Spring 框架的一個關鍵組件是面向方面的編程(AOP)框架。面向方面的編程需要把程序邏輯分解成不同的部分稱為所謂的關注點。跨一個應用程序的多個點的功能被稱為橫切關注點，這些橫切關注點在概念上獨立于應用程序的業(yè)務邏輯。有各種各樣的常見的很好的方面的例子，如日志記錄、審計、聲明式事務、安全性和緩存等。

一些AOP術語：

(1) aspect：一個模塊具有一組提供橫切需求的 APIs。例如，一個日志模塊為了記錄日志將被 AOP 方面調(diào)用。應用程序可以擁有任意數(shù)量的方面，這取決于需求。
(2) joint point：相當于ABAP類里可以被增強的method
(3) advice：這是實際行動之前或之后執(zhí)行的方法。這是在程序執(zhí)行期間通過 Spring AOP 框架實際被調(diào)用的代碼。相當于ABAP的pre/post/overwrite exit.
(4) weaving: Weaving 把方面連接到其它的應用程序類型或者對象上，并創(chuàng)建一個被通知的對象。這些可以在編譯時，類加載時和運行時完成。

為了使用 aop 命名空間標簽，需要導入 spring-aop j架構，如下所述：

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" xmlns:aop="http://www.springframework.org/schema/aop"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd "><!-- bean definition & AOP specific configuration --></beans>

看個具體的例子：

(1) 新建一個Logging.java:

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()); } }

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" xmlns:aop="http://www.springframework.org/schema/aop"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd "><aop:config><aop:aspect id="log" ref="logging"><aop:pointcut id="selectAll" expression="execution(* com.tutorialspoint.*.*(..))"/><aop:before pointcut-ref="selectAll" method="beforeAdvice"/><aop:after pointcut-ref="selectAll" method="afterAdvice"/><aop:after-returning pointcut-ref="selectAll" returning="retVal"method="afterReturningAdvice"/><aop:after-throwing pointcut-ref="selectAll" throwing="ex"method="AfterThrowingAdvice"/></aop:aspect></aop:config><!-- Definition for student bean --><bean id="student" class="com.sap.Student"><property name="name" value="Zara" /><property name="age" value="11"/> </bean><!-- Definition for logging aspect --><bean id="logging" class="com.sap.Logging"/> </beans>

MainApp.java:

import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class MainApp {public static void main(String[] args) {try {ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");Student student = (Student) context.getBean("student");student.getName();student.getAge(); student.printThrowException();}catch (Exception e) {System.out.println("Jerry ends here!");}} }

輸出：

Jul 26, 2020 11:13:45 AM org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@5b80350b: startup date [Sun Jul 26 11:13:45 CST 2020]; root of context hierarchy Jul 26, 2020 11:13:45 AM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions INFO: Loading XML bean definitions from class path resource [Beans.xml] 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 Jerry ends here!

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