Read Model Data In Jersey MVC JSP Templates Without "it."
Jersey, the JAX-RS reference implementation, includes an
supporting the rendering of views by JSP templates. The application passes a
model object to the framework, where the model object implements properties
providing the data to render in the JSP template. Jersey exposes the model
object to the JSP template as a request attribute named “
it”. So to read a
model property, a JSP template must evaluate an EL expression reading a
property of this object, for example,
In Spring MVC, you don’t have to write a specific prefix at the start of an EL expression to read model data. The model is a key-value map, and the framework exposes every entry of the map as a request attribute.
To avoid cluttering JSP templates with “
it.”, I wrote a
custom ELResolver which exposes model properties as implicit objects,
allowing a JSP template to read a model property with an EL expression like
custom servlet context listener
registers the custom ELResolver when the application starts. To use
it, define a listener in the
<listener> <listener-class>com.github.pukkaone.jsp.ViewableModelELResolverListener</listener-class> </listener>
The custom ELResolver gets the model object from the request attribute named
it”, then uses reflection to resolve a name to a property of the object.
Assuming the requested property name is key, the following steps are tried:
- If the object is a Map, then lookup the value from the Map using key as the key.
- If the object has a method named key with non-void return type, then use the return value from calling the method.
- If the object has a method named
getkey with the first letter of key capitalized and non-void return type, then use the return value from calling the method.
- If the object has a field named key, then get the field value.
Finally, if the value acquired from the previous steps is an object implementing Callable, then use the return value from invoking it.