spring CacheEvaluationContext 源码
spring CacheEvaluationContext 代码
文件路径：/spring-context/src/main/java/org/springframework/cache/interceptor/CacheEvaluationContext.java
/*
* Copyright 2002-2016 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.cache.interceptor;
import java.lang.reflect.Method;
import java.util.HashSet;
import java.util.Set;
import org.springframework.context.expression.MethodBasedEvaluationContext;
import org.springframework.core.ParameterNameDiscoverer;
import org.springframework.lang.Nullable;
/**
* Cache specific evaluation context that adds a method parameters as SpEL
* variables, in a lazy manner. The lazy nature eliminates unneeded
* parsing of classes byte code for parameter discovery.
*
* <p>Also define a set of "unavailable variables" (i.e. variables that should
* lead to an exception right the way when they are accessed). This can be useful
* to verify a condition does not match even when not all potential variables
* are present.
*
* <p>To limit the creation of objects, an ugly constructor is used
* (rather than a dedicated 'closure'-like class for deferred execution).
*
* @author Costin Leau
* @author Stephane Nicoll
* @author Juergen Hoeller
* @since 3.1
*/
class CacheEvaluationContext extends MethodBasedEvaluationContext {
private final Set<String> unavailableVariables = new HashSet<>(1);
CacheEvaluationContext(Object rootObject, Method method, Object[] arguments,
ParameterNameDiscoverer parameterNameDiscoverer) {
super(rootObject, method, arguments, parameterNameDiscoverer);
}
/**
* Add the specified variable name as unavailable for that context.
* Any expression trying to access this variable should lead to an exception.
* <p>This permits the validation of expressions that could potentially a
* variable even when such variable isn't available yet. Any expression
* trying to use that variable should therefore fail to evaluate.
*/
public void addUnavailableVariable(String name) {
this.unavailableVariables.add(name);
}
/**
* Load the param information only when needed.
*/
@Override
@Nullable
public Object lookupVariable(String name) {
if (this.unavailableVariables.contains(name)) {
throw new VariableNotAvailableException(name);
}
return super.lookupVariable(name);
}
}
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