/*
* 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 javax.el;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.lang.ref.WeakReference;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Properties;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
/**
*
* @since 2.1
*/
public abstract class ExpressionFactory {
private static final boolean IS_SECURITY_ENABLED =
(System.getSecurityManager() != null);
private static final String SERVICE_RESOURCE_NAME =
"META-INF/services/javax.el.ExpressionFactory";
private static final String PROPERTY_NAME = "javax.el.ExpressionFactory";
private static final String PROPERTY_FILE;
private static final CacheValue nullTcclFactory = new CacheValue();
private static ConcurrentMap<CacheKey, CacheValue> factoryCache
= new ConcurrentHashMap<CacheKey, CacheValue>();
static {
if (IS_SECURITY_ENABLED) {
PROPERTY_FILE = AccessController.doPrivileged(
new PrivilegedAction<String>(){
@Override
public String run() {
return System.getProperty("java.home") + File.separator +
"lib" + File.separator + "el.properties";
}
}
);
} else {
PROPERTY_FILE = System.getProperty("java.home") + File.separator + "lib" +
File.separator + "el.properties";
}
}
/**
* Coerce the supplied object to the requested type.
*
* @param obj The object to be coerced
* @param expectedType The type to which the object should be coerced
*
* @return An instance of the requested type.
*
* @throws ELException
* If the conversion fails
*/
public abstract Object coerceToType(Object obj, Class<?> expectedType)
throws ELException;
/**
* Create a new value expression.
*
* @param context The EL context for this evaluation
* @param expression The String representation of the value expression
* @param expectedType The expected type of the result of evaluating the
* expression
*
* @return A new value expression formed from the input parameters
*
* @throws NullPointerException
* If the expected type is <code>null</code>
* @throws ELException
* If there are syntax errors in the provided expression
*/
public abstract ValueExpression createValueExpression(ELContext context,
String expression, Class<?> expectedType)
throws NullPointerException, ELException;
public abstract ValueExpression createValueExpression(Object instance,
Class<?> expectedType);
/**
* Create a new method expression instance.
*
* @param context The EL context for this evaluation
* @param expression The String representation of the method
* expression
* @param expectedReturnType The expected type of the result of invoking the
* method
* @param expectedParamTypes The expected types of the input parameters
*
* @return A new method expression formed from the input parameters.
*
* @throws NullPointerException
* If the expected parameters types are <code>null</code>
* @throws ELException
* If there are syntax errors in the provided expression
*/
public abstract MethodExpression createMethodExpression(ELContext context,
String expression, Class<?> expectedReturnType,
Class<?>[] expectedParamTypes) throws ELException,
NullPointerException;
/**
* Create a new {@link ExpressionFactory}. The class to use is determined by
* the following search order:
* <ol>
* <li>services API (META-INF/services/javax.el.ExpressionFactory)</li>
* <li>$JRE_HOME/lib/el.properties - key javax.el.ExpressionFactory</li>
* <li>javax.el.ExpressionFactory</li>
* <li>Platform default implementation -
* org.apache.el.ExpressionFactoryImpl</li>
* </ol>
* @return the new ExpressionFactory
*/
public static ExpressionFactory newInstance() {
return newInstance(null);
}
/**
* Create a new {@link ExpressionFactory} passing in the provided
* {@link Properties}. Search order is the same as {@link #newInstance()}.
*
* @param properties the properties to be passed to the new instance (may be null)
* @return the new ExpressionFactory
*/
public static ExpressionFactory newInstance(Properties properties) {
ExpressionFactory result = null;
ClassLoader tccl = Thread.currentThread().getContextClassLoader();
CacheValue cacheValue;
Class<?> clazz;
if (tccl == null) {
cacheValue = nullTcclFactory;
} else {
CacheKey key = new CacheKey(tccl);
cacheValue = factoryCache.get(key);
if (cacheValue == null) {
CacheValue newCacheValue = new CacheValue();
cacheValue = factoryCache.putIfAbsent(key, newCacheValue);
if (cacheValue == null) {
cacheValue = newCacheValue;
}
}
}
final Lock readLock = cacheValue.getLock().readLock();
readLock.lock();
try {
clazz = cacheValue.getFactoryClass();
} finally {
readLock.unlock();
}
if (clazz == null) {
String className = null;
try {
final Lock writeLock = cacheValue.getLock().writeLock();
writeLock.lock();
try {
className = cacheValue.getFactoryClassName();
if (className == null) {
className = discoverClassName(tccl);
cacheValue.setFactoryClassName(className);
}
if (tccl == null) {
clazz = Class.forName(className);
} else {
clazz = tccl.loadClass(className);
}
cacheValue.setFactoryClass(clazz);
} finally {
writeLock.unlock();
}
} catch (ClassNotFoundException e) {
throw new ELException(
"Unable to find ExpressionFactory of type: " + className,
e);
}
}
try {
Constructor<?> constructor = null;
// Do we need to look for a constructor that will take properties?
