是否可以找到给定包中的所有类或接口？ （快速查看例如Package，似乎没有。）
答案 0 :(得分：342)
由于类加载器的动态特性，这是不可能的。类加载器不需要告诉VM它可以提供哪些类，而是只需要处理类的请求，并且必须返回一个类或抛出异常。
但是，如果您编写自己的类加载器，或检查类路径及其罐子，则可以找到此信息。这将通过文件系统操作，而不是反射。甚至可能有图书馆可以帮助你做到这一点。
如果有类生成或远程交付，您将无法发现这些类。
普通方法是在某处注册您需要在文件中访问的类，或者在不同的类中引用它们。或者只是在命名时使用约定。
附录：The Reflections Library将允许您在当前类路径中查找类。它可用于获取包中的所有类：
Reflections reflections = new Reflections("my.project.prefix");
Set<Class<? extends Object>> allClasses =
reflections.getSubTypesOf(Object.class);
答案 1 :(得分：175)
您应该查看开源Reflections library。有了它，您可以轻松实现您想要的目标。
首先，设置反射索引（因为默认情况下禁用搜索所有类，所以它有点乱）：
List<ClassLoader> classLoadersList = new LinkedList<ClassLoader>();
classLoadersList.add(ClasspathHelper.contextClassLoader());
classLoadersList.add(ClasspathHelper.staticClassLoader());
Reflections reflections = new Reflections(new ConfigurationBuilder()
.setScanners(new SubTypesScanner(false /* don't exclude Object.class */), new ResourcesScanner())
.setUrls(ClasspathHelper.forClassLoader(classLoadersList.toArray(new ClassLoader[0])))
.filterInputsBy(new FilterBuilder().include(FilterBuilder.prefix("org.your.package"))));
然后，您可以查询给定包中的所有对象：
Set<Class<?>> classes = reflections.getSubTypesOf(Object.class);
答案 2 :(得分：111)
Google Guava 14包含一个新类ClassPath，其中包含三种扫描顶级类的方法：
getTopLevelClasses() getTopLevelClasses(String packageName) getTopLevelClassesRecursive(String packageName) 有关详细信息，请参阅ClassPath javadocs。
答案 3 :(得分：98)
您可以使用ClassLoader使用this method 1 。
/**
* 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 此方法最初取自http://snippets.dzone.com/posts/show/4831，即互联网档案的archived，与现在相关联。该代码段也可在https://dzone.com/articles/get-all-classes-within-package处找到。
答案 4 :(得分：82)
此示例适用于Spring 4，但您也可以在早期版本中找到类路径扫描程序。
// create scanner and disable default filters (that is the 'false' argument)
final ClassPathScanningCandidateComponentProvider provider = new ClassPathScanningCandidateComponentProvider(false);
// add include filters which matches all the classes (or use your own)
provider.addIncludeFilter(new RegexPatternTypeFilter(Pattern.compile(".*")));
// get matching classes defined in the package
final Set<BeanDefinition> classes = provider.findCandidateComponents("my.package.name");
// this is how you can load the class type from BeanDefinition instance
for (BeanDefinition bean: classes) {
Class<?> clazz = Class.forName(bean.getBeanClassName());
// ... do your magic with the class ...
