GWT RPC 的使用方式

开发GWT RPC开发时。在GWT 2.2环境下。

我遇到了一些问题。不过今天把问题解决。以下是我的开发过程

首先导入GWT2.2 Sample目录下的DynaTable工程。

这里我使用创建新工程，导入已存在文件至项目中，过程如下所示：

new WindowBuilder 选中GWT java Project

至下一步，选中已经存在的GWT 项目DynaTable，并将工程命名为DynaTable。

通过查看该示例源代码。

我发现：

1.在DynaTable.gwt.xml文件中

<module rename-to="dynatable">

<inherits name='com.google.gwt.user.User' />

<inherits name='com.google.gwt.rpc.RPC' />

<entry-point class='com.google.gwt.sample.dynatable.client.DynaTable' />

<servlet path='/calendar'

class='com.google.gwt.sample.dynatable.server.SchoolCalendarServiceImpl' />

</module>

2.在Web.xml文件中

<?xml version="1.0" encoding="UTF-8"?>

<web-app>

<!-- Default page to serve -->

<welcome-file-list>

<welcome-file>DynaTable.html</welcome-file>

</welcome-file-list>

<!-- Servlets -->

<servlet>

<servlet-name>calendar</servlet-name>

<servlet-class>com.google.gwt.sample.dynatable.server.SchoolCalendarServiceImpl</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>calendar</servlet-name>

<url-pattern>/dynatable/calendar</url-pattern>

</servlet-mapping>

</web-app>

3.在SchoolCalendarServiceAsync.java文件中

package com.google.gwt.sample.dynatable.client;

import com.google.gwt.user.client.rpc.AsyncCallback;

/**

* The interface for the RPC server endpoint that provides school calendar

* information for clients that will be calling asynchronously.

*/

public interface SchoolCalendarServiceAsync {

void getPeople(int startIndex, int maxCount, AsyncCallback<Person[]> callback);

}

4.在SchoolCalendarService.java文件中

package com.google.gwt.sample.dynatable.client;

import com.google.gwt.rpc.client.RpcService;

/**

* The interface for the RPC server endpoint to get school calendar information.

*/

public interface SchoolCalendarService extends RpcService {

Person[] getPeople(int startIndex, int maxCount);

}

5.在SchoolCalendarServiceImpl.java文件中

。。。。。

public Person[] getPeople(int startIndex, int maxCount) {

int peopleCount = people.size();

int start = startIndex;

if (start >= peopleCount) {

return NO_PEOPLE;

}

int end = Math.min(startIndex + maxCount, peopleCount);

if (start == end) {

return NO_PEOPLE;

}

int resultCount = end - start;

Person[] results = new Person[resultCount];

for (int from = start, to = 0; to < resultCount; ++from, ++to) {

results[to] = people.get(from);

}

return results;

}

6.在SchoolCalendarWidget.java文件中

.....................

public CalendarProvider() {

// Initialize the service.

//

calService = (SchoolCalendarServiceAsync) GWT.create(SchoolCalendarService.class);

// By default, we assume we'll make RPCs to a servlet, but see

// updateRowData(). There is special support for canned RPC responses.

// (Which is a totally demo hack, by the way :-)

//

ServiceDefTarget target = (ServiceDefTarget) calService;

// Use a module-relative URLs to ensure that this client code can find

// its way home, even when the URL changes (as might happen when you

// deploy this as a webapp under an external servlet container).

String moduleRelativeURL = GWT.getModuleBaseURL() + "calendar";

target.setServiceEntryPoint(moduleRelativeURL);

}

.........................

以上则是该实现RPC的全部细节

这跟我以前用的那个GWT Windows下面的不一样。

下面我再介绍一下实现GWT Window 2.0的那个例子。自已参考源码写的

1.在GreetingService.java文件中

import com.google.gwt.core.client.GWT;

import com.google.gwt.user.client.rpc.RemoteService;

import com.google.gwt.user.client.rpc.RemoteServiceRelativePath;

import com.google.gwt.user.client.rpc.ServiceDefTarget;

@RemoteServiceRelativePath("GreetingServiceImpl")

public interface GreetingService extends RemoteService {

public String getGreetingHello(String greetingHello);

public static class Util {

public static GreetingServiceAsync getInstance() {

return GWT.create(GreetingService.class);

}

}

}

2.在GreetingServiceAsync.java文件中

import com.google.gwt.user.client.rpc.AsyncCallback;

public interface GreetingServiceAsync {

public void getGreetingHello(String greetingHello, AsyncCallback<String> callback);

}

3.在实现类中

// TODO Auto-generated method stub

Button button = new Button("测试按钮");

button.addListener(new ButtonListenerAdapter() {

@Override

public void onClick(Button button, EventObject e) {

// TODO Auto-generated method stub

super.onClick(button, e);

AsyncCallback<String> callback = new AsyncCallback<String>() {

public void onFailure(Throwable caught) {

// TODO Auto-generated method stub

Window.alert(caught.toString());

}

public void onSuccess(String result) {

// TODO Auto-generated method stub

Window.alert(result.toString());

}

};

gsa.getGreetingHello("hellowrold", callback);

}

});

RootPanel.get("hellodiv").add(button);

4.并在Main.gwt.xml中

<?xml version="1.0" encoding="UTF-8" standalone="no"?>

<module>

<!-- Inherit the core Web Toolkit stuff. -->

<inherits name="com.google.gwt.user.User" />

<!-- Specify the app entry point class. -->

<entry-point class="com.cystal.gwt.client.Main" />

<inherits name="com.google.gwt.user.theme.standard.Standard" />

<!-- <inherits name="com.google.gwt.user.theme.chrome.Chrome"/> -->

<!-- <inherits name="com.google.gwt.user.theme.dark.Dark"/> -->

<!-- 设置 Servlet -->

<servlet class="com.cystal.gwt.server.GreetingServiceImpl"

path="/GreetingServiceImpl" />

<!-- 继承使用Ext框架类 -->

<inherits name="com.gwtext.GwtExt" />

<!-- 使用Ext样式与javascript库 -->

<stylesheet src="js/ext/resources/css/ext-all.css" />

<script src="js/ext/adapter/ext/ext-base.js" />

<script src="js/ext/ext-all.js" />

</module>

5.在server实现类中

import com.cystal.gwt.client.GreetingService;

import com.google.gwt.user.server.rpc.RemoteServiceServlet;

public class GreetingServiceImpl extends RemoteServiceServlet implements GreetingService {

public String getGreetingHello(String greetingHello) {

// TODO Auto-generated method stub

return "你好:/t"+greetingHello;

}

}

最后我们看看web.xml文件

<?xml version="1.0" encoding="UTF-8"?>

<web-app>

<servlet>

<servlet-name>shell</servlet-name>

<servlet-class>com.google.gwt.dev.shell.GWTShellServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>shell</servlet-name>

<url-pattern>/*</url-pattern>

</servlet-mapping>

</web-app>

注意这里没有注册GreetingServiceImpl 的Servlet,urlpattern了，同第一种方式不同。

注意我们在实际开发过程中还是要使用第一种方式的比较多。

附GWT RPC结构图（源于官网）