EntityFileParser.java

/*
 * Copyright 2006 Wilfred Springer
 *
 * Licensed 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 "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.agilejava.maven.docbkx;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.LineNumberReader;

import org.codehaus.plexus.util.StringInputStream;

/**
 * A crude parser for parsing an entity file. Required to extract the files
 * describing the parameters from the parameter declarations.
 *
 * @author Wilfred Springer
 */
public class EntityFileParser {

    /**
     * Parses the entity file, invoking operations on the visitor for every
     * entity found.
     *
     * @param in
     *            The InputStream to parse.
     * @param visitor
     *            The visitor receiving the events.
     * @throws IOException
     *             The exception thrown when we can't read from the InputStream.
     */
    public static void parse(InputStream in, EntityVisitor visitor)
            throws IOException {
        LineNumberReader reader = new LineNumberReader(
                new InputStreamReader(in));
        String line = null;
        while ((line = reader.readLine()) != null) {
            if (line.indexOf("SYSTEM") > -1) {
                String[] parts = line.split(" ");
                String name = parts[1];
                String systemId = parts[3].substring(1, parts[3].length() - 2);
                visitor.visitSystemEntity(name, systemId);
            }
        }
    }

    /**
     * A simple interface to be implemented by objects traversing the contents
     * of an entity file.
     *
     */
    public interface EntityVisitor {

        /**
         * Invoked whenever the parser encounters a system entity.
         *
         * @param name The name of the entity.
         * @param systemId The system id of the entity.
         */
        void visitSystemEntity(String name, String systemId);

    }

    /**
     * Tests the parser.
     *
     * TODO: Take this out.
     *
     * @param args
     */
    public final static void main(String[] args) {
        StringBuffer builder = new StringBuffer();
        builder.append("<!ENTITY foo SYSTEM \"bar\">\n");
        builder.append("<!ENTITY bar SYSTEM \"foo\">\n");
        StringInputStream in = new StringInputStream(builder.toString());
        try {
            EntityFileParser.parse(in, new EntityVisitor() {

                public void visitSystemEntity(String name, String systemId) {
                    System.out.println("Name: " + name);
                    System.out.println("SystemId: " + systemId);
                }

            });
        } catch (IOException ioe) {
            ioe.printStackTrace();
        }
    }

}