src/java/org/apache/velocity/runtime/parser/node/NodeUtils.java

/*
 * The Apache Software License, Version 1.1
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 * reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
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 * 1. Redistributions of source code must retain the above copyright
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 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
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package org.apache.velocity.runtime.parser.node;

import org.apache.velocity.context.Context;
import org.apache.velocity.context.InternalContextAdapter;
import org.apache.velocity.runtime.parser.*;

/**
 * Utilities for dealing with the AST node structure.
 *
 * @author <a href="mailto:jvanzyl@periapt.com">Jason van Zyl</a>
 * @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
 * @version $Id: NodeUtils.java,v 1.11 2001/03/19 03:01:47 geirm Exp $
 */
public class NodeUtils
{
    /**
     * Collect all the <SPECIAL_TOKEN>s that
     * are carried along with a token. Special
     * tokens do not participate in parsing but
     * can still trigger certain lexical actions.
     * In some cases you may want to retrieve these
     * special tokens, this is simply a way to
     * extract them.
     */
    public static String specialText(Token t)
    {
        String specialText = "";
        
        if (t.specialToken == null || t.specialToken.image.startsWith("##") )
            return specialText;
            
        Token tmp_t = t.specialToken;
        
        while (tmp_t.specialToken != null)
            tmp_t = tmp_t.specialToken;
        
        while (tmp_t != null)
        {
            String st = tmp_t.image;

            StringBuffer sb = new StringBuffer();

            for(int i = 0; i < st.length(); i++)
            {
                char c = st.charAt(i);

                if ( c == '#' || c == '$' )
                    sb.append( c );
            }
            
            // specialText += tmp_t.image;
            specialText += sb.toString();

            tmp_t = tmp_t.next;
        }            

        return specialText;
    }
    
    /**
     * Utility method to interpolate context variables
     * into string literals. So that the following will
     * work:
     *
     * #set $name = "candy"
     * $image.getURI("${name}.jpg")
     *
     * And the string literal argument will
     * be transformed into "candy.jpg" before
     * the method is executed.
     */
    public static String interpolate(String argStr, Context vars)
    {
        StringBuffer argBuf = new StringBuffer();

        for (int cIdx = 0 ; cIdx < argStr.length();)
        {
            char ch = argStr.charAt(cIdx);

            switch (ch)
            {
                case '$':
                    StringBuffer nameBuf = new StringBuffer();
                    for (++cIdx ; cIdx < argStr.length(); ++cIdx)
                    {
                        ch = argStr.charAt(cIdx);
                        if (ch == '_' || ch == '-' || Character.isLetterOrDigit(ch))
                            nameBuf.append(ch);
                        else if (ch == '{' || ch == '}')
                            continue;  
                        else
                            break;
                    }

                    if (nameBuf.length() > 0)
                    {
                        Object value = vars.get(nameBuf.toString());

                        if (value == null)
                            argBuf.append("$").append(nameBuf.toString());
                        else
                            argBuf.append(value.toString());
                    }
                    break;

                default:
                    argBuf.append(ch);
                    ++cIdx;
                    break;
            }
        }

        return argBuf.toString();
    }
}