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Groovy example source code file (AbstractReaderSource.java)

This example Groovy source code file (AbstractReaderSource.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Groovy tags/keywords

abstractreadersource, bufferedreader, bufferedreader, compiler, compilerconfiguration, exception, exception, illegalargumentexception, io, ioexception, readersource, string, string, the, the

The Groovy AbstractReaderSource.java source code

/*
 * Copyright 2003-2007 the original author or authors.
 *
 * 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 org.codehaus.groovy.control.io;

import java.io.BufferedReader;
import java.io.IOException;

import org.codehaus.groovy.control.CompilerConfiguration;
import org.codehaus.groovy.control.Janitor;

/**
 * For ReaderSources that can choose a parent class, a base that
 * provides common functionality.
 *
 * @author <a href="mailto:cpoirier@dreaming.org">Chris Poirier
 * @version $Id: AbstractReaderSource.java 16798 2009-06-28 02:13:41Z hamletdrc $
 */

public abstract class AbstractReaderSource implements ReaderSource {
    protected CompilerConfiguration configuration;   // Configuration data

    public AbstractReaderSource(CompilerConfiguration configuration) {
        if (configuration == null) {
            throw new IllegalArgumentException("Compiler configuration must not be null!");
            // ... or more relaxed?
            // configuration = CompilerConfiguration.DEFAULT;
        }
        this.configuration = configuration;
    }

    /**
     * Returns true if the source can be restarted (ie. if getReader()
     * will return non-null on subsequent calls.
     */
    public boolean canReopenSource() {
        return true;
    }

    private BufferedReader lineSource = null;    // If set, a reader on the current source file
    private String line = null;    // The last line read from the current source file
    private int number = 0;       // The last line number read

    /**
     * Returns a line from the source, or null, if unavailable.  If
     * you supply a Janitor, resources will be cached.
     */
    public String getLine(int lineNumber, Janitor janitor) {
        // If the source is already open and is passed the line we
        // want, close it.
        if (lineSource != null && number > lineNumber) {
            cleanup();
        }

        // If the line source is closed, try to open it.
        if (lineSource == null) {
            try {
                lineSource = new BufferedReader(getReader());
            } catch (Exception e) {
                // Ignore
            }
            number = 0;
        }

        // Read until the appropriate line number.
        if (lineSource != null) {
            while (number < lineNumber) {
                try {
                    line = lineSource.readLine();
                    number++;
                }
                catch (IOException e) {
                    cleanup();
                }
            }

            if (janitor == null) {
                final String result = line;   // otherwise cleanup() will wipe out value
                cleanup();
                return result;
            } else {
                janitor.register(this);
            }
        }

        return line;
    }

    /**
     * Cleans up any cached resources used by getLine().
     */
    public void cleanup() {
        if (lineSource != null) {
            try {
                lineSource.close();
            } catch (Exception e) {
                // Ignore
            }
        }

        lineSource = null;
        line = null;
        number = 0;
    }

}

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