javax.el.StaticFieldELResolver Maven / Gradle / Ivy
Show all versions of javaee-api Show documentation
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright (c) 2012 Oracle and/or its affiliates. All rights reserved.
*
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can
* obtain a copy of the License at
* https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
* or packager/legal/LICENSE.txt. See the License for the specific
* language governing permissions and limitations under the License.
*
* When distributing the software, include this License Header Notice in each
* file and include the License file at packager/legal/LICENSE.txt.
*
* GPL Classpath Exception:
* Oracle designates this particular file as subject to the "Classpath"
* exception as provided by Oracle in the GPL Version 2 section of the License
* file that accompanied this code.
*
* Modifications:
* If applicable, add the following below the License Header, with the fields
* enclosed by brackets [] replaced by your own identifying information:
* "Portions Copyright [year] [name of copyright owner]"
*
* Contributor(s):
* If you wish your version of this file to be governed by only the CDDL or
* only the GPL Version 2, indicate your decision by adding "[Contributor]
* elects to include this software in this distribution under the [CDDL or GPL
* Version 2] license." If you don't indicate a single choice of license, a
* recipient has the option to distribute your version of this file under
* either the CDDL, the GPL Version 2 or to extend the choice of license to
* its licensees as provided above. However, if you add GPL Version 2 code
* and therefore, elected the GPL Version 2 license, then the option applies
* only if the new code is made subject to such option by the copyright
* holder.
*/
package javax.el;
import java.util.Iterator;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.Constructor;
import java.beans.FeatureDescriptor;
/**
* An {@link ELResolver} for resolving static fields, enum constants and
* static methods. Also handles constructor calls as a special case.
* The resolver handles base objects of the type {@link ELClass}, which
* is usually generated by an EL implementation.
*
* @see ELClass
* @since EL 3.0
*/
public class StaticFieldELResolver extends ELResolver {
/**
* Returns the value of a static field.
* If the base object is an instance of ELClass and the
* property is String, the
* propertyResolved property of the ELContext
* object must be set to true by this resolver, before
* returning. If this property is not true after this
* method is called, the caller should ignore the return value.
*
* If the property is a public static field of class specified in
* ELClass, return the value of the static field.
* An Enum constant is a
* public static field of an Enum object, and is a special case of this.
* @param context The context of this evaluation.
* @param base An ELClass.
* @param property A static field name.
* @return If the propertyResolved property of
* ELContext was set to true, then
* the static field value.
* @throws NullPointerException if context is null.
* @throws PropertyNotFoundException if the specified class does not exist,
* or if the field is not a public static filed of the class,
* or if the field is inaccessible.
*/
@Override
public Object getValue(ELContext context, Object base, Object property) {
if (context == null) {
throw new NullPointerException();
}
if (base instanceof ELClass && property instanceof String) {
Class klass = ((ELClass)base).getKlass();
String fieldName = (String) property;
try {
context.setPropertyResolved(base, property);
Field field = klass.getField(fieldName);
int mod = field.getModifiers();
if (Modifier.isPublic(mod) && Modifier.isStatic(mod)) {
return field.get(null);
}
} catch (NoSuchFieldException ex) {
} catch (IllegalAccessException ex) {
}
throw new PropertyNotFoundException(
ELUtil.getExceptionMessageString(context,
"staticFieldReadError",
new Object[] { klass.getName(), fieldName}));
}
return null;
}
/**
* Attempts to write to a static field.
* If the base object is an instance of ELClassand the
* property is String, a PropertyNotWritableException
* will always be thrown, because writing to a static field is not
* allowed.
* @param context The context of this evaluation.
* @param base An ELClass
* @param property The name of the field
* @param value The value to set the field of the class to.
* @throws NullPointerException if context is null
* @throws PropertyNotWritableException
*/
@Override
public void setValue(ELContext context, Object base, Object property,
Object value) {
if (context == null) {
throw new NullPointerException();
}
if (base instanceof ELClass && property instanceof String) {
Class klass = ((ELClass)base).getKlass();
String fieldName = (String) property;
throw new PropertyNotWritableException(
ELUtil.getExceptionMessageString(context,
"staticFieldWriteError",
new Object[] { klass.getName(), fieldName}));
}
}
/**
*
Invokes a public static method or the constructor for a class.
*
* If the base object is an instance of ELClass and the
* method is a String,
* the propertyResolved property of the
* ELContext object must be set to true
* by the resolver, before returning. If this property is not
* true after this method is called, the caller
* should ignore the return value.
