In this post, We will learn about the Spring AOP Before and After Advice Using Annotations Example using a Demo Project.
One of the very important key units of Spring Framework is the Aspect-oriented programming (AOP) framework. Aspect-Oriented Programming helps us to provide functionalities to break down program logic into distinct parts or modules is called AOP concerns. The functions that spread across multiple sections of an application are called cross-cutting concerns and these cross-cutting concerns functionalities must be separate from the application’s business logic. There are various good examples of aspects like logging, authentication, transaction management, auditing, spring-security, caching, etc.
The key concept of modularity is Object-Oriented Programming is the class, whereas in AOP the unit of modularity is the aspect. Spring dependency Injection usually helps us to lose coupling our application objects from each other and AOP helps us to decouple cross-cutting concerns from the objects that they affect.
Spring AOP provides interceptors to intercept an application. For example, when a method is executed, We can add extra functionality before or after the method execution.
Types of Advice
Spring AOP has five kinds of advice mentioned as Below −
SR.NO | ADVICE & DESCRIPTION |
---|---|
1 | before
This advice executes before a join point, but this advice does not have the ability to prevent execution flow to proceed to the join point (unless it throws an exception). |
2 | after
This advice is executed after a join point completes normally: for example if a method returns without throwing an exception. |
3 | after-returning
This advice runs after the method execution only if the method completes successfully. |
4 | after-throwing
This advice is executed if a method exiting by throwing an exception. |
5 | around
This is the most powerful kind of advice We can use around advice to perform custom behavior before and after the method invocation. This advice is also responsible to select whether to proceed to the joinpoint or to perform the advised method execution by returning its own return value or throwing an exception. |
In this demo project, We will learn about before and after Advice using annotations:
pom.xml
We need to add spring and spring-aspects dependencies in Maven pom.xml file
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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.kkhindigyan.org</groupId> <artifactId>SpringAopWithBeforeAndAfterAdviceUsingAnnotationExample</artifactId> <version>0.0.1-SNAPSHOT</version> <properties> <org.springframework.version>5.2.13.RELEASE</org.springframework.version> <org.spring.aop.version>5.2.13.RELEASE</org.spring.aop.version> </properties> <dependencies> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>${org.springframework.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-aspects</artifactId> <version>${org.spring.aop.version}</version> </dependency> </dependencies> </project> |
Account.java
The model class which hold Account information data
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package com.kkhindigyan.org.model; public class Account { private String accountNumber; private String accountDescription; public Account(String accountNumber, String accountDescription) { this.accountNumber = accountNumber; this.accountDescription = accountDescription; } public String getAccountNumber() { return accountNumber; } public String getAccountDescription() { return accountDescription; } @Override public String toString() { return "Account [accountNumber=" + accountNumber + ", accountDescription=" + accountDescription + "]"; } } |
AccountService.java
AccountService interface
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package com.kkhindigyan.org.service; import com.kkhindigyan.org.model.Account; public interface AccountService { public abstract void updateAccountBalance(Account account, Long amount); } |
AccountServiceImpl.java
AccountService interface implementation class
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package com.kkhindigyan.org.service.impl; import org.springframework.stereotype.Service; import com.kkhindigyan.org.model.Account; import com.kkhindigyan.org.service.AccountService; @Service("accountService") public class AccountServiceImpl implements AccountService { @Override public void updateAccountBalance(Account account,Long amount){ System.out.println("Account No:"+account.getAccountNumber()+", Amount:"+amount); } } |
AccountServiceAspect.java
In this java class, we have defined two methods beforeAdvice & afterAdvice which accepts JoinPoint as a method argument and annotated with @Before & @After to mark before & after advice.
The Aspects classes are usually Similar to other normal Spring bean and may have methods and fields just like any other class except that they will be annotated with @Aspect.
we have defined a method selectAll () for pointcut that will match the execution of updateAccountBalance(Account account,Long amount) method available in the AccountServiceImpl class under the package com.kkhindigyan.org.service.impl
We can declare either of the five advices using @{AdviceName} annotations as defined in the code below.
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package com.kkhindigyan.org.service.aop; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.aspectj.lang.JoinPoint; import org.aspectj.lang.annotation.After; import org.aspectj.lang.annotation.Aspect; import org.aspectj.lang.annotation.Before; import org.aspectj.lang.annotation.Pointcut; import org.springframework.stereotype.Component; import com.kkhindigyan.org.model.Account; @Aspect @Component public class AccountServiceAspect { private static Log log = LogFactory.getLog(AccountServiceAspect.class.getName()); @Before(value = "selectAll()") public void beforeAdvice(JoinPoint joinPoint) { Object[] args = joinPoint.getArgs(); for (Object object : args) { if( object instanceof Account) { System.out.println((Account)object); }else if(object instanceof Long) { System.out.println("Amount to be transferred ="+(Long)object); } } log.info("Before Method:"+joinPoint.getSignature()); } @After(value ="selectAll()") public void afterAdvice(JoinPoint joinPoint) { log.info("After Method:"+joinPoint.getSignature()); } @Pointcut("execution(* com.kkhindigyan.org.service.impl.AccountServiceImpl.*(..))") public void selectAll() { } } |
MyConfig.java
This is the Spring Java-based Config file(replacement of applicationContext.xml file). Here We have used @EnableAspectJAutoProxy annotation to enable @AspectJ support in Spring AOP.
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package com.kkhindigyan.org.config; import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration; import org.springframework.context.annotation.EnableAspectJAutoProxy; @Configuration @EnableAspectJAutoProxy(proxyTargetClass=true) @ComponentScan({"com.kkhindigyan.org.service.aop,com.kkhindigyan.org.service.impl"}) public class MyConfig { } |
ClientTest.java
This ClientTest class gets the AccountService bean from the applicationContext.xml file and calls the updateAccountBalance method of the EmployeeService after that before & after advice called automatically.
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package com.kkhindigyan.org.client; import org.springframework.context.annotation.AnnotationConfigApplicationContext; import org.springframework.context.support.AbstractApplicationContext; import com.kkhindigyan.org.config.MyConfig; import com.kkhindigyan.org.model.Account; import com.kkhindigyan.org.service.AccountService; import com.kkhindigyan.org.service.impl.AccountServiceImpl; public class ClientTest { public static void main(String[] args) { AbstractApplicationContext ctx = null; try { ctx = new AnnotationConfigApplicationContext(MyConfig.class); AccountService accountService = ctx.getBean("accountService", AccountServiceImpl.class); accountService.updateAccountBalance(new Account("6770865432", "Money tranfer"), 5000L); } catch (Exception e) { e.printStackTrace(); }finally { if(ctx != null) ctx.close(); } } } |
If you run ClientTest.java as Java Application then it will give the below output:
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Account [accountNumber=6770865432, accountDescription=Money tranfer] Amount to be transferred =5000 Jun 19, 2021 10:57:02 AM com.kkhindigyan.org.service.aop.AccountServiceAspect beforeAdvice INFO: Before Method:void com.kkhindigyan.org.service.impl.AccountServiceImpl.updateAccountBalance(Account,Long) Account No:6770865432, Amount:5000 Jun 19, 2021 10:57:02 AM com.kkhindigyan.org.service.aop.AccountServiceAspect afterAdvice INFO: After Method:void com.kkhindigyan.org.service.impl.AccountServiceImpl.updateAccountBalance(Account,Long) |
That’s all about Spring AOP Before and After Advice Using Annotations Example
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