}
注意：在版本14中，API仍标记为 @Beta ，因此请注意生产代码。
final ClassLoader loader = Thread.currentThread().getContextClassLoader();
for (final ClassPath.ClassInfo info : ClassPath.from(loader).getTopLevelClasses()) {
if (info.getName().startsWith("my.package.")) {
final Class<?> clazz = info.load();
// do something with your clazz
}
}
答案 5 :(得分：35)
你好。我总是遇到上述解决方案（以及其他网站）的一些问题 作为开发人员，我正在为API编写插件。 API禁止使用任何外部库或第三方工具。该设置还包含jar或zip文件中的代码和直接位于某些目录中的类文件的混合。所以我的代码必须能够在每个设置中工作。经过大量研究后，我提出了一种方法，该方法至少可以在所有可能的设置中使用95％。
以下代码基本上是一直有效的过度杀伤方法。
此代码扫描给定包中包含的所有类。它仅适用于当前ClassLoader中的所有类。
/**
* 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;
}
这三种方法使您能够查找给定包中的所有类 你这样使用它：
getClassesForPackage("package.your.classes.are.in");
该方法首先获取当前ClassLoader。然后它获取包含所述包的所有资源并迭代这些URL。然后它创建一个URLConnection并确定我们拥有什么类型的URl。它可以是目录（FileURLConnection），也可以是jar或zip文件（JarURLConnection）内的目录。根据我们的连接类型，将调用两种不同的方法。
首先让我们看看如果它是FileURLConnection会发生什么
它首先检查传递的文件是否存在并且是否是目录。如果是这种情况，则检查它是否是类文件。如果是这样，将创建Class对象并将其放入ArrayList。如果它不是类文件而是目录，我们只需迭代它并执行相同的操作。所有其他案例/文件都将被忽略。
如果URLConnection是JarURLConnection，则将调用其他私有帮助方法。此方法迭代zip / jar存档中的所有条目。如果一个条目是类文件并且在包内，则将创建Class对象并将其存储在ArrayList中。
在解析完所有资源之后（main方法）返回ArrayList包含给定包中所有当前ClassLoader知道的类。
如果该过程在任何时候失败，将会抛出ClassNotFoundException，其中包含有关确切原因的详细信息。
答案 6 :(得分：14)
不使用任何额外的库：
package test;
import java.io.DataInputStream;
import java.io.InputStream;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
public class Test {
public static void main(String[] args) throws Exception{
List<Class> classes = getClasses(Test.class.getClassLoader(),"test");
for(Class c:classes){
System.out.println("Class: "+c);
}
}
public static List<Class> getClasses(ClassLoader cl,String pack) throws Exception{
String dottedPackage = pack.replaceAll("[/]", ".");
List<Class> classes = new ArrayList<Class>();
URL upackage = cl.getResource(pack);
DataInputStream dis = new DataInputStream((InputStream) upackage.getContent());
String line = null;
while ((line = dis.readLine()) != null) {
if(line.endsWith(".class")) {
classes.add(Class.forName(dottedPackage+"."+line.substring(0,line.lastIndexOf('.'))));
}
}
return classes;
}
}
答案 7 :(得分：13)
通常，类加载器不允许扫描类路径上的所有类。但通常唯一使用的类加载器是UrlClassLoader，我们可以从中检索目录和jar文件列表（请参阅getURLs）并逐个打开它们以列出可用的类。这种方法称为类路径扫描，在Scannotation和Reflections中实现。
Reflections reflections = new Reflections("my.package");
Set<Class<? extends Object>> classes = reflections.getSubTypesOf(Object.class);
另一种方法是使用Java Pluggable Annotation Processing API编写注释处理器，它将在编译时收集所有带注释的类，并构建索引文件以供运行时使用。此机制在ClassIndex库中实现：
// package-info.java
@IndexSubclasses
package my.package;
// your code
Iterable<Class> classes = ClassIndex.getPackageClasses("my.package");
请注意，由于Java编译器会自动发现类路径中的任何处理器，因此扫描完全自动化无需额外设置。
答案 8 :(得分：6)
我写了FastClasspathScanner来解决这个问题。它处理许多不同类型的类路径扫描任务，具有简单的API，适用于许多不同的ClassLoader和类路径环境，经过精心并行化，并针对高速和低内存消耗进行了高度优化。它甚至可以生成类图的GraphViz可视化，显示类如何相互连接。
对于查找给定包中所有类或接口的原始问题，您可以执行以下操作：
List<String> classNames = new FastClasspathScanner("com.mypackage").scan()
.getNamesOfAllClasses();
有许多可能的变体 - 请参阅文档（上面链接）以获取完整信息。
答案 9 :(得分：5)
我是这样做的。我扫描所有子文件夹（子包），我不尝试加载匿名类：
/**
* Attempts to list all the classes in the specified package as determined
* by the context class loader, recursively, avoiding anonymous classes
*
* @param pckgname
* the package name to search
* @return a list of classes that exist within that package
* @throws ClassNotFoundException
* if something went wrong
*/
private static List<Class> getClassesForPackage(String pckgname) throws ClassNotFoundException {
// This will hold a list of directories matching the pckgname. There may be more than one if a package is split over multiple jars/paths
ArrayList<File> directories = new ArrayList<File>();
String packageToPath = pckgname.replace('.', '/');
try {
ClassLoader cld = Thread.currentThread().getContextClassLoader();
if (cld == null) {
