Description of the Example Servlet

The example servlet, rwdemo, makes a connection to a Reality database and calls a DataBasic subroutine that returns its own input parameters to the browser. The example servlet:

• Extends HttpServlet.

• Calls the HttpServlet  init()  method, then calls init()  from the RealWeb class to start a thread to timeout connections.

• Overrides doPost()  to handle any post requests.

  doPost()  is to work in exactly the same way as doGet(), so it simply calls doGet().

• Overrides doGet(), which is the usual entry point to the servlet.

  Whenever the web server receives a GET request for this servlet, the server invokes doGet(), passing it  an HttpServletRequest  parameter and an HttpServletResponse  parameter.

  Overrides getServletInfo()  to return the string "Sample RealWeb Servlet".

• Includes a section of commented code showing the RW.SAMPLE subroutine to be called by rwdemo.

  The comments describe how the subroutine, which simply returns its input parameters, must be created, compiled, catalogued, then enabled. Remote Basic subroutines can be enabled for remote access by user-ids with a specified security profile (see Securing the Database Using SSM). The URL used to call the subroutine via rwdemo  is shown.

• Calls RSC.execute() to run the DataBasic subroutine.

  When the RealWebUrl  object is created, the subroutine name is placed in  URL.command. HttpServletRequest  provides methods to extract the query string and the servlet path, which are used as the two input parameters to RW.SAMPLE. When executed, RW.SAMPLE returns these two parameters to the browser, displaying, for example:

  First parameter is a query
  Second parameter is /servlet/rwdemo

doGet()

doGet()  does the following:

• Uses methods provided by HttpServletResponse  to set the content type for the response and to get an output stream.

• Creates an HTML page header to display the text RealWeb Demo Servlet. In addition to building the HTML page header, the servlet could use methods provided by  HttpServletRequest  to build an HTML form requesting input from the user and append this input to the URL, to be passed as parameters to RW.SAMPLE. In this example, parameters to be passed to the subroutine are entered as part of the URL.

• Creates an instance of the RealWebUrl class, splitting up the different sections of the calling URL and putting the information into the following usable fields:

  pathInfo the rest of the path after the servlet name;

  debug set to true if the first path component contains Debug (see Debugging);

  section the first path component following servlet name, or the Debug keyword;

  command the second path component following servlet name, or the Debug keyword;

  page the third path component following servlet name, or the Debug keyword

• Calls RealWeb.getConnection to get a connection to the database. This will return a current connection or create a new one. The RealWeb  class extends RSCConnection, so making available the methods within RSCConnection.

• Calls the local execute()  method (see later code) to execute the Remote Basic subroutine.

• Makes the connection available again.

• Completes the HTML page.