415 lines
14 KiB
Java
415 lines
14 KiB
Java
/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package javax.el;
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import java.io.File;
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import java.io.FileInputStream;
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import java.io.FileNotFoundException;
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import java.io.IOException;
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import java.io.InputStream;
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import java.lang.ref.WeakReference;
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import java.lang.reflect.Constructor;
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import java.lang.reflect.InvocationTargetException;
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import java.lang.reflect.Method;
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import java.security.AccessController;
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import java.security.PrivilegedAction;
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import java.util.Iterator;
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import java.util.Map;
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import java.util.Properties;
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import java.util.ServiceLoader;
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import java.util.concurrent.ConcurrentHashMap;
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import java.util.concurrent.ConcurrentMap;
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import java.util.concurrent.locks.Lock;
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import java.util.concurrent.locks.ReadWriteLock;
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import java.util.concurrent.locks.ReentrantReadWriteLock;
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/**
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*
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* @since 2.1
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*/
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public abstract class ExpressionFactory {
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private static final boolean IS_SECURITY_ENABLED =
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(System.getSecurityManager() != null);
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private static final String PROPERTY_NAME = "javax.el.ExpressionFactory";
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private static final String PROPERTY_FILE;
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private static final CacheValue nullTcclFactory = new CacheValue();
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private static final ConcurrentMap<CacheKey, CacheValue> factoryCache =
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new ConcurrentHashMap<>();
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static {
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if (IS_SECURITY_ENABLED) {
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PROPERTY_FILE = AccessController.doPrivileged(
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new PrivilegedAction<String>(){
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@Override
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public String run() {
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return System.getProperty("java.home") + File.separator +
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"lib" + File.separator + "el.properties";
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}
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}
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);
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} else {
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PROPERTY_FILE = System.getProperty("java.home") + File.separator + "lib" +
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File.separator + "el.properties";
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}
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}
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/**
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* Create a new {@link ExpressionFactory}. The class to use is determined by
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* the following search order:
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* <ol>
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* <li>services API (META-INF/services/javax.el.ExpressionFactory)</li>
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* <li>$JRE_HOME/lib/el.properties - key javax.el.ExpressionFactory</li>
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* <li>javax.el.ExpressionFactory</li>
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* <li>Platform default implementation -
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* org.apache.el.ExpressionFactoryImpl</li>
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* </ol>
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* @return the new ExpressionFactory
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*/
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public static ExpressionFactory newInstance() {
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return newInstance(null);
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}
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/**
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* Create a new {@link ExpressionFactory} passing in the provided
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* {@link Properties}. Search order is the same as {@link #newInstance()}.
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*
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* @param properties the properties to be passed to the new instance (may be null)
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* @return the new ExpressionFactory
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*/
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public static ExpressionFactory newInstance(Properties properties) {
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ExpressionFactory result = null;
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ClassLoader tccl = Util.getContextClassLoader();
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CacheValue cacheValue;
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Class<?> clazz;
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if (tccl == null) {
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cacheValue = nullTcclFactory;
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} else {
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CacheKey key = new CacheKey(tccl);
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cacheValue = factoryCache.get(key);
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if (cacheValue == null) {
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CacheValue newCacheValue = new CacheValue();
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cacheValue = factoryCache.putIfAbsent(key, newCacheValue);
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if (cacheValue == null) {
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cacheValue = newCacheValue;
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}
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}
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}
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final Lock readLock = cacheValue.getLock().readLock();
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readLock.lock();
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try {
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clazz = cacheValue.getFactoryClass();
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} finally {
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readLock.unlock();
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}
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if (clazz == null) {
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String className = null;
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try {
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final Lock writeLock = cacheValue.getLock().writeLock();
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writeLock.lock();
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try {
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className = cacheValue.getFactoryClassName();
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if (className == null) {
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className = discoverClassName(tccl);
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cacheValue.setFactoryClassName(className);
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}
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if (tccl == null) {
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clazz = Class.forName(className);
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} else {
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clazz = tccl.loadClass(className);
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}
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cacheValue.setFactoryClass(clazz);
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} finally {
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writeLock.unlock();
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}
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} catch (ClassNotFoundException e) {
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throw new ELException(Util.message(null, "expressionFactory.cannotFind", className), e);
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}
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}
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try {
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Constructor<?> constructor = null;
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// Do we need to look for a constructor that will take properties?
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if (properties != null) {
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try {
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constructor = clazz.getConstructor(Properties.class);
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} catch (SecurityException se) {
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throw new ELException(se);
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} catch (NoSuchMethodException nsme) {
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// This can be ignored
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// This is OK for this constructor not to exist
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}
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}
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if (constructor == null) {
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result = (ExpressionFactory) clazz.getConstructor().newInstance();
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} else {
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result =
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(ExpressionFactory) constructor.newInstance(properties);
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}
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} catch (InvocationTargetException e) {
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Throwable cause = e.getCause();
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Util.handleThrowable(cause);
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throw new ELException(Util.message(null, "expressionFactory.cannotCreate", clazz.getName()), e);
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} catch (ReflectiveOperationException | IllegalArgumentException e) {
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throw new ELException(Util.message(null, "expressionFactory.cannotCreate", clazz.getName()), e);
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}
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return result;
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}
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/**
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* Create a new value expression.