throw new ClassNotFoundException("Can't get class loader.");
}
// Ask for all resources for the packageToPath
Enumeration<URL> resources = cld.getResources(packageToPath);
while (resources.hasMoreElements()) {
directories.add(new File(URLDecoder.decode(resources.nextElement().getPath(), "UTF-8")));
}
} catch (NullPointerException x) {
throw new ClassNotFoundException(pckgname + " does not appear to be a valid package (Null pointer exception)");
} catch (UnsupportedEncodingException encex) {
throw new ClassNotFoundException(pckgname + " does not appear to be a valid package (Unsupported encoding)");
} catch (IOException ioex) {
throw new ClassNotFoundException("IOException was thrown when trying to get all resources for " + pckgname);
}
ArrayList<Class> classes = new ArrayList<Class>();
// For every directoryFile identified capture all the .class files
while (!directories.isEmpty()){
File directoryFile = directories.remove(0);
if (directoryFile.exists()) {
// Get the list of the files contained in the package
File[] files = directoryFile.listFiles();
for (File file : files) {
// we are only interested in .class files
if ((file.getName().endsWith(".class")) && (!file.getName().contains("$"))) {
// removes the .class extension
int index = directoryFile.getPath().indexOf(packageToPath);
String packagePrefix = directoryFile.getPath().substring(index).replace('/', '.');;
try {
String className = packagePrefix + '.' + file.getName().substring(0, file.getName().length() - 6);
classes.add(Class.forName(className));
} catch (NoClassDefFoundError e)
{
// do nothing. this class hasn't been found by the loader, and we don't care.
}
} else if (file.isDirectory()){ // If we got to a subdirectory
directories.add(new File(file.getPath()));
}
}
} else {
throw new ClassNotFoundException(pckgname + " (" + directoryFile.getPath() + ") does not appear to be a valid package");
}
}
return classes;
}
答案 10 :(得分：4)
是的，使用很少的API，你可以，这就是我喜欢这样做的方式，面对这个问题我正在使用hibernate core＆amp;必须找到用某个注释注释的类。
将这些作为自定义注释，使用该注释标记要拾取的类。
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface EntityToBeScanned {
}
然后用
标记你的课程@EntityToBeScanned
public MyClass{
}
使这个实用程序类具有以下方法
public class ClassScanner {
public static Set<Class<?>> allFoundClassesAnnotatedWithEntityToBeScanned(){
Reflections reflections = new Reflections(".*");
Set<Class<?>> annotated = reflections.getTypesAnnotatedWith(EntityToBeScanned.class);
return annotated;
}
}
调用 allFoundClassesAnnotatedWithEntityToBeScanned（）方法，以获取找到的 Set 类。
您将需要下面提供的库
<!-- https://mvnrepository.com/artifact/com.google.guava/guava -->
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>21.0</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.javassist/javassist -->
<dependency>
<groupId>org.javassist</groupId>
<artifactId>javassist</artifactId>
<version>3.22.0-CR1</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.reflections/reflections -->
<dependency>
<groupId>org.reflections</groupId>
<artifactId>reflections</artifactId>
<version>0.9.10</version>
</dependency>
答案 11 :(得分：4)
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
它适用于BOTH基于文件的类路径和jar文件。
如果你跑步＆＃39;制作＆＃39;签出项目后，它将打印出来：
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.
答案 12 :(得分：3)
您需要在类路径中查找每个类加载器条目：
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，只需在右侧子目录中查找：
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，请检查它的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，一旦你拥有包的所有类名，你可以尝试用反射加载它们并分析它们是类还是接口等。
答案 13 :(得分：3)
我一直在尝试使用Reflections库，但是在使用它时遇到了一些问题，而且我应该包含太多的jar只是为了简单地获取包上的类。
我会在这个重复的问题中发布我找到的解决方案：How to get all classes names in a package?
answer was written by sp00m;我添加了一些更正以使其有效：
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，只需将find方法调用为此示例中提到的sp00n： 如果需要，我已经添加了类的实例的创建。
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();
//...
