Transmit Value by Customized Annotation in AOP Interception

1 Mydoing.javapackage sh.fudan.cxiao.MyAnno.annotation;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;@Retention (RetentionPolicy.RUNTIME) @ Target (ElementType.METHOD) public @ interface Mydoing {String name ();}

2 MyService.javapackage sh.fudan.cxiao.MyAnno.business;import org.springframework.stereotype.Component;import sh.fudan.cxiao.MyAnno.annotation.Mydoing;@Componentpublic class MyService {@ Mydoing (name= "# n") public int doSomething (int n) {System.out.println ("Executing pointcut function, i.e. Business operation"); return 100 minutes;}}

3 SupportingComponent.javapackage sh.fudan.cxiao.MyAnno.component;import java.lang.reflect.Method;import org.aspectj.lang.ProceedingJoinPoint;import org.aspectj.lang.annotation.Around;import org.aspectj.lang.annotation.Aspect;import org.aspectj.lang.reflect.MethodSignature;import org.springframework.core.DefaultParameterNameDiscoverer;import org.springframework.expression.EvaluationContext;import org.springframework.expression.Expression;import org.springframework.expression.ExpressionParser;import org.springframework.expression.spel.standard.SpelExpressionParser;import org.springframework.expression.spel.support.StandardEvaluationContext Import org.springframework.stereotype.Component;import sh.fudan.cxiao.MyAnno.annotation.Mydoing;@Component@Aspectpublic class SupportingComponent {@ Around ("@ annotation (sh.fudan.cxiao.MyAnno.annotation.Mydoing)") public Object doExtraThingForMydoingAnno (ProceedingJoinPoint joinPoint) throws Throwable {System.out.print ("before pointcut execution, get details of the annotation item 'name' on pointcut"); String nameEL = ""; MethodSignature signature = (MethodSignature) joinPoint.getSignature () Method method = joinPoint.getTarget (). GetClass (). GetMethod (signature.getName (), signature.getMethod (). GetParameterTypes ()); Mydoing mydoing = method.getAnnotation (Mydoing.class); nameEL = mydoing.name (); / / i.e. # n System.out.println ("=" + nameEL); System.out.print (nameEL + "'s value comes from the parameter with the same name on pointcut") / 1. Create parser ExpressionParser parser = new SpelExpressionParser (); Expression expression = parser.parse_Expression (nameEL); / / 2. Set up evaluation context EvaluationContext context = new StandardEvaluationContext (); Object [] args = joinPoint.getArgs (); / / the running time arguments value on pointcut DefaultParameterNameDiscoverer discoverer = new DefaultParameterNameDiscoverer (); String [] parameterNames = discoverer.getParameterNames (method) / / parameter names on pointcut / / put the parameter name on pointcut and relevant running argument value into context for (int I = 0; I < parameterNames.length; iTunes +) {context.setVariable (parameterNames [I], args [I]) } / / 3. Parsing (To get the value of placeholder in annotation on pointcut) / / get the value of the running time argument whose name is same as details of the annotation item 'name' on pointcut, i.e. # n Integer In = (Integer) expression.getValue (context); System.out.println (", value is" + In); int base= 1000; if (In%2==0) base=2000 If (In==0) / / Do not execute pointcut when the argument equals zero return-1; Integer result = (Integer) joinPoint.proceed (); / / execute the pointcut System.out.println ("after pointcut execution, subsequently process the returned value from pointcut."); result + = base + In; return result; / / the returned value should be compatible with the returned type from pointcut}}

4 MyAnnoApplication.javapackage sh.fudan.cxiao.MyAnno;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.context.ApplicationContext;import org.springframework.context.annotation.AnnotationConfigApplicationContext;import sh.fudan.cxiao.MyAnno.business.MyService;@SpringBootApplicationpublic class MyAnnoApplication {public static void main (String [] args) {ApplicationContext ctx = new AnnotationConfigApplicationContext (MyAnnoApplication.class); MyService myService = ctx.getBean (MyService.class) System.out.println ("The result is" + myService.doSomething (5)); System.out.println ("The result is" + myService.doSomething (6)); System.out.println ("The result is" + myService.doSomething (0));}}

5 the snapshot of running