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Exerimental Minimal Tomcat for Programmatic Use
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.tomcat.util.compat;
import java.lang.reflect.Field;
import java.security.PrivilegedExceptionAction;
import java.util.concurrent.Callable;
import java.util.concurrent.CompletionException;
import javax.security.auth.Subject;
import org.apache.tomcat.util.res.StringManager;
/**
* This is the base implementation class for JRE compatibility and provides an implementation based on Java 17.
* Sub-classes may extend this class and provide alternative implementations for later JRE versions
*/
public class JreCompat {
private static final JreCompat instance;
private static final boolean graalAvailable;
private static final boolean jre19Available;
private static final boolean jre21Available;
private static final boolean jre22Available;
private static final StringManager sm = StringManager.getManager(JreCompat.class);
static {
boolean result = false;
try {
Class nativeImageClazz = Class.forName("org.graalvm.nativeimage.ImageInfo");
result = Boolean.TRUE.equals(nativeImageClazz.getMethod("inImageCode").invoke(null));
} catch (ClassNotFoundException e) {
// Must be Graal
} catch (ReflectiveOperationException | IllegalArgumentException e) {
// Should never happen
}
graalAvailable = result || System.getProperty("org.graalvm.nativeimage.imagecode") != null;
// This is Tomcat 11.0.x with a minimum Java version of Java 17.
// Look for the highest supported JVM first
if (Jre22Compat.isSupported()) {
instance = new Jre22Compat();
jre22Available = true;
jre21Available = true;
jre19Available = true;
} else if (Jre21Compat.isSupported()) {
instance = new Jre21Compat();
jre22Available = false;
jre21Available = true;
jre19Available = true;
} else if (Jre19Compat.isSupported()) {
instance = new Jre19Compat();
jre22Available = false;
jre21Available = false;
jre19Available = true;
} else {
instance = new JreCompat();
jre22Available = false;
jre21Available = false;
jre19Available = false;
}
}
public static JreCompat getInstance() {
return instance;
}
public static boolean isGraalAvailable() {
return graalAvailable;
}
public static boolean isJre19Available() {
return jre19Available;
}
public static boolean isJre21Available() {
return jre21Available;
}
public static boolean isJre22Available() {
return jre22Available;
}
// Java 17 implementations of Java 19 methods
/**
* Obtains the executor, if any, used to create the provided thread.
*
* @param thread The thread to examine
*
* @return The executor, if any, that created the provided thread
*
* @throws NoSuchFieldException If a field used via reflection to obtain the executor cannot be found
* @throws SecurityException If a security exception occurs while trying to identify the executor
* @throws IllegalArgumentException If the instance object does not match the class of the field when obtaining a
* field value via reflection
* @throws IllegalAccessException If a field is not accessible due to access restrictions
*/
public Object getExecutor(Thread thread)
throws NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException {
Object result = null;
// Runnable wrapped by Thread
// "target" in Sun/Oracle JDK
// "runnable" in IBM JDK
// "action" in Apache Harmony
Object target = null;
for (String fieldName : new String[] { "target", "runnable", "action" }) {
try {
Field targetField = thread.getClass().getDeclaredField(fieldName);
targetField.setAccessible(true);
target = targetField.get(thread);
break;
} catch (NoSuchFieldException nfe) {
continue;
}
}
// "java.util.concurrent" code is in public domain,
// so all implementations are similar including our
// internal fork.
if (target != null && target.getClass().getCanonicalName() != null && (target.getClass().getCanonicalName()
.equals("org.apache.tomcat.util.threads.ThreadPoolExecutor.Worker") ||
target.getClass().getCanonicalName().equals("java.util.concurrent.ThreadPoolExecutor.Worker"))) {
Field executorField = target.getClass().getDeclaredField("this$0");
executorField.setAccessible(true);
result = executorField.get(target);
}
return result;
}
// Java 17 implementations of Java 21 methods
/**
* Create a thread builder for virtual threads using the given name to name the threads.
*
* @param name The base name for the threads
*
* @return The thread buidler for virtual threads
*/
public Object createVirtualThreadBuilder(String name) {
throw new UnsupportedOperationException(sm.getString("jreCompat.noVirtualThreads"));
}
/**
* Create a thread with the given thread builder and use it to execute the given runnable.
*
* @param threadBuilder The thread builder to use to create a thread
* @param command The command to run
*/
public void threadBuilderStart(Object threadBuilder, Runnable command) {
throw new UnsupportedOperationException(sm.getString("jreCompat.noVirtualThreads"));
}
/*
* This is a slightly different usage of JreCompat.
*
* Subject.doAs() was deprecated in Java 18 and replaced with Subject.callAs(). As of Java 23, calling
* Subject.doAs() will trigger an UnsupportedOperationException unless the java.security.manager system property is
* set. To avoid Tomcat installations using Spnego authentication having to set this value, JreCompat is used to
* call Subject.callAs() instead.
*
* Because Java versions 18 to 22 inclusive support both the old and the new method, the switch over can occur at
* any Java version from 18 to 22 inclusive. Java 21 onwards was selected as it as an LTS version and that removes
* the need to add a Jre18Compat class.
*
* So, the slightly longer description for this method is:
*
* Java 17 implementation of a method replaced between Java 18 and 22 with the replacement method being used by
* Tomcat when running on Java 21 onwards.
*/
@SuppressWarnings("removal")
public T callAs(Subject subject, Callable action) throws CompletionException {
try {
return Subject.doAs(subject, new PrivilegedExceptionAction() {
@Override
public T run() throws Exception {
return action.call();
}
});
} catch (Exception e) {
throw new CompletionException(e);
}
}
}