Yyy

src/main/java/com/github/hcsp/annotation/CacheClassDecorator.java

@@ -9,6 +9,7 @@ public class CacheClassDecorator {
     // 注意，缓存的实现需要是线程安全的
     public static <T> Class<T> decorate(Class<T> klass) {
         return klass;
+
     }
 
     public static void main(String[] args) throws Exception {

src/main/java/com/github/hcsp/annotation/Useless/AnnotationPractise.java

@@ -0,0 +1,14 @@
+package com.github.hcsp.annotation.Useless;
+
+public class AnnotationPractise {
+    @Log
+    void queryDatabase() {
+        System.out.println("queryDatabase...");
+    }
+
+    @Log
+    void selectDatabase() {
+        System.out.println("selectDatabase...");
+    }
+
+}

src/main/java/com/github/hcsp/annotation/Useless/Log.java

@@ -0,0 +1,14 @@
+package com.github.hcsp.annotation.Useless;
+
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Target(ElementType.METHOD)
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Log {
+
+
+}

src/main/java/com/github/hcsp/annotation/Useless/Main.java

@@ -0,0 +1,67 @@
+package com.github.hcsp.annotation.Useless;
+
+import net.bytebuddy.ByteBuddy;
+import net.bytebuddy.description.method.MethodDescription;
+import net.bytebuddy.implementation.MethodDelegation;
+import net.bytebuddy.implementation.bind.annotation.SuperCall;
+import net.bytebuddy.matcher.ElementMatcher;
+
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.List;
+import java.util.concurrent.Callable;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class Main {
+    public static void main(String[] args) throws InvocationTargetException, NoSuchMethodException, InstantiationException, IllegalAccessException {
+        AnnotationPractise annotationPractise = enhanceAnnotation();
+        annotationPractise.selectDatabase();
+        annotationPractise.queryDatabase();
+    }
+
+
+
+    private static AnnotationPractise enhanceAnnotation() throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
+        return new ByteBuddy()
+                //动态的生成AnnotationPractise的子类
+                .subclass(AnnotationPractise.class)
+                //匹配带Log注解的方法
+                .method(new FilterAnnotationWithLog())
+                //将方法拦截并委托给LoggerInterceptor
+                .intercept(MethodDelegation.to(LoggerInterceptor.class))
+                .make()
+                .load(Main.class.getClassLoader())
+                .getLoaded()
+                .getConstructor()
+                .newInstance();
+    }
+
+    public static class FilterAnnotationWithLog implements ElementMatcher<MethodDescription> {
+
+        @Override
+        public boolean matches(MethodDescription target) {
+            //获取自身所有的方法，并将其转换为流
+            List<String> collect = Stream.of(AnnotationPractise.class.getDeclaredMethods())
+                    //过滤出方法的注解为Log的方法
+                    .filter(method -> method.getAnnotation(Log.class) != null)
+                    .map(Method::getName)
+                    .collect(Collectors.toList());
+            System.out.println(target.getName());
+            return collect.contains(target.getName());
+        }
+    }
+
+    public static class LoggerInterceptor {
+        public static void log(@SuperCall Callable<Void> zuper)
+                throws Exception {
+            System.out.println("Calling database");
+            try {
+                zuper.call();
+            } finally {
+                System.out.println("Returned from database");
+            }
+        }
+    }
+
+}