/*
* Copyright 2002-2020 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.aop.support;
import org.aopalliance.intercept.MethodInvocation;
import org.springframework.aop.DynamicIntroductionAdvice;
import org.springframework.aop.IntroductionInterceptor;
import org.springframework.aop.ProxyMethodInvocation;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
Convenient implementation of the IntroductionInterceptor interface. Subclasses merely need to extend this class and implement the interfaces
to be introduced themselves. In this case the delegate is the subclass
instance itself. Alternatively a separate delegate may implement the
interface, and be set via the delegate bean property.
Delegates or subclasses may implement any number of interfaces.
All interfaces except IntroductionInterceptor are picked up from
the subclass or delegate by default.
The suppressInterface method can be used to suppress interfaces implemented by the delegate but which should not be introduced to the owning AOP proxy.
An instance of this class is serializable if the delegate is.
Author: Rod Johnson, Juergen Hoeller See Also: Since: 16.11.2003
/**
* Convenient implementation of the
* {@link org.springframework.aop.IntroductionInterceptor} interface.
*
* <p>Subclasses merely need to extend this class and implement the interfaces
* to be introduced themselves. In this case the delegate is the subclass
* instance itself. Alternatively a separate delegate may implement the
* interface, and be set via the delegate bean property.
*
* <p>Delegates or subclasses may implement any number of interfaces.
* All interfaces except IntroductionInterceptor are picked up from
* the subclass or delegate by default.
*
* <p>The {@code suppressInterface} method can be used to suppress interfaces
* implemented by the delegate but which should not be introduced to the owning
* AOP proxy.
*
* <p>An instance of this class is serializable if the delegate is.
*
* @author Rod Johnson
* @author Juergen Hoeller
* @since 16.11.2003
* @see #suppressInterface
* @see DelegatePerTargetObjectIntroductionInterceptor
*/
@SuppressWarnings("serial")
public class DelegatingIntroductionInterceptor extends IntroductionInfoSupport
implements IntroductionInterceptor {
Object that actually implements the interfaces.
May be "this" if a subclass implements the introduced interfaces.
/**
* Object that actually implements the interfaces.
* May be "this" if a subclass implements the introduced interfaces.
*/
@Nullable
private Object delegate;
Construct a new DelegatingIntroductionInterceptor, providing
a delegate that implements the interfaces to be introduced.
Params: - delegate – the delegate that implements the introduced interfaces
/**
* Construct a new DelegatingIntroductionInterceptor, providing
* a delegate that implements the interfaces to be introduced.
* @param delegate the delegate that implements the introduced interfaces
*/
public DelegatingIntroductionInterceptor(Object delegate) {
init(delegate);
}
Construct a new DelegatingIntroductionInterceptor.
The delegate will be the subclass, which must implement
additional interfaces.
/**
* Construct a new DelegatingIntroductionInterceptor.
* The delegate will be the subclass, which must implement
* additional interfaces.
*/
protected DelegatingIntroductionInterceptor() {
init(this);
}
Both constructors use this init method, as it is impossible to pass
a "this" reference from one constructor to another.
Params: - delegate – the delegate object
/**
* Both constructors use this init method, as it is impossible to pass
* a "this" reference from one constructor to another.
* @param delegate the delegate object
*/
private void init(Object delegate) {
Assert.notNull(delegate, "Delegate must not be null");
this.delegate = delegate;
implementInterfacesOnObject(delegate);
// We don't want to expose the control interface
suppressInterface(IntroductionInterceptor.class);
suppressInterface(DynamicIntroductionAdvice.class);
}
Subclasses may need to override this if they want to perform custom
behaviour in around advice. However, subclasses should invoke this
method, which handles introduced interfaces and forwarding to the target.
/**
* Subclasses may need to override this if they want to perform custom
* behaviour in around advice. However, subclasses should invoke this
* method, which handles introduced interfaces and forwarding to the target.
*/
@Override
@Nullable
public Object invoke(MethodInvocation mi) throws Throwable {
if (isMethodOnIntroducedInterface(mi)) {
// Using the following method rather than direct reflection, we
// get correct handling of InvocationTargetException
// if the introduced method throws an exception.
Object retVal = AopUtils.invokeJoinpointUsingReflection(this.delegate, mi.getMethod(), mi.getArguments());
// Massage return value if possible: if the delegate returned itself,
// we really want to return the proxy.
if (retVal == this.delegate && mi instanceof ProxyMethodInvocation) {
Object proxy = ((ProxyMethodInvocation) mi).getProxy();
if (mi.getMethod().getReturnType().isInstance(proxy)) {
retVal = proxy;
}
}
return retVal;
}
return doProceed(mi);
}
Proceed with the supplied MethodInterceptor. Subclasses can override this method to intercept method invocations on the target object which is useful when an introduction needs to monitor the object that it is introduced into. This method is never called for MethodInvocations on the introduced interfaces. /**
* Proceed with the supplied {@link org.aopalliance.intercept.MethodInterceptor}.
* Subclasses can override this method to intercept method invocations on the
* target object which is useful when an introduction needs to monitor the object
* that it is introduced into. This method is <strong>never</strong> called for
* {@link MethodInvocation MethodInvocations} on the introduced interfaces.
*/
@Nullable
protected Object doProceed(MethodInvocation mi) throws Throwable {
// If we get here, just pass the invocation on.
return mi.proceed();
}
}