Handling Errors- Vaadin Applications
Handling Errors is very important in every application.This ensures that the application runs smoothly and users are notified incase the data they submit is not valid.For example,think of a field where the user is required to enter a email,if he/she adds firstname,the application should notify the user error made.
Handling Errors ensures data integrity and validity.Handling Errors in vaadin application can be done by using built in functions added in a components.This can be declared by setting component error
Handling Errors
1.Error indicator and Message
Run below code in your eclipse IDE.
package com.example.writers;
import com.vaadin.Application;
import com.vaadin.terminal.UserError;
import com.vaadin.ui.Alignment;
import com.vaadin.ui.Button;
import com.vaadin.ui.TextField;
import com.vaadin.ui.Button.ClickEvent;
import com.vaadin.ui.VerticalLayout;
import com.vaadin.ui.Window;
import com.vaadin.ui.Window.CloseEvent;
/**
* Main application class.
*/
public class WritersApplication extends Application {
Window mainWindow;//defining new variables
TextField field;//defining textfield variable
Button register;//register button
ForgotPassword forgot;
@Override
public void init() {
mainWindow = new Window("Closing Window application");//Application main Window.All other subwindows will be added here
field= new TextField("Enter Code");//creating new textfield
field.setComponentError(null);//setting error component
mainWindow.addComponent(field);//adding textfield to the mainwindow
register=new Button("Register");//creating register button
register.addListener(new Button.ClickListener()//adding listener to the button
{
@Override
public void buttonClick(ClickEvent event) {
// TODO Auto-generated method stub
if (!((String)field.getValue()).matches("^\\w*$"))// if user enters one of these characters error is displayed
{
field.setComponentError( new UserError("Must be letters"));//error message
}
else{
field.setComponentError(null);//incase user enters letters or numbers no error to be displayed
}
}
});
mainWindow.addComponent(register);//add button to the mainwindow
((VerticalLayout)mainWindow.getLayout())
.setComponentAlignment(register, Alignment.BOTTOM_LEFT);
setMainWindow(mainWindow);//setting mainwindow
}
}
After running above code,You should be able to see result in the captioned image below.
Above code introduces some very new methods.setComponentError( new UserError(“Must be letters”)) method is responsible for displaying error when the user enters other characters that are not letters or numbers.
Forms in Vaadin have a special way of displaying errors.The fields in the form all have error indicator field and also a special message in a error indicator area.
