Commons IO example source code file (TailerTest.java)

This example Commons IO source code file (TailerTest.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 - Commons IO tags/keywords

exception, exception, expected, file, file, io, line, line, list, ok, should, tailer, testtailerlistener, testtailerlistener, thread, threading, threads, util

The Commons IO TailerTest.java source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.commons.io.input;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Executor;
import java.util.concurrent.ScheduledThreadPoolExecutor;

import org.apache.commons.io.FileUtils;
import org.apache.commons.io.IOUtils;
import org.apache.commons.io.testtools.FileBasedTestCase;

/**
 * Tests for {@link Tailer}.
 *
 * @version $Id: TailerTest.java 1006295 2010-10-10 14:15:51Z niallp $
 */
public class TailerTest extends FileBasedTestCase {

    public TailerTest(String name) {
        super(name);
    }

    @Override
    protected void tearDown() throws Exception {
        FileUtils.deleteDirectory(getTestDirectory());
    }

    public void testTailer() throws Exception {

        // Create & start the Tailer
        long delay = 50;
        final File file = new File(getTestDirectory(), "tailer1-test.txt");
        createFile(file, 0);
        final TestTailerListener listener = new TestTailerListener();
        final Tailer tailer = new Tailer(file, listener, delay, false);
        final Thread thread = new Thread(tailer);
        thread.start();

        // Write some lines to the file
        write(file, "Line one", "Line two");
        Thread.sleep(delay * 2);
        List<String> lines = listener.getLines();
        assertEquals("1 line count", 2, lines.size());
        assertEquals("1 line 1", "Line one", lines.get(0));
        assertEquals("1 line 2", "Line two", lines.get(1));
        listener.clear();

        // Write another line to the file
        write(file, "Line three");
        Thread.sleep(delay * 2);
        lines = listener.getLines();
        assertEquals("2 line count", 1, lines.size());
        assertEquals("2 line 3", "Line three", lines.get(0));
        listener.clear();

        // Check file does actually have all the lines
        lines = FileUtils.readLines(file);
        assertEquals("3 line count", 3, lines.size());
        assertEquals("3 line 1", "Line one", lines.get(0));
        assertEquals("3 line 2", "Line two", lines.get(1));
        assertEquals("3 line 3", "Line three", lines.get(2));

        // Delete & re-create
        file.delete();
        createFile(file, 0);
        Thread.sleep(delay * 2);

        // Write another line
        write(file, "Line four");
        Thread.sleep(delay * 2);
        lines = listener.getLines();
        assertEquals("4 line count", 1, lines.size());
        assertEquals("4 line 3", "Line four", lines.get(0));
        listener.clear();

        // Stop
        tailer.stop();
        thread.interrupt();
        Thread.sleep(delay * 2);
        write(file, "Line five");
        assertEquals("4 line count", 0, listener.getLines().size());
        assertNull("Should not generate Exception", listener.exception);
        assertEquals("Expected init to be called", 1 , listener.initialised);
        assertEquals("fileNotFound should not be called", 0 , listener.notFound);
        assertEquals("fileRotated should be be called", 1 , listener.rotated);
    }

    protected void createFile(File file, long size)
        throws IOException {
        super.createFile(file, size);

        // try to make sure file is found
        // (to stop continuum occasionally failing)
        RandomAccessFile reader = null;
        try {
            while (reader == null) {
                try {
                    reader = new RandomAccessFile(file.getPath(), "r");
                } catch (FileNotFoundException e) {
                }
                try {
                    Thread.sleep(200L);
                } catch (InterruptedException e) {
                    // ignore
                }
            }
        } finally {
            IOUtils.closeQuietly(reader);
        }
    }

    /** Append some lines to a file */
    private void write(File file, String... lines) throws Exception {
        FileWriter writer = null;
        try {
            writer = new FileWriter(file, true);
            for (String line : lines) {
                writer.write(line + "\n");
            }
        } finally {
            IOUtils.closeQuietly(writer);
        }
    }

    public void testStopWithNoFile() throws Exception {
        final File file = new File(getTestDirectory(),"nosuchfile");
        assertFalse("nosuchfile should not exist", file.exists());
        final TestTailerListener listener = new TestTailerListener();
        int delay = 100;
        int idle = 50; // allow time for thread to work
        final Tailer tailer = Tailer.create(file, listener, delay, false);
        Thread.sleep(idle);
        tailer.stop();
        Thread.sleep(delay+idle);
        assertNull("Should not generate Exception", listener.exception);
        assertEquals("Expected init to be called", 1 , listener.initialised);
        assertTrue("fileNotFound should be called", listener.notFound > 0);
        assertEquals("fileRotated should be not be called", 0 , listener.rotated);
    }

    public void testStopWithNoFileUsingExecutor() throws Exception {
        final File file = new File(getTestDirectory(),"nosuchfile");
        assertFalse("nosuchfile should not exist", file.exists());
        TestTailerListener listener = new TestTailerListener();
        int delay = 100;
        int idle = 50; // allow time for thread to work
        Tailer tailer = new Tailer(file, listener, delay, false);
        Executor exec = new ScheduledThreadPoolExecutor(1);
        exec.execute(tailer);
        Thread.sleep(idle);
        tailer.stop();
        Thread.sleep(delay+idle);
        assertNull("Should not generate Exception", listener.exception);
        assertEquals("Expected init to be called", 1 , listener.initialised);
        assertTrue("fileNotFound should be called", listener.notFound > 0);
        assertEquals("fileRotated should be not be called", 0 , listener.rotated);
    }

    /**
     * Test {@link TailerListener} implementation.
     */
    private static class TestTailerListener implements TailerListener {

        private final List<String> lines = new ArrayList();

        volatile Exception exception = null;
        
        volatile int notFound = 0;

        volatile int rotated = 0;
        
        volatile int initialised = 0;

        public void handle(String line) {
            lines.add(line);
        }
        public List<String> getLines() {
            return lines;
        }
        public void clear() {
            lines.clear();
        }
        public void handle(Exception e) {
            exception = e;
        }
        public void init(Tailer tailer) {
            initialised++; // not atomic, but OK because only updated here.
        }
        public void fileNotFound() {
            notFound++; // not atomic, but OK because only updated here.
        }
        public void fileRotated() {
            rotated++; // not atomic, but OK because only updated here.
        }
    }
}