Application Server with custom HTML tags in JAVA

General information for the business: An application server handles the client requests, reading the files on the server and processing whatever needs to be done.
Kind of development: Customization of existing program
Description of requirements/functionality: I want to implement a prototype of an application server able to handle custom tags. A simple example of such a custom tag is , which will insert the current time in place of the tag. Another example is , inserting the request parameters in a table, or , showing all get parameters. More complicated tags will pass parameters, specifying certain restrictions on the action. An example could be , asking to only show the parameter called user.
The tags themselves are classes a software engineer can define and place in the classpath. This means you cannot hard-code them, but will have to rely on reflection to instantiate and invoke them. An example tag (Time) has been provided.
Specific technologies required: Java
Extra notes: