是否有可能找到给定包中的所有类或接口?(快速看了一下e.g. Package，似乎没有。)
当前回答
我一直在尝试使用Reflections库，但在使用它时遇到了一些问题，而且为了简单地获取包上的类，我应该包含太多的jar。
我将在这个重复的问题中发布一个解决方案:如何在包中获得所有类的名称?
答案由sp00m撰写;我添加了一些更正，使其工作:
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.Enumeration;
import java.util.LinkedList;
import java.util.List;
public final class ClassFinder {
private final static char DOT = '.';
private final static char SLASH = '/';
private final static String CLASS_SUFFIX = ".class";
private final static String BAD_PACKAGE_ERROR = "Unable to get resources from path '%s'. Are you sure the given '%s' package exists?";
public final static List<Class<?>> find(final String scannedPackage) {
final ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
final String scannedPath = scannedPackage.replace(DOT, SLASH);
final Enumeration<URL> resources;
try {
resources = classLoader.getResources(scannedPath);
} catch (IOException e) {
throw new IllegalArgumentException(String.format(BAD_PACKAGE_ERROR, scannedPath, scannedPackage), e);
}
final List<Class<?>> classes = new LinkedList<Class<?>>();
while (resources.hasMoreElements()) {
final File file = new File(resources.nextElement().getFile());
classes.addAll(find(file, scannedPackage));
}
return classes;
}
private final static List<Class<?>> find(final File file, final String scannedPackage) {
final List<Class<?>> classes = new LinkedList<Class<?>>();
if (file.isDirectory()) {
for (File nestedFile : file.listFiles()) {
classes.addAll(find(nestedFile, scannedPackage));
}
//File names with the $1, $2 holds the anonymous inner classes, we are not interested on them.
} else if (file.getName().endsWith(CLASS_SUFFIX) && !file.getName().contains("$")) {
final int beginIndex = 0;
final int endIndex = file.getName().length() - CLASS_SUFFIX.length();
final String className = file.getName().substring(beginIndex, endIndex);
try {
final String resource = scannedPackage + DOT + className;
classes.add(Class.forName(resource));
} catch (ClassNotFoundException ignore) {
}
}
return classes;
}
}
要使用它，只需调用本例中提到的sp00n的find方法: 如果需要的话，我还添加了类实例的创建。
List<Class<?>> classes = ClassFinder.find("com.package");
ExcelReporting excelReporting;
for (Class<?> aClass : classes) {
Constructor constructor = aClass.getConstructor();
//Create an object of the class type
constructor.newInstance();
//...
}
其他回答
你需要查找类路径中的每个类装入器条目:
String pkg = "org/apache/commons/lang";
ClassLoader cl = ClassLoader.getSystemClassLoader();
URL[] urls = ((URLClassLoader) cl).getURLs();
for (URL url : urls) {
System.out.println(url.getFile());
File jar = new File(url.getFile());
// ....
}
如果条目是目录，只需在右边的子目录中查找:
if (jar.isDirectory()) {
File subdir = new File(jar, pkg);
if (!subdir.exists())
continue;
File[] files = subdir.listFiles();
for (File file : files) {
if (!file.isFile())
continue;
if (file.getName().endsWith(".class"))
System.out.println("Found class: "
+ file.getName().substring(0,
file.getName().length() - 6));
}
}
如果条目是文件，并且它是jar，检查它的ZIP条目:
else {
// try to open as ZIP
try {
ZipFile zip = new ZipFile(jar);
for (Enumeration<? extends ZipEntry> entries = zip
.entries(); entries.hasMoreElements();) {
ZipEntry entry = entries.nextElement();
String name = entry.getName();
if (!name.startsWith(pkg))
continue;
name = name.substring(pkg.length() + 1);
if (name.indexOf('/') < 0 && name.endsWith(".class"))
System.out.println("Found class: "
+ name.substring(0, name.length() - 6));
}
} catch (ZipException e) {
System.out.println("Not a ZIP: " + e.getMessage());
} catch (IOException e) {
System.err.println(e.getMessage());
}
}
现在，一旦包中有了所有的类名，就可以尝试用反射加载它们，并分析它们是类还是接口等等。
你可以使用这个使用ClassLoader的method1。
/**
* Scans all classes accessible from the context class loader which belong to the given package and subpackages.
*
* @param packageName The base package
* @return The classes
* @throws ClassNotFoundException
* @throws IOException
*/
private static Class[] getClasses(String packageName)
throws ClassNotFoundException, IOException {
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
assert classLoader != null;
String path = packageName.replace('.', '/');
Enumeration<URL> resources = classLoader.getResources(path);
List<File> dirs = new ArrayList<File>();
while (resources.hasMoreElements()) {
URL resource = resources.nextElement();
dirs.add(new File(resource.getFile()));
}
ArrayList<Class> classes = new ArrayList<Class>();
for (File directory : dirs) {
classes.addAll(findClasses(directory, packageName));
}
return classes.toArray(new Class[classes.size()]);
}
/**
* Recursive method used to find all classes in a given directory and subdirs.
*
* @param directory The base directory
* @param packageName The package name for classes found inside the base directory
* @return The classes
* @throws ClassNotFoundException
*/
private static List<Class> findClasses(File directory, String packageName) throws ClassNotFoundException {
List<Class> classes = new ArrayList<Class>();
if (!directory.exists()) {
return classes;
}
File[] files = directory.listFiles();
for (File file : files) {
if (file.isDirectory()) {
assert !file.getName().contains(".");
classes.addAll(findClasses(file, packageName + "." + file.getName()));
} else if (file.getName().endsWith(".class")) {
classes.add(Class.forName(packageName + '.' + file.getName().substring(0, file.getName().length() - 6)));
}
}
return classes;
}
__________ 1 .该方法最初取自http://snippets.dzone.com/posts/show/4831，由互联网档案馆存档，如现在所示。该代码片段也可以在https://dzone.com/articles/get-all-classes-within-package上获得。
这是非常有可能的，但是如果没有像Reflections这样的附加库，这就很难了。 这很困难，因为你没有完整的工具来获取类名。 然后，我取ClassFinder类的代码:
package play.util;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
/**
* Created by LINKOR on 26.05.2017 in 15:12.
* Date: 2017.05.26
*/
public class FileClassFinder {
private JarFile file;
private boolean trouble;
public FileClassFinder(String filePath) {
try {
file = new JarFile(filePath);
} catch (IOException e) {
trouble = true;
}
}
public List<String> findClasses(String pkg) {
ArrayList<String> classes = new ArrayList<>();
Enumeration<JarEntry> entries = file.entries();
while (entries.hasMoreElements()) {
JarEntry cls = entries.nextElement();
if (!cls.isDirectory()) {
String fileName = cls.getName();
String className = fileName.replaceAll("/", ".").replaceAll(File.pathSeparator, ".").substring(0, fileName.lastIndexOf('.'));
if (className.startsWith(pkg)) classes.add(className.substring(pkg.length() + 1));
}
}
return classes;
}
}
我整理了一个简单的github项目来解决这个问题:
https://github.com/ddopson/java-class-enumerator
它既适用于基于文件的类路径，也适用于jar文件。
如果你在签出项目后运行'make'，它将打印出以下内容:
Cleaning...
rm -rf build/
Building...
javac -d build/classes src/pro/ddopson/ClassEnumerator.java src/test/ClassIShouldFindOne.java src/test/ClassIShouldFindTwo.java src/test/subpkg/ClassIShouldFindThree.java src/test/TestClassEnumeration.java
Making JAR Files...
jar cf build/ClassEnumerator_test.jar -C build/classes/ .
jar cf build/ClassEnumerator.jar -C build/classes/ pro
Running Filesystem Classpath Test...
