org.springframework.context.expression.MethodBasedEvaluationContext Maven / Gradle / Ivy
/*
* 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
*
* 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.context.expression;
import java.lang.reflect.Method;
import org.springframework.core.ParameterNameDiscoverer;
import org.springframework.expression.spel.support.StandardEvaluationContext;
import org.springframework.util.ObjectUtils;
/**
* A method-based {@link org.springframework.expression.EvaluationContext} that
* provides explicit support for method-based invocations.
*
* Expose the actual method arguments using the following aliases:
*
* - pX where X is the index of the argument (p0 for the first argument)
* - aX where X is the index of the argument (a1 for the second argument)
* - the name of the parameter as discovered by a configurable {@link ParameterNameDiscoverer}
*
*
* @author Stephane Nicoll
* @since 4.2
*/
public class MethodBasedEvaluationContext extends StandardEvaluationContext {
private final Method method;
private final Object[] args;
private final ParameterNameDiscoverer paramDiscoverer;
private boolean paramLoaded = false;
public MethodBasedEvaluationContext(Object rootObject, Method method, Object[] args,
ParameterNameDiscoverer paramDiscoverer) {
super(rootObject);
this.method = method;
this.args = args;
this.paramDiscoverer = paramDiscoverer;
}
@Override
public Object lookupVariable(String name) {
Object variable = super.lookupVariable(name);
if (variable != null) {
return variable;
}
if (!this.paramLoaded) {
lazyLoadArguments();
this.paramLoaded = true;
variable = super.lookupVariable(name);
}
return variable;
}
/**
* Load the param information only when needed.
*/
protected void lazyLoadArguments() {
// shortcut if no args need to be loaded
if (ObjectUtils.isEmpty(this.args)) {
return;
}
// save arguments as indexed variables
for (int i = 0; i < this.args.length; i++) {
setVariable("a" + i, this.args[i]);
setVariable("p" + i, this.args[i]);
}
String[] parameterNames = this.paramDiscoverer.getParameterNames(this.method);
// save parameter names (if discovered)
if (parameterNames != null) {
for (int i = 0; i < parameterNames.length; i++) {
setVariable(parameterNames[i], this.args[i]);
}
}
}
}