}
答案 14 :(得分：2)
我刚写了一个util类，它包含了测试方法，你可以检查一下〜
IteratePackageUtil.java：
package eric.j2se.reflect;
import java.util.Set;
import org.reflections.Reflections;
import org.reflections.scanners.ResourcesScanner;
import org.reflections.scanners.SubTypesScanner;
import org.reflections.util.ClasspathHelper;
import org.reflections.util.ConfigurationBuilder;
import org.reflections.util.FilterBuilder;
/**
* an util to iterate class in a package,
*
* @author eric
* @date Dec 10, 2013 12:36:46 AM
*/
public class IteratePackageUtil {
/**
* <p>
* Get set of all class in a specified package recursively. this only support lib
* </p>
* <p>
* class of sub package will be included, inner class will be included,
* </p>
* <p>
* could load class that use the same classloader of current class, can't load system packages,
* </p>
*
* @param pkg
* path of a package
* @return
*/
public static Set<Class<? extends Object>> getClazzSet(String pkg) {
// prepare reflection, include direct subclass of Object.class
Reflections reflections = new Reflections(new ConfigurationBuilder().setScanners(new SubTypesScanner(false), new ResourcesScanner())
.setUrls(ClasspathHelper.forClassLoader(ClasspathHelper.classLoaders(new ClassLoader[0])))
.filterInputsBy(new FilterBuilder().includePackage(pkg)));
return reflections.getSubTypesOf(Object.class);
}
public static void test() {
String pkg = "org.apache.tomcat.util";
Set<Class<? extends Object>> clazzSet = getClazzSet(pkg);
for (Class<? extends Object> clazz : clazzSet) {
System.out.println(clazz.getName());
}
}
public static void main(String[] args) {
test();
}
}
答案 15 :(得分：2)
Aleksander Blomskøld's solution对我的参数化测试@RunWith(Parameterized.class)无效。测试被正确命名，也找到了但未执行的地方：
-------------------------------------------------------
T E S T S
-------------------------------------------------------
Running some.properly.named.test.run.with.maven.SomeTest
Tests run: 0, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.123 sec
已报告类似问题here。
在我的情况下，@Parameters正在创建包中每个类的实例。在IDE中本地运行时，测试运行良好。但是，在运行Maven时，没有找到AleksanderBlomskøld解决方案的类。
我确实让它与以下剪辑一起工作，这是受到DavidPärsson对AleksanderBlomskøld的答案的评论的启发：
Reflections reflections = new Reflections(new ConfigurationBuilder()
.setScanners(new SubTypesScanner(false /* don't exclude Object.class */), new ResourcesScanner())
.addUrls(ClasspathHelper.forJavaClassPath())
.filterInputsBy(new FilterBuilder()
.include(FilterBuilder.prefix(basePackage))));
Set<Class<?>> subTypesOf = reflections.getSubTypesOf(Object.class);
答案 16 :(得分：2)
几乎所有答案都使用Reflections或从文件系统中读取类文件。如果您尝试从文件系统中读取类，则在将应用程序打包为JAR或其他时可能会出错。此外，您可能不希望为此目的使用单独的库。
这是另一种纯Java方法，而不依赖于文件系统。
import javax.tools.JavaFileObject;
import javax.tools.StandardJavaFileManager;
import javax.tools.StandardLocation;
import javax.tools.ToolProvider;
import java.io.File;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import java.util.stream.StreamSupport;
public class PackageUtil {
public static Collection<Class> getClasses(final String pack) throws Exception {
final StandardJavaFileManager fileManager = ToolProvider.getSystemJavaCompiler().getStandardFileManager(null, null, null);
return StreamSupport.stream(fileManager.list(StandardLocation.CLASS_PATH, pack, Collections.singleton(JavaFileObject.Kind.CLASS), false).spliterator(), false)
.map(javaFileObject -> {
try {
final String[] split = javaFileObject.getName()
.replace(".class", "")
.replace(")", "")
.split(Pattern.quote(File.separator));
final String fullClassName = pack + "." + split[split.length - 1];
return Class.forName(fullClassName);
} catch (ClassNotFoundException e) {
throw new RuntimeException(e);
}
})
.collect(Collectors.toCollection(ArrayList::new));
}
}
Java 8不是必须的。您可以使用for循环而不是stream。 你可以像这样测试它
public static void main(String[] args) throws Exception {
final String pack = "java.nio.file"; // Or any other package
PackageUtil.getClasses(pack).stream().forEach(System.out::println);
}
答案 17 :(得分：1)
值得一提
如果您希望获得某个包下所有类的列表，可以通过以下方式使用$：
Reflection这将创建一个类列表，以后您可以根据需要使用它们。
答案 18 :(得分：1)
这是非常可能的，但如果没有像Reflections这样的额外库，则很难......