if (properties != null) {
try {
constructor = clazz.getConstructor(Properties.class);
} catch (SecurityException se) {
throw new ELException(se);
} catch (NoSuchMethodException nsme) {
// This can be ignored
// This is OK for this constructor not to exist
}
}
if (constructor == null) {
result = (ExpressionFactory) clazz.newInstance();
} else {
result =
(ExpressionFactory) constructor.newInstance(properties);
}
} catch (InstantiationException e) {
throw new ELException(
"Unable to create ExpressionFactory of type: " + clazz.getName(),
e);
} catch (IllegalAccessException e) {
throw new ELException(
"Unable to create ExpressionFactory of type: " + clazz.getName(),
e);
} catch (IllegalArgumentException e) {
throw new ELException(
"Unable to create ExpressionFactory of type: " + clazz.getName(),
e);
} catch (InvocationTargetException e) {
Throwable cause = e.getCause();
if (cause instanceof ThreadDeath) {
throw (ThreadDeath) cause;
}
if (cause instanceof VirtualMachineError) {
throw (VirtualMachineError) cause;
}
throw new ELException(
"Unable to create ExpressionFactory of type: " + clazz.getName(),
e);
}
return result;
}
/**
* Key used to cache ExpressionFactory discovery information per class
* loader. The class loader reference is never {@code null}, because
* {@code null} tccl is handled separately.
*/
private static class CacheKey {
private final int hash;
private final WeakReference<ClassLoader> ref;
public CacheKey(ClassLoader cl) {
hash = cl.hashCode();
ref = new WeakReference<ClassLoader>(cl);
}
@Override
public int hashCode() {
return hash;
}
@Override
public boolean equals(Object obj) {
if (obj == this) {
return true;
}
if (!(obj instanceof CacheKey)) {
return false;
}
ClassLoader thisCl = ref.get();
if (thisCl == null) {
return false;
}
return thisCl == ((CacheKey) obj).ref.get();
}
}
private static class CacheValue {
private final ReadWriteLock lock = new ReentrantReadWriteLock();
private String className;
private WeakReference<Class<?>> ref;
public CacheValue() {
}
public ReadWriteLock getLock() {
return lock;
}
public String getFactoryClassName() {
return className;
}
public void setFactoryClassName(String className) {
this.className = className;
}
public Class<?> getFactoryClass() {
return ref != null ? ref.get() : null;
}
public void setFactoryClass(Class<?> clazz) {
ref = new WeakReference<Class<?>>(clazz);
}
}
/**
* Discover the name of class that implements ExpressionFactory.
*
* @param tccl
* {@code ClassLoader}
* @return Class name. There is default, so it is never {@code null}.
*/
private static String discoverClassName(ClassLoader tccl) {
String className = null;
// First services API
className = getClassNameServices(tccl);
if (className == null) {
if (IS_SECURITY_ENABLED) {
className = AccessController.doPrivileged(
new PrivilegedAction<String>() {
@Override
public String run() {
return getClassNameJreDir();
}
}
);
} else {
// Second el.properties file
className = getClassNameJreDir();
}
}
if (className == null) {
if (IS_SECURITY_ENABLED) {
className = AccessController.doPrivileged(
new PrivilegedAction<String>() {
@Override
public String run() {
return getClassNameSysProp();
}
}
);
} else {
// Third system property
className = getClassNameSysProp();
}
}
if (className == null) {
// Fourth - default
className = "org.apache.el.ExpressionFactoryImpl";
}
return className;
}
private static String getClassNameServices(ClassLoader tccl) {
InputStream is = null;
if (tccl == null) {
is = ClassLoader.getSystemResourceAsStream(SERVICE_RESOURCE_NAME);
} else {
is = tccl.getResourceAsStream(SERVICE_RESOURCE_NAME);
}
if (is != null) {
String line = null;
BufferedReader br = null;
InputStreamReader isr = null;
try {
isr = new InputStreamReader(is, "UTF-8");
br = new BufferedReader(isr);
line = br.readLine();
if (line != null && line.trim().length() > 0) {
return line.trim();
}
} catch (UnsupportedEncodingException e) {
// Should never happen with UTF-8
// If it does - ignore & return null
} catch (IOException e) {
throw new ELException("Failed to read " + SERVICE_RESOURCE_NAME,
e);
} finally {
try {
if (br != null) {
br.close();
}
} catch (IOException ioe) {/*Ignore*/}
try {
if (isr != null) {
isr.close();
}
} catch (IOException ioe) {/*Ignore*/}
try {
is.close();
} catch (IOException ioe) {/*Ignore*/}
}
}
return null;
}
private static String getClassNameJreDir() {
File file = new File(PROPERTY_FILE);
if (file.canRead()) {
InputStream is = null;
try {
is = new FileInputStream(file);
Properties props = new Properties();
props.load(is);
String value = props.getProperty(PROPERTY_NAME);
if (value != null && value.trim().length() > 0) {
return value.trim();
}
} catch (FileNotFoundException e) {
// Should not happen - ignore it if it does
} catch (IOException e) {
throw new ELException("Failed to read " + PROPERTY_FILE, e);
} finally {
if (is != null) {
try {
is.close();
} catch (IOException e) {
// Ignore
}
}
}
}
return null;
}
private static final String getClassNameSysProp() {
String value = System.getProperty(PROPERTY_NAME);
if (value != null && value.trim().length() > 0) {
return value.trim();
}
return null;
}
}