org.rocksdb.NativeLibraryLoader Maven / Gradle / Ivy
// Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
package org.rocksdb;
import java.io.*;
import java.nio.file.Files;
import java.nio.file.StandardCopyOption;
import org.rocksdb.util.Environment;
/**
* This class is used to load the RocksDB shared library from within the jar.
* The shared library is extracted to a temp folder and loaded from there.
*/
public class NativeLibraryLoader {
//singleton
private static final NativeLibraryLoader instance = new NativeLibraryLoader();
private static boolean initialized = false;
private static final String sharedLibraryName = Environment.getSharedLibraryName("rocksdb");
private static final String jniLibraryName = Environment.getJniLibraryName("rocksdb");
private static final String jniLibraryFileName = Environment.getJniLibraryFileName("rocksdb");
private static final String tempFilePrefix = "librocksdbjni";
private static final String tempFileSuffix = Environment.getJniLibraryExtension();
/**
* Get a reference to the NativeLibraryLoader
*
* @return The NativeLibraryLoader
*/
public static NativeLibraryLoader getInstance() {
return instance;
}
/**
* Firstly attempts to load the library from java.library.path,
* if that fails then it falls back to extracting
* the library from the classpath
* {@link org.rocksdb.NativeLibraryLoader#loadLibraryFromJar(java.lang.String)}
*
* @param tmpDir A temporary directory to use
* to copy the native library to when loading from the classpath.
* If null, or the empty string, we rely on Java's
* {@link java.io.File#createTempFile(String, String)}
* function to provide a temporary location.
* The temporary file will be registered for deletion
* on exit.
*
* @throws java.io.IOException if a filesystem operation fails.
*/
public synchronized void loadLibrary(final String tmpDir) throws IOException {
try {
System.loadLibrary(sharedLibraryName);
} catch(final UnsatisfiedLinkError ule1) {
try {
System.loadLibrary(jniLibraryName);
} catch(final UnsatisfiedLinkError ule2) {
loadLibraryFromJar(tmpDir);
}
}
}
/**
* Attempts to extract the native RocksDB library
* from the classpath and load it
*
* @param tmpDir A temporary directory to use
* to copy the native library to. If null,
* or the empty string, we rely on Java's
* {@link java.io.File#createTempFile(String, String)}
* function to provide a temporary location.
* The temporary file will be registered for deletion
* on exit.
*
* @throws java.io.IOException if a filesystem operation fails.
*/
void loadLibraryFromJar(final String tmpDir)
throws IOException {
if (!initialized) {
System.load(loadLibraryFromJarToTemp(tmpDir).getAbsolutePath());
initialized = true;
}
}
File loadLibraryFromJarToTemp(final String tmpDir)
throws IOException {
final File temp;
if (tmpDir == null || tmpDir.isEmpty()) {
temp = File.createTempFile(tempFilePrefix, tempFileSuffix);
} else {
final File parentDir = new File(tmpDir);
if (!parentDir.exists()) {
throw new RuntimeException(
"Directory: " + parentDir.getAbsolutePath() + " does not exist!");
}
temp = new File(parentDir, jniLibraryFileName);
if (temp.exists() && !temp.delete()) {
throw new RuntimeException("File: " + temp.getAbsolutePath()
+ " already exists and cannot be removed.");
}
if (!temp.createNewFile()) {
throw new RuntimeException("File: " + temp.getAbsolutePath()
+ " could not be created.");
}
}
if (!temp.exists()) {
throw new RuntimeException("File " + temp.getAbsolutePath() + " does not exist.");
} else {
temp.deleteOnExit();
}
// attempt to copy the library from the Jar file to the temp destination
try (final InputStream is = getClass().getClassLoader().
getResourceAsStream(jniLibraryFileName)) {
if (is == null) {
throw new RuntimeException(jniLibraryFileName + " was not found inside JAR.");
} else {
Files.copy(is, temp.toPath(), StandardCopyOption.REPLACE_EXISTING);
}
}
return temp;
}
/**
* Private constructor to disallow instantiation
*/
private NativeLibraryLoader() {
}
}