pipeline", e);
}
}
public void transform(HttpServletRewrite event, InputStream input, OutputStream output) throws IOException
{
// just do a copy if no transformers have been added
if (pipeline.isEmpty()) {
Streams.copy(input, output);
}
// delegate if there is only one transformer
else if (pipeline.size() == 1) {
pipeline.get(0).transform(event, input, output);
}
// multiple transformers
else {
// prepar for the first transformation step
InputStream in = input;
OutputStream out = new ByteArrayOutputStream();
for (int i = 0; i < pipeline.size(); i++) {
// run transformation
pipeline.get(i).transform(event, in, out);
// if it isn't the last transformation step -> prepare next one
if (i < pipeline.size() - 1) {
// prepare input for next iteration
ByteArrayOutputStream lastOutput = (ByteArrayOutputStream) out;
in = new ByteArrayInputStream(lastOutput.toByteArray());
// if the next transform step is the last one, write directly to the output
if (i == pipeline.size() - 2) {
out = output;
}
// other steps write into the last byte array again
else {
lastOutput.reset();
}
}
}
}
}
@Override
public String toString()
{
return "" + pipeline;
}
}