org.zodiac.template.velocity.impl.VelocityRuntimeInstance Maven / Gradle / Ivy

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package org.zodiac.template.velocity.impl;

import java.io.Reader;

import org.apache.velocity.Template;
import org.apache.velocity.runtime.RuntimeInstance;
import org.apache.velocity.runtime.parser.ParseException;
import org.apache.velocity.runtime.parser.node.ASTStringLiteral;
import org.apache.velocity.runtime.parser.node.Node;
import org.apache.velocity.runtime.parser.node.SimpleNode;
import org.zodiac.template.velocity.impl.parser.ASTStringLiteralEnhanced;
import org.zodiac.template.velocity.impl.parser.SimpleNodeUtil;

/**
 * 扩展了velocity的RuntimeInstance类，实现一个功能，使 ReferenceInsertionEventHandler可以感知被拦截的引用是否位于
 * StringLiteral中。 例如：
 * 
 * EscapeSupport可以根据引用的位置，来决定是否要对结果进行escape转义。下面的velocity语句将不会被转义：
 * 
 * 
 *  * #set ($value = "hello, $name")
 * 
 * 
 * 通过调用InterpolationUtil.isInInterpolation(context)即可知晓此细节。
 * 
 * 
 * 通过velocity configuration： runtime.interpolate.string.literals.hack可以开关此特性，默认值为 true。
 * 
 *
 */
public class VelocityRuntimeInstance extends RuntimeInstance {

    private static final String INTERPOLATION_HACK_KEY = "runtime.interpolate.string.literals.hack";
    private static final Boolean INTERPOLATION_HACK_DEFAULT = true;

    private boolean interpolationHack;

    public VelocityRuntimeInstance() {
        super();
    }

    @Override
    public synchronized void init() {
        super.init();
        interpolationHack = getConfiguration().getBoolean(INTERPOLATION_HACK_KEY, INTERPOLATION_HACK_DEFAULT);
    }

    @Override
    public SimpleNode parse(Reader reader, Template template) throws ParseException {
        SimpleNode node = super.parse(reader, template);
        if (interpolationHack) {
            node = traversNode(node);
        }
        return node;
    }

    private SimpleNode traversNode(SimpleNode node) {
        int length = node.jjtGetNumChildren();
        for (int i = 0; i < length; i++) {
            Node child = node.jjtGetChild(i);

            if (child instanceof ASTStringLiteral) {
                replaceStringLiteral(node, (ASTStringLiteral)child, i);
            }

            if (child instanceof SimpleNode) {
                traversNode((SimpleNode)child);
            }
        }
        return node;
    }

    private void replaceStringLiteral(SimpleNode parent, ASTStringLiteral strLit, int index) {
        if (!(strLit instanceof ASTStringLiteralEnhanced)) {
            SimpleNodeUtil.jjtSetChild(parent, new ASTStringLiteralEnhanced(strLit), index);
        }
    }

}