Add abstract Sentinel aspect class for extension (alibaba#214)

sentinel-extension/sentinel-annotation-aspectj/src/main/java/com/alibaba/csp/sentinel/annotation/aspectj/AbstractSentinelAspect.java

@@ -0,0 +1,203 @@
+/*
+ * Copyright 1999-2018 Alibaba Group Holding Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.alibaba.csp.sentinel.annotation.aspectj;
+
+import com.alibaba.csp.sentinel.annotation.SentinelResource;
+import com.alibaba.csp.sentinel.slots.block.BlockException;
+import com.alibaba.csp.sentinel.slots.block.degrade.DegradeException;
+import com.alibaba.csp.sentinel.util.MethodUtil;
+import com.alibaba.csp.sentinel.util.StringUtil;
+import org.aspectj.lang.ProceedingJoinPoint;
+import org.aspectj.lang.reflect.MethodSignature;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+import java.util.Arrays;
+
+/**
+ * @author chua
+ * @date 2018/10/31
+ */
+public abstract class AbstractSentinelAspect {
+
+    private final Logger logger = LoggerFactory.getLogger(AbstractSentinelAspect.class);
+
+    protected String getResourceName(String resourceName, Method method) {
+        // If resource name is present in annotation, use this value.
+        if (StringUtil.isNotBlank(resourceName)) {
+            return resourceName;
+        }
+        // Parse name of target method.
+        return MethodUtil.resolveMethodName(method);
+    }
+
+    protected Object handleBlockException(ProceedingJoinPoint pjp, SentinelResource annotation, BlockException ex)
+        throws Exception {
+        // Execute fallback for degrading if configured.
+        Object[] originArgs = pjp.getArgs();
+        if (isDegradeFailure(ex)) {
+            Method method = extractFallbackMethod(pjp, annotation.fallback());
+            if (method != null) {
+                return method.invoke(pjp.getTarget(), originArgs);
+            }
+        }
+        // Execute block handler if configured.
+        Method blockHandler = extractBlockHandlerMethod(pjp, annotation.blockHandler(), annotation.blockHandlerClass());
+        if (blockHandler != null) {
+            // Construct args.
+            Object[] args = Arrays.copyOf(originArgs, originArgs.length + 1);
+            args[args.length - 1] = ex;
+            if (isStatic(blockHandler)) {
+                return blockHandler.invoke(null, args);
+            }
+            return blockHandler.invoke(pjp.getTarget(), args);
+        }
+        // If no block handler is present, then directly throw the exception.
+        throw ex;
+    }
+
+    private boolean isDegradeFailure(/*@NonNull*/ BlockException ex) {
+        return ex instanceof DegradeException;
+    }
+
+    private Method extractFallbackMethod(ProceedingJoinPoint pjp, String fallbackName) {
+        if (StringUtil.isBlank(fallbackName)) {
+            return null;
+        }
+        Class<?> clazz = pjp.getTarget().getClass();
+        MethodWrapper m = ResourceMetadataRegistry.lookupFallback(clazz, fallbackName);
+        if (m == null) {
+            // First time, resolve the fallback.
+            Method method = resolveFallbackInternal(pjp, fallbackName);
+            // Cache the method instance.
+            ResourceMetadataRegistry.updateFallbackFor(clazz, fallbackName, method);
+            return method;
+        }
+        if (!m.isPresent()) {
+            return null;
+        }
+        return m.getMethod();
+    }
+
+    private Method resolveFallbackInternal(ProceedingJoinPoint pjp, /*@NonNull*/ String name) {
+        Method originMethod = resolveMethod(pjp);
+        Class<?>[] parameterTypes = originMethod.getParameterTypes();
+        return findMethod(false, pjp.getTarget().getClass(), name, originMethod.getReturnType(), parameterTypes);
+    }
+
+    private Method extractBlockHandlerMethod(ProceedingJoinPoint pjp, String name, Class<?>[] locationClass) {
+        if (StringUtil.isBlank(name)) {
+            return null;
+        }
+
+        boolean mustStatic = locationClass != null && locationClass.length >= 1;
+        Class<?> clazz;
+        if (mustStatic) {
+            clazz = locationClass[0];
+        } else {
+            // By default current class.
