You will also need the following AspectJ libraries on the CLASSPATH of your application. These libraries are available in the 'lib' directory of an AspectJ installation, otherwise you can download them from the internet.
An aspect is declared using the element, and the backing bean is referenced using the ref attribute as follows −
Here "aBean" will be configured and dependency injected just like any other Spring bean as you have seen in the previous chapters.
A pointcut helps in determining the join points (ie methods) of interest to be executed with different advices. While working with XML Schema-based configuration, pointcut will be defined as follows −
The following example defines a pointcut named 'businessService' that will match the execution of getName() method available in the Student class under the package com.tutorialspoint −
You can declare any of the five advices inside an using the > element as given below −
You can use same doRequiredTask or different methods for different advices. These methods will be defined as a part of aspect module.
To understand the above-mentioned concepts related to XML Schema-based AOP, let us write an example which will implement few of the advices. To write our example with few advices, let us have a working Eclipse IDE in place and take the following steps to create a Spring application −
| Step | Description |
|---|---|
| 1 | Create a project with a name SpringExample and create a package com.tutorialspoint under the src folder in the created project. |
| 2 | Add required Spring libraries using Add External JARs option as explained in the Spring Hello World Example chapter. |
| 3 | Add Spring AOP specific libraries aspectjrt.jar, aspectjweaver.jar and aspectj.jar in the project. |
| 4 | Create Java classes Logging, Student and MainApp under the com.tutorialspoint package. |
| 5 | Create Beans configuration file Beans.xml under the src folder. |
| 6 | The final step is to create the content of all the Java files and Bean Configuration file and run the application as explained below. |
Here is the content of Logging.java file. This is actually a sample of aspect module which defines the methods to be called at various points.
package com.tutorialspoint; public class Logging < /** * This is the method which I would like to execute * before a selected method execution. */ public void beforeAdvice()< System.out.println("Going to setup student profile."); >/** * This is the method which I would like to execute * after a selected method execution. */ public void afterAdvice() < System.out.println("Student profile has been setup."); >/** * This is the method which I would like to execute * when any method returns. */ public void afterReturningAdvice(Object retVal) < System.out.println("Returning:" + retVal.toString() ); >/** * This is the method which I would like to execute * if there is an exception raised. */ public void AfterThrowingAdvice(IllegalArgumentException ex) < System.out.println("There has been an exception: " + ex.toString()); >>
Following is the content of the Student.java file
package com.tutorialspoint; public class Student < private Integer age; private String name; public void setAge(Integer age) < this.age = age; >public Integer getAge() < System.out.println("Age : " + age ); return age; >public void setName(String name) < this.name = name; >public String getName() < System.out.println("Name : " + name ); return name; >public void printThrowException() < System.out.println("Exception raised"); throw new IllegalArgumentException(); >>
Following is the content of the MainApp.java file
package com.tutorialspoint; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class MainApp < public static void main(String[] args) < ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml"); Student student = (Student) context.getBean("student"); student.getName(); student.getAge(); student.printThrowException(); >>
Following is the configuration file Beans.xml
Once you are done creating the source and bean configuration files, let us run the application. If everything is fine with your application, it will print the following message −
Going to setup student profile. Name : Zara Student profile has been setup. Returning:Zara Going to setup student profile. Age : 11 Student profile has been setup. Returning:11 Going to setup student profile. Exception raised Student profile has been setup. There has been an exception: java.lang.IllegalArgumentException . other exception content
The above defined selects all the methods defined under the package com.tutorialspoint. Let us suppose, you want to execute your advice before or after a particular method, you can define your pointcut to narrow down your execution by replacing stars (*) in pointcut definition with the actual class and method names. Following is a modified XML configuration file to show the concept −
If you execute the sample application with these configuration changes, it will print the following message −
Going to setup student profile. Name : Zara Student profile has been setup. Age : 11 Exception raised . other exception content