java -classpath build/classes test.TestClassEnumeration
ClassDiscovery: Package: 'test' becomes Resource: 'file:/Users/Dopson/work/other/java-class-enumeration/build/classes/test'
ClassDiscovery: Reading Directory '/Users/Dopson/work/other/java-class-enumeration/build/classes/test'
ClassDiscovery: FileName 'ClassIShouldFindOne.class' => class 'test.ClassIShouldFindOne'
ClassDiscovery: FileName 'ClassIShouldFindTwo.class' => class 'test.ClassIShouldFindTwo'
ClassDiscovery: FileName 'subpkg' => class 'null'
ClassDiscovery: Reading Directory '/Users/Dopson/work/other/java-class-enumeration/build/classes/test/subpkg'
ClassDiscovery: FileName 'ClassIShouldFindThree.class' => class 'test.subpkg.ClassIShouldFindThree'
ClassDiscovery: FileName 'TestClassEnumeration.class' => class 'test.TestClassEnumeration'
Running JAR Classpath Test...
java -classpath build/ClassEnumerator_test.jar test.TestClassEnumeration
ClassDiscovery: Package: 'test' becomes Resource: 'jar:file:/Users/Dopson/work/other/java-class-enumeration/build/ClassEnumerator_test.jar!/test'
ClassDiscovery: Reading JAR file: '/Users/Dopson/work/other/java-class-enumeration/build/ClassEnumerator_test.jar'
ClassDiscovery: JarEntry 'META-INF/' => class 'null'
ClassDiscovery: JarEntry 'META-INF/MANIFEST.MF' => class 'null'
ClassDiscovery: JarEntry 'pro/' => class 'null'
ClassDiscovery: JarEntry 'pro/ddopson/' => class 'null'
ClassDiscovery: JarEntry 'pro/ddopson/ClassEnumerator.class' => class 'null'
ClassDiscovery: JarEntry 'test/' => class 'null'
ClassDiscovery: JarEntry 'test/ClassIShouldFindOne.class' => class 'test.ClassIShouldFindOne'
ClassDiscovery: JarEntry 'test/ClassIShouldFindTwo.class' => class 'test.ClassIShouldFindTwo'
ClassDiscovery: JarEntry 'test/subpkg/' => class 'null'
ClassDiscovery: JarEntry 'test/subpkg/ClassIShouldFindThree.class' => class 'test.subpkg.ClassIShouldFindThree'
ClassDiscovery: JarEntry 'test/TestClassEnumeration.class' => class 'test.TestClassEnumeration'
Tests Passed.
另见我的另一个答案
你好。我总是对上面的解决方案(以及其他网站上的)有一些问题。 我，作为一名开发人员，正在为API编程一个插件。该API防止使用任何外部库或第三方工具。设置还包括jar或zip文件中的代码和直接位于某些目录中的类文件。所以我的代码必须能够解决每一个设置。经过大量的研究，我想出了一个方法，可以在所有可能的设置中至少95%的情况下工作。
下面的代码基本上是总是有效的overkill方法。
代码:
这段代码扫描给定包中包含的所有类。它只对当前ClassLoader中的所有类有效。
/**
* Private helper method
*
* @param directory
* The directory to start with
* @param pckgname
* The package name to search for. Will be needed for getting the
* Class object.
* @param classes
* if a file isn't loaded but still is in the directory
* @throws ClassNotFoundException
*/
private static void checkDirectory(File directory, String pckgname,
ArrayList<Class<?>> classes) throws ClassNotFoundException {
File tmpDirectory;
if (directory.exists() && directory.isDirectory()) {
final String[] files = directory.list();
for (final String file : files) {
if (file.endsWith(".class")) {
try {
classes.add(Class.forName(pckgname + '.'
+ file.substring(0, file.length() - 6)));
} catch (final NoClassDefFoundError e) {
// do nothing. this class hasn't been found by the
// loader, and we don't care.
}
} else if ((tmpDirectory = new File(directory, file))
.isDirectory()) {
checkDirectory(tmpDirectory, pckgname + "." + file, classes);
}
}
}
}
/**
* Private helper method.
*
* @param connection
* the connection to the jar
* @param pckgname
* the package name to search for
* @param classes
* the current ArrayList of all classes. This method will simply
* add new classes.
