GWT有两种与服务端进行交互的技术：GWT RPC和基于普通AJAX的远程交互技术。这里只介绍GWT RPC技术。
一个完整的RPC服务至少包含三个Java文件：
1、客户端远程接口类，需要继承RemoteService类
2、客户端远程接口类的异步类，异步类的名称格式是： 客户端远程接口类名 + Async 后缀
3、服务器端的远程接口类，需要继承RemoteServiceServlet类和实现客户端远程接口类
客户端相关的类必须位于client包及其子包下，服务器端相关的类必须位于server包及其子包下。
1、客户端远程接口类 源码
Java代码 
- /**
- * 客户端远程接口类需要继承RemoteService类
- */
- public interface PersonService extends RemoteService {
- public Person getPerson(String name, int age) throws RuntimeException;
- //使用内部类创建客户端远程接口类的异步类
- public static class Utils{
- private static PersonServiceAsync serviceAsync;
- public static PersonServiceAsync getInstance(){
- if(serviceAsync==null){
- serviceAsync = (PersonServiceAsync) GWT.create(PersonService.class);
- }
- return serviceAsync;
- }
- }
- }
/**
* 客户端远程接口类需要继承RemoteService类
*/
public interface PersonService extends RemoteService {
public Person getPerson(String name, int age) throws RuntimeException;
//使用内部类创建客户端远程接口类的异步类
public static class Utils{
private static PersonServiceAsync serviceAsync;
public static PersonServiceAsync getInstance(){
if(serviceAsync==null){
serviceAsync = (PersonServiceAsync) GWT.create(PersonService.class);
}
return serviceAsync;
}
}
}
2、客户端远程接口类的异步类 源码
Java代码
- /**
- * 异步接口的方法返回值均为void，并且其对应的每个方法都比原接口多一个类型为AsyncCallback的参数
- */
- public interface PersonServiceAsync {
- public void getPerson(String name, int age, AsyncCallback callback) throws RuntimeException;
- }
/**
* 异步接口的方法返回值均为void，并且其对应的每个方法都比原接口多一个类型为AsyncCallback的参数
*/
public interface PersonServiceAsync {
public void getPerson(String name, int age, AsyncCallback callback) throws RuntimeException;
}
3、服务器端的远程接口类 源码
Java代码
- /**
- * 实现类要继承RemoteServiceServlet类
- */
- public class PersonServiceImpl extends RemoteServiceServlet implements PersonService {
- public Person getPerson(String name, int age) throws RuntimeException {
- //与HTTP的交互
- HttpServletRequest request = this.getThreadLocalRequest();
- HttpServletResponse response = this.getThreadLocalResponse();
- HttpSession session = request.getSession();
- return new Person(name, age);
- }
- }
/**
* 实现类要继承RemoteServiceServlet类
*/
public class PersonServiceImpl extends RemoteServiceServlet implements PersonService {
public Person getPerson(String name, int age) throws RuntimeException {
//与HTTP的交互
HttpServletRequest request = this.getThreadLocalRequest();
HttpServletResponse response = this.getThreadLocalResponse();
HttpSession session = request.getSession();
return new Person(name, age);
}
}
4、交互过程中传递的对象
Java代码
- /**
- * 在GWT RPC中，如果要交互的数据（方法的参数和返回值）是一个复杂类型的话，
- * 那么这个类要实现IsSerializable接口，来使该类能被正常序列化和反序列化。
- */
- public class Person implements IsSerializable {
- private String name;
- private int age;
- public Person(){
- }
- public Person(String name, int age){
- this.name = name;
- this.age = age;
- }
- //省略getter、setter方法
- }
/**
* 在GWT RPC中，如果要交互的数据（方法的参数和返回值）是一个复杂类型的话，
* 那么这个类要实现IsSerializable接口，来使该类能被正常序列化和反序列化。
*/
public class Person implements IsSerializable {
private String name;
private int age;
public Person(){
}
public Person(String name, int age){
this.name = name;
this.age = age;
}
//省略getter、setter方法
}
5、GWT应用入口点类需要实现EntryPoint接口，其源码如下
Java代码
- public class Index implements EntryPoint {
- public void onModuleLoad() {
- Button button = new Button("Click me");
- VerticalPanel vPanel = new VerticalPanel();
- vPanel.setWidth("100%");
- vPanel.setHorizontalAlignment(VerticalPanel.ALIGN_CENTER);
- vPanel.add(button);
- RootPanel.get().add(vPanel);
- //按钮的单击事件
- button.addClickListener(new ClickListener() {
- public void onClick(Widget sender) {
- //初始化Service接口
- PersonServiceAsync personService = PersonService.Utils.getInstance();
- //为Service代理描述Service接入点的URL
- ServiceDefTarget target = (ServiceDefTarget)personService;
- String path = GWT.getModuleBaseURL() + "PersonService";
- target.setServiceEntryPoint(path);
- //发出RPC请求
- personService.getPerson("cjm", 100, new AsyncCallback(){
- public void onSuccess(Object result) {
- Person person = (Person)result;
- Window.alert(person.getName());
- }
- public void onFailure(Throwable caught) {
- Window.alert(caught.getMessage());
- }
- });
- }
- });
- }
- }
public class Index implements EntryPoint {
public void onModuleLoad() {
Button button = new Button("Click me");
VerticalPanel vPanel = new VerticalPanel();
vPanel.setWidth("100%");
vPanel.setHorizontalAlignment(VerticalPanel.ALIGN_CENTER);
vPanel.add(button);
RootPanel.get().add(vPanel);
//按钮的单击事件
button.addClickListener(new ClickListener() {
public void onClick(Widget sender) {
//初始化Service接口
PersonServiceAsync personService = PersonService.Utils.getInstance();
//为Service代理描述Service接入点的URL
ServiceDefTarget target = (ServiceDefTarget)personService;
String path = GWT.getModuleBaseURL() + "PersonService";
target.setServiceEntryPoint(path);
//发出RPC请求
personService.getPerson("cjm", 100, new AsyncCallback(){
public void onSuccess(Object result) {
Person person = (Person)result;
Window.alert(person.getName());
}
public void onFailure(Throwable caught) {
Window.alert(caught.getMessage());
}
});
}
});
}
}
6、在Index.gwt.xml文件中增加以下配置信息
将RPC服务与GWT应用入口点类关联起来
Xml代码
- <servlet path="/PersonService" class="com.cjm.server.PersonServiceImpl"/>
<servlet path="/PersonService" class="com.cjm.server.PersonServiceImpl"/>
7、在web.xml文件增加以下配置信息
Xml代码
- <!-- 在宿主模式下启动应用时，此servlet是必须的 -->
- <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>
- <!-- RPC服务配置 -->
- <servlet>
- <servlet-name>PersonService</servlet-name>
- <servlet-class>com.cjm.server.PersonServiceImpl</servlet-class>
- </servlet>
- <servlet-mapping>
- <servlet-name>PersonService</servlet-name>
- <url-pattern>/PersonService</url-pattern>
- </servlet-mapping>