Defining Filters, Servlets, and Listeners

HydraExpress Servlet Development Guide
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6.4 Defining Filters, Servlets, and Listeners

Each filter, servlet, or listener implementation must contain a macro that expands to a create function. The Agent uses this function to load an instance of the class.

The name of each macro starts with RWSF_DEFINE. HydraExpress includes two macros for each type of object, as shown in Table 2:

Table 2: Macros for defining filters, servlets, and listeners

Macro	Expands to Function Name
`RWSF_DEFINE_SERVLET(ServletClass)`	`createServletClass`
`RWSF_DEFINE_SERVLET_NAME(ServletClass,` `functionName)`	`functionName`
`RWSF_DEFINE_LISTENER(ListenerClass)`	`createListenerClass`
`RWSF_DEFINE_LISTENER_NAME(ListenerClass,` `functionName)`	`functionName`
`RWSF_DEFINE_FILTER(FilterClass)`	`createFilterClass`
`RWSF_DEFINE_FILTER_NAME(FilterClass,` `functionName)`	`functionName`

Of the two versions of each servlet, listener, and filter macro in Table 2, the first listed uses the default function name "create<typeofClass>". For example, the macro RWSF_DEFINE_SERVLET(MyServlet) expands to the function createMyServlet in the class, MyServlet. The Agent uses the function to construct an instance of the servlet.

RWSF_DEFINE_SERVLET(MyServlet)

This is referenced in the servlet configuration file web.xml:

<servlet>
    <servlet-name>MyServlet</servlet-name>
    <servlet-class>MyServlet_library.createMyServlet</servlet-class>
  </servlet>

The second macro, RWSF_DEFINE_SERVLET_NAME(ServletClass, functionName) allows you to create a custom function name that is more relevant to your own applications, such as:

RWSF_DEFINE_SERVLET_NAME(MyServletClass, generateServlet)

In this example, the function name will be generateServlet instead of createServletClass, and web.xml will define the servlet like this:

<servlet>
    <servlet-name>MyServlet</servlet-name>
    <servlet-class>MyServlet_library.generateServlet</servlet-class>
  </servlet>

Note the servlet configuration above indicates that class MyServlet has been built into the shared library, MyServlet_library.

See Chapter 4 for information on adding filters, listeners, and servlets to the servlet container.

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