/*
* Copyright 2002-2009 the original author or authors.
*
* Licensed 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 org.springframework.expression;
/**
* A property accessor is able to read (and possibly write) to object properties. The interface places no restrictions
* and so implementors are free to access properties directly as fields or through getters or in any other way they see
* as appropriate. A resolver can optionally specify an array of target classes for which it should be called - but if
* it returns null from getSpecificTargetClasses() then it will be called for all property references and given a chance
* to determine if it can read or write them. Property resolvers are considered to be ordered and each will be called in
* turn. The only rule that affects the call order is that any naming the target class directly in
* getSpecifiedTargetClasses() will be called first, before the general resolvers.
*
* @author Andy Clement
* @since 3.0
*/
public interface PropertyAccessor {
/**
* Return an array of classes for which this resolver should be called. Returning null indicates this is a general
* resolver that can be called in an attempt to resolve a property on any type.
* @return an array of classes that this resolver is suitable for (or null if a general resolver)
*/
Class[] getSpecificTargetClasses();
/**
* Called to determine if a resolver instance is able to access a specified property on a specified target object.
* @param context the evaluation context in which the access is being attempted
* @param target the target object upon which the property is being accessed
* @param name the name of the property being accessed
* @return true if this resolver is able to read the property
* @throws AccessException if there is any problem determining whether the property can be read
*/
boolean canRead(EvaluationContext context, Object target, String name) throws AccessException;
/**
* Called to read a property from a specified target object
* @param context the evaluation context in which the access is being attempted
* @param target the target object upon which the property is being accessed
* @param name the name of the property being accessed
* @return a TypedValue object wrapping the property value read and a type descriptor for it
* @throws AccessException if there is any problem accessing the property value
*/
TypedValue read(EvaluationContext context, Object target, String name) throws AccessException;
/**
* Called to determine if a resolver instance is able to write to a specified property on a specified target object.
* @param context the evaluation context in which the access is being attempted
* @param target the target object upon which the property is being accessed
* @param name the name of the property being accessed
* @return true if this resolver is able to write to the property
* @throws AccessException if there is any problem determining whether the property can be written to
*/
boolean canWrite(EvaluationContext context, Object target, String name) throws AccessException;
/**
* Called to write to a property on a specified target object. Should only succeed if canWrite() also returns true.
* @param context the evaluation context in which the access is being attempted
* @param target the target object upon which the property is being accessed
* @param name the name of the property being accessed
* @param newValue the new value for the property
* @throws AccessException if there is any problem writing to the property value
*/
void write(EvaluationContext context, Object target, String name, Object newValue) throws AccessException;
}
|