/*
* Copyright (c) 2005, 2016, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
package javax.tools;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Iterator;
import java.util.ServiceConfigurationError;
import java.util.ServiceLoader;
/**
* Provides methods for locating tool providers, for example,
* providers of compilers. This class complements the
* functionality of {@link java.util.ServiceLoader}.
*
* @author Peter von der Ahé
* @since 1.6
*/
public class ToolProvider {
private static final String systemJavaCompilerModule = "jdk.compiler";
private static final String systemJavaCompilerName = "com.sun.tools.javac.api.JavacTool";
/**
* Returns the Java™ programming language compiler provided
* with this platform.
* <p>The file manager returned by calling
* {@link JavaCompiler#getStandardFileManager getStandardFileManager}
* on this compiler supports paths provided by any
* {@linkplain java.nio.file.FileSystem filesystem}.</p>
* @return the compiler provided with this platform or
* {@code null} if no compiler is provided
* @implNote This implementation returns the compiler provided
* by the {@code jdk.compiler} module if that module is available,
* and {@code null} otherwise.
*/
public static JavaCompiler getSystemJavaCompiler() {
return getSystemTool(JavaCompiler.class,
systemJavaCompilerModule, systemJavaCompilerName);
}
private static final String systemDocumentationToolModule = "jdk.javadoc";
private static final String systemDocumentationToolName = "jdk.javadoc.internal.api.JavadocTool";
/**
* Returns the Java™ programming language documentation tool provided
* with this platform.
* <p>The file manager returned by calling
* {@link DocumentationTool#getStandardFileManager getStandardFileManager}
* on this tool supports paths provided by any
* {@linkplain java.nio.file.FileSystem filesystem}.</p>
* @return the documentation tool provided with this platform or
* {@code null} if no documentation tool is provided
* @implNote This implementation returns the tool provided
* by the {@code jdk.javadoc} module if that module is available,
* and {@code null} otherwise.
*/
public static DocumentationTool getSystemDocumentationTool() {
return getSystemTool(DocumentationTool.class,
systemDocumentationToolModule, systemDocumentationToolName);
}
/**
* Returns a class loader that may be used to load system tools,
* or {@code null} if no such special loader is provided.
* @implSpec This implementation always returns {@code null}.
* @deprecated This method is subject to removal in a future version of
* Java SE.
* Use the {@link java.util.spi.ToolProvider system tool provider} or
* {@link java.util.ServiceLoader service loader} mechanisms to
* locate system tools as well as user-installed tools.
* @return a class loader, or {@code null}
*/
@Deprecated
public static ClassLoader getSystemToolClassLoader() {
return null;
}
private static final boolean useLegacy;
static {
Class<?> c = null;
try {
c = Class.forName("java.lang.reflect.Module");
} catch (Throwable t) {
}
useLegacy = (c == null);
}
/**
* Get an instance of a system tool using the service loader.
* @implNote By default, this returns the implementation in the specified module.
* For limited backward compatibility, if this code is run on an older version
* of the Java platform that does not support modules, this method will
* try and create an instance of the named class. Note that implies the
* class must be available on the system class path.
* @param <T> the interface of the tool
* @param clazz the interface of the tool
* @param moduleName the name of the module containing the desired implementation
* @param className the class name of the desired implementation
* @return the specified implementation of the tool
*/
private static <T> T getSystemTool(Class<T> clazz, String moduleName, String className) {
if (useLegacy) {
try {
return Class.forName(className, true, ClassLoader.getSystemClassLoader()).
asSubclass(clazz).getConstructor().newInstance();
} catch (ReflectiveOperationException e) {
throw new Error(e);
}
}
try {
ServiceLoader<T> sl = ServiceLoader.load(clazz, ClassLoader.getSystemClassLoader());
for (Iterator<T> iter = sl.iterator(); iter.hasNext(); ) {
T tool = iter.next();
if (matches(tool, moduleName))
return tool;
}
} catch (ServiceConfigurationError e) {
throw new Error(e);
}
return null;
}
/**
* Determine if this is the desired tool instance.
* @param <T> the interface of the tool
* @param tool the instance of the tool
* @param moduleName the name of the module containing the desired implementation
* @return true if and only if the tool matches the specified criteria
*/
private static <T> boolean matches(T tool, String moduleName) {
PrivilegedAction<Boolean> pa = () -> {
// for now, use reflection to implement
// return moduleName.equals(tool.getClass().getModule().getName());
try {
Method getModuleMethod = Class.class.getDeclaredMethod("getModule");
Object toolModule = getModuleMethod.invoke(tool.getClass());
Method getNameMethod = toolModule.getClass().getDeclaredMethod("getName");
String toolModuleName = (String) getNameMethod.invoke(toolModule);
return moduleName.equals(toolModuleName);
} catch (InvocationTargetException | NoSuchMethodException | IllegalAccessException e) {
return false;
}
};
return AccessController.doPrivileged(pa);
}
}