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package org.apache.cayenne.access.jdbc;

import java.io.IOException;
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.Node;

/**
 * A custom Velocity directive to describe a conditional chunk of a {@link ChainDirective chain}.
 * Usage of chunk is the following:
 * 
 * 
 * #chunk()...#end - e.g. #chunk()A = 5#end
 * #chunk(condition)...#end - e.g. #chunk($a)A = $a#end
* *

If condition is evaluated to false, chunk is not included in the chain, * if it is true, chunk is included, and if it is not the first chunk, it is * prefixed with chain join. * * @since 1.1 * @author Andrei Adamchik */ public class ChunkDirective extends Directive { public String getName() { return "chunk"; } public int getType() { return BLOCK; } public boolean render(InternalContextAdapter context, Writer writer, Node node) throws IOException, ResourceNotFoundException, ParseErrorException, MethodInvocationException { // first child is an expression, second is BLOCK if (node.jjtGetNumChildren() > 1 && !node.jjtGetChild(0).evaluate(context)) { // return value is really meaningless in Velocity...whatever return false; } // BLOCK is the last child Node block = node.jjtGetChild(node.jjtGetNumChildren() - 1); block.render(context, writer); return true; } }





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