Spring AOP – AfterThrows Advice

Requirement : In case a particular method call throws an exception, a log needs to be printed.

Step 1 :

Changes in IteratorImpl class to mock an exception being thrown.
No change in IteratorImpl interface

File : Iterator.java

package com.simpleCodeStuffs.aop;
public interface Iterator {
void goPrevious();
void goNext();
}

File : IteratorImpl.java

package com.simpleCodeStuffs.aop;
public class IteratorImpl implements Iterator{
String flowName;
public void goNext() {
System.out.println("goNext Method Called on flow - "+flowName);
throw new RuntimeException();
}
public void goPrevious(){
System.out.println("goPrevious Method called on flow - "+flowName);
}
public String getFlowName() {
return flowName;
}
public void setFlowName(String flowName) {
this.flowName = flowName;
}
}

Step 2 :

Create a new class AopExampleAfterThrows to implement the new functionality

File : AopExampleAfterThrows.java

package com.simpleCodeStuffs.aop;
import org.springframework.aop.ThrowsAdvice;
public class AopExampleAfterThrows implements ThrowsAdvice {
public void afterThrowing(RuntimeException runtimeException) {
System.out.println("Logging step : Exception thrown by the method ");
}
}

Step 3 :

Changes in the aopBeans.xml file. Similar to the Before Advice and After returns Advice,
create the advisor and advice beans

File : aopBeans.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC
    "-//SPRING//DTD BEAN//EN"
    "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
        <!-- Bean Classes -->
 <bean id="beanTarget" class="com.simpleCodeStuffs.aop.IteratorImpl">
                <property name="flowName" value="existing code" />
        </bean>

        <!-- Bean configuration -->
<bean id="businesslogicbean" 

 class="org.springframework.aop.framework.ProxyFactoryBean">
        <property name="proxyInterfaces">
                <value>com.simpleCodeStuffs.aop.Iterator</value>
        </property>
        <property name="target">
                <ref local="beanTarget" />
        </property>
        <property name="interceptorNames">
                <list>
                        <value>theAfterThrowingAdvisor</value>
                </list>
        </property>
</bean>
<bean id="theAfterThrowingAdvisor"
  class="org.springframework.aop.support.RegexpMethodPointcutAdvisor">
        <property name="advice">
                <ref local="theAfterThrowingAdvice" />
        </property>
        <property name="pattern">
                <value>.*</value>
        </property>
</bean>
<bean id="theAfterThrowingAdvice"  

class="com.simpleCodeStuffs.aop.AopExampleAfterThrows" />
</beans> 

Step 4 :

No major change in the Main class. Simply place a call to the method that throws a mock exception.

File : SpringAopMain.java

package com.simpleCodeStuffs.aop;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.context.support.FileSystemXmlApplicationContext;
public class SpringAopMain {
public static void main(String[] args) {
// Read the configuration file
ApplicationContext context =
new ClassPathXmlApplicationContext("aopBeans.xml");
// Instantiate an object
Iterator IteratorInterface = (Iterator) context. 

getBean("businesslogicbean");
// Execute the public method of the bean
IteratorInterface.goNext();
}
}