java – AspectJ切入点表达式匹配任何位置的参数注释

我试图定义一个切入点表达式,以匹配包含使用特定注释注释的参数的方法,而不管参数是什么位置.在我的情况下,我正在寻找@Constraint注释.例如:

匹配方式:

public void method1(@Constraint Car car)

public void method2(String id, @Constraint Plane plane)

public void method3(Wheel wheel, @Constraint List<Train> trains, @Constraint Plane plane)

public void method4(Motor motor, @Constraint Set<Train> trains, Bicycle bike, Wheel wheel)

public void method5(Wing wing, Motorcycle moto, @Constraint Truck truck, Bicycle bike, Wheel wheel)

到目前为止,我没有运气尝试过以下表达式:

@Before("execution(public * *.*(..)) and @args(com.example.Constraint)") // there can be only one parameter
@Before("execution(public * *.*(..)) and @args(..,com.example.Constraint)") // parameter must be in last position
@Before("execution(public * *.*(..)) and @args(com.example.Constraint,..)") // parameter must be in first position
@Before("execution(public * *.*(..)) and (@args(com.example.Constraint,..) or @args(..,com.example.Constraint))") // parameter must be in first or last position, nothing in between
@Before("execution(public * *.*(..)) and @args(..,com.example.Constraint,..)") // Invalid

有人可以指出我正确的解决方案吗?甚至有可能吗

最佳答案
您不能通过AspectJ中的args()绑定任意位置的参数,因为这可能导致模糊.假设您有两个或多个相同类型的参数(或在这种情况下由相同的注释类型注释).哪一个应该绑定到命名的args()参数?所以呢

execution(public * *(.., @Deprecated (*), ..))

可以作为一个独立的表达(请注意星星附近的括号),它不可能与args()结合使用.所以如果你不想拦截方法执行本身,还要找到给定注释的第一个或者所有的参数,你需要做的只是我在另一篇文章中显示的.我有点重复自己,但是为了让答案不被再次删除,

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

@Retention(RetentionPolicy.RUNTIME)
public @interface Constraint {}
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class Application {
    public void method1(@Constraint int i) {}
    public void method2(String id, @Constraint float f) {}
    public void method3(int i, @Constraint List<String> strings, @Constraint String s) {}
    public void method4(int i, @Constraint Set<Integer> numbers, float f, boolean b) {}
    public void method5(boolean b, String s, @Constraint String s2, float f, int i) {}
    public void notIntercepted(boolean b, String s, String s2, float f, int i) {}

    public static void main(String[] args) {
        List<String> strings = new ArrayList<String>();
        strings.add("foo");
        strings.add("bar");
        Set<Integer> numbers = new HashSet<Integer>();
        numbers.add(11);
        numbers.add(22);
        numbers.add(33);

        Application app = new Application();
        app.method1(1);
        app.method2("foo", 1f);
        app.method3(1, strings, "foo");
        app.method4(1, numbers, 1f, true);
        app.method5(false, "foo", "bar", 1f, 1);
        app.notIntercepted(false, "foo", "bar", 1f, 1);
    }
}
import java.lang.annotation.Annotation;

import org.aspectj.lang.SoftException;
import org.aspectj.lang.reflect.MethodSignature;

public aspect ArgCatcherAspect {
    before() : execution(public * *(.., @Constraint (*), ..)) {
        System.out.println(thisJoinPointStaticPart);
        MethodSignature signature = (MethodSignature) thisJoinPoint.getSignature();
        String methodName = signature.getMethod().getName();
        Class<?>[] parameterTypes = signature.getMethod().getParameterTypes();
        Annotation[][] annotations;
        try {
            annotations = thisJoinPoint.getTarget().getClass().
                getMethod(methodName, parameterTypes).getParameterAnnotations();
        } catch (Exception e) {
            throw new SoftException(e);
        }
        int i = 0;
        for (Object arg : thisJoinPoint.getArgs()) {
            for (Annotation annotation : annotations[i]) {
                if (annotation.annotationType() == Constraint.class)
                    System.out.println("  " + annotation + " -> " + arg);
            }
            i++;
        }
    }
}

正如你所看到的,获取给定参数的注释比它的声明类型要棘手一些,但基本上它的工作方式与上一篇文章中的方法相同,即通过迭代参数列表.

转载注明原文:java – AspectJ切入点表达式匹配任何位置的参数注释 - 代码日志