java - Spring AOP : Passing parameter in aspect method

Question

我是 Spring AOP 新手，并尝试使用 aop:around 创建一个演示。

一个简单的 Bean 类:

public class Employee {

private String name;
public String getName() {
    System.out.println("Name: " + name);
    return name;
}
public void setName(String name) {
    this.name = name;
}
}

方面实现:

public class PrintingAspect {

public void performPrinting(ProceedingJoinPoint point){
    try {
        System.out.println("Before Printing!!!");
        point.proceed();        
        System.out.println("After Printing!!!");
    } catch (Throwable e) {         
        System.out.println("Exception Printing");
    }
}
}

上下文 XML:

<bean id="aspect" class="com.aop.aspect.PrintingAspect">        
</bean>    
<bean id="employee" class="com.aop.model.Employee">
    <property name="name" value="XXX"></property>
</bean>
<aop:config>
    <aop:pointcut id="empName" expression="execution(* com.aop.model.Employee.getName(..))"/>
    <aop:aspect ref="aspect">            
        <aop:around pointcut-ref="empName" method="performPrinting"/>
    </aop:aspect>
</aop:config>

应用程序.java

public class App 
{
public static void main( String[] args )
{
    ApplicationContext context = new ClassPathXmlApplicationContext("spring-context.xml");
    Employee empl = (Employee)context.getBean("employee");
    System.out.println("Employee Names: " + empl.getName());
}
}

我得到的o/p是:

打印前!!! 姓名:XXX 打印后!!! 员工姓名:空

为什么最后一个为空？

Answer 1

一种方法是进行以下更改:

XML:

<aop:pointcut id="empName"
        expression="execution(* com.example.Employee.getName(..))" />

Java:

public void performPrinting(ProceedingJoinPoint jp) { // Here empl is coming null
    System.out.println("Before Printing!!!");
    System.out.println(((Employee)jp.getTarget()).getName()); // empl is coming as NULL
    System.out.println("After Printing!!!");
}

换句话说，您可以访问目标，它是为应用 AOP 建议而被代理的对象。