Spring Aop ProxyFactoryBean and ProxyFactory and ClassCastException - spring

Question

When i use ProxyFactoryBean to get proxy object, I get a ClassCastException，but when i use ProxyFactory's getProxy() to get a proxy object, it works properly. I use Spring 4.x.
Definition of Two Beans，WaiterTest and Seller:
public class WaiterTest {
public void greetTo(String name){
System.out.println("waiter greet to " + name +"...");
}
public void serveTo(String name){
System.out.println("waiter serving " + name + "...");
}
}
public class Seller {
public void greetTo(String name){
System.out.println("seller greet to " +name + "...");
}
}
Definition of Advice：
public class GreetingBeforeAdvice implements MethodBeforeAdvice{
public void before(Method method, Object[] args, Object obj) throws Throwable{
System.out.println(obj.getClass().getName() + "." + method.getName());
String clientName =(String) args[0];
System.out.println("How are you! Mr." + clientName +".");
}
}
Definition of Advisor：
public class GreetingAdvisor extends StaticMethodMatcherPointcutAdvisor {
public boolean matches(Method method, Class clazz) {
return "greetTo".equals(method.getName());
}
public ClassFilter getClassFilter() {
return new ClassFilter() {
public boolean matches(Class clazz) {
return WaiterTest.class.isAssignableFrom(clazz);
}
};
}
}
Test Class：
public class TestGreetingBeforeAdvisor {
public static void main(String[] args) {
//method one： use by ProxyFactory
WaiterTest targetWaiterTest = new WaiterTest();
Seller targetSeller = new Seller();
GreetingBeforeAdvice advice = new GreetingBeforeAdvice();
GreetingAdvisor advisor = new GreetingAdvisor();
advisor.setAdvice(advice);
ProxyFactory pf = new ProxyFactory();
pf.setTarget(targetWaiterTest);
pf.addAdvisor(advisor);
pf.setOptimize(true);
WaiterTest proxy = (WaiterTest) pf.getProxy();
proxy.greetTo("John");
proxy.serveTo("Tom");
ProxyFactory pf1 = new ProxyFactory();
pf1.setTarget(targetSeller);
pf1.addAdvisor(advisor);
Seller seller = (Seller) pf1.getProxy();
seller.greetTo("John");
System.out.println("=============");
//method two：Spring xml，use ProxyFactoryBean
ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
WaiterTest test = (WaiterTest) ctx.getBean("waiterTest");
test .greetTo("John");
test .serveTo("John");
}
}
Beans.xml：
<bean id="waiterTarget" class="com.xxx.springaop.advisor.WaiterTest"/>
<bean id="sellerTarget" class="com.xxx.springaop.advisor.Seller"/>
<bean id="greetingAdvice1" class="com.xxx.springaop.advisor.GreetingBeforeAdvice"/>
<bean id="greetingAdvisor" class="com.xxx.springaop.advisor.GreetingAdvisor"
p:advice-ref="greetingAdvice1"/>
<bean id="parent" abstract="true" class="org.springframework.aop.framework.ProxyFactoryBean"
p:interceptorNames="greetingAdvisor"
p:proxyTargetClass="true"/>
<bean id="waiterTest" parent="parent" p:target-ref="waiterTarget"/>
<bean id="seller" parent="parent" p:target-ref="sellerTarget"/>
result:
com.xxx.springaop.advisor.WaiterTest.greetTo
How are you! Mr.John.
waiter greet to John...
waiter serving Tom...
seller greet to John...
=============
Exception in thread "main" java.lang.ClassCastException: com.sun.proxy.$Proxy12 cannot be cast to com.xxx.springaop.advisor.WaiterTest
at com.xxx.springaop.advisor.TestGreetingBeforeAdvisor.main(TestGreetingBeforeAdvisor.java:48)
Summarize：
WaiterTest proxy = (WaiterTest) pf.getProxy(); //success
WaiterTest test = (WaiterTest) ctx.getBean("waiterTest");//fail,ClassCastException
Why?

Answer 1

I was not able to reproduce your problem, but I did some refactoring on your code, and this works just fine for me. Maybe it helps you as well at least as a starting point..
Waiter.java
public class Waiter {
public void greetTo(String name) {
System.out.println("waiter greet to " + name + "...");
}
public void serveTo(String name) {
System.out.println("waiter serving " + name + "...");
}
}
GreetingBeforeAdvice.java
import org.springframework.aop.MethodBeforeAdvice;
import java.lang.reflect.Method;
public class GreetingBeforeAdvice implements MethodBeforeAdvice {
#Override
public void before(Method method, Object[] args, Object obj) throws Throwable {
String clientName = (String) args[0];
System.out.println("How are you! Mr." + clientName + ".");
}
}
GreetingAdvisor.java
import org.springframework.aop.ClassFilter;
import org.springframework.aop.support.StaticMethodMatcherPointcutAdvisor;
import java.lang.reflect.Method;
public class GreetingAdvisor extends StaticMethodMatcherPointcutAdvisor {
public boolean matches(Method method, Class clazz) {
return "greetTo".equals(method.getName());
}
public ClassFilter getClassFilter() {
return new ClassFilter() {
public boolean matches(Class clazz) {
return Waiter.class.isAssignableFrom(clazz);
}
};
}
}
beans.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd">
<bean id="waiter" class="Waiter"/>
<!-- Advisor Configuration -->
<bean id="greetingAdvice" class="GreetingBeforeAdvice"/>
<bean id="greetingAdvisor" class="GreetingAdvisor">
<property name="advice" ref="greetingAdvice"/>
</bean>
<bean id="waiterProxyFactory" class="org.springframework.aop.framework.ProxyFactoryBean">
<property name="interceptorNames">
<list>
<value>greetingAdvisor</value>
</list>
</property>
<property name="target" ref="waiter"/>
</bean>
</beans>
and finally App.java
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class App {
public static void main(String[] args) {
ApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml");
final Waiter waiter = (Waiter) ctx.getBean("waiterProxyFactory");
waiter.greetTo("Koray Tugay");
waiter.serveTo("Koray Tugay");
}
}
The output for me is as follows using Spring 4.3.12:
How are you! Mr.Koray Tugay.
waiter greet to Koray Tugay...
waiter serving Koray Tugay...

Answer 2

I would say you have not configured 'target' object in you ProxyFactoryBean definition. A proxy cannot be created if it does not have a target.