+            clazz = pjp.getTarget().getClass();
+        }
+        MethodWrapper m = ResourceMetadataRegistry.lookupBlockHandler(clazz, name);
+        if (m == null) {
+            // First time, resolve the block handler.
+            Method method = resolveBlockHandlerInternal(pjp, name, clazz, mustStatic);
+            // Cache the method instance.
+            ResourceMetadataRegistry.updateBlockHandlerFor(clazz, name, method);
+            return method;
+        }
+        if (!m.isPresent()) {
+            return null;
+        }
+        return m.getMethod();
+    }
+
+    private Method resolveBlockHandlerInternal(ProceedingJoinPoint pjp, /*@NonNull*/ String name, Class<?> clazz,
+                                               boolean mustStatic) {
+        Method originMethod = resolveMethod(pjp);
+        Class<?>[] originList = originMethod.getParameterTypes();
+        Class<?>[] parameterTypes = Arrays.copyOf(originList, originList.length + 1);
+        parameterTypes[parameterTypes.length - 1] = BlockException.class;
+        return findMethod(mustStatic, clazz, name, originMethod.getReturnType(), parameterTypes);
+    }
+
+    private boolean checkStatic(boolean mustStatic, Method method) {
+        return !mustStatic || isStatic(method);
+    }
+
+    private Method findMethod(boolean mustStatic, Class<?> clazz, String name, Class<?> returnType,
+                              Class<?>... parameterTypes) {
+        Method[] methods = clazz.getDeclaredMethods();
+        for (Method method : methods) {
+            if (name.equals(method.getName()) && checkStatic(mustStatic, method)
+                && returnType.isAssignableFrom(method.getReturnType())
+                && Arrays.equals(parameterTypes, method.getParameterTypes())) {
+
+                logger.info("Resolved method [{}] in class [{}]", name, clazz.getCanonicalName());
+                return method;
+            }
+        }
+        // Current class not found, find in the super classes recursively.
+        Class<?> superClass = clazz.getSuperclass();
+        if (superClass != null && !Object.class.equals(superClass)) {
+            return findMethod(mustStatic, superClass, name, returnType, parameterTypes);
+        } else {
+            String methodType = mustStatic ? " static" : "";
+            logger.error("Cannot find{} method [{}] in class [{}] with parameters {}",
+                methodType, name, clazz.getCanonicalName(), Arrays.toString(parameterTypes));
+            return null;
+        }
+    }
+
+    private boolean isStatic(Method method) {
+        return Modifier.isStatic(method.getModifiers());
+    }
+
+    protected Method resolveMethod(ProceedingJoinPoint joinPoint) {
+        MethodSignature signature = (MethodSignature)joinPoint.getSignature();
+        Class<?> targetClass = joinPoint.getTarget().getClass();
+
+        Method method = getDeclaredMethodFor(targetClass, signature.getName(),
+            signature.getMethod().getParameterTypes());
+        if (method == null) {
+            throw new IllegalStateException("Cannot resolve target method: " + signature.getMethod().getName());
+        }
+        return method;
+    }
+
+    /**
+     * Get declared method with provided name and parameterTypes in given class and its super classes.
+     * All parameters should be valid.
+     *
+     * @param clazz          class where the method is located
+     * @param name           method name
+     * @param parameterTypes method parameter type list
+     * @return resolved method, null if not found
+     */
+    private Method getDeclaredMethodFor(Class<?> clazz, String name, Class<?>... parameterTypes) {
+        try {
+            return clazz.getDeclaredMethod(name, parameterTypes);
+        } catch (NoSuchMethodException e) {
+            Class<?> superClass = clazz.getSuperclass();
+            if (superClass != null) {
+                return getDeclaredMethodFor(superClass, name, parameterTypes);
+            }
+        }
+        return null;
+    }
+}