bradleyross.j2ee.servlets

Class GetWebPage

java.lang.Object

javax.servlet.GenericServlet

javax.servlet.http.HttpServlet

bradleyross.j2ee.servlets.GetWebPage

All Implemented Interfaces:

Serializable, Servlet, ServletConfig

public class GetWebPage
extends HttpServlet

Servlet that will return the contents of a web page that is contained on a different web site (under consideration). This is a proposed class that has not yet been implemented.

• The name of the file to be retrieved is obtained using HttpServletRequest.getPathInfo().
• The MIME type is obtained from the file name using URLConnection.guessContentTypeFromName(String)
• The name of the INIT parameter containing the document root is given by the parameter DocumentRootParameter. If the parameter is not specified for the servlet, the default name is DocumentRoot.
• If the INIT parameter LogFile has been set, it is used as the location for a log file for the servlet.

Consideration should be given to increasing security for the servlet. The first step would be to stop file names from containing two periods in a row.

Author:

Bradley Ross

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected ServletConfig	config ServletConfig object as passed to the init method.
protected ServletContext	context ServletContext object containing information for the entire web application.
protected String	fileRoot Name of root directory for reading files.
protected String	fileRootParameter Name of parameter containing the location of the document root.
protected int	instanceNumber Identifies this instance of the servlet.
protected String	lineSeparator Character string indicating end of line.
protected String	logFile Name of log file.
protected boolean	logFileActive If true, place messages in log file.
protected static int	runningInstanceNumber Keeps track of how many instances of this servlet have been opened by the application server.
protected int	runningServiceNumber Keeps track of the different instances of the service method that are running.
private static long	serialVersionUID ID number to satisfy SERIALIZABLE interface.
protected boolean	valid Servlet has a valid configuration when true.

Constructor Summary

Constructors

Constructor and Description
GetWebPage()

Method Summary

Methods

Modifier and Type	Method and Description
protected void	createLogEntry(String message)
protected void	createLogEntry(String message, int serviceNumber)
protected void	createLogEntry(String message, Throwable e, int serviceNumber)
void	destroy() Run when object for processing servlet is no longer needed and is destroyed.
void	init(ServletConfig configIn) Run when object is created for processing calls to servlet.
static void	main(String[] args) This provides an error message if it is attempted to run this class as a Java application rather than a Java servlet.
void	service(HttpServletRequest req, HttpServletResponse res) Processes request to a servlet.

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doGet, doHead, doOptions, doPost, doPut, doTrace, getLastModified, service

Methods inherited from class javax.servlet.GenericServlet

getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, log, log

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

serialVersionUID

private static final long serialVersionUID

ID number to satisfy SERIALIZABLE interface.

See Also:

Constant Field Values

runningInstanceNumber

protected static int runningInstanceNumber

Keeps track of how many instances of this servlet have been opened by the application server.

There is a problem in that Tomcat does not appear to treating this as a static value. The idea was that the application server could run multiple GetFile objects and would use this parameter to set the value of instanceNumber so that log files for the different objects would go to different files. Instead, the value appears to be zero each time the init method is called. The init method should only be called once for each GetFile object.

instanceNumber

protected int instanceNumber

Identifies this instance of the servlet.

It was intended that this variable would identify the GetFile object if the application server was running multiple instances of the GetFile class.

runningServiceNumber

protected int runningServiceNumber

Keeps track of the different instances of the service method that are running.

config

protected ServletConfig config

ServletConfig object as passed to the init method.

context

protected ServletContext context

ServletContext object containing information for the entire web application.

fileRootParameter

protected String fileRootParameter

Name of parameter containing the location of the document root.

fileRoot

protected String fileRoot

Name of root directory for reading files.

logFile

protected String logFile

Name of log file.

logFileActive

protected boolean logFileActive

If true, place messages in log file.

lineSeparator

protected String lineSeparator

Character string indicating end of line.

valid

protected boolean valid

Servlet has a valid configuration when true.

Constructor Detail

GetWebPage

public GetWebPage()

Method Detail

init

public void init(ServletConfig configIn)
          throws ServletException

Run when object is created for processing calls to servlet.

The application server can create multiple objects for a single servlet to improve performance.

Specified by:

init in interface Servlet

Overrides:

init in class GenericServlet

Throws:

ServletException

destroy

public void destroy()

Run when object for processing servlet is no longer needed and is destroyed.

Specified by:

destroy in interface Servlet

Overrides:

destroy in class GenericServlet

createLogEntry

protected void createLogEntry(String message)

createLogEntry

protected void createLogEntry(String message,
                  int serviceNumber)

createLogEntry

protected void createLogEntry(String message,
                  Throwable e,
                  int serviceNumber)

service

public void service(HttpServletRequest req,
           HttpServletResponse res)
             throws IOException

Processes request to a servlet.

There can be many instances of the service method running at the same time. This must be taken into account when coding this method.

It may be necessary to change this file so that the information is recorded to a byte array and then repeated as necessary until success is achieved.

Overrides:

service in class HttpServlet

Parameters:

req - Object containing request information

res - Object containing response information

Throws:

IOException

See Also:

HttpServletRequest, HttpServletResponse, IOException

main

public static void main(String[] args)

This provides an error message if it is attempted to run this class as a Java application rather than a Java servlet.

Parameters:

args - Not used at this time