带注释参数的切入点匹配方法 [英] Pointcut matching methods with annotated parameters

问题描述

我需要创建一个切入点与方法匹配的方面，如果:

I need to create an aspect with a pointcut matching a method if:

1. 用 MyAnnotationForMethod 注释
2. 它的一个参数(可以有多个)使用 @MyAnnotationForParam 进行注释(但也可以有其他注释).

方面类看起来像这样

@Pointcut("execution(@MyAnnotationForMethod * *(..,@aspects.MyAnnotationForParam Object, ..)) && args(obj)")
void myPointcut(JoinPoint thisJoinPoint, Object obj) {
}

@Before("myPointcut(thisJoinPoint ,  obj)")
public void doStuffOnParam(JoinPoint thisJoinPoint, Object obj) {
    LOGGER.info("doStuffOnParam :"+obj);
}

注解方法

@MyAnnotationForMethod
public string theMethod(String a, @MyAnnotationForParam @OtherAnnotation Object obj, Object b){ 
    LOGGER.info(a+obj+b);
}

使用 eclipse -> 警告:在切入点:

With eclipse -> warnings : On the poincut :

Multiple markers at this line 
    - no match for this type name: MyAnnotationForMethod [Xlint:invalidAbsoluteTypeName] 
    - no match for this type name: aspects.MyAnnotationForParam On the before : advice defined in xxx.xxx.xxx.xxx.MyAspect has not been applied [Xlint:adviceDidNotMatch]

使用来自 http://download.eclipse.org/tools/ajdt 的最后一个 aspectJ 插件/35/更新

使用aspectj 1.6.9的maven命令行

With maven command line using aspectj 1.6.9

[WARNING] no match for this type name: MyAnnotationForMethod [Xlint:invalidAbsoluteTypeName]
[WARNING] no match for this type name: aspects.MyAnnotationForParam [Xlint:invalidAbsoluteTypeName]
[WARNING] advice defined in xxx.xxx.xxx.xxx.MyAspect has not been applied [Xlint:adviceDidNotMatch]

注释:

package com.xxx.xxx.annotation;
// standard imports stripped
@Documented
@Target( { FIELD, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
public @interface @MyAnnotationForParam {}

和

package com.xxx.xxx.annotation;
// standard imports stripped
@Target(METHOD)
@Retention(RUNTIME)
@Documented
public @interface MyAnnotationForMethod {}

当然它不能正常工作.

你能告诉我有什么问题吗?

Can you tell me what is wrong ?

谢谢.

推荐答案

更新:

好的，我能找到的最好的参考是在这个页面上:注释、切入点和建议.

OK, the best reference I could find is on this page: Annotations, Pointcuts and Advice.

您可以匹配方法，但是您将无法捕获参数(只有方法和注释).所以你要做的是结合切入点匹配和反射.像这样:

You can match the method, however you won't be able to catch the parameter (just the method and the annotation). So what you will have to do is a combination of pointcut matching and reflection. Something like this:

@Pointcut(
    "execution(@com.xxx.xxx.annotation.MyAnnotationForMethod * *(.., @com.xxx.xxx.annotation.MyAnnotationForParam (*), ..))")
public void annotatedMethod(){}

@Before("annotatedMethod()")
public void doStuffOnParam(final JoinPoint jp){
    final Signature signature = jp.getSignature();
    if(signature instanceof MethodSignature){
        final MethodSignature ms = (MethodSignature) signature;

        final Method method = ms.getMethod();
        final String[] parameterNames = ms.getParameterNames();
        final Class<?>[] parameterTypes = ms.getParameterTypes();
        final Annotation[][] parameterAnnotations =
            method.getParameterAnnotations();
        for(int i = 0; i < parameterAnnotations.length; i++){
            final Annotation[] annotations = parameterAnnotations[i];
            final MyAnnotationForParam paramAnnotation =
                getAnnotationByType(annotations, MyAnnotationForParam.class);
            if(paramAnnotation != null){
                this.processParameter(ms.toShortString(),
                    parameterNames[i],
                    parameterTypes[i],
                    paramAnnotation);
            }

        }
    }
}

/**
 * In an array of annotations, find the annotation of the specified type, if any.
 * @return the annotation if available, or null
 */
@SuppressWarnings("unchecked")
private static <T extends Annotation> T getAnnotationByType(final Annotation[] annotations,
    final Class<T> clazz){

    T result = null;
    for(final Annotation annotation : annotations){
        if(clazz.isAssignableFrom(annotation.getClass())){
            result = (T) annotation;
            break;
        }
    }
    return result;
}

/**
 * Do some processing based on what we found.
 * @param signature method signature
 * @param paramName parameter name
 * @param paramType parameter type
 * @param paramAnnotation annotation we found
 */
private void processParameter(final String signature,
    final String paramName,
    final Class<?> paramType,
    final MyAnnotationForParam paramAnnotation){

    System.out.println(MessageFormat.format(
        "Found parameter ''{0}'' \n  of type ''{1}'' \n  with annotation ''{2}'' \n  in method ''{3}''",
        paramName,
        paramType,
        paramAnnotation,
        signature));
}

这是我对上述方面的测试类:

Here is my test class for the above aspect:

public class TestClass{

    @MyAnnotationForMethod
    public void simpleTestMethod(@MyAnnotationForParam final String param1){
        System.out.println("Method body (simple)");
    };

    @MyAnnotationForMethod
    public void complexTestMethod(final String param1,
        @MyAnnotationForParam final Float param2,
        @MyAnnotationForParam final Boolean param3){
        System.out.println("Method body (complex)");
    };

    public static void main(final String[] args){
        System.out.println("Starting up");
        final TestClass testObject = new TestClass();
        testObject.simpleTestMethod("Hey");
        testObject.complexTestMethod("Hey", 123.4f, false);
        System.out.println("Finished");
    }

}

这是输出:

Starting up
Found parameter 'param1' 
  of type 'class java.lang.String' 
  with annotation '@com.xxx.xxx.annotation.MyAnnotationForParam()' 
  in method 'TestClass.simpleTestMethod(..)'
Method body (simple)
Found parameter 'param2' 
  of type 'class java.lang.Float' 
  with annotation '@com.xxx.xxx.annotation.MyAnnotationForParam()' 
  in method 'TestClass.complexTestMethod(..)'
Found parameter 'param3' 
  of type 'class java.lang.Boolean' 
  with annotation '@com.xxx.xxx.annotation.MyAnnotationForParam()' 
  in method 'TestClass.complexTestMethod(..)'
Method body (complex)
Finished

提示

你可能想要缓存很多，没有必要在每次执行时解析每个注解的每个参数.保留一个映射，指明哪个方法的哪个参数带有注解，并只处理这些参数.

Hint

You will probably want to cache a lot of this, there is no need to parse every parameter of every annotation in every execution. Keep a map of which parameter of which method carries the annotation and process only those parameters.

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