Binds the value(s) of a form parameter contained within a request entity body to a resource method parameter. Values are URL decoded unless this is disabled using the Encoded annotation. A default value can be specified using the DefaultValue annotation. If the request entity body is absent or is an unsupported media type, the default value is used. The type T of the annotated parameter must either:

1. Be a primitive type
2. Have a constructor that accepts a single String argument
3. Have a static method named valueOf or fromString that accepts a single String argument (see, for example, Integer#valueOf(String))
4. Have a registered implementation of jakarta.ws.rs.ext.ParamConverterProvider JAX-RS extension SPI that returns a jakarta.ws.rs.ext.ParamConverter instance capable of a "from string" conversion for the type.
5. Be List<T>, Set<T>, SortedSet<T> or T[] array, where T satisfies 2, 3 or 4 above. The resulting collection is read-only.

If the type is not one of the collection types listed in 5 above and the form parameter is represented by multiple values then the first value (lexically) of the parameter is used.

If this annotation is used to bind form parameters, a JAX-RS implementation MUST use the entity provider API to create a jakarta.ws.rs.core.Form and derive the values from this instance. If there is at least one FormParam for a resource method, JAX-RS implementations MUST support a jakarta.ws.rs.core.Form entity parameter for the same method. Support for other entity parameter types is OPTIONAL.

Note that, whilst the annotation target permits use on fields and methods, this annotation is only required to be supported on resource method parameters.