com.google.common.reflect.ClassPath Maven / Gradle / Ivy
Show all versions of guava Show documentation
/*
* Copyright (C) 2012 The Guava 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 com.google.common.reflect;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.StandardSystemProperty.JAVA_CLASS_PATH;
import static com.google.common.base.StandardSystemProperty.PATH_SEPARATOR;
import static java.util.logging.Level.WARNING;
import com.google.common.annotations.Beta;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.CharMatcher;
import com.google.common.base.Predicate;
import com.google.common.base.Splitter;
import com.google.common.collect.FluentIterable;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Maps;
import com.google.common.collect.MultimapBuilder;
import com.google.common.collect.SetMultimap;
import com.google.common.collect.Sets;
import com.google.common.io.ByteSource;
import com.google.common.io.CharSource;
import com.google.common.io.Resources;
import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URISyntaxException;
import java.net.URL;
import java.net.URLClassLoader;
import java.nio.charset.Charset;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.Map.Entry;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.jar.Attributes;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
import java.util.jar.Manifest;
import java.util.logging.Logger;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* Scans the source of a {@link ClassLoader} and finds all loadable classes and resources.
*
* Warning: Current limitations:
*
*
* - Looks only for files and JARs in URLs available from {@link URLClassLoader} instances or
* the {@linkplain ClassLoader#getSystemClassLoader() system class loader}.
*
- Only understands {@code file:} URLs.
*
*
* In the case of directory classloaders, symlinks are supported but cycles are not traversed.
* This guarantees discovery of each unique loadable resource. However, not all possible
* aliases for resources on cyclic paths will be listed.
*
* @author Ben Yu
* @since 14.0
*/
@Beta
public final class ClassPath {
private static final Logger logger = Logger.getLogger(ClassPath.class.getName());
private static final Predicate IS_TOP_LEVEL =
new Predicate() {
@Override
public boolean apply(ClassInfo info) {
return info.className.indexOf('$') == -1;
}
};
/** Separator for the Class-Path manifest attribute value in jar files. */
private static final Splitter CLASS_PATH_ATTRIBUTE_SEPARATOR =
Splitter.on(" ").omitEmptyStrings();
private static final String CLASS_FILE_NAME_EXTENSION = ".class";
private final ImmutableSet resources;
private ClassPath(ImmutableSet resources) {
this.resources = resources;
}
/**
* Returns a {@code ClassPath} representing all classes and resources loadable from {@code
* classloader} and its ancestor class loaders.
*
* Warning: {@code ClassPath} can find classes and resources only from:
*
*
* - {@link URLClassLoader} instances' {@code file:} URLs
*
- the {@linkplain ClassLoader#getSystemClassLoader() system class loader}. To search the
* system class loader even when it is not a {@link URLClassLoader} (as in Java 9), {@code
* ClassPath} searches the files from the {@code java.class.path} system property.
*
*
* @throws IOException if the attempt to read class path resources (jar files or directories)
* failed.
*/
public static ClassPath from(ClassLoader classloader) throws IOException {
DefaultScanner scanner = new DefaultScanner();
scanner.scan(classloader);
return new ClassPath(scanner.getResources());
}
/**
* Returns all resources loadable from the current class path, including the class files of all
* loadable classes but excluding the "META-INF/MANIFEST.MF" file.
*/
public ImmutableSet getResources() {
return resources;
}
/**
* Returns all classes loadable from the current class path.
*
* @since 16.0
*/
public ImmutableSet getAllClasses() {
return FluentIterable.from(resources).filter(ClassInfo.class).toSet();
}
/** Returns all top level classes loadable from the current class path. */
public ImmutableSet getTopLevelClasses() {
return FluentIterable.from(resources).filter(ClassInfo.class).filter(IS_TOP_LEVEL).toSet();
}
/** Returns all top level classes whose package name is {@code packageName}. */
public ImmutableSet getTopLevelClasses(String packageName) {
checkNotNull(packageName);
ImmutableSet.Builder builder = ImmutableSet.builder();
for (ClassInfo classInfo : getTopLevelClasses()) {
if (classInfo.getPackageName().equals(packageName)) {
builder.add(classInfo);
}
}
return builder.build();
}
/**
* Returns all top level classes whose package name is {@code packageName} or starts with {@code
* packageName} followed by a '.'.
