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Regular Expression Parser Source Code 


package com.architech.parser;

import com.architech.entry.Attribute;
import com.architech.entry.Entry;
import java.io.BufferedWriter;
import java.util.StringTokenizer;
import java.util.Vector;

// import clases from the "gnu.regexp" package for Regular Expressions
import gnu.regexp.RE;
import gnu.regexp.REMatch;


public class rspRegExpParser extends rspParser
{
    private final static String PARAM_REG_EXPR = "regularExpression";
    private final static String PARAM_ATTR_NAMES = "attributeNames";
    private final static String ATTR_NAMES_TOKEN = ";";
    private final static String DEFAULT_ATTR_NAME_PREFIX = "ATTR_NAME_";
    private RE mRegExp;
    private Vector mAttributeNames;
    private Vector mFullAttributeNames;


    // Reads Parser's parameters and creates the regular expression object
    // and the attribute names Vectors.

    public void initParser() throws Exception
    {
        String regExpPattern = getParam(PARAM_REG_EXPR);
        if (regExpPattern == null) {
            regExpPattern = "";
        }
        mRegExp = new RE(regExpPattern);

        mAttributeNames = new Vector();
        String attrNames = getParam(PARAM_ATTR_NAMES);
        if (attrNames != null) {
            StringTokenizer st = new StringTokenizer(attrNames, ATTR_NAMES_TOKEN);
            while (st.hasMoreTokens()) {
                mAttributeNames.add(st.nextToken());
            }
        }

        mFullAttributeNames = (Vector)mAttributeNames.clone();
        int missingAttrNum = mRegExp.getNumSubs() - mFullAttributeNames.size();
        for (int i=0; i<missingAttrNum; i++) {
            mFullAttributeNames.add(DEFAULT_ATTR_NAME_PREFIX + i);
        }
    }


    // Reads a line from the input and parses it against the regular expression
    // If the line matches the regular expression returns an Entry object
    // populated with Attributes matching the subexpressions; otherwise -
    // returns an Entry object with no Attributes.

    public Entry readEntry() throws Exception
    {
        String line = getReader().readLine();
        if (line == null) {
            return null;
        }

        Entry entry = new Entry();
        if (mRegExp.isMatch(line)) {
            REMatch match = mRegExp.getMatch(line);

            for (int i=1; i<=mRegExp.getNumSubs(); i++) {
                String attrValue = match.toString(i);
                entry.addAttributeValue(mFullAttributeNames.elementAt(i-1), attrValue);
            }
        }
        return entry;
    }


    // This method actually iterates the Attributes corresponding to the
    // "mAttributeNames" elements and forms a single string from their values.
    // If the resulting string matches the regular expression it is writen on a
    // single line in the output; otherwise - nothing is written in the output.

    public void writeEntry(Entry entry) throws Exception
    {
        String line = "";
        for (int i=0; i<mAttributeNames.size(); i++) {
            Attribute attr = entry.getAttribute((String)mAttributeNames.elementAt(i));
            if (attr != null) {
                line = line + attr.getValue();
            }
        }

        if (mRegExp.isMatch(line)) {
            BufferedWriter out = getWriter();
            out.write(line);
            out.newLine();
        }
        else {
            debug("Entry (" + line + ") did not match the regular expression.");
        }
    }


    // Returns version information.

    public String getVersion()
    {
        String revision = "$Revision: 1.4 $";
        String date = "$Date: 2001/09/21 11:34:43 $";
        return revision + "\n" + date;
    }

}

 

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