/*
* Copyright 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.data.rest.core.projection;
import java.lang.reflect.Method;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.expression.BeanFactoryResolver;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.Expression;
import org.springframework.expression.ParserContext;
import org.springframework.expression.common.TemplateParserContext;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;
/**
* {@link MethodInterceptor} to invoke a SpEL expression to compute the method result. Will forward the resolution to a
* delegate {@link MethodInterceptor} if no {@link Value} annotation is found.
*
* @author Oliver Gierke
*/
class SpelEvaluatingMethodInterceptor implements MethodInterceptor {
private final SpelExpressionParser parser;
private final ParserContext parserContext;
private final EvaluationContext evaluationContext;
private final MethodInterceptor delegate;
/**
* Creates a new {@link SpelEvaluatingMethodInterceptor} delegating to the given {@link MethodInterceptor} as fallback
* and exposing the given target object via {@code target} to the SpEl expressions. If a {@link BeanFactory} is given,
* bean references in SpEl expressions can be resolved as well.
*
* @param delegate must not be {@literal null}.
* @param target must not be {@literal null}.
* @param beanFactory can be {@literal null}.
*/
public SpelEvaluatingMethodInterceptor(MethodInterceptor delegate, Object target, BeanFactory beanFactory) {
Assert.notNull(delegate, "Delegate MethodInterceptor must not be null!");
Assert.notNull(target, "TargetObject must not be null!");
StandardEvaluationContext evaluationContext = new StandardEvaluationContext(new TargetWrapper(target));
if (beanFactory != null) {
evaluationContext.setBeanResolver(new BeanFactoryResolver(beanFactory));
}
this.evaluationContext = evaluationContext;
this.parser = new SpelExpressionParser();
this.parserContext = new TemplateParserContext();
this.delegate = delegate;
}
/*
* (non-Javadoc)
* @see org.aopalliance.intercept.MethodInterceptor#invoke(org.aopalliance.intercept.MethodInvocation)
*/
@Override
public Object invoke(MethodInvocation invocation) throws Throwable {
Method method = invocation.getMethod();
Value annotation = method.getAnnotation(Value.class);
if (annotation == null || !StringUtils.hasText(annotation.value())) {
return delegate.invoke(invocation);
}
Expression expression = parser.parseExpression(annotation.value(), parserContext);
return expression.getValue(evaluationContext);
}
/**
* Wrapper class to expose an object to the SpEL expression as {@code target}.
*
* @author Oliver Gierke
*/
static class TargetWrapper {
private final Object target;
public TargetWrapper(Object target) {
this.target = target;
}
/**
* @return the target
*/
public Object getTarget() {
return target;
}
}
}