*/
public ImmutableSet getTopLevelClassesRecursive(String packageName) {
checkNotNull(packageName);
String packagePrefix = packageName + '.';
ImmutableSet.Builder builder = ImmutableSet.builder();
for (ClassInfo classInfo : getTopLevelClasses()) {
if (classInfo.getName().startsWith(packagePrefix)) {
builder.add(classInfo);
}
}
return builder.build();
}
/**
* Represents a class path resource that can be either a class file or any other resource file
* loadable from the class path.
*
* @since 14.0
*/
@Beta
public static class ResourceInfo {
private final String resourceName;
final ClassLoader loader;
static ResourceInfo of(String resourceName, ClassLoader loader) {
if (resourceName.endsWith(CLASS_FILE_NAME_EXTENSION)) {
return new ClassInfo(resourceName, loader);
} else {
return new ResourceInfo(resourceName, loader);
}
}
ResourceInfo(String resourceName, ClassLoader loader) {
this.resourceName = checkNotNull(resourceName);
this.loader = checkNotNull(loader);
}
/**
* Returns the url identifying the resource.
*
* See {@link ClassLoader#getResource}
*
* @throws NoSuchElementException if the resource cannot be loaded through the class loader,
* despite physically existing in the class path.
*/
public final URL url() {
URL url = loader.getResource(resourceName);
if (url == null) {
throw new NoSuchElementException(resourceName);
}
return url;
}
/**
* Returns a {@link ByteSource} view of the resource from which its bytes can be read.
*
* @throws NoSuchElementException if the resource cannot be loaded through the class loader,
* despite physically existing in the class path.
* @since 20.0
*/
public final ByteSource asByteSource() {
return Resources.asByteSource(url());
}
/**
* Returns a {@link CharSource} view of the resource from which its bytes can be read as
* characters decoded with the given {@code charset}.
*
* @throws NoSuchElementException if the resource cannot be loaded through the class loader,
* despite physically existing in the class path.
* @since 20.0
*/
public final CharSource asCharSource(Charset charset) {
return Resources.asCharSource(url(), charset);
}
/** Returns the fully qualified name of the resource. Such as "com/mycomp/foo/bar.txt". */
public final String getResourceName() {
return resourceName;
}
@Override
public int hashCode() {
return resourceName.hashCode();
}
@Override
public boolean equals(Object obj) {
if (obj instanceof ResourceInfo) {
ResourceInfo that = (ResourceInfo) obj;
return resourceName.equals(that.resourceName) && loader == that.loader;
}
return false;
}
// Do not change this arbitrarily. We rely on it for sorting ResourceInfo.
@Override
public String toString() {
return resourceName;
}
}
/**
* Represents a class that can be loaded through {@link #load}.
*
* @since 14.0
*/
@Beta
public static final class ClassInfo extends ResourceInfo {
private final String className;
ClassInfo(String resourceName, ClassLoader loader) {
super(resourceName, loader);
this.className = getClassName(resourceName);
}
/**
* Returns the package name of the class, without attempting to load the class.
*
*
Behaves identically to {@link Package#getName()} but does not require the class (or
* package) to be loaded.
*/
public String getPackageName() {
return Reflection.getPackageName(className);
}
/**
* Returns the simple name of the underlying class as given in the source code.
*
*
Behaves identically to {@link Class#getSimpleName()} but does not require the class to be
* loaded.
*/
public String getSimpleName() {
int lastDollarSign = className.lastIndexOf('$');
if (lastDollarSign != -1) {
String innerClassName = className.substring(lastDollarSign + 1);
// local and anonymous classes are prefixed with number (1,2,3...), anonymous classes are
// entirely numeric whereas local classes have the user supplied name as a suffix
return CharMatcher.digit().trimLeadingFrom(innerClassName);
}
String packageName = getPackageName();
if (packageName.isEmpty()) {
return className;
}
// Since this is a top level class, its simple name is always the part after package name.
return className.substring(packageName.length() + 1);
}
/**
* Returns the fully qualified name of the class.
*
*
Behaves identically to {@link Class#getName()} but does not require the class to be
* loaded.