* @throws ClassNotFoundException
* if a file isn't loaded but still is in the jar file
* @throws IOException
* if it can't correctly read from the jar file.
*/
private static void checkJarFile(JarURLConnection connection,
String pckgname, ArrayList<Class<?>> classes)
throws ClassNotFoundException, IOException {
final JarFile jarFile = connection.getJarFile();
final Enumeration<JarEntry> entries = jarFile.entries();
String name;
for (JarEntry jarEntry = null; entries.hasMoreElements()
&& ((jarEntry = entries.nextElement()) != null);) {
name = jarEntry.getName();
if (name.contains(".class")) {
name = name.substring(0, name.length() - 6).replace('/', '.');
if (name.contains(pckgname)) {
classes.add(Class.forName(name));
}
}
}
}
/**
* Attempts to list all the classes in the specified package as determined
* by the context class loader
*
* @param pckgname
* the package name to search
* @return a list of classes that exist within that package
* @throws ClassNotFoundException
* if something went wrong
*/
public static ArrayList<Class<?>> getClassesForPackage(String pckgname)
throws ClassNotFoundException {
final ArrayList<Class<?>> classes = new ArrayList<Class<?>>();
try {
final ClassLoader cld = Thread.currentThread()
.getContextClassLoader();
if (cld == null)
throw new ClassNotFoundException("Can't get class loader.");
final Enumeration<URL> resources = cld.getResources(pckgname
.replace('.', '/'));
URLConnection connection;
for (URL url = null; resources.hasMoreElements()
&& ((url = resources.nextElement()) != null);) {
try {
connection = url.openConnection();
if (connection instanceof JarURLConnection) {
checkJarFile((JarURLConnection) connection, pckgname,
classes);
} else if (connection instanceof FileURLConnection) {
try {
checkDirectory(
new File(URLDecoder.decode(url.getPath(),
"UTF-8")), pckgname, classes);
} catch (final UnsupportedEncodingException ex) {
throw new ClassNotFoundException(
pckgname
+ " does not appear to be a valid package (Unsupported encoding)",
ex);
}
} else
throw new ClassNotFoundException(pckgname + " ("
+ url.getPath()
+ ") does not appear to be a valid package");
} catch (final IOException ioex) {
throw new ClassNotFoundException(
"IOException was thrown when trying to get all resources for "
+ pckgname, ioex);
}
}
} catch (final NullPointerException ex) {
throw new ClassNotFoundException(
pckgname
+ " does not appear to be a valid package (Null pointer exception)",
ex);
} catch (final IOException ioex) {
throw new ClassNotFoundException(
"IOException was thrown when trying to get all resources for "
+ pckgname, ioex);
}
return classes;
}
这三个方法使您能够查找给定包中的所有类。 你可以这样使用它:
getClassesForPackage("package.your.classes.are.in");
解释:
该方法首先获取当前的ClassLoader。然后，它获取包含该包的所有资源，并迭代这些url。然后它创建一个URLConnection并确定我们拥有的URl类型。它可以是一个目录(FileURLConnection)，也可以是一个jar或zip文件中的目录(JarURLConnection)。根据我们所拥有的连接类型，将调用两个不同的方法。
首先让我们看看如果它是一个FileURLConnection会发生什么。 它首先检查传递的File是否存在，是否为目录。如果是这样，它会检查它是否是类文件。如果是这样，一个Class对象将被创建并放入数组列表中。如果它不是一个类文件，而是一个目录，我们只需迭代它，并做同样的事情。所有其他案例/文件将被忽略。
如果URLConnection是JarURLConnection，另一个私有助手方法将被调用。此方法迭代zip/jar存档中的所有条目。如果一个条目是一个类文件，并且在包内部，一个class对象将被创建并存储在ArrayList中。
在所有资源被解析后，它(main方法)返回包含给定包中当前ClassLoader所知道的所有类的ArrayList。
如果进程在任何时候失败，将抛出一个ClassNotFoundException，其中包含关于确切原因的详细信息。
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