/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 pojo.provider;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import org.apache.tuscany.sca.interfacedef.Operation;
import org.apache.tuscany.sca.invocation.Invoker;
import org.apache.tuscany.sca.invocation.Message;
import org.osoa.sca.ServiceRuntimeException;

/**
 * Implements an invoker for POJO component implementations.
 * 
 * The invoker is responsible for handling invocations of a business operation.
 * Input business data is passed to the invoke method in a Message object.
 * The invoke method is responsible for handling the invocation and returning a Message with
 * the output business data. 
 * 
 * In this example we are simply delegating the operation invocations to the
 * corresponding methods on the POJO implementation class using Java reflection.
 * 
 * Depending on the type of implementation being handled, more sophisticated invokers can
 * use other techniques to delegate the invocation to the implementation artifact directly, call a
 * runtime engine like a BPEL engine or an XQuery engine (this is what the Tuscany 
 * implementation-bpel and implementation-xquery extensions do) or just completely handle the
 * invocation in the invoker itself if the implementation has a fixed behavior for example.
 */
class POJOImplementationInvoker implements Invoker {

    private Object pojoInstance;
    private Method method;
    
    POJOImplementationInvoker(Object pojoInstance, Operation operation, Method method) {
        this.pojoInstance = pojoInstance;
        this.method = method;
    }
    
    public Message invoke(Message msg) {
        try {
            msg.setBody(method.invoke(pojoInstance, (Object[])msg.getBody()));
        } catch (InvocationTargetException e) {
            msg.setFaultBody(e);
        } catch (Exception e) {
            throw new ServiceRuntimeException(e);
        }
        return msg;
    }
    
}