How does Java expression language resolve boolean attributes? (in JSF 1.2)

Question

So we all know that #{someBean.value} will try and get the content of some property on someBean called value. It will look for g

Answer 1

It's authoritatively documented in both the JavaBeans Spec and EL Specification.

To take the boolean property as an example, it's described in chapter 8.3.2 of JavaBeans spec:

8.3.2 Boolean properties

In addition, for boolean properties, we allow a getter method to match the pattern:

public boolean is();

This “is<PropertyName>” method may be provided instead of a “get<PropertyName>” method, or it may be provided in addition to a “get<PropertyName>” method.

In either case, if the “is<PropertyName>” method is present for a boolean property then we will use the “is<PropertyName>” method to read the property value.

An example boolean property might be:

    public boolean isMarsupial();
    public void setMarsupial(boolean m);

So, #{bean.marsupial} expects exactly the above getter/setter pair.

And in chapter 1.18.5 of EL spec:

1.18.5 Coerce A to Boolean

• If A is null or "", return false
• Otherwise, if A is a Boolean, return A
• Otherwise, if A is a String, and Boolean.valueOf(A) does not throw an exception, return it

See also:

• javax.el.PropertyNotFoundException: Property 'foo' not readable on type java.lang.Boolean
• Java: how to name boolean properties