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* 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
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* KIND, either express or implied. See the License for the
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package org.apache.cayenne.access.jdbc;
import java.io.IOException;
import java.io.StringWriter;
import java.io.Writer;
import org.apache.velocity.context.InternalContextAdapter;
import org.apache.velocity.exception.MethodInvocationException;
import org.apache.velocity.exception.ParseErrorException;
import org.apache.velocity.exception.ResourceNotFoundException;
import org.apache.velocity.runtime.directive.Directive;
import org.apache.velocity.runtime.parser.node.ASTDirective;
import org.apache.velocity.runtime.parser.node.Node;
/**
* A custom Velocity directive to conditionally join a number of {@link ChunkDirective chunks}.
* Usage of chain is the following:
*
* <pre>
* #chain(operator) - e.g. #chain(' AND ')
* #chain(operator prefix) - e.g. #chain(' AND ' 'WHERE ')</pre>
*
* <p><code>operator</code> (e.g. AND, OR, etc.) is used to join chunks that are included
* in a chain. <code>prefix</code> is inserted if a chain contains at least one chunk.
* </p>
*
* @since 1.1
* @author Andrei Adamchik
*/
public class ChainDirective extends Directive {
public String getName() {
return "chain";
}
public int getType() {
return BLOCK;
}
public boolean render(InternalContextAdapter context, Writer writer, Node node)
throws
IOException,
ResourceNotFoundException,
ParseErrorException,
MethodInvocationException {
int size = node.jjtGetNumChildren();
if (size == 0) {
return true;
}
// BLOCK is the last child
Node block = node.jjtGetChild(node.jjtGetNumChildren() - 1);
String join = (size > 1) ? (String) node.jjtGetChild(0).value(context) : "";
String prefix = (size > 2) ? (String) node.jjtGetChild(1).value(context) : "";
// if there is a conditional prefix, use a separate buffer ofr children
StringWriter childWriter = new StringWriter(30);
int len = block.jjtGetNumChildren();
int includedChunks = 0;
for (int i = 0; i < len; i++) {
Node child = block.jjtGetChild(i);
// if this is a "chunk", evaluate its expression and prepend join if included...
if (child instanceof ASTDirective
&& "chunk".equals(((ASTDirective) child).getDirectiveName())) {
if (child.jjtGetNumChildren() < 2
|| child.jjtGetChild(0).evaluate(context)) {
if (includedChunks > 0) {
childWriter.write(join);
}
includedChunks++;
}
}
child.render(context, childWriter);
}
if (includedChunks > 0) {
childWriter.flush();
writer.write(prefix);
writer.write(childWriter.toString());
}
return true;
}
}