Jonathan Lalou's Blog

Posts Tagged ‘RPC’

Context

In a GWT application, you have to use RPC calls, using entities which are package in external jar archives. With Eclipse, no error appears ; yet when you build the project with Maven2, you get this message:

[java][INFO] [ERROR] Errors in ‘file:/C:/eclipse/workspace/myGwtProject/src/java/com/lalou/jonathan/web/gwt/client/component/JonathanPanel.java’
(…)
[INFO] [ERROR] Line 24: No source code is available for type com.lalou.jonathan.domain.MyEntity; did you forget to inherit a required module?
(…)
[INFO] Finding entry point classes[/java]

Fix

In related jar

In the project to which MyEntity belongs to (here: my/depended/project):

• create a file com/lalou/jonathan/MyDependedProject.gwt.xml, with as content:

  [xml]<module>
  <source path="">
  <include name="**/MyEntity.java"/>
  </source>
  </module>[/xml]

• In the pom.xml:
  • Add the source MyEntity.java in built jar. This way, the Java file itself will be considered as a resource, like an XML or property file. To perform this, the quickest manner is to add the following block in the pom.xml:
    [xml]<resources>
    <resource>
    <directory>${basedir}/src/java</directory>
    <includes>
    <include>**/MyEntity.java</include>
    </includes>
    </resource>
    </resources>[/xml]
  • Add an <include>**/*.gwt.xml</include> so that to have to MyDependedProject.gwt.xml file in the built jar.

  In GWT project

  In your *.gwt.xml file, add the dependency:

  [xml]<inherits name=’com.lalou.jonathan.MyDependedProject’ />[/xml]

  Caution!

  All these operations need be done on all dependencies -either direct or indirect-. Therefore, possibly you may have a huge amount of code to be got.
  Another issue appears when you use a jar of which you do not have the source code, such as in the case of tiers API for instance.

Let’s assume you have a “Hello World” GWT application. You need emulate a basic RPC call (RMI, EJB, etc.). Here is the program:

Under the *.gwt.client folder:

Create an service interface:

[java]@RemoteServiceRelativePath("fooService")
public interface FooService extends RemoteService {
public String getHelloFoo(String totoName);
}[/java]

Create another interface for asynchronous call. You can notice the method name differs lightly from the one in the other interface:

[java]public interface FooServiceAsync {
void getHelloFoo(String fooName, AsyncCallback<String> callback);
}[/java]

Under the *.gwt.server folder, create an implementation for service interface:

[java]public class FooServiceImpl extends RemoteServiceServlet implements FooService {
public FooServiceImpl() {
// TODO init
}

public String getHelloFoo(String fooName) {
// TODO call actual service
return "hello world!";
}
}[/java]

In the web.xml file, add the following blocks:

[xml] <!– Servlets –>
<servlet>
<servlet-name>fooService</servlet-name>
<servlet-class>com…….server.FooServiceImpl</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>fooService</servlet-name>
<url-pattern>/ivargwt/fooService</url-pattern>
</servlet-mapping>
[/xml]

The tags content match the argument given as parameter to RemoteServiceRelativePath annotation above.

From then, in your concrete code, you can instantiate the service and call remote method:

[java]FooServiceAsync fooService = GWT.create(FooService.class);
fooService.getHelloFoo("how are you?", new AsyncCallback<String>() {

public void onSuccess(String result) {
MessageBox.alert("OK", result, null);
}

public void onFailure(Throwable caught) {
MessageBox.alert("ERROR", "rpc call error-" + caught.getLocalizedMessage(), null);
}
});
[/java]

Now you can compile, package your war and deploy under Tomcat or WebLogic.

NB: special to “black-belt GWT guy” David Chau from SFEIR.