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.context.expression; 018 019import java.util.Map; 020 021import org.springframework.core.DefaultParameterNameDiscoverer; 022import org.springframework.core.ParameterNameDiscoverer; 023import org.springframework.expression.Expression; 024import org.springframework.expression.spel.standard.SpelExpressionParser; 025import org.springframework.lang.Nullable; 026import org.springframework.util.Assert; 027import org.springframework.util.ObjectUtils; 028 029/** 030 * Shared utility class used to evaluate and cache SpEL expressions that 031 * are defined on {@link java.lang.reflect.AnnotatedElement}. 032 * 033 * @author Stephane Nicoll 034 * @since 4.2 035 * @see AnnotatedElementKey 036 */ 037public abstract class CachedExpressionEvaluator { 038 039 private final SpelExpressionParser parser; 040 041 private final ParameterNameDiscoverer parameterNameDiscoverer = new DefaultParameterNameDiscoverer(); 042 043 044 /** 045 * Create a new instance with the specified {@link SpelExpressionParser}. 046 */ 047 protected CachedExpressionEvaluator(SpelExpressionParser parser) { 048 Assert.notNull(parser, "SpelExpressionParser must not be null"); 049 this.parser = parser; 050 } 051 052 /** 053 * Create a new instance with a default {@link SpelExpressionParser}. 054 */ 055 protected CachedExpressionEvaluator() { 056 this(new SpelExpressionParser()); 057 } 058 059 060 /** 061 * Return the {@link SpelExpressionParser} to use. 062 */ 063 protected SpelExpressionParser getParser() { 064 return this.parser; 065 } 066 067 /** 068 * Return a shared parameter name discoverer which caches data internally. 069 * @since 4.3 070 */ 071 protected ParameterNameDiscoverer getParameterNameDiscoverer() { 072 return this.parameterNameDiscoverer; 073 } 074 075 076 /** 077 * Return the {@link Expression} for the specified SpEL value 078 * <p>Parse the expression if it hasn't been already. 079 * @param cache the cache to use 080 * @param elementKey the element on which the expression is defined 081 * @param expression the expression to parse 082 */ 083 protected Expression getExpression(Map<ExpressionKey, Expression> cache, 084 AnnotatedElementKey elementKey, String expression) { 085 086 ExpressionKey expressionKey = createKey(elementKey, expression); 087 Expression expr = cache.get(expressionKey); 088 if (expr == null) { 089 expr = getParser().parseExpression(expression); 090 cache.put(expressionKey, expr); 091 } 092 return expr; 093 } 094 095 private ExpressionKey createKey(AnnotatedElementKey elementKey, String expression) { 096 return new ExpressionKey(elementKey, expression); 097 } 098 099 100 /** 101 * An expression key. 102 */ 103 protected static class ExpressionKey implements Comparable<ExpressionKey> { 104 105 private final AnnotatedElementKey element; 106 107 private final String expression; 108 109 protected ExpressionKey(AnnotatedElementKey element, String expression) { 110 Assert.notNull(element, "AnnotatedElementKey must not be null"); 111 Assert.notNull(expression, "Expression must not be null"); 112 this.element = element; 113 this.expression = expression; 114 } 115 116 @Override 117 public boolean equals(@Nullable Object other) { 118 if (this == other) { 119 return true; 120 } 121 if (!(other instanceof ExpressionKey)) { 122 return false; 123 } 124 ExpressionKey otherKey = (ExpressionKey) other; 125 return (this.element.equals(otherKey.element) && 126 ObjectUtils.nullSafeEquals(this.expression, otherKey.expression)); 127 } 128 129 @Override 130 public int hashCode() { 131 return this.element.hashCode() * 29 + this.expression.hashCode(); 132 } 133 134 @Override 135 public String toString() { 136 return this.element + " with expression \"" + this.expression + "\""; 137 } 138 139 @Override 140 public int compareTo(ExpressionKey other) { 141 int result = this.element.toString().compareTo(other.element.toString()); 142 if (result == 0) { 143 result = this.expression.compareTo(other.expression); 144 } 145 return result; 146 } 147 } 148 149}