Difference between value and binding

Question

What is the difference between using value and binding with JavaServer Faces, and when would you use one as opposed to the other? To make it clearer what my question is, a coup

Answer 1

value attribute represents the value of the component. It is the text that you see inside your text box when you open the page in browser.

binding attribute is used to bind your component to a bean property. For an example in your code your inputText component is bound to the bean like this.

#{backing_hello.inputText}`

It means that you can access the whole component and all its properties in your code as a UIComponent object. You can do lot of works with the component because now it is available in your java code. For an example you can change its style like this.

public HtmlInputText getInputText() {
    inputText.setStyle("color:red");
    return inputText;
}

Or simply to disable the component according to a bean property

if(someBoolean) {
  inputText.setDisabled(true);
}

and so on....

Answer 2

Sometimes we don't really need to apply the value of UIComponent to a bean property. For example you might need to access the UIComponent and work with it without applying its value to the model property. In such cases it's good to use a backing bean rather than a regular bean. On the other hand in some situations we might need to work with the values of the UIComponent without any need of programmatic access to them. In this case you can just go with the regular beans.

So, the rule is that use a backing bean only when you need programmatic access to the components declared in the view. In other cases use the regular beans.