/*
* Copyright 2002-2014 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.cache.interceptor;
import java.lang.reflect.Method;
import java.util.Collection;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import org.springframework.cache.Cache;
import org.springframework.core.DefaultParameterNameDiscoverer;
import org.springframework.core.ParameterNameDiscoverer;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.Expression;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.util.ObjectUtils;
/**
* Utility class handling the SpEL expression parsing.
* Meant to be used as a reusable, thread-safe component.
*
* <p>Performs internal caching for performance reasons
* using {@link MethodCacheKey}.
*
* @author Costin Leau
* @author Phillip Webb
* @author Sam Brannen
* @author Stephane Nicoll
* @since 3.1
*/
class ExpressionEvaluator {
/**
* Indicate that there is no result variable.
*/
public static final Object NO_RESULT = new Object();
/**
* Indicate that the result variable cannot be used at all.
*/
public static final Object RESULT_UNAVAILABLE = new Object();
/**
* The name of the variable holding the result object.
*/
public static final String RESULT_VARIABLE = "result";
private final SpelExpressionParser parser = new SpelExpressionParser();
// shared param discoverer since it caches data internally
private final ParameterNameDiscoverer paramNameDiscoverer = new DefaultParameterNameDiscoverer();
private final Map<ExpressionKey, Expression> keyCache = new ConcurrentHashMap<ExpressionKey, Expression>(64);
private final Map<ExpressionKey, Expression> conditionCache = new ConcurrentHashMap<ExpressionKey, Expression>(64);
private final Map<ExpressionKey, Expression> unlessCache = new ConcurrentHashMap<ExpressionKey, Expression>(64);
private final Map<MethodCacheKey, Method> targetMethodCache = new ConcurrentHashMap<MethodCacheKey, Method>(64);
/**
* Create an {@link EvaluationContext} without a return value.
* @see #createEvaluationContext(Collection, Method, Object[], Object, Class, Object)
*/
public EvaluationContext createEvaluationContext(Collection<? extends Cache> caches,
Method method, Object[] args, Object target, Class<?> targetClass) {
return createEvaluationContext(caches, method, args, target, targetClass, NO_RESULT);
}
/**
* Create an {@link EvaluationContext}.
* @param caches the current caches
* @param method the method
* @param args the method arguments
* @param target the target object
* @param targetClass the target class
* @param result the return value (can be {@code null}) or
* {@link #NO_RESULT} if there is no return at this time
* @return the evaluation context
*/
public EvaluationContext createEvaluationContext(Collection<? extends Cache> caches,
Method method, Object[] args, Object target, Class<?> targetClass, Object result) {
CacheExpressionRootObject rootObject = new CacheExpressionRootObject(caches,
method, args, target, targetClass);
CacheEvaluationContext evaluationContext = new CacheEvaluationContext(rootObject,
this.paramNameDiscoverer, method, args, targetClass, this.targetMethodCache);
if (result == RESULT_UNAVAILABLE) {
evaluationContext.addUnavailableVariable(RESULT_VARIABLE);
}
else if (result != NO_RESULT) {
evaluationContext.setVariable(RESULT_VARIABLE, result);
}
return evaluationContext;
}
public Object key(String keyExpression, MethodCacheKey methodKey, EvaluationContext evalContext) {
return getExpression(this.keyCache, keyExpression, methodKey).getValue(evalContext);
}
public boolean condition(String conditionExpression, MethodCacheKey methodKey, EvaluationContext evalContext) {
return getExpression(this.conditionCache, conditionExpression, methodKey).getValue(evalContext, boolean.class);
}
public boolean unless(String unlessExpression, MethodCacheKey methodKey, EvaluationContext evalContext) {
return getExpression(this.unlessCache, unlessExpression, methodKey).getValue(evalContext, boolean.class);
}
private Expression getExpression(Map<ExpressionKey, Expression> cache, String expression, MethodCacheKey methodKey) {
ExpressionKey key = createKey(methodKey, expression);
Expression expr = cache.get(key);
if (expr == null) {
expr = this.parser.parseExpression(expression);
cache.put(key, expr);
}
return expr;
}
private ExpressionKey createKey(MethodCacheKey methodCacheKey, String expression) {
return new ExpressionKey(methodCacheKey, expression);
}
private static class ExpressionKey {
private final MethodCacheKey methodCacheKey;
private final String expression;
public ExpressionKey(MethodCacheKey methodCacheKey, String expression) {
this.methodCacheKey = methodCacheKey;
this.expression = expression;
}
@Override
public boolean equals(Object other) {
if (this == other) {
return true;
}
if (!(other instanceof ExpressionKey)) {
return false;
}
ExpressionKey otherKey = (ExpressionKey) other;
return (this.methodCacheKey.equals(otherKey.methodCacheKey) &&
ObjectUtils.nullSafeEquals(this.expression, otherKey.expression));
}
@Override
public int hashCode() {
return this.methodCacheKey.hashCode() * 29 + (this.expression != null ? this.expression.hashCode() : 0);
}
}
}