这很难，因为你没有完整的工具来获得课程名称
而且，我接受了ClassFinder类的代码：
package play.util;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
/**
* Created by LINKOR on 26.05.2017 in 15:12.
* Date: 2017.05.26
*/
public class FileClassFinder {
private JarFile file;
private boolean trouble;
public FileClassFinder(String filePath) {
try {
file = new JarFile(filePath);
} catch (IOException e) {
trouble = true;
}
}
public List<String> findClasses(String pkg) {
ArrayList<String> classes = new ArrayList<>();
Enumeration<JarEntry> entries = file.entries();
while (entries.hasMoreElements()) {
JarEntry cls = entries.nextElement();
if (!cls.isDirectory()) {
String fileName = cls.getName();
String className = fileName.replaceAll("/", ".").replaceAll(File.pathSeparator, ".").substring(0, fileName.lastIndexOf('.'));
if (className.startsWith(pkg)) classes.add(className.substring(pkg.length() + 1));
}
}
return classes;
}
}
答案 19 :(得分：1)
如果您没有使用任何动态类加载器，则可以搜索类路径，并为每个条目搜索目录或JAR文件。
答案 20 :(得分：0)
基于@Staale's answer，并且为了不依赖第三方库，我将通过检查第一个包物理位置来实现文件系统方法：
import java.io.File;
import java.io.FileFilter;
import java.util.ArrayList;
...
Class<?>[] foundClasses = new Class<?>[0];
final ArrayList<Class<?>> foundClassesDyn = new ArrayList<Class<?>>();
new java.io.File(
klass.getResource(
"/" + curPackage.replace( "." , "/")
).getFile()
).listFiles(
new java.io.FileFilter() {
public boolean accept(java.io.File file) {
final String classExtension = ".class";
if ( file.isFile()
&& file.getName().endsWith(classExtension)
// avoid inner classes
&& ! file.getName().contains("$") )
{
try {
String className = file.getName();
className = className.substring(0, className.length() - classExtension.length());
foundClassesDyn.add( Class.forName( curPackage + "." + className ) );
} catch (ClassNotFoundException e) {
e.printStackTrace(System.out);
}
}
return false;
}
}
);
foundClasses = foundClassesDyn.toArray(foundClasses);
答案 21 :(得分：0)
如果您只是想加载一组相关的类，那么Spring可以帮助您。
Spring可以在一行代码中实例化实现给定接口的所有类的列表或映射。列表或映射将包含实现该接口的所有类的实例。
话虽如此，作为从文件系统中加载类列表的替代方法，而不是在您要加载的所有类中实现相同的接口，无论包和使用Spring为您提供所有的实例他们。这样，您可以加载（并实例化）您想要的所有类，无论它们在哪个包中。
另一方面，如果将它们全部放在包中是你想要的，那么只需让该包中的所有类实现给定的接口。
答案 22 :(得分：0)
普通java： FindAllClassesUsingPlainJavaReflectionTest.java
@Slf4j
class FindAllClassesUsingPlainJavaReflectionTest {
private static final Function<Throwable, RuntimeException> asRuntimeException = throwable -> {
log.error(throwable.getLocalizedMessage());
return new RuntimeException(throwable);
};
private static final Function<String, Collection<Class<?>>> findAllPackageClasses = basePackageName -> {
Locale locale = Locale.getDefault();
Charset charset = StandardCharsets.UTF_8;
val fileManager = ToolProvider.getSystemJavaCompiler()
.getStandardFileManager(/* diagnosticListener */ null, locale, charset);
StandardLocation location = StandardLocation.CLASS_PATH;
JavaFileObject.Kind kind = JavaFileObject.Kind.CLASS;
Set<JavaFileObject.Kind> kinds = Collections.singleton(kind);
val javaFileObjects = Try.of(() -> fileManager.list(location, basePackageName, kinds, /* recurse */ true))
.getOrElseThrow(asRuntimeException);
String pathToPackageAndClass = basePackageName.replace(".", File.separator);
Function<String, String> mapToClassName = s -> {
String prefix = Arrays.stream(s.split(pathToPackageAndClass))
