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/*
* Copyright 2002-2018 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
*
* https://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;
import java.util.List;
import org.springframework.lang.Nullable;
/**
* Expressions are executed in an evaluation context. It is in this context that
* references are resolved when encountered during expression evaluation.
*
* There is a default implementation of this EvaluationContext interface:
* {@link org.springframework.expression.spel.support.StandardEvaluationContext}
* which can be extended, rather than having to implement everything manually.
*
* @author Andy Clement
* @author Juergen Hoeller
* @since 3.0
*/
public interface EvaluationContext {
/**
* Return the default root context object against which unqualified
* properties/methods/etc should be resolved. This can be overridden
* when evaluating an expression.
*/
TypedValue getRootObject();
/**
* Return a list of accessors that will be asked in turn to read/write a property.
*/
List getPropertyAccessors();
/**
* Return a list of resolvers that will be asked in turn to locate a constructor.
*/
List getConstructorResolvers();
/**
* Return a list of resolvers that will be asked in turn to locate a method.
*/
List getMethodResolvers();
/**
* Return a bean resolver that can look up beans by name.
*/
@Nullable
BeanResolver getBeanResolver();
/**
* Return a type locator that can be used to find types, either by short or
* fully qualified name.
*/
TypeLocator getTypeLocator();
/**
* Return a type converter that can convert (or coerce) a value from one type to another.
*/
TypeConverter getTypeConverter();
/**
* Return a type comparator for comparing pairs of objects for equality.
*/
TypeComparator getTypeComparator();
/**
* Return an operator overloader that may support mathematical operations
* between more than the standard set of types.
*/
OperatorOverloader getOperatorOverloader();
/**
* Set a named variable within this evaluation context to a specified value.
* @param name the name of the variable to set
* @param value the value to be placed in the variable
*/
void setVariable(String name, @Nullable Object value);
/**
* Look up a named variable within this evaluation context.
* @param name variable to lookup
* @return the value of the variable, or {@code null} if not found
*/
@Nullable
Object lookupVariable(String name);
}