*/
public String getName() {
return className;
}
/**
* Loads (but doesn't link or initialize) the class.
*
* @throws LinkageError when there were errors in loading classes that this class depends on.
* For example, {@link NoClassDefFoundError}.
*/
public Class load() {
try {
return loader.loadClass(className);
} catch (ClassNotFoundException e) {
// Shouldn't happen, since the class name is read from the class path.
throw new IllegalStateException(e);
}
}
@Override
public String toString() {
return className;
}
}
/**
* Abstract class that scans through the class path represented by a {@link ClassLoader} and calls
* {@link #scanDirectory} and {@link #scanJarFile} for directories and jar files on the class path
* respectively.
*/
abstract static class Scanner {
// We only scan each file once independent of the classloader that resource might be associated
// with.
private final Set scannedUris = Sets.newHashSet();
public final void scan(ClassLoader classloader) throws IOException {
for (Entry entry : getClassPathEntries(classloader).entrySet()) {
scan(entry.getKey(), entry.getValue());
}
}
@VisibleForTesting
final void scan(File file, ClassLoader classloader) throws IOException {
if (scannedUris.add(file.getCanonicalFile())) {
scanFrom(file, classloader);
}
}
/** Called when a directory is scanned for resource files. */
protected abstract void scanDirectory(ClassLoader loader, File directory) throws IOException;
/** Called when a jar file is scanned for resource entries. */
protected abstract void scanJarFile(ClassLoader loader, JarFile file) throws IOException;
private void scanFrom(File file, ClassLoader classloader) throws IOException {
try {
if (!file.exists()) {
return;
}
} catch (SecurityException e) {
logger.warning("Cannot access " + file + ": " + e);
// TODO(emcmanus): consider whether to log other failure cases too.
return;
}
if (file.isDirectory()) {
scanDirectory(classloader, file);
} else {
scanJar(file, classloader);
}
}
private void scanJar(File file, ClassLoader classloader) throws IOException {
JarFile jarFile;
try {
jarFile = new JarFile(file);
} catch (IOException e) {
// Not a jar file
return;
}
try {
for (File path : getClassPathFromManifest(file, jarFile.getManifest())) {
scan(path, classloader);
}
scanJarFile(classloader, jarFile);
} finally {
try {
jarFile.close();
} catch (IOException ignored) {
}
}
}
/**
* Returns the class path URIs specified by the {@code Class-Path} manifest attribute, according
* to JAR
* File Specification. If {@code manifest} is null, it means the jar file has no manifest,
* and an empty set will be returned.
*/
@VisibleForTesting
static ImmutableSet getClassPathFromManifest(File jarFile, @Nullable Manifest manifest) {
if (manifest == null) {
return ImmutableSet.of();
}
ImmutableSet.Builder builder = ImmutableSet.builder();
String classpathAttribute =
manifest.getMainAttributes().getValue(Attributes.Name.CLASS_PATH.toString());
if (classpathAttribute != null) {
for (String path : CLASS_PATH_ATTRIBUTE_SEPARATOR.split(classpathAttribute)) {
URL url;
try {
url = getClassPathEntry(jarFile, path);
} catch (MalformedURLException e) {
// Ignore bad entry
logger.warning("Invalid Class-Path entry: " + path);
continue;
}
if (url.getProtocol().equals("file")) {
builder.add(toFile(url));
}
}
}
return builder.build();
}
@VisibleForTesting
static ImmutableMap getClassPathEntries(ClassLoader classloader) {
LinkedHashMap entries = Maps.newLinkedHashMap();
// Search parent first, since it's the order ClassLoader#loadClass() uses.
ClassLoader parent = classloader.getParent();
if (parent != null) {
entries.putAll(getClassPathEntries(parent));
}
for (URL url : getClassLoaderUrls(classloader)) {
if (url.getProtocol().equals("file")) {
File file = toFile(url);
if (!entries.containsKey(file)) {
entries.put(file, classloader);
}
}
}
return ImmutableMap.copyOf(entries);
}
private static ImmutableList getClassLoaderUrls(ClassLoader classloader) {
if (classloader instanceof URLClassLoader) {
return ImmutableList.copyOf(((URLClassLoader) classloader).getURLs());
}
if (classloader.equals(ClassLoader.getSystemClassLoader())) {
return parseJavaClassPath();
}
return ImmutableList.of();
}
/**
* Returns the URLs in the class path specified by the {@code java.class.path} {@linkplain
* System#getProperty system property}.
