/*
* Copyright 2014 Attila Szegedi, Daniel Dekany, Jonathan Revusky
*
* 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 freemarker.core;
import java.io.IOException;
import freemarker.template.Template;
import freemarker.template.TemplateDateModel;
import freemarker.template.TemplateException;
/**
* Not yet public; subject to change.
*
* <p>
* Known compatibility risks when using this post-processor:
* <ul>
* <li>{@link TemplateDateModel}-s that care to explicitly check if their nested content is {@code null} might start to
* complain that you have specified a body despite that the directive doesn't support that. Directives should use
* {@link NestedContentNotSupportedException#check(freemarker.template.TemplateDirectiveBody)} instead of a simple
* {@code null}-check to avoid this problem.</li>
* <li>
* Software that uses {@link DirectiveCallPlace#isNestedOutputCacheable()} will always get {@code false}, because
* interruption checks ({@link ThreadInterruptionCheck} elements) are, obviously, not cacheable. This should only
* impact the performance.
* <li>
* Software that investigates the AST will see the injected {@link ThreadInterruptionCheck} elements. As of this
* writing the AST API-s aren't published, also such software need to be able to deal with new kind of elements
* anyway, so this shouldn't be a problem.
* </ul>
*/
class ThreadInterruptionSupportTemplatePostProcessor extends TemplatePostProcessor {
@Override
public void postProcess(Template t) throws TemplatePostProcessorException {
final TemplateElement te = t.getRootTreeNode();
addInterruptionChecks(te);
}
private void addInterruptionChecks(final TemplateElement te) throws TemplatePostProcessorException {
if (te == null) {
return;
}
final TemplateElement nestedBlock = te.getNestedBlock();
// Deepest-first recursion:
if (nestedBlock != null) {
addInterruptionChecks(nestedBlock);
}
final int regulatedChildrenCount = te.getRegulatedChildCount();
for (int i = 0; i < regulatedChildrenCount; i++) {
addInterruptionChecks(te.getRegulatedChild(i));
}
// Because nestedElements (means fixed schema for the children) and nestedBlock (means no fixed schema) are
// mutually exclusive, and we only care about the last kind:
if (te.isNestedBlockRepeater()) {
if (regulatedChildrenCount != 0) {
// Only elements that use nestedBlock instead of regulatedChildren should be block repeaters.
// Note that nestedBlock and nestedElements are (should be) mutually exclusive.
throw new BugException();
}
try {
final ThreadInterruptionCheck interruptedChk = new ThreadInterruptionCheck(te);
if (nestedBlock == null) {
te.setNestedBlock(interruptedChk);
} else {
final MixedContent nestedMixedC;
if (nestedBlock instanceof MixedContent) {
nestedMixedC = (MixedContent) nestedBlock;
} else {
nestedMixedC = new MixedContent();
nestedMixedC.setLocation(te.getUnboundTemplate(), 0, 0, 0, 0);
nestedMixedC.addElement(nestedBlock);
te.setNestedBlock(nestedMixedC);
}
nestedMixedC.addElement(0, interruptedChk);
}
} catch (ParseException e) {
throw new TemplatePostProcessorException("Unexpected error; see cause", e);
}
}
}
/**
* Check if the current thread's "interrupted" flag is set, and throws
* {@link TemplateProcessingThreadInterruptedException} if it is. We inject this to some points in the AST.
*/
static class ThreadInterruptionCheck extends TemplateElement {
private ThreadInterruptionCheck(TemplateElement te) throws ParseException {
setLocation(te.getUnboundTemplate(), te.beginColumn, te.beginLine, te.beginColumn, te.beginLine);
}
@Override
void accept(Environment env) throws TemplateException, IOException {
// As the API doesn't allow throwing InterruptedException here (nor anywhere else, most importantly,
// Template.process can't throw it), we must not clear the "interrupted" flag of the thread.
if (Thread.currentThread().isInterrupted()) {
throw new TemplateProcessingThreadInterruptedException();
}
}
@Override
protected String dump(boolean canonical) {
return canonical ? "" : "<#--" + getNodeTypeSymbol() + "--#>";
}
@Override
String getNodeTypeSymbol() {
return "##threadInterruptionCheck";
}
@Override
int getParameterCount() {
return 0;
}
@Override
Object getParameterValue(int idx) {
throw new IndexOutOfBoundsException();
}
@Override
ParameterRole getParameterRole(int idx) {
throw new IndexOutOfBoundsException();
}
@Override
boolean isNestedBlockRepeater() {
return false;
}
}
/**
* Indicates that the template processing thread's "interrupted" flag was found to be set.
*
* <p>ATTENTION: This is used by https://github.com/kenshoo/freemarker-online. Don't break backward
* compatibility without updating that project too!
*/
static class TemplateProcessingThreadInterruptedException extends RuntimeException {
TemplateProcessingThreadInterruptedException() {
super("Template processing thread \"interrupted\" flag was set.");
}
}
}