Java Platform, Enterprise Edition (Java EE) 8 The Java EE Tutorial

## Binding Converters, Listeners, and Validators to Managed Bean Properties

As described in Adding Components to a Page Using HTML Tag Library Tags, a page author can bind converter, listener, and validator implementations to managed bean properties using the `binding` attributes of the tags that are used to register the implementations on components.

This technique has similar advantages to binding component instances to managed bean properties, as described in Binding Component Values and Instances to Managed Bean Properties. In particular, binding a converter, listener, or validator implementation to a managed bean property yields the following benefits.

- The managed bean can instantiate the implementation instead of allowing the page author to do so.

- The managed bean can programmatically modify the attributes of the implementation. In the case of a custom implementation, the only other way to modify the attributes outside of the implementation class would be to create a custom tag for it and require the page author to set the attribute values from the page.

Whether you are binding a converter, listener, or validator to a managed bean property, the process is the same for any of the implementations.

- Nest the converter, listener, or validator tag within an appropriate component tag.

- Make sure that the managed bean has a property that accepts and returns the converter, listener, or validator implementation class that you want to bind to the property.

- Reference the managed bean property using a value expression from the `binding` attribute of the converter, listener, or validator tag.

For example, say that you want to bind the standard `DateTime` converter to a managed bean property because you want to set the formatting pattern of the user’s input in the managed bean rather than on the Facelets page. First, the page registers the converter onto the component by nesting the `f:convertDateTime` tag within the component tag. Then, the page references the property with the `binding` attribute of the `f:convertDateTime` tag:

    <h:inputText value="#{loginBean.birthDate}">
        <f:convertDateTime binding="#{loginBean.convertDate}" />
    </h:inputText>

The `convertDate` property would look something like this:

    private DateTimeConverter convertDate;
    public DateTimeConverter getConvertDate() {
        ...
        return convertDate;
    }
    public void setConvertDate(DateTimeConverter convertDate) {
        convertDate.setPattern("EEEEEEEE, MMM dd, yyyy");
        this.convertDate = convertDate;
    }

See Writing Properties Bound to Converters, Listeners, or Validators for more information on writing managed bean properties for converter, listener, and validator implementations.

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