创建 MockupDB 和 MessagingBean
清单 3 所示的 MockupDB 是个单体类，模拟客户订单的数据库。所有订单都硬编码在这个类中。真实应用程序可能使用关系数据库系统，但这个示例对我们的目的来说足够了。
清单 3. MockupDB
package db;
import java.util.Hashtable;
import java.util.Map;
public class MockupDB {
private static MockupDB instance=new MockupDB();
private String[] orders=new String[4];
private Map orderDetails=new Hashtable();
private Map customerDetails=new Hashtable();
private MockupDB()
{
String ordStart="ORD";
orders[0]=ordStart+"000408015";
orders[1]=ordStart+"001600023";
orders[2]=ordStart+"000042000";
orders[3]=ordStart+"011235813";
orderDetails.put(orders[0],"1. WebSphere Everyplace Connection Manager<br/>"+
"2. WebSphere Portal");
orderDetails.put(orders[1],"1. DB2 Universal Database<br/>2. DB2 Everyplace");
orderDetails.put(orders[2],"1. Tivoli Access Manager for e-business <br/>2."+
"Tivoli Directory Integrator");
orderDetails.put(orders[3],"1. IBM System z9<br/>2. IBM System p5 550 Express");
customerDetails.put(orders[0],"<b>Systems and Technology Group</b><br/>"+
"Some Road<br/>Finland");
customerDetails.put(orders[1],"<b>Global Financing</b><br/>Another Street"+
"<br/>Finland");
customerDetails.put(orders[2],"<b>Software</b><br/>Yet Another Road"+
"<br/>Finland");
customerDetails.put(orders[3],"<b>Global Services</b><br/>Still Another "+
"Street<br/>Finland");
}
public static MockupDB getInstance()
{
return instance;
}
public String[] getOrders()
{
return orders;
}
public String getOrderDetails(String orderNro)
{
return (String)orderDetails.get(orderNro);
}
public String getCustomerDetails(String orderNro)
{
return (String)customerDetails.get(orderNro);
}
}
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清单 4 所示的 MessagingBean 是个简单的 POJO，有两个方法，都接受订单号，但是分别返回订单细节和客户细节。MessagingBean 从 MockupDB 得到细节。
清单 4. MessagingBean
package msg;
import javax.servlet.http.HttpSession;
import db.MockupDB;
public class MessagingBean {
public MessagingBean()
{
}
public String getOrderDetails(String orderNumber,HttpSession httpSession)
{
String orderDetails=MockupDB.getInstance().getOrderDetails(orderNumber)
httpSession.setAttribute("orderDetailsOrderNumber",orderNumber);
httpSession.setAttribute("orderDetails",orderDetails);
return orderDetails;
}
public String getCustomerDetails(String orderNumber,HttpSession httpSession)
{
String customerDetails=MockupDB.getInstance().getCustomerDetails(orderNumber);
httpSession.setAttribute("customerDetailsOrderNumber",orderNumber);
httpSession.setAttribute("customerDetails",customerDetails);
return customerDetails;
}
}
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MessagingBean 还把订单细节和客户细节添加到 HttpSession。
javascriptFunctions.jsp
javascriptFunctions.jsp 导入了来自 DWR 的 javascript 库（engine.js）并动态地创建库 MessagingBean.js。注意，MessagingBean.js 使用的名称与 dwr.xml（清单 2）中的 JavaBean 的名称相同；实际上，DWR 生成 MessagingBean.js。DWR 框架使用 engine.js 库；作为开发人员，通常不需要考虑直接使用它。
如清单 5 所示，sendOrderNr() 函数调用 清单 4 中定义的 MessagingBean 函数。DWR 自动把 HttpSession 添加到方法调用。javascript 函数中的最后一个参数是 callback 函数。在稍后创建的 portlet JSP 中，包含这个 JSP。
清单 5. javascriptFunctions.jsp
<%@ page contentType="text/html"
import="java.util.*,javax.portlet.*,interportletmessagingusingajax.*" %>
<%@taglib uri="http://java.sun.com/portlet" prefix="portlet" %>
<portlet:defineObjects/>
<SCRIPT type="text/javascript"
src='<%= renderResponse.encodeURL(renderRequest.getContextPath() +
"/dwr/interface/MessagingBean.js") %>'>
</SCRIPT>
<SCRIPT type="text/javascript"
src='<%= renderResponse.encodeURL(renderRequest.getContextPath() +
"/dwr/engine.js") %>'>
</SCRIPT>
<SCRIPT type="text/javascript">
function <portlet:namespace />sendOrderNr(orderNr)
{
document.getElementById("orderDetailsOrderNumber").innerHTML=orderNr;
document.getElementById("customerDetailsOrderNumber").innerHTML=orderNr;
MessagingBean.getOrderDetails(orderNr,<portlet:namespace />showOrderDetails);
MessagingBean.getCustomerDetails(orderNr,<portlet:namespace />showCustomerDetails);
return false;
}
function <portlet:namespace />showOrderDetails(orderDetails)
{
document.getElementById("orderDetails").innerHTML=orderDetails;
return false;
}
function <portlet:namespace />showCustomerDetails(customerDetails)
{
document.getElementById("customerDetails").innerHTML=customerDetails;
return false;
}
</SCRIPT>
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