更新时间:2023-01-10 18:42:00
以下代码实现了Java 9+中的模块路径扫描(拼图)。它找到callstack上的所有类,然后为每个类引用调用 classRef.getModule()。getLayer()。getConfiguration()。modules()
,返回aa 列表< ResolvedModule>
,而不仅仅是列表< Module>
。 ( ResolvedModule
允许您访问模块资源,而模块
则不允许。)给定 ResolvedModule
每个模块的引用,你可以调用 .reference()
方法来获取 ModuleReference
对于一个模块。 ModuleReference#open()
为您提供 ModuleReader
,它允许您使用 ModuleReader #list(),或者使用打开资源> Optional< InputStream> ModuleReader #open(resourcePath)
或可选< ByteBuffer> ModuleReader#读取(resourcePath)
。然后,在完成模块后,关闭 ModuleReader
。这在我见过的任何地方都没有记录。要弄清楚这一切是非常困难的。但这里是代码,希望其他人能从中受益。
The following code achieves module path scanning in Java 9+ (Jigsaw). It finds all classes on the callstack, then for each class reference, calls classRef.getModule().getLayer().getConfiguration().modules()
, which returns a a List<ResolvedModule>
, rather than just a List<Module>
. (ResolvedModule
gives you access to the module resources, whereas Module
does not.) Given a ResolvedModule
reference for each module, you can call the .reference()
method to get the ModuleReference
for a module. ModuleReference#open()
gives you a ModuleReader
, which allows you to list the resources in a module, using ModuleReader#list()
, or to open a resource using Optional<InputStream> ModuleReader#open(resourcePath)
or Optional<ByteBuffer> ModuleReader#read(resourcePath)
. You then close the ModuleReader
when you're done with the module. This is not documented anywhere that I have seen. It was very difficult to figure all this out. But here is the code, in the hope that someone else will benefit from this.
请注意,即使在JDK9 +中,您仍然可以使用传统的classpath元素和模块路径元素,对于完整的模块路径+类路径扫描,您应该使用适当的类路径扫描解决方案,例如 ClassGraph ,支持使用以下机制进行模块扫描(免责声明,我是作者)。
Note that even in JDK9+, you can still utilize traditional classpath elements along with module path elements, so for a complete module path + classpath scan, you should probably use a proper classpath scanning solution, such as ClassGraph, which supports module scanning using the below mechanism (disclaimer, I am the author).
package main;
import java.lang.StackWalker.Option;
import java.lang.module.ModuleReader;
import java.lang.module.ModuleReference;
import java.lang.module.ResolvedModule;
import java.net.URI;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.AbstractMap.SimpleEntry;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Deque;
import java.util.HashSet;
import java.util.List;
import java.util.Map.Entry;
import java.util.Optional;
import java.util.Set;
import java.util.stream.Stream;
public class Java9Scanner {
private static final class CallerResolver extends SecurityManager {
/** Get classes in the call stack. */
@Override
protected Class<?>[] getClassContext() {
return super.getClassContext();
}
}
/** Recursively find the topological sort order of ancestral layers. */
private static void findLayerOrder(ModuleLayer layer,
Set<ModuleLayer> visited, Deque<ModuleLayer> layersOut) {
if (visited.add(layer)) {
List<ModuleLayer> parents = layer.parents();
for (int i = 0; i < parents.size(); i++) {
findLayerOrder(parents.get(i), visited, layersOut);
}
layersOut.push(layer);
}
}
/** Get ModuleReferences from a Class reference. */
private static List<Entry<ModuleReference, ModuleLayer>> findModuleRefs(
Class<?>[] callStack) {
Deque<ModuleLayer> layerOrder = new ArrayDeque<>();
Set<ModuleLayer> visited = new HashSet<>();
for (int i = 0; i < callStack.length; i++) {
ModuleLayer layer = callStack[i].getModule().getLayer();
findLayerOrder(layer, visited, layerOrder);
}
Set<ModuleReference> addedModules = new HashSet<>();
List<Entry<ModuleReference, ModuleLayer>> moduleRefs = new ArrayList<>();
for (ModuleLayer layer : layerOrder) {
Set<ResolvedModule> modulesInLayerSet = layer.configuration()
.modules();
final List<Entry<ModuleReference, ModuleLayer>> modulesInLayer =
new ArrayList<>();
for (ResolvedModule module : modulesInLayerSet) {
modulesInLayer
.add(new SimpleEntry<>(module.reference(), layer));
}
// Sort modules in layer by name for consistency
Collections.sort(modulesInLayer,
