ELResolver.java
/*
* 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.util.Iterator;
/**
* @author Jacob Hookom [jacob/hookom.net]
*/
public abstract class ELResolver {
public static final String TYPE = "type";
public static final String RESOLVABLE_AT_DESIGN_TIME = "resolvableAtDesignTime";
/**
* Obtain the value of the given property on the given object using the given context.
*
* @param context The EL context for this evaluation
* @param base The base object on which the property is to be found
* @param property The property whose value is to be returned
*
* @return the value of the provided property
*
* @throws NullPointerException If the supplied context is <code>null</code>
* @throws PropertyNotFoundException If the base/property combination provided to the resolver is one that the
* resolver can handle but no match was found or a match was found but was not
* readable
* @throws ELException Wraps any exception throw whilst resolving the property
*/
public abstract Object getValue(ELContext context, Object base, Object property);
/**
* Invokes a method on the the given object.
*
* @param context The EL context for this evaluation
* @param base The base object on which the method is to be found
* @param method The method to invoke
* @param paramTypes The types of the parameters of the method to invoke
* @param params The parameters with which to invoke the method
*
* @return This default implementation always returns <code>null</code>
*
* @since EL 2.2
*/
public Object invoke(ELContext context, Object base, Object method, Class<?>[] paramTypes, Object[] params) {
return null;
}
/**
* Obtain the most generally acceptable type that may be used to set the given property on the given object using
* the given context.
*
* @param context The EL context for this evaluation
* @param base The base object on which the property is to be found
* @param property The property whose type is to be returned
*
* @return the most general type that maybe used to set the provided property or {@code null} if the resolver is
* read-only.
*
* @throws NullPointerException If the supplied context is <code>null</code>
* @throws PropertyNotFoundException If the base/property combination provided to the resolver is one that the
* resolver can handle but no match was found or a match was found but was not
* readable
* @throws ELException Wraps any exception throw whilst resolving the property
*/
public abstract Class<?> getType(ELContext context, Object base, Object property);
/**
* Set the value of the given property on the given object using the given context.
*
* @param context The EL context for this evaluation
* @param base The base object on which the property is to be found
* @param property The property whose value is to be set
* @param value The value to set the property to
*
* @throws NullPointerException If the supplied context is <code>null</code>
* @throws PropertyNotFoundException If the base/property combination provided to the resolver is one that the
* resolver can handle but no match was found
* @throws PropertyNotWritableException If the base/property combination provided to the resolver is one that the
* resolver can handle but the property was not writable
* @throws ELException Wraps any exception throw whilst resolving the property
*/
public abstract void setValue(ELContext context, Object base, Object property, Object value);
/**
* Determine if the given property on the given object is read-only using the given context.
*
* @param context The EL context for this evaluation
* @param base The base object on which the property is to be found
* @param property The property to be checked for read only status
*
* @return <code>true</code> if the identified property is read only, otherwise <code>false</code>
*
* @throws NullPointerException If the supplied context is <code>null</code>
* @throws PropertyNotFoundException If the base/property combination provided to the resolver is one that the
* resolver can handle but no match was found
* @throws ELException Wraps any exception throw whilst resolving the property
*/
public abstract boolean isReadOnly(ELContext context, Object base, Object property);
/**
* Obtain the feature descriptors for the resolvable properties of the given object.
*
* @param context The context in which the examination takes place
* @param base The object to examine
*
* @return An iterator, possibly empty, of feature descriptors of the given object
*/
public abstract Iterator<java.beans.FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base);
/**
* Obtain the most common type that is acceptable for the given base object.
*
* @param context The context in which the examination takes place
* @param base The object to examine
*
* @return {code null} if the most common type cannot be determine, otherwise the most common type
*/
public abstract Class<?> getCommonPropertyType(ELContext context, Object base);
/**
* Converts the given object to the given type.
*
* @param context The EL context for this evaluation
* @param obj The object to convert
* @param type The type to which the object should be converted
*
* @return This default implementation always returns <code>null</code>
*
* @since EL 3.0
*/
public Object convertToType(ELContext context, Object obj, Class<?> type) {
context.setPropertyResolved(false);
return null;
}
}