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*
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* @param context The EL context for this evaluation
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* @param expression The String representation of the value expression
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* @param expectedType The expected type of the result of evaluating the
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* expression
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*
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* @return A new value expression formed from the input parameters
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*
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* @throws NullPointerException
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* If the expected type is <code>null</code>
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* @throws ELException
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* If there are syntax errors in the provided expression
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*/
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public abstract ValueExpression createValueExpression(ELContext context,
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String expression, Class<?> expectedType);
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public abstract ValueExpression createValueExpression(Object instance,
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Class<?> expectedType);
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/**
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* Create a new method expression instance.
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*
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* @param context The EL context for this evaluation
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* @param expression The String representation of the method
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* expression
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* @param expectedReturnType The expected type of the result of invoking the
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* method
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* @param expectedParamTypes The expected types of the input parameters
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*
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* @return A new method expression formed from the input parameters.
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*
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* @throws NullPointerException
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* If the expected parameters types are <code>null</code>
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* @throws ELException
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* If there are syntax errors in the provided expression
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*/
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public abstract MethodExpression createMethodExpression(ELContext context,
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String expression, Class<?> expectedReturnType,
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Class<?>[] expectedParamTypes);
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/**
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* Coerce the supplied object to the requested type.
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*
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* @param obj The object to be coerced
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* @param expectedType The type to which the object should be coerced
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*
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* @return An instance of the requested type.
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*
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* @throws ELException
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* If the conversion fails
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*/
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public abstract Object coerceToType(Object obj, Class<?> expectedType);
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/**
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* @return This default implementation returns null
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*
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* @since EL 3.0
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*/
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public ELResolver getStreamELResolver() {
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return null;
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}
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/**
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* @return This default implementation returns null
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*
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* @since EL 3.0
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*/
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public Map<String,Method> getInitFunctionMap() {
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return null;
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}
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/**
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* Key used to cache ExpressionFactory discovery information per class
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* loader. The class loader reference is never {@code null}, because
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* {@code null} tccl is handled separately.
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*/
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private static class CacheKey {
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private final int hash;
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private final WeakReference<ClassLoader> ref;
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public CacheKey(ClassLoader cl) {
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hash = cl.hashCode();
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ref = new WeakReference<>(cl);
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}
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@Override
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public int hashCode() {
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return hash;
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}
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@Override
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public boolean equals(Object obj) {
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if (obj == this) {
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return true;
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}
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if (!(obj instanceof CacheKey)) {
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return false;
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}
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ClassLoader thisCl = ref.get();
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if (thisCl == null) {
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return false;
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}
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return thisCl == ((CacheKey) obj).ref.get();
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}
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}
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private static class CacheValue {
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private final ReadWriteLock lock = new ReentrantReadWriteLock();
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private String className;
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private WeakReference<Class<?>> ref;
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public CacheValue() {
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}
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public ReadWriteLock getLock() {
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return lock;
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}
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public String getFactoryClassName() {
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return className;
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}
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public void setFactoryClassName(String className) {
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this.className = className;
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}
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public Class<?> getFactoryClass() {
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return ref != null ? ref.get() : null;
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}
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public void setFactoryClass(Class<?> clazz) {
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ref = new WeakReference<Class<?>>(clazz);
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}
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}
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/**
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* Discover the name of class that implements ExpressionFactory.
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*
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* @param tccl
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* {@code ClassLoader}
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* @return Class name. There is default, so it is never {@code null}.
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*/
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private static String discoverClassName(ClassLoader tccl) {
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String className = null;
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// First services API
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className = getClassNameServices(tccl);
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if (className == null) {
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if (IS_SECURITY_ENABLED) {
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className = AccessController.doPrivileged(
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new PrivilegedAction<String>() {
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@Override
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public String run() {
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return getClassNameJreDir();
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}
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}
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);
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} else {
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// Second el.properties file
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className = getClassNameJreDir();
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}
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}
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if (className == null) {
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if (IS_SECURITY_ENABLED) {
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className = AccessController.doPrivileged(
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new PrivilegedAction<String>() {
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@Override
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public String run() {
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return getClassNameSysProp();
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}
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}
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);
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} else {
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// Third system property
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className = getClassNameSysProp();
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}
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}
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if (className == null) {
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// Fourth - default
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className = "org.apache.el.ExpressionFactoryImpl";
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}
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return className;
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}
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private static String getClassNameServices(ClassLoader tccl) {
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ExpressionFactory result = null;
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ServiceLoader<ExpressionFactory> serviceLoader = ServiceLoader.load(ExpressionFactory.class, tccl);
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Iterator<ExpressionFactory> iter = serviceLoader.iterator();
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while (result == null && iter.hasNext()) {
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result = iter.next();
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}
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if (result == null) {
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return null;
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}
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return result.getClass().getName();
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}
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private static String getClassNameJreDir() {
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File file = new File(PROPERTY_FILE);
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if (file.canRead()) {
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try (InputStream is = new FileInputStream(file)){
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Properties props = new Properties();
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props.load(is);
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String value = props.getProperty(PROPERTY_NAME);
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if (value != null && value.trim().length() > 0) {
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return value.trim();
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}
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} catch (FileNotFoundException e) {
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// Should not happen - ignore it if it does
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} catch (IOException e) {
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throw new ELException(Util.message(null, "expressionFactory.readFailed", PROPERTY_FILE), e);
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}
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}
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return null;
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}
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private static final String getClassNameSysProp() {
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String value = System.getProperty(PROPERTY_NAME);
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if (value != null && value.trim().length() > 0) {
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return value.trim();
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}
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return null;
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}
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}
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