*/
@VisibleForTesting // TODO(b/65488446): Make this a public API.
static ImmutableList parseJavaClassPath() {
ImmutableList.Builder urls = ImmutableList.builder();
for (String entry : Splitter.on(PATH_SEPARATOR.value()).split(JAVA_CLASS_PATH.value())) {
try {
try {
urls.add(new File(entry).toURI().toURL());
} catch (SecurityException e) { // File.toURI checks to see if the file is a directory
urls.add(new URL("file", null, new File(entry).getAbsolutePath()));
}
} catch (MalformedURLException e) {
logger.log(WARNING, "malformed classpath entry: " + entry, e);
}
}
return urls.build();
}
/**
* Returns the absolute uri of the Class-Path entry value as specified in JAR
* File Specification. Even though the specification only talks about relative urls,
* absolute urls are actually supported too (for example, in Maven surefire plugin).
*/
@VisibleForTesting
static URL getClassPathEntry(File jarFile, String path) throws MalformedURLException {
return new URL(jarFile.toURI().toURL(), path);
}
}
@VisibleForTesting
static final class DefaultScanner extends Scanner {
private final SetMultimap resources =
MultimapBuilder.hashKeys().linkedHashSetValues().build();
ImmutableSet getResources() {
ImmutableSet.Builder builder = ImmutableSet.builder();
for (Entry entry : resources.entries()) {
builder.add(ResourceInfo.of(entry.getValue(), entry.getKey()));
}
return builder.build();
}
@Override
protected void scanJarFile(ClassLoader classloader, JarFile file) {
Enumeration entries = file.entries();
while (entries.hasMoreElements()) {
JarEntry entry = entries.nextElement();
if (entry.isDirectory() || entry.getName().equals(JarFile.MANIFEST_NAME)) {
continue;
}
resources.get(classloader).add(entry.getName());
}
}
@Override
protected void scanDirectory(ClassLoader classloader, File directory) throws IOException {
Set currentPath = new HashSet<>();
currentPath.add(directory.getCanonicalFile());
scanDirectory(directory, classloader, "", currentPath);
}
/**
* Recursively scan the given directory, adding resources for each file encountered. Symlinks
* which have already been traversed in the current tree path will be skipped to eliminate
* cycles; otherwise symlinks are traversed.
*
* @param directory the root of the directory to scan
* @param classloader the classloader that includes resources found in {@code directory}
* @param packagePrefix resource path prefix inside {@code classloader} for any files found
* under {@code directory}
* @param currentPath canonical files already visited in the current directory tree path, for
* cycle elimination
*/
private void scanDirectory(
File directory, ClassLoader classloader, String packagePrefix, Set currentPath)
throws IOException {
File[] files = directory.listFiles();
if (files == null) {
logger.warning("Cannot read directory " + directory);
// IO error, just skip the directory
return;
}
for (File f : files) {
String name = f.getName();
if (f.isDirectory()) {
File deref = f.getCanonicalFile();
if (currentPath.add(deref)) {
scanDirectory(deref, classloader, packagePrefix + name + "/", currentPath);
currentPath.remove(deref);
}
} else {
String resourceName = packagePrefix + name;
if (!resourceName.equals(JarFile.MANIFEST_NAME)) {
resources.get(classloader).add(resourceName);
}
}
}
}
}
@VisibleForTesting
static String getClassName(String filename) {
int classNameEnd = filename.length() - CLASS_FILE_NAME_EXTENSION.length();
return filename.substring(0, classNameEnd).replace('/', '.');
}
// TODO(benyu): Try java.nio.file.Paths#get() when Guava drops JDK 6 support.
@VisibleForTesting
static File toFile(URL url) {
checkArgument(url.getProtocol().equals("file"));
try {
return new File(url.toURI()); // Accepts escaped characters like %20.
} catch (URISyntaxException e) { // URL.toURI() doesn't escape chars.
return new File(url.getPath()); // Accepts non-escaped chars like space.
}
}
}