org.springframework.context.expression.MethodBasedEvaluationContext Maven / Gradle / Ivy
/*
* Copyright 2002-2018 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.context.expression;
import java.lang.reflect.Method;
import java.util.Arrays;
import org.springframework.core.ParameterNameDiscoverer;
import org.springframework.expression.spel.support.StandardEvaluationContext;
import org.springframework.lang.Nullable;
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
* @author Juergen Hoeller
* @since 4.2
*/
public class MethodBasedEvaluationContext extends StandardEvaluationContext {
private final Method method;
private final Object[] arguments;
private final ParameterNameDiscoverer parameterNameDiscoverer;
private boolean argumentsLoaded = false;
public MethodBasedEvaluationContext(Object rootObject, Method method, Object[] arguments,
ParameterNameDiscoverer parameterNameDiscoverer) {
super(rootObject);
this.method = method;
this.arguments = arguments;
this.parameterNameDiscoverer = parameterNameDiscoverer;
}
@Override
@Nullable
public Object lookupVariable(String name) {
Object variable = super.lookupVariable(name);
if (variable != null) {
return variable;
}
if (!this.argumentsLoaded) {
lazyLoadArguments();
this.argumentsLoaded = 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.arguments)) {
return;
}
// Expose indexed variables as well as parameter names (if discoverable)
String[] paramNames = this.parameterNameDiscoverer.getParameterNames(this.method);
int paramCount = (paramNames != null ? paramNames.length : this.method.getParameterCount());
int argsCount = this.arguments.length;
for (int i = 0; i < paramCount; i++) {
Object value = null;
if (argsCount > paramCount && i == paramCount - 1) {
// Expose remaining arguments as vararg array for last parameter
value = Arrays.copyOfRange(this.arguments, i, argsCount);
}
else if (argsCount > i) {
// Actual argument found - otherwise left as null
value = this.arguments[i];
}
setVariable("a" + i, value);
setVariable("p" + i, value);
if (paramNames != null && paramNames[i] != null) {
setVariable(paramNames[i], value);
}
}
}
}