AOP configuration based on xml file

• The notification class object is delivered to Spring for management, that is, the notification class object is configured

  <! -- 1. Configure the Logger object (here is the notification class) -- >
  <bean id="logger" class="com.mypro.utils.Logger"></bean>

• Use the aop:config tab to start the AOP configuration

  <aop:config></aop:config>

• Using the aop:aspect tag inside the aop:config tag indicates the configuration aspect

  • id attribute: provides a unique id for the facet

  • ref attribute: Specifies the id of the Bean of the notification class

  <aop:config>
      <aop:aspect id="loggerAdvice" ref="logger"></aop:aspect>
  </aop:config>

• Use the corresponding label inside the aop:aspect label to configure the notification type

  • Pre notice label: aop:before

  • Post notification label: AOP: after returning

  • Exception notification label: AOP: after throwing

  • Final notice label: aop:after

  • Common properties of the above notice labels

    • Method property: the method used to specify the notification class

    • Pointcut ref property: id used to specify the unique identity of the configured pointcut expression

    • Pointcut property: used to specify a pointcut expression, which means to enhance methods in the business layer

      • The standard format of pointcut expression: execution (access modifier return value type package name. Package name.. class name. Method name (parameter list)) is only for one method

      • All in one notation:

        * *..*.*(..)

      • The evolution from the standard format to the all-in-one collocation

        • Access modifiers can be omitted

        • The return value can be replaced by the wildcard * to indicate any return value*

        • The package name can also be replaced by wildcard characters. If there are several packages, there will be several **

        • The package name can also be simplified:... Indicates the current package and all subpackages *

        • The class name can also be replaced by the wildcard * to represent any class **

        • Method names can also be replaced by wildcards to represent any method *.. **

        • parameter list

          • Can be a basic data type example int

          • It can be reference type to write package name. Example of class name java.lang.String

          • You can use wildcard. To represent any data type, but you must have the parameter *.. * (.)

          • You can add another wildcard. It indicates whether there is a parameter *.. *. * (..)

        • You can add wildcards as needed

  • Configure pointcut expressions

    • Label: aop:pointcut

    • Attribute: id unique identification, expression configured expression

    • classification

      • Place the aop:pointcut label anywhere inside the aop:aspect label, only for the current section

      • The aop:pointcut label can only be placed above the outside of the first aop:aspect label. Any aspect can be used

    <aop:pointcut id="pt1" expression="execution(* com.mypro.service.impl.*.*(..))"></aop:point>

    Full AOP profile

    <bean id="logger" class="com.mypro.service.impl.WordsServiceImpl"></bean>
    <aop:config>
        <aop:aspect id="loggerAdvice" ref="logger">
            <aop:pointcut id="pt1" expression="execution(* com.mypro.service.impl.*.*(..))"></aop:point>
            <aop:before method="beforeInfo" pointcut-ref="pt1"></aop:before>
            <aop:after-returning method="afterReturningInfo" pointcut-ref="pt1"></aop:after-returning>
            <aop:after-throwing method="afterThrowingInfo" pointcut-ref="pt1"></aop:after-throwing>
            <aop:after method="afterInfo" pointcut-ref="pt1"></aop:after>
        </aop:aspect>
    </aop:config>

  • Orbit notification label: aop:around. Properties are the same as the properties of other notification labels, and the function of surround notification is to complete the notification labels in the above-mentioned 4 by encoding. You only need to configure this surround notification label in the xml file, and the encoding is implemented in the notification class

    <bean id="logger" class="com.mypro.service.impl.WordsServiceImpl"></bean>
    <aop:config>
        <aop:aspect id="loggerAdvice" ref="logger">
            <aop:pointcut id="pt1" expression="execution(* com.mypro.service.impl.*.*(..))"></aop:pointcut>
            <aop:around method="aroundInfo" poinitcut-ref="pt1"></aop:around>
        </aop:aspect>
    </aop:config>

    Then, in the notification class (in this case, the Logger class), the aroundInfo method writes functions similar to the above four notifications.

    Analysis: through the surround notification code in the dynamic agent, it is found that the surround notification of the dynamic agent has a clear pointcut method call, but our method does not

    Solution: the Spring framework provides us with an interface, proceed ingjoinpoint, which has a procedure method, which is equivalent to explicitly calling the pointcut method. The interface can be used as a method parameter around the notification. When the program is executed, the Spring framework will provide us with the implementation class call of the interface

    import org.aspectj.lang.ProceedingJoinPoint;
    public class Logger{
        public Object aroundInfo(){
            Object rtValue = null;
            try{
                System.out.println("Before advice");
                // Get the parameters needed for method execution
                Object[] args = pjp.getArgs();
                // Explicitly call business layer methods (pointcut methods)
                rtValue = pjp.proceed(args);
                System.out.println("Post notification");
                return rtValue;
            }catch(Throwable t){      // It must be used. Throwable Catching anomalies
                System.out.println("Exception notification");
                throw new RuntimeException(t);
            }finally{
                System.out.println("Final notice");
            }
        }
    }