SyncProxy allows you to invoke GWT RPC services from pure Java (no JSNI) code.
From version 0.1.2, you can invoke your RPC services deployed on AppEngine.

This post shows you how to use this new feature of SyncProxy.

For example, we have an helloApp application and a RPC service GreetingService

@RemoteServiceRelativePath("greet")
public interface GreetingService extends RemoteService {
  String greetServer(String name);
}

And the service implementation is as below

public class GreetingServiceImpl extends RemoteServiceServlet
      implements GreetingService {
  public String greetServer(String name) {
    return "Hello, " + name;
  }
}

Assume the application is deployed on AppEngine and the servlet URL is configured at http://example.appspot.com/helloApp/greet

Create new proxy instance for the service interface:

private static GreetingService rpcService =
  SyncProxy.newProxyInstance(GreetingService.class,
        "http://example.appspot.com/helloApp", "greet");

This will create a new proxy instance which implements your GreetingService.

Then invoke the service method.

String result = rpcService.greetServer("SyncProxy");

We modify our service implement which enforce user to login to access to the service:

public class GreetingServiceImpl extends RemoteServiceServlet
      implements GreetingService {
  public String greetServer(String name) {
    // implement the security
    UserService userService = UserServiceFactory.getUserService();
    if (!userService.isUserLoggedIn()){
      throw new RuntimeException("Access Denied");
    }
    // We can also enforce only admin user can access to the service
    /*
    if (!userService.isUserAdmin()){
      throw new RuntimeException("Access Denied");
    }
    */

    return "Hello, " + name;
  }
}

Before invoke the secured service, you have to login to the application.

SyncProxy.loginGAE("https://example.appspot.com",
    "http://example.appspot.com/helloApp/greet",
    "yourusername@gmail.com", "yourpassword");

Then invoke the service method.

String result = rpcService.greetServer("SyncProxy");

Get SyncProxy (with source code) at our Downloads page

gwtXP uses JFace data binding (with modifications) and Expression Language concepts to allow you declare binding expression like <g:textBox text="${user.userId}"/>.

This post shows how to use data binding (property binding, list binding and table binding) in gwtXP to build gwt applications. It also shows how to build a scrollable table. See the demo.

We use following bound bean during this post. See the examples page for complete source code.

public class User{
  private transient PropertyChangeSupport changeSupport = new PropertyChangeSupport(this);

  private String userId;
  private String fullName;
  private Date dob;
  private String email;
  private int numberOfWrongPassword;
  private String password;
  private Boolean enabled;
  ...
  // getter and setter methods
}

Bind a bean’s property to a GWT widget’s property. gwtXP supports most of common widgets such as Label, TextBox, PasswordTextBox, CheckBox, RadioButton, Button, etc.

Below shows some basic binding examples:

<g:label text="${user.userId}"/>

<g:textBox text="${user.userId}"/>

If you require the build-in user ‘admin’ can not be changed, you can disable the text box for userId value of ‘admin’:

<g:textBox text="${user.userId}" enabled="${user.userId != 'admin'}"/>

For example, you require the admin can set new password for enabled user only, e.g the password text box will be enabled if user.enabled is true.

<g:passwordTextBox text="${user.password}" enabled="${user.enabled}"/>

<g:checkBox value="${user.enabled}"/>

The data binding has build-in data converter which converts one object to another object, for example from Date to String, Number to String, etc and vice versa. Some converter requires additional ‘pattern’ attribute. The ‘pattern’ attribute describe how a converter format/parse data. If no ‘pattern’ specified, the converter uses the default one.

In gwtXP, simply add ‘pattern’ attribute to the tag as below:

<g:textBox text="${user.dob}" pattern="MM/dd/yyyy"/>

The converter also validate user input against the specified pattern.

You can declare the validator which validate the user input as below:

<g:textBox text="${user.email}" validator="${emailValidator}"/>

The validator must implement the IValidator interface.

When the validating the data, validator will report a status (whether OK or error). By default, when error occurs during validation process, we add an ‘error’ style to the widget. To display the error message, we use a special errors tag as below:

<g:errors errorMessage="There was errors during validating your data."/>

Of course, you can internationalize the error message as below:

<g:errors errorMessage="${constants.multipleErrors}"/>

Read full article »

I received some emails asking how to setup and run gwtXP examples in IDEs.

This post shows how to do it in Eclipse. I recommend to use Google Plugin for Eclipse during developing GWT applications.

In your Eclipse IDE, select File – New

- Type in the project name and the package
- Select “Use Google Web Toolkit” check box and click Finish button.

• Open project properties dialog: Right-click on Hello project and select Properties from pop-up menu
• Go to Run/Debug Settings section
• Click on the “Hello” launch configuration and click Edit button

  

• In the Edit Configuration dialog, click on Arguments tab and change the Working directory option from “Other” to “Default”

  

• Click OK
• Go to Java Build Path section, click on “Add External JARs” and select the gwtXP.jar you downloaded from http://www.gdevelop.com/w/downloads/
• Click OK

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