SCA交互模型

1.使用对话

   (1) 对话范围的不同级别

   Composite: 所有请求在组合的整个生命周期都被分发到同一个类实例。一个经典的场景是计数器，每当特定服务被调

   用就增加一次计数。

   Conversation: 利用相关性创建进行中的客户端与目标服务之间的对话。第一个服务被调用时 对话开始，结束操作被

   调用时回话终止。客户端需要比较智能以支持这项功能。

   Request: 与Servlet的请求范围类似，对远程接口的请求进入到SCA运行时，处理该请求，指导线程完成处理。只有

   SCA客户端支持该级别。

   Stateless: 默认不维持任何回话。

   (2)下面用Composite范围来作示例：

   带有会话注解的SessionManager接口类：

   @Remotable
   @Conversational  //将服务标记为会话式的服务操作
   public interface SessionManager {
        public void initialize();
        public int getSessionId();
   }

   带有会话注解的SessionManagerImpl实现类：

   @Service (SessionManager.class)
   @Scope ("COMPOSITE") //标明服务的范围
   @EagerInit //SCA domain 启动时初始化
   public class SessionManagerImpl implements SessionManager {
         private int sessionId = 0;
         public int getSessionId() {
                return sessionId;
         }

         @Init //类初始化时调用的方法 ，使用@EagerInit注解时必须使用的
         public void initialize() {   
                Random r = new Random();
                sessionId = r.nextInt(300000);
         }
    } 

    配置文件：problemMgmt421.composite

    <composite xmlns="http://www.osoa.org/xmlns/sca/1.0"
            targetNamespace="http://opensoa.book.chapter4"
            xmlns:hw="http://opensoa.book.chapter4"
            name="ProblemManagementComposite">

            <service name="ProblemTicketComponent"   promote="ProblemTicketComponent">
                    <binding.ws uri="http://localhost:8085/ProblemTicketService" />
            </service>

            <component name="ProblemTicketComponent">
                  <implementation.java
                         class="opensoa.book.chapter4_21.impl.ProblemTicketComponentImpl" />
           
                  <property name="username">[e-mail]</property>
                  <property name="password">mypassword1</property>

                  <reference name="createTicket" target="CreateTicketComponent" />
            </component>

            <component name="CreateTicketComponent">
                     <implementation.java
                            class="opensoa.book.chapter4_21.impl.CreateTicketComponentImpl" />

                     <reference name="sessionManager" target="SessionManagerComponent" />
           </component>

           <component name="SessionManagerComponent">
                     <implementation.java
                              class="opensoa.book.chapter4_21.impl.SessionManagerImpl" />
           </component>
    </composite>

2. 理解回调

    会调是一种双向通信，客户端请求服务，服务提供者或服务器通过给定的接口或操作“回调”客户端。它被认为是一种

    异步的通信，因为服务器不像通常的Web服务或RPC风格的通信那样通过同步的回复返回结果。创建回调服务有以下

    几个步骤：

    (1)创建回调接口：定义之行回调时调用的操作

    @Remotable
    public interface EventNotificationCallback {
         void success(boolean status);
    }

    (2)创建服务接口和实现：增加回调注解

    @Remotable
    @Callback(EventNotificationCallback.class) //指定回调
    public interface EventNotificationComponent {
           @OneWay //给出回调方法类型
           public void notify(TicketDO ticket);
    }

 

    @Service(EventNotificationComponent.class)
    public class EventNotificationComponentImpl  implements EventNotificationComponent {

        @Callback //注入回调类
        protected EventNotificationCallback callback;
  
        public void notify(TicketDO ticket) {

        try {
                Thread.sleep(4000); //休眠40秒
        } catch (InterruptedException e) {
                e.printStackTrace();
        }
                callback.success(true); //执行回调操作
        }
   }

   (3) 创建或修改客户端类，实现第一步中定义的回调接口，增加到第二步中创建的服务的引用，修改业务逻辑以使用服

   务端组件的功能。

   @Service(CreateTicketComponent.class)
   public class CreateTicketComponentImpl implements CreateTicketComponent,

            EventNotificationCallback { //实现回调接口

            @Reference
            protected SessionManager sessionManager;
 
           @Reference
           protected EventNotificationComponent eventNotifier;
  
           int ticketId = 0;
  
           public CreateTicketComponentImpl() {
                   super();
                   System.out.println("CreateTicketComponentImpl instantiated...");
           }

           public int create(TicketDO ticket) {
                   System.out.println("createTicket sessionManager: " + sessionManager.getSessionId());
                   Random r = new Random();
                   ticketId = r.nextInt(300000);
                   eventNotifier.notify(ticket);
                   return ticketId;
           }

           public void success(boolean status) { //调用方法
                   System.out.println("Notify results: " + status);
     
           }
    }

    (4) 修改composite文件以支持装配集

    <composite xmlns="http://www.osoa.org/xmlns/sca/1.0"
           targetNamespace="http://opensoa.book.chapter4"
           xmlns:hw="http://opensoa.book.chapter4"
           name="ProblemManagementComposite">

          <property name="credentials" type="hw:CredentialsType">
                <hw:Credentials>
                   <hw:username>[e-mail]</hw:username>
                   <hw:password>mypassword1</hw:password>
                </hw:Credentials>
          </property>

          <service name="ProblemTicketComponent" promote="ProblemTicketComponent">
                   <binding.ws uri="http://localhost:8085/ProblemTicketService" />
          </service>

          <component name="ProblemTicketComponent">
                <implementation.java
                     class="opensoa.book.chapter4_22.impl.ProblemTicketComponentImpl" />

                <property name="username" source="$credentials//*[local-name()='username']" />
                <property name="password" source="$credentials//*[local-name()='password']" />

                <reference name="createTicket" target="CreateTicketComponent" />
          </component>

          <component name="CreateTicketComponent">
                <implementation.java
                      class="opensoa.book.chapter4_22.impl.CreateTicketComponentImpl" />

                <reference name="sessionManager" target="SessionManagerComponent" />
                <!--定义要注入的引用-->
                <reference name="eventNotifier" target="EventNotificationComponent">

                <!--指明回调接口-->
                <interface.java
                       interface="opensoa.book.chapter4_22.EventNotificationComponent"
                       callbackInterface="opensoa.book.chapter4_22.EventNotificationCallback" />
               </reference>

          </component>

          <component name="SessionManagerComponent">
                <implementation.java
                       class="opensoa.book.chapter4_22.impl.SessionManagerImpl" />
          </component>

          <component name="EventNotificationComponent">
                 <implementation.java
                        class="opensoa.book.chapter4_22.impl.EventNotificationComponentImpl" />
          </component>

    </composite>