gwt Client-Server 交互原形模型

曾永新

2023-12-01

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<display-name>ccgwt</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>dealwith</servlet-name>
<servlet-class>response.DealWith</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>dealwith</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>
</web-app>
<%@ page contentType="text/html; charset=GBK"%>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Ajax-Demo</title>
<script type="text/javascript">
function createXMLHttpRequest(){
if (window.ActiveXObject){
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
}
else if(window.XMLHttpRequest){
xmlHttp = new XMLHttpRequest();
}
}
function sendRequest(){
createXMLHttpRequest();
var url;
url="getServerTime.do?person=Ihavegotyou";
xmlHttp.open("POST",url,true);
xmlHttp.onreadystatechange = handleStateChange;
xmlHttp.send();
}
function handleStateChange(){
if (xmlHttp.readyState == 4){
if (xmlHttp.status == 200){
document.getElementById("serverTime").value=xmlHttp.responseText;
}
}
}
</script>
</head>
<form action="#">
<input disabled type="TEXT" id="serverTime" value="这里显示服务器时间">
<input align="absmiddle" type="button" value="点击获取服务器时间" onclick="sendRequest();" />
</form>
</body>
</html>

DealWith.java

java 代码

package response;
import javax.servlet.*;
import javax.servlet.http.*;
public class DealWith extends HttpServlet {
private static final String CONTENT_TYPE = "text/xml; charset=GBK";
private static final String URIS[] = { "getServerTime.do", "others.do" };
public void init() throws ServletException {
}
public void doPost(HttpServletRequest request, HttpServletResponse response) {
response.setContentType(CONTENT_TYPE);
if (request.getRequestURI().indexOf(URIS[0]) != -1) {
try {
java.util.Calendar cal = java.util.Calendar.getInstance();
java.text.SimpleDateFormat fmt = new java.text.SimpleDateFormat(
"yyyy-MM-dd hh:mm:ss");
String time = fmt.format(cal.getTime());
response.getWriter().print(time);
} catch (Exception e) {
e.printStackTrace();
}
}
}
public void doGet(HttpServletRequest request, HttpServletResponse response) {
doPost(request, response);
}
// Clean up resources
public void destroy() {
}
}

清楚上面的模型,就会更加理解GWT RPC(Remote Procedure Calls)的几个步骤：

Creating Services
How to build a service interface from scratch.
Implementing Services
Implement your service interface as a servlet.
Actually Making a Call
How to actually make a remote procedure call from the client.
Serializable Types(不必要)
Using GWT's automatic serialization well.
Handling Exceptions
Handle exceptions due to failed calls or thrown from the server.
Getting Used to Asynchronous Calls
Asynchronous calls are tricky at first, but ultimately your users will thank you.

gwt Client-Server 交互原形模型

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