* Invoke the public static method specified by method.
* The process involved in the method selection is
* the same as that used in {@link BeanELResolver}.
*
* As a special case, if the name of the method is "<init>", the
* constructor for the class will be invoked.
*
* @param base An ELClass
* @param method When coerced to a String,
* the simple name of the method.
* @param paramTypes An array of Class objects identifying the
* method's formal parameter types, in declared order.
* Use an empty array if the method has no parameters.
* Can be null, in which case the method's formal
* parameter types are assumed to be unknown.
* @param params The parameters to pass to the method, or
* null if no parameters.
* @return The result of the method invocation (null if
* the method has a void return type).
* @throws MethodNotFoundException if no suitable method can be found.
* @throws ELException if an exception was thrown while performing
* (base, method) resolution. The thrown exception must be
* included as the cause property of this exception, if
* available. If the exception thrown is an
* InvocationTargetException, extract its
* cause and pass it to the
* ELException constructor.
*/
@Override
public Object invoke(ELContext context,
Object base,
Object method,
Class[] paramTypes,
Object[] params) {
if (context == null) {
throw new NullPointerException();
}
if (!(base instanceof ELClass && method instanceof String)) {
return null;
}
Class klass = ((ELClass)base).getKlass();
String name = (String) method;
Object ret;
if ("".equals(name)) {
Constructor constructor =
ELUtil.findConstructor(klass, paramTypes, params);
ret = ELUtil.invokeConstructor(context, constructor, params);
} else {
Method meth =
ELUtil.findMethod(klass, name, paramTypes, params, true);
ret = ELUtil.invokeMethod(context, meth, null, params);
}
context.setPropertyResolved(base, method);
return ret;
}
/**
* Returns the type of a static field.
* If the base object is an instance of ELClassand the
* property is a String,
* the propertyResolved property of the
* ELContext object must be set to true
* by the resolver, before returning. If this property is not
* true after this method is called, the caller can
* safely assume no value has been set.
*
* If the property string is a public static field of class specified in
* ELClass, return the type of the static field.
* @param context The context of this evaluation.
* @param base An ELClass.
* @param property The name of the field.
* @return If the propertyResolved property of
* ELContext was set to true, then
* the type of the type of the field.
* @throws NullPointerException if context is null.
* @throws PropertyNotFoundException if field is not a public static
* filed of the class, or if the field is inaccessible.
*/
@Override
public Class getType(ELContext context, Object base, Object property) {
if (context == null) {
throw new NullPointerException();
}
if (base instanceof ELClass && property instanceof String) {
Class klass = ((ELClass)base).getKlass();
String fieldName = (String) property;
try {
context.setPropertyResolved(true);
Field field = klass.getField(fieldName);
int mod = field.getModifiers();
if (Modifier.isPublic(mod) && Modifier.isStatic(mod)) {
return field.getType();
}
} catch (NoSuchFieldException ex) {
}
throw new PropertyNotFoundException(
ELUtil.getExceptionMessageString(context,
"staticFieldReadError",
new Object[] { klass.getName(), fieldName}));
}
return null;
}
/**
* Inquires whether the static field is writable.
* If the base object is an instance of ELClassand the
* property is a String,
* the propertyResolved property of the
* ELContext object must be set to true
* by the resolver, before returning. If this property is not
* true after this method is called, the caller can
* safely assume no value has been set.
*
* Always returns a true because writing to a static field
* is not allowed.
* @param context The context of this evaluation.
* @param base An ELClass.
* @param property The name of the bean.
* @return true
* @throws NullPointerException if context is null.
*/
@Override
public boolean isReadOnly(ELContext context, Object base, Object property) {
if (context == null) {
throw new NullPointerException();
}
if (base instanceof ELClass && property instanceof String) {
Class klass = ((ELClass)base).getKlass();
context.setPropertyResolved(true);
}
return true;
}
/**
* Returns the properties that can be resolved.
* Always returns null, since there is no reason to
* iterate through a list of one element: field name.
* @param context The context of this evaluation.
* @param base An ELClass.
* @return null.
*/
@Override
public Iterator getFeatureDescriptors(
ELContext context, Object base) {
return null;
}
/**
* Returns the type of the property.
* Always returns String.class, since a field name is a String.
* @param context The context of this evaluation.
* @param base An ELClass.
* @return String.class.
*/
@Override
public Class getCommonPropertyType(ELContext context, Object base) {
return String.class;
}
}