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core-java-io/src/test/java/com/baeldung/filechannel/FileChannelUnitTest.java
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package com.baeldung.filechannel; | ||
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import static org.junit.Assert.assertEquals; | ||
import static org.junit.Assert.assertNotNull; | ||
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import java.io.ByteArrayOutputStream; | ||
import java.io.FileInputStream; | ||
import java.io.FileOutputStream; | ||
import java.io.IOException; | ||
import java.io.RandomAccessFile; | ||
import java.nio.ByteBuffer; | ||
import java.nio.MappedByteBuffer; | ||
import java.nio.channels.FileChannel; | ||
import java.nio.channels.FileLock; | ||
import java.nio.charset.StandardCharsets; | ||
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import org.junit.Test; | ||
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public class FileChannelUnitTest { | ||
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@Test | ||
public void givenFile_whenReadWithFileChannelUsingRandomAccessFile_thenCorrect() throws IOException { | ||
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try (RandomAccessFile reader = new RandomAccessFile("src/test/resources/test_read.in", "r"); | ||
FileChannel channel = reader.getChannel(); | ||
ByteArrayOutputStream out = new ByteArrayOutputStream();) { | ||
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int bufferSize = 1024; | ||
if (bufferSize > channel.size()) { | ||
bufferSize = (int) channel.size(); | ||
} | ||
ByteBuffer buff = ByteBuffer.allocate(bufferSize); | ||
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while (channel.read(buff) > 0) { | ||
out.write(buff.array(), 0, buff.position()); | ||
buff.clear(); | ||
} | ||
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String fileContent = new String(out.toByteArray(), StandardCharsets.UTF_8); | ||
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assertEquals("Hello world", fileContent); | ||
} | ||
} | ||
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@Test | ||
public void givenFile_whenReadWithFileChannelUsingFileInputStream_thenCorrect() throws IOException { | ||
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try (ByteArrayOutputStream out = new ByteArrayOutputStream(); | ||
FileInputStream fin = new FileInputStream("src/test/resources/test_read.in"); | ||
FileChannel channel = fin.getChannel();) { | ||
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int bufferSize = 1024; | ||
if (bufferSize > channel.size()) { | ||
bufferSize = (int) channel.size(); | ||
} | ||
ByteBuffer buff = ByteBuffer.allocate(bufferSize); | ||
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while (channel.read(buff) > 0) { | ||
out.write(buff.array(), 0, buff.position()); | ||
buff.clear(); | ||
} | ||
String fileContent = new String(out.toByteArray(), StandardCharsets.UTF_8); | ||
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assertEquals("Hello world", fileContent); | ||
} | ||
} | ||
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@Test | ||
public void givenFile_whenReadAFileSectionIntoMemoryWithFileChannel_thenCorrect() throws IOException { | ||
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try (RandomAccessFile reader = new RandomAccessFile("src/test/resources/test_read.in", "r"); | ||
FileChannel channel = reader.getChannel(); | ||
ByteArrayOutputStream out = new ByteArrayOutputStream();) { | ||
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MappedByteBuffer buff = channel.map(FileChannel.MapMode.READ_ONLY, 6, 5); | ||
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if (buff.hasRemaining()) { | ||
byte[] data = new byte[buff.remaining()]; | ||
buff.get(data); | ||
assertEquals("world", new String(data, StandardCharsets.UTF_8)); | ||
} | ||
} | ||
} | ||
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@Test | ||
public void whenWriteWithFileChannelUsingRandomAccessFile_thenCorrect() throws IOException { | ||
String file = "src/test/resources/test_write_using_filechannel.txt"; | ||
try (RandomAccessFile writer = new RandomAccessFile(file, "rw"); | ||
FileChannel channel = writer.getChannel();) { | ||
ByteBuffer buff = ByteBuffer.wrap("Hello world".getBytes(StandardCharsets.UTF_8)); | ||
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channel.write(buff); | ||
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// now we verify whether the file was written correctly | ||
RandomAccessFile reader = new RandomAccessFile(file, "r"); | ||
assertEquals("Hello world", reader.readLine()); | ||
reader.close(); | ||
} | ||
} | ||
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@Test | ||
public void givenFile_whenWriteAFileUsingLockAFileSectionWithFileChannel_thenCorrect() throws IOException { | ||
try (RandomAccessFile reader = new RandomAccessFile("src/test/resources/test_read.in", "rw"); | ||
FileChannel channel = reader.getChannel(); | ||
FileLock fileLock = channel.tryLock(6, 5, Boolean.FALSE);) { | ||
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assertNotNull(fileLock); | ||
} | ||
} | ||
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@Test | ||
public void givenFile_whenReadWithFileChannelGetPosition_thenCorrect() throws IOException { | ||
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try (ByteArrayOutputStream out = new ByteArrayOutputStream(); | ||
RandomAccessFile reader = new RandomAccessFile("src/test/resources/test_read.in", "r"); | ||
FileChannel channel = reader.getChannel();) { | ||
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int bufferSize = 1024; | ||
if (bufferSize > channel.size()) { | ||
bufferSize = (int) channel.size(); | ||
} | ||
ByteBuffer buff = ByteBuffer.allocate(bufferSize); | ||
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while (channel.read(buff) > 0) { | ||
out.write(buff.array(), 0, buff.position()); | ||
buff.clear(); | ||
} | ||
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// the original file is 11 bytes long, so that's where the position pointer should be | ||
assertEquals(11, channel.position()); | ||
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channel.position(4); | ||
assertEquals(4, channel.position()); | ||
} | ||
} | ||
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@Test | ||
public void whenGetFileSize_thenCorrect() throws IOException { | ||
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try (RandomAccessFile reader = new RandomAccessFile("src/test/resources/test_read.in", "r"); | ||
FileChannel channel = reader.getChannel();) { | ||
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// the original file is 11 bytes long, so that's where the position pointer should be | ||
assertEquals(11, channel.size()); | ||
} | ||
} | ||
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@Test | ||
public void whenTruncateFile_thenCorrect() throws IOException { | ||
String input = "this is a test input"; | ||
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FileOutputStream fout = new FileOutputStream("src/test/resources/test_truncate.txt"); | ||
FileChannel channel = fout.getChannel(); | ||
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ByteBuffer buff = ByteBuffer.wrap(input.getBytes()); | ||
channel.write(buff); | ||
buff.flip(); | ||
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channel = channel.truncate(5); | ||
assertEquals(5, channel.size()); | ||
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fout.close(); | ||
channel.close(); | ||
} | ||
} |
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this |
1 change: 1 addition & 0 deletions
1
core-java-io/src/test/resources/test_write_using_filechannel.txt
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Hello world |
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distributionBase=GRADLE_USER_HOME | ||
distributionPath=wrapper/dists | ||
distributionUrl=https\://services.gradle.org/distributions/gradle-5.4-bin.zip | ||
zipStoreBase=GRADLE_USER_HOME | ||
zipStorePath=wrapper/dists | ||
distributionUrl=https\://services.gradle.org/distributions/gradle-4.4-bin.zip |
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