.findFirst()
.orElse("");
return s.replaceFirst(prefix, "")
.replaceAll(File.separator, ".");
};
return StreamSupport.stream(javaFileObjects.spliterator(), /* parallel */ true)
.filter(javaFileObject -> javaFileObject.getKind().equals(kind))
.map(FileObject::getName)
.map(fileObjectName -> fileObjectName.replace(".class", ""))
.map(mapToClassName)
.map(className -> Try.of(() -> Class.forName(className))
.getOrElseThrow(asRuntimeException))
.collect(Collectors.toList());
};
@Test
@DisplayName("should get classes recursively in given package")
void test() {
Collection<Class<?>> classes = findAllPackageClasses.apply(getClass().getPackage().getName());
assertThat(classes).hasSizeGreaterThan(4);
classes.stream().map(String::valueOf).forEach(log::info);
}
}
PS：为了简化处理错误等的样板，我在这里使用vavr和lombok库
其他实现可以在my GitHub daggerok/java-reflection-find-annotated-classes-or-methods repo
中找到答案 23 :(得分：0)
那呢：
public static List<Class<?>> getClassesForPackage(final String pkgName) throws IOException, URISyntaxException {
final String pkgPath = pkgName.replace('.', '/');
final URI pkg = Objects.requireNonNull(ClassLoader.getSystemClassLoader().getResource(pkgPath)).toURI();
final ArrayList<Class<?>> allClasses = new ArrayList<Class<?>>();
Path root;
if (pkg.toString().startsWith("jar:")) {
try {
root = FileSystems.getFileSystem(pkg).getPath(pkgPath);
} catch (final FileSystemNotFoundException e) {
root = FileSystems.newFileSystem(pkg, Collections.emptyMap()).getPath(pkgPath);
}
} else {
root = Paths.get(pkg);
}
final String extension = ".class";
try (final Stream<Path> allPaths = Files.walk(root)) {
allPaths.filter(Files::isRegularFile).forEach(file -> {
try {
final String path = file.toString().replace('/', '.');
final String name = path.substring(path.indexOf(pkgName), path.length() - extension.length());
allClasses.add(Class.forName(name));
} catch (final ClassNotFoundException | StringIndexOutOfBoundsException ignored) {
}
});
}
return allClasses;
}
然后可以重载该函数：
public static List<Class<?>> getClassesForPackage(final Package pkg) throws IOException, URISyntaxException {
return getClassesForPackage(pkg.getName());
}
如果需要测试：
public static void main(final String[] argv) throws IOException, URISyntaxException {
for (final Class<?> cls : getClassesForPackage("my.package")) {
System.out.println(cls);
}
for (final Class<?> cls : getClassesForPackage(MyClass.class.getPackage())) {
System.out.println(cls);
}
}
如果您的IDE没有导入助手：
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.nio.file.FileSystemNotFoundException;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Objects;
import java.util.stream.Stream;
有效：
来自您的IDE
用于JAR文件
没有外部依赖项
答案 24 :(得分：0)
我找不到一个简单的事情来干短活。所以就在这里，我拧了一段时间后自己做了：
Reflections reflections =
new Reflections(new ConfigurationBuilder()
.filterInputsBy(new FilterBuilder().includePackage(packagePath))
.setUrls(ClasspathHelper.forPackage(packagePath))
.setScanners(new SubTypesScanner(false)));
Set<String> typeList = reflections.getAllTypes();
答案 25 :(得分：0)
如果您在春天，可以使用PathMatchingResourcePatternResolver;
PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
Resource[] resources = resolver.getResources("classpath*:some/package/name/*.class");
Arrays.asList(resources).forEach(r->{
...
});
答案 26 :(得分：-3)
这是不可能的，因为包中的所有类都可能没有被加载，而你总是知道类的包。