(e1, e2) -> e1.getKey().descriptor().name()
.compareTo(e2.getKey().descriptor().name()));
// To be safe, dedup ModuleReferences, in case a module occurs in multiple
// layers and reuses its ModuleReference (no idea if this can happen)
for (Entry<ModuleReference, ModuleLayer> m : modulesInLayer) {
if (addedModules.add(m.getKey())) {
moduleRefs.add(m);
}
}
}
return moduleRefs;
}
/** Get the classes in the call stack. */
private static Class<?>[] getCallStack() {
// Try StackWalker (JDK 9+)
PrivilegedAction<Class<?>[]> stackWalkerAction = new PrivilegedAction<Class<?>[]>() {
@Override
public Class<?>[] run() {
List<Class<?>> stackFrameClasses = new ArrayList<>();
StackWalker.getInstance(Option.RETAIN_CLASS_REFERENCE)
.forEach(sf -> stackFrameClasses
.add(sf.getDeclaringClass()));
return stackFrameClasses.toArray(new Class<?>[0]);
}
};
try {
// Try with doPrivileged()
return AccessController
.doPrivileged(stackWalkerAction);
} catch (Exception e) {
}
try {
// Try without doPrivileged()
return stackWalkerAction.run();
} catch (Exception e) {
}
// Try SecurityManager
PrivilegedAction<Class<?>[]> callerResolverAction = new PrivilegedAction<Class<?>[]>() {
@Override
public Class<?>[] run() {
return new CallerResolver().getClassContext();
}
};
try {
// Try with doPrivileged()
return AccessController
.doPrivileged(callerResolverAction);
} catch (Exception e) {
}
try {
// Try without doPrivileged()
return callerResolverAction.run();
} catch (Exception e) {
}
// As a fallback, use getStackTrace() to try to get the call stack
try {
throw new Exception();
} catch (final Exception e) {
final List<Class<?>> classes = new ArrayList<>();
for (final StackTraceElement elt : e.getStackTrace()) {
try {
classes.add(Class.forName(elt.getClassName()));
} catch (final Throwable e2) {
// Ignore
}
}
if (classes.size() > 0) {
return classes.toArray(new Class<?>[0]);
} else {
// Last-ditch effort -- include just this class in the call stack
return new Class<?>[] { Java9Scanner.class };
}
}
}
/**
* Return true if the given module name is a system module. There can be
* system modules in layers above the boot layer.
*/
private static boolean isSystemModule(
final ModuleReference moduleReference) {
URI location = moduleReference.location().orElse(null);
if (location == null) {
return true;
}
final String scheme = location.getScheme();
return scheme != null && scheme.equalsIgnoreCase("jrt");
}
public static void main(String[] args) throws Exception {
// Get ModuleReferences for modules of all classes in call stack,
List<Entry<ModuleReference, ModuleLayer>> systemModuleRefs = new ArrayList<>();
List<Entry<ModuleReference, ModuleLayer>> nonSystemModuleRefs = new ArrayList<>();
Class<?>[] callStack = getCallStack();
List<Entry<ModuleReference, ModuleLayer>> moduleRefs = findModuleRefs(
callStack);
// Split module refs into system and non-system modules based on module name
for (Entry<ModuleReference, ModuleLayer> m : moduleRefs) {
(isSystemModule(m.getKey()) ? systemModuleRefs
: nonSystemModuleRefs).add(m);
}
// List system modules
System.out.println("\nSYSTEM MODULES:\n");
for (Entry<ModuleReference, ModuleLayer> e : systemModuleRefs) {
ModuleReference ref = e.getKey();
System.out.println(" " + ref.descriptor().name());
}
// Show info for non-system modules
System.out.println("\nNON-SYSTEM MODULES:");
for (Entry<ModuleReference, ModuleLayer> e : nonSystemModuleRefs) {
ModuleReference ref = e.getKey();
ModuleLayer layer = e.getValue();
System.out.println("\n " + ref.descriptor().name());
System.out.println(
" Version: " + ref.descriptor().toNameAndVersion());
System.out.println(
" Packages: " + ref.descriptor().packages());
System.out.println(" ClassLoader: "
+ layer.findLoader(ref.descriptor().name()));
Optional<URI> location = ref.location();
if (location.isPresent()) {
System.out.println(" Location: " + location.get());
}
try (ModuleReader moduleReader = ref.open()) {
Stream<String> stream = moduleReader.list();
stream.forEach(s -> System.out.println(" File: " + s));
}
}
}
}