001/* 002 * Copyright 2002-2018 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.expression; 018 019import java.util.List; 020 021/** 022 * Expressions are executed in an evaluation context. It is in this context that 023 * references are resolved when encountered during expression evaluation. 024 * 025 * <p>There is a default implementation of this EvaluationContext interface: 026 * {@link org.springframework.expression.spel.support.StandardEvaluationContext} 027 * which can be extended, rather than having to implement everything manually. 028 * 029 * @author Andy Clement 030 * @author Juergen Hoeller 031 * @since 3.0 032 */ 033public interface EvaluationContext { 034 035 /** 036 * Return the default root context object against which unqualified 037 * properties/methods/etc should be resolved. This can be overridden 038 * when evaluating an expression. 039 */ 040 TypedValue getRootObject(); 041 042 /** 043 * Return a list of accessors that will be asked in turn to read/write a property. 044 */ 045 List<PropertyAccessor> getPropertyAccessors(); 046 047 /** 048 * Return a list of resolvers that will be asked in turn to locate a constructor. 049 */ 050 List<ConstructorResolver> getConstructorResolvers(); 051 052 /** 053 * Return a list of resolvers that will be asked in turn to locate a method. 054 */ 055 List<MethodResolver> getMethodResolvers(); 056 057 /** 058 * Return a bean resolver that can look up beans by name. 059 */ 060 BeanResolver getBeanResolver(); 061 062 /** 063 * Return a type locator that can be used to find types, either by short or 064 * fully qualified name. 065 */ 066 TypeLocator getTypeLocator(); 067 068 /** 069 * Return a type converter that can convert (or coerce) a value from one type to another. 070 */ 071 TypeConverter getTypeConverter(); 072 073 /** 074 * Return a type comparator for comparing pairs of objects for equality. 075 */ 076 TypeComparator getTypeComparator(); 077 078 /** 079 * Return an operator overloader that may support mathematical operations 080 * between more than the standard set of types. 081 */ 082 OperatorOverloader getOperatorOverloader(); 083 084 /** 085 * Set a named variable within this evaluation context to a specified value. 086 * @param name variable to set 087 * @param value value to be placed in the variable 088 */ 089 void setVariable(String name, Object value); 090 091 /** 092 * Look up a named variable within this evaluation context. 093 * @param name variable to lookup 094 * @return the value of the variable, or {@code null} if not found 095 */ 096 Object lookupVariable(String name); 097 098}