javax.el.ExpressionFactory Maven / Gradle / Ivy
/*
* 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.File;
import java.io.IOException;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.util.Properties;
import org.apache.geronimo.osgi.locator.ProviderLocator;
/**
*
* @since 2.1
*/
public abstract class ExpressionFactory {
private static final String PLATFORM_DEFAULT_FACTORY_CLASS = "org.apache.el.ExpressionFactoryImpl";
private static final String SYSTEM_PROPERTY_NAME = "javax.el.ExpressionFactory";
private static final String JAVA_RUNTIME_PROPERTY_FILE_LOCATION = "lib" + File.separator + "el.properties";
static {
try {
ELUtils.setCachedExpressionFactory(newInstance());
} catch (Exception e) {
}
}
public abstract Object coerceToType(Object obj, Class expectedType) throws ELException;
public abstract ValueExpression createValueExpression(ELContext context, String expression, Class expectedType) throws NullPointerException, ELException;
public abstract ValueExpression createValueExpression(Object instance, Class expectedType);
public abstract MethodExpression createMethodExpression(ELContext context, String expression, Class expectedReturnType, Class[] expectedParamTypes) throws ELException, NullPointerException;
public static ExpressionFactory newInstance() {
return newInstance(null);
}
public static ExpressionFactory newInstance(Properties properties) {
Class implClass = loadExpressionFactoryImplClass();
if (properties == null) {
return newInstance0(implClass);
}
try {
Constructor constructor = implClass.getConstructor(Properties.class);
try {
return (ExpressionFactory) constructor.newInstance(properties);
} catch (IllegalArgumentException e) {
throw new ELException("Fail to create ExpressionFactory instance", e);
} catch (InstantiationException e) {
throw new ELException("Fail to create ExpressionFactory instance", e);
} catch (IllegalAccessException e) {
throw new ELException("Fail to create ExpressionFactory instance", e);
} catch (InvocationTargetException e) {
throw new ELException("Fail to create ExpressionFactory instance", e);
}
} catch (SecurityException e) {
throw new ELException("Fail to get constuctor from ExpressionFactory implementation class", e);
} catch (NoSuchMethodException e) {
return newInstance0(implClass);
}
}
private static ExpressionFactory newInstance0(Class implClass) {
try {
return (ExpressionFactory) implClass.newInstance();
} catch (IllegalAccessException e) {
throw new ELException("Fail to create ExpressionFactory instance", e);
} catch (InstantiationException e) {
throw new ELException("Fail to create ExpressionFactory instance", e);
}
}
private static String lookupExpressionFactoryImplClass() {
String implClassName = lookupByJREPropertyFile();
if (implClassName == null) {
implClassName = System.getProperty(SYSTEM_PROPERTY_NAME);
if (implClassName == null) {
implClassName = PLATFORM_DEFAULT_FACTORY_CLASS;
}
}
return implClassName;
}
private static Class lookupByServiceEntryURL(ClassLoader cl) throws ClassNotFoundException {
// use the common lookup/parsing logic for the service files.
return ProviderLocator.getServiceClass(ExpressionFactory.class.getName(), ExpressionFactory.class, cl);
}
private static String lookupByJREPropertyFile() {
try {
return ProviderLocator.lookupByJREPropertyFile(JAVA_RUNTIME_PROPERTY_FILE_LOCATION, SYSTEM_PROPERTY_NAME);
} catch (IOException e) {
throw new ELException("Fail to read configuration file", e);
}
}
private static Class loadExpressionFactoryImplClass() {
String implClassName = null;
try {
ClassLoader cl = Thread.currentThread().getContextClassLoader();
if (cl == null) {
cl = ClassLoader.getSystemClassLoader();
}
// check the META-INF/services defintions first
Class cls = lookupByServiceEntryURL(cl);
if (cls != null) {
return cls;
}
// try resolving using the alternate property lookups (always returns
// something, since there is a default
implClassName = lookupExpressionFactoryImplClass();
return ProviderLocator.loadClass(implClassName, ExpressionFactory.class, cl);
} catch (ClassNotFoundException e) {
// can be thrown either as a result of a classloading failure in the service
// lookup or a failure to directly load the class
if (implClassName != null) {
throw new ELException("Fail to load implementation class " + implClassName, e);
}
else {
throw new ELException("Fail to load implementation class", e);
}
}
}
}