/*
* 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.cocoon.pipeline;
import java.io.OutputStream;
import java.util.LinkedList;
import java.util.ListIterator;
import java.util.Map;
import org.apache.cocoon.pipeline.component.Consumer;
import org.apache.cocoon.pipeline.component.Finisher;
import org.apache.cocoon.pipeline.component.PipelineComponent;
import org.apache.cocoon.pipeline.component.Producer;
import org.apache.cocoon.pipeline.component.Starter;
import org.apache.cocoon.pipeline.util.StringRepresentation;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* Basic pipeline implementation that collects the {@link PipelineComponent}s
* and connects them with each other.
*/
public abstract class AbstractPipeline<T extends PipelineComponent> implements Pipeline<T> {
private final LinkedList<T> components = new LinkedList<T>();
private final Log logger = LogFactory.getLog(this.getClass());
private boolean setupDone;
/**
* {@inheritDoc}
*
* @see org.apache.cocoon.pipeline.Pipeline#addComponent(org.apache.cocoon.pipeline.component.PipelineComponent)
*/
public void addComponent(T pipelineComponent) {
if (this.setupDone) {
throw new SetupException(new IllegalStateException(
"Pass all pipeline components to the pipeline before calling this method."));
}
if (this.logger.isDebugEnabled()) {
this.logger.debug("Adding component " + pipelineComponent + " to pipeline [" + this + "].");
}
this.components.add(pipelineComponent);
}
/**
* {@inheritDoc}
*
* @see org.apache.cocoon.pipeline.Pipeline#execute()
*/
public void execute() throws Exception {
if (!this.setupDone) {
throw new ProcessingException(new IllegalStateException(
"The pipeline wasn't setup correctly. Call #setup() first."));
}
this.invokeStarter();
}
/**
* {@inheritDoc}
*
* @see org.apache.cocoon.pipeline.Pipeline#getContentType()
*/
public String getContentType() {
return this.getFinisher().getContentType();
}
public long getLastModified() {
return -1;
}
/**
* {@inheritDoc}
*
* @see org.apache.cocoon.pipeline.Pipeline#setConfiguration(java.util.Map)
*/
public void setConfiguration(Map<String, ? extends Object> parameters) {
// do nothing
}
/**
* {@inheritDoc}
*
* @see org.apache.cocoon.pipeline.Pipeline#setup(java.io.OutputStream,
* java.util.Map)
*/
public void setup(OutputStream outputStream) {
this.setup(outputStream, null);
}
/**
* {@inheritDoc}
*
* @see org.apache.cocoon.pipeline.Pipeline#setup(java.io.OutputStream,
* java.util.Map)
*/
public void setup(OutputStream outputStream, Map<String, Object> parameters) {
if (outputStream == null) {
throw new SetupException("An output stream must be passed.");
}
this.setupComponents(outputStream, parameters);
this.setupDone = true;
}
@Override
public String toString() {
return StringRepresentation.buildString(this, "components=" + this.getComponents());
}
protected LinkedList<T> getComponents() {
return this.components;
}
protected Finisher getFinisher() {
return (Finisher) this.components.getLast();
}
protected void invokeStarter() {
if (this.logger.isDebugEnabled()) {
this.logger.debug("Invoking first component of " + this);
}
try {
Starter starter = (Starter) this.components.getFirst();
starter.execute();
} finally {
for (PipelineComponent pipelineComponent : this.getComponents()) {
pipelineComponent.finish();
}
}
}
protected void setupComponents(OutputStream outputStream, Map<String, Object> parameters) {
PipelineComponent first = this.components.getFirst();
// first component must be a Starter
if (!(first instanceof Starter)) {
String msg = "Cannot execute pipeline, first pipeline component is no starter";
this.logger.error(msg);
throw new SetupException(new IllegalStateException(msg));
}
// last component must be a Finisher
PipelineComponent last = this.components.getLast();
if (!(last instanceof Finisher)) {
String msg = "Cannot execute pipeline, last pipeline component is no finisher";
this.logger.error(msg);
throw new SetupException(new IllegalStateException(msg));
}
// now try to link the components, always two components at a time
// start at the first component
PipelineComponent currentComponent = first;
first.setup(parameters);
// next component to link is the second in the list
for (ListIterator<T> i = this.components.listIterator(1); i.hasNext();) {
// link the current with the next component
PipelineComponent nextComponent = i.next();
this.linkComponents(currentComponent, nextComponent);
// now advance to the next component
currentComponent = nextComponent;
currentComponent.setup(parameters);
}
// configure the finisher
((Finisher) last).setOutputStream(outputStream);
}
private void linkComponents(PipelineComponent firstComponent, PipelineComponent secondComponent) {
if (this.logger.isDebugEnabled()) {
this.logger.debug("Going to link the component " + firstComponent + " with " + secondComponent + ".");
}
// first component must be a Producer
if (!(firstComponent instanceof Producer)) {
String msg = "Cannot link components: First component (" + firstComponent + ") is no producer.";
throw new SetupException(new IllegalStateException(msg));
}
// second component must be a Consumer
if (!(secondComponent instanceof Consumer)) {
String msg = "Cannot link components: Second component (" + secondComponent + ") is no consumer.";
throw new SetupException(new IllegalStateException(msg));
}
// let the Producer accept the Consumer (the Producer might reject it)
((Producer) firstComponent).setConsumer((Consumer) secondComponent);
}
}