ServiceWrapperInterceptor.java

/* ServiceWrapperInterceptor.java
 *
 * Copyright 2009-2015 Comcast Interactive Media, LLC.
 *
 * 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 org.fishwife.jrugged.spring;

import java.util.Map;
import java.util.concurrent.Callable;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;

import org.fishwife.jrugged.CircuitBreaker;
import org.fishwife.jrugged.PerformanceMonitor;
import org.fishwife.jrugged.ServiceWrapper;

/**
 * A Spring interceptor that allows wrapping a method invocation with
 * a {@link ServiceWrapper} (for example, a {@link CircuitBreaker} or
 * {@link PerformanceMonitor}).
 */
public class ServiceWrapperInterceptor implements MethodInterceptor {

    private Map<String, ServiceWrapper> methodMap;

    /** See if the given method invocation is one that needs to be
     * called through a {@link ServiceWrapper}, and if so, do so.
     * @param invocation the {@link MethodInvocation} in question
     * @return whatever the underlying method call would normally
     * return
     * @throws Throwable that the method call would generate, or
     *   that the {@link ServiceWrapper} would generate when tripped.
     */
    public Object invoke(final MethodInvocation invocation) throws Throwable {
        String methodName = invocation.getMethod().getName();

        if (!shouldWrapMethodCall(methodName)) {
            return invocation.proceed();
        }
        else {
            ServiceWrapper wrapper = methodMap.get(methodName);

            return wrapper.invoke(new Callable<Object>() {
                    public Object call() throws Exception {
                        try {
                            return invocation.proceed();
                        } catch (Throwable e) {
                            if (e instanceof Exception)
                                throw (Exception) e;
                            else if (e instanceof Error)
                                throw (Error) e;
                            else
                                throw new RuntimeException(e);
                        }
                    }
                });
        }
    }

    private boolean shouldWrapMethodCall(String methodName) {
        if (methodMap == null) {
            return true; // Wrap all by default
        }

        if (methodMap.get(methodName) != null) {
            return true; //Wrap a specific method
        }

        // If I get to this point, I should not wrap the call.
        return false;
    }

    /** Specifies which methods will be wrapped with which ServiceWrappers.
     *  @param methodMap the mapping!
     */
    public void setMethods(Map<String, ServiceWrapper> methodMap)  {
        this.methodMap = methodMap;
    }
}