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Kiwi is a utility library. We really like Google's Guava, and also use Apache Commons.
But if they don't have something we need, and we think it is useful, this is where we put it.
package org.kiwiproject.jar;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import static com.google.common.collect.Lists.newArrayList;
import static java.util.Collections.emptyList;
import static java.util.Objects.isNull;
import static java.util.stream.Collectors.toUnmodifiableList;
import static org.kiwiproject.base.KiwiPreconditions.checkArgumentNotNull;
import static org.kiwiproject.collect.KiwiLists.isNotNullOrEmpty;
import static org.kiwiproject.collect.KiwiLists.isNullOrEmpty;
import com.google.common.annotations.VisibleForTesting;
import lombok.experimental.UtilityClass;
import lombok.extern.slf4j.Slf4j;
import java.io.File;
import java.net.URL;
import java.net.URLDecoder;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.function.Predicate;
import java.util.jar.Manifest;
import java.util.stream.StreamSupport;
/**
* Utilities for working with Java JAR files.
*/
@Slf4j
@UtilityClass
public class KiwiJars {
/**
* Get the path components of the JAR file path that the given class lives in, or an empty list if the path
* components could not be obtained.
*
* @param classInJar the class which resides in the JAR you want to find
* @return a mutable list of path components if found, or an immutable empty list if not found
* or an exception is thrown attempting to get the path
*/
public static List getPathComponents(Class classInJar) {
checkArgumentNotNull(classInJar, "classInJar cannot be null");
try {
var codeSource = classInJar.getProtectionDomain().getCodeSource();
checkNotNull(codeSource, "Code source for %s is null", classInJar);
var encodedJarPath = codeSource.getLocation().getPath();
var decodedJarPath = URLDecoder.decode(encodedJarPath, StandardCharsets.UTF_8);
return newArrayList(decodedJarPath.trim().split(File.separator));
} catch (Exception e) {
return logExceptionAndReturnEmptyList(e, classInJar);
}
}
@VisibleForTesting
static List logExceptionAndReturnEmptyList(Exception ex, Class classInJar) {
LOG.error("Error getting Jar path components for {}! (turn on DEBUG logging to see stack traces)", classInJar);
LOG.debug("Exception related to {}:", classInJar, ex);
return emptyList();
}
/**
* Get the path of the JAR file that the given class lives in, or an empty {@link Optional} if the path
* could not be obtained for any reason.
*
* @param classInJar the class which resides in the JAR you want to find
* @return optional containing the path if found, or an empty optional
*/
public static Optional getPath(Class classInJar) {
var pathComponents = getPathComponents(classInJar);
return joined(pathComponents);
}
/**
* Get the directory path of the JAR file that the given class lives in, or an empty {@link Optional}
* if the path could not be obtained for any reason.
*
* @param classInJar the class which resides in the JAR you want to find
* @return optional containing the directory path if found, or an empty optional
*/
public static Optional getDirectoryPath(Class classInJar) {
var pathComponents = getPathComponents(classInJar);
checkState(isNotNullOrEmpty(pathComponents), "there must be at least one path component!");
return joined(pathComponents.subList(0, pathComponents.size() - 1));
}
@VisibleForTesting
static Optional joined(List parts) {
if (isNullOrEmpty(parts)) {
return Optional.empty();
}
return Optional.of(String.join(File.separator, parts));
}
/**
* Resolves a given entry name from the manifest file (if found) in the current class loader.
*
* @param manifestEntryName The name of the property to resolve
* @return an {@link Optional} containing the resolved value or {@code Optional.empty()} if not
*/
public static Optional readSingleValueFromJarManifest(String manifestEntryName) {
return readSingleValueFromJarManifest(KiwiJars.class.getClassLoader(), manifestEntryName, null);
}
/**
* Resolves a given entry name from the manifest file (if found) from the given class loader.
