在開發分散式系統，用的框架是EJB，其中需要呼叫Bean，這裡分析兩種EJB呼叫的方法。

遠端呼叫

通過Remote介面，找到EJB服務的Bean代理，然後由代理和Bean實現互動，返回呼叫的結果。

• Remote介面@remote

Bean的客戶端直接與EJB物件打交道，而不是Bean實現類。所以EJB必須複製Bean物件的每一個方法，Remote Interface告訴EJB物件自動生成工具需要賦值Bean類的哪些方法。

<!-- 客戶bean -->
	<jee:local-slsb id="EditTrainingProgramBean"
		jndi-name="java:global/itoo-basic-editTrainingprogram-ear/itoo-basic-editTrainingprogram-core/editTrainingProgramsBeanImpl!com.tgb.itoo.basic.service.EditTrainingProgramBean"
		business-interface="com.tgb.itoo.basic.service.EditTrainingProgramBean" />

	<bean name="editTrainingProgramsController"
		class="com.tgb.itoo.basic.controller.EditTrainingProgramsController">
		<property name="editTrainingProgramBean" ref="EditTrainingProgramBean"></property>
	</bean>
 

@Remote(PubliceditTrainingProgramBean.class)  
@TransactionManagement(TransactionManagementType.CONTAINER)  
@TransactionAttribute(TransactionAttributeType.REQUIRED)  
public class PubliceditTrainingProgramBeanImpl extends  
        BaseBeanImpl<PubliceditTrainingProgram> implements PubliceditTrainingProgramBean {  
    editTrainingProgramBeanImpl editTrainingProgramBeanImpl = new editTrainingProgramBeanImpl();  
    private editTrainingProgramBean editTrainingProgramBean = null;  
    private editTrainingProgramGradeCollegeBean editTrainingProgramGradeCollegeBean;  
    private CourseRoundBean courseRoundBean;  
  
    public PubliceditTrainingProgramBeanImpl() {  
        /* 培養計劃 */  
        String ronndAddress = "itoo-basic-editTrainingProgram-ear/itoo-basic-editTrainingProgram-core-0.0.1-SNAPSHOT/editTrainingProgramBeanImpl!com.tgb.itoo.basic.service.editTrainingProgramBean";  
          
        try {  
            editTrainingProgramBean = (editTrainingProgramBean) this  
                    .lookupRemoteBean(ronndAddress);              
  
        } catch (NamingException e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
        }  
          
        editTrainingProgram roundResult = new editTrainingProgram();  
        roundResult = editTrainingProgramBean.saveRound(roundid, beginTime,  
                endTime, leaststTime, dataBaseName);  
  
    }  
}
 

• 本地呼叫@local

有時Bean的呼叫並不經過網路，比如在同一個容器中不同Bean之間的呼叫，使用者可以使用Local物件來呼叫Bean例項。

客戶端必須與被呼叫的Bean在同一個JVM環境中，可以是web應用或者其他的企業Bean。

package EJBTest;
/**
 * 本地呼叫-客戶端
 * @author bobo
 *
 */
public class EJBRemotecontroller {
	// 注入services層
		private EditTrainingProgramBean editTrainingProgramBean;

		/**
		 * services層get方法
		 * 
		 * @return
		 */
		public EditTrainingProgramBean EditTrainingProgramBean() {
			return editTrainingProgramBean;
		}

		/**
		 * services層set方法
		 * 
		 * @param editTrainingProgramBean
		 */
		public void setEditTrainingProgramBean(
				EditTrainingProgramBean editTrainingProgramBean) {
			this.editTrainingProgramBean = editTrainingProgramBean;
		}
		/**
		 * 日誌
		 */
		private static final Logger logger = Logger.getLogger(EditTrainingProgramsController.class.getName());

		/**
		 * 培養計劃
		 */
		@RequestMapping("/tremList")
		public String toTremList(HttpServletRequest request,
				HttpServletResponse response) throws Exception  {
			String dataBaseName=(String) request.getSession().getAttribute (CloudContext.DatabaseName)+"_basic";
			try{
				// 查詢所有的學期名稱顯示到介面上
				List<DictionaryNow> tremList = editTrainingProgramBean.queryTremList(
						"學期",  dataBaseName);
				if (tremList.size() > 0) {
					request.setAttribute("tremlist", tremList);
				} else {
					request.setAttribute("tremlist", "");
				}

				// 獲取專業id和專業名稱
				String institutionId = request.getParameter("institutionId");
				String institutionName = new String(request.getParameter(
						"institutionName").getBytes("ISO-8859-1"));
				request.setAttribute("institutionId", institutionId);
				request.setAttribute("institutionName", institutionName);
			}catch (Exception e) {
				e.printStackTrace();
				logger.error("QuestionController.addAllUser called error {}",e);
		        //輸入日誌之後將異常丟擲
		        throw e;

			}
			return "/tremList";
		}
}
 

兩種呼叫方法，主要取決於是否在不同Bean容器中。小型系統考慮效能最好用本地呼叫，分散式系統會部署到不同的伺服器和JVM中，選擇遠端呼叫。