*
* @param classLoader The class loader to find the manifest file to search
* @param manifestEntryName The name of the property to resolve
* @return an {@link Optional} containing the resolved value or {@code Optional.empty()} if not
*/
public static Optional readSingleValueFromJarManifest(ClassLoader classLoader, String manifestEntryName) {
return readSingleValueFromJarManifest(classLoader, manifestEntryName, null);
}
/**
* Resolves a given entry name from the manifest file (if found) from the given class loader.
*
* @param classLoader The class loader to find the manifest file to search
* @param manifestEntryName The name of the property to resolve
* @param manifestFilter An optional filter that can be used to filter down manifest files if there are more than one.
* @return an {@link Optional} containing the resolved value or {@code Optional.empty()} if not
* @implNote If this code is called from a "fat-jar" with single manifest file, then the filter predicate is not needed. The predicate filter is
* really only needed if there are multiple jars loaded in the classpath all containing manifest files.
*/
@SuppressWarnings("java:S2259")
public static Optional readSingleValueFromJarManifest(ClassLoader classLoader, String manifestEntryName, Predicate manifestFilter) {
try {
List urls;
if (isNull(manifestFilter)) {
var manifestUrl = Optional.ofNullable(classLoader.getResource("META-INF/MANIFEST.MF"));
urls = manifestUrl.map(List::of).orElse(null);
} else {
var urlIterator = classLoader.getResources("META-INF/MANIFEST.MF").asIterator();
Iterable urlIterable = () -> urlIterator;
urls = StreamSupport
.stream((urlIterable).spliterator(), false)
.filter(manifestFilter)
.collect(toUnmodifiableList());
}
LOG.trace("Using manifest URL(s): {}", urls);
if (isNullOrEmpty(urls)) {
return Optional.empty();
}
return urls.stream().map(url -> readEntry(url, manifestEntryName))
.flatMap(Optional::stream)
.findFirst();
} catch (Exception e) {
LOG.warn("Unable to locate {} from JAR", manifestEntryName, e);
return Optional.empty();
}
}
private static Optional readEntry(URL url, String manifestEntryName) {
try (var in = url.openStream()) {
var manifest = new Manifest(in);
return readEntry(manifest, manifestEntryName);
} catch (Exception e) {
LOG.warn("Unable to read manifest", e);
return Optional.empty();
}
}
private static Optional readEntry(Manifest manifest, String manifestEntryName) {
return Optional.ofNullable(manifest.getMainAttributes().getValue(manifestEntryName));
}
/**
* Resolves all of the given entry names from the manifest (if found) from the current class loader.
*
* @param manifestEntryNames an array of names to resolve from the manifest
* @return a {@code Map} of resolved entries
*/
public static Map readValuesFromJarManifest(String... manifestEntryNames) {
return readValuesFromJarManifest(KiwiJars.class.getClassLoader(), null, manifestEntryNames);
}
/**
* Resolves all of the given entry names from the manifest (if found) from the given class loader.
*
* @param classLoader the classloader to search for manifest files in
* @param manifestEntryNames an array of names to resolve from the manifest
* @return a {@code Map} of resolved entries
*/
public static Map readValuesFromJarManifest(ClassLoader classLoader, String... manifestEntryNames) {
return readValuesFromJarManifest(classLoader, null, manifestEntryNames);
}
/**
* Resolves all of the given entry names from the manifest (if found) from the given class loader.
*
* @param classLoader the classloader to search for manifest files in
* @param manifestFilter a predicate filter used to limit which jar files to search for a manifest file
* @param manifestEntryNames an array of names to resolve from the manifest
* @return a {@code Map} of resolved entries
* @implNote If this code is called from a "fat-jar" with single manifest file, then the filter predicate is not needed. The predicate filter is
* really only needed if there are multiple jars loaded in the classpath all containing manifest files.
*/
public static Map readValuesFromJarManifest(ClassLoader classLoader, Predicate manifestFilter, String... manifestEntryNames) {
var entries = new HashMap();
Arrays.stream(manifestEntryNames).forEach(manifestEntryName -> {
var entry = readSingleValueFromJarManifest(classLoader, manifestEntryName, manifestFilter);
entry.ifPresent(value -> entries.put(manifestEntryName, value));
});
return entries;
}
}