GetFile (tutorials-common 0.0.1-SNAPSHOT API)

java.lang.Object
- javax.servlet.GenericServlet
- - javax.servlet.http.HttpServlet
  - - bradleyross.j2ee.servlets.GetFile

All Implemented Interfaces:

Serializable, Servlet, ServletConfig
```
public class GetFile
extends HttpServlet
```
Servlet for displaying a file based on the URL sent to the server.
- 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.
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` Send messages to log file if true.
`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.
`protected boolean`	`valid` Servlet has a valid configuration when true.

Constructor Summary

Constructors
Constructor and Description

GetFile()

Constructors
Constructor and Description
`GetFile()`

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`protected void`	`createLogEntry(String message)` Place a record in the log file.
`protected void`	`createLogEntry(String message, int serviceNumber)` Place a record in the log file.
`protected void`	`createLogEntry(String message, Throwable e, int serviceNumber)` Place a message in the log file.
`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
  - 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
```
    Send messages to log file if true.
  - lineSeparator
```
protected String lineSeparator
```
    Character string indicating end of line.
  - valid
```
protected boolean valid
```
    Servlet has a valid configuration when true.
- Constructor Detail
  - GetFile
```
public GetFile()
```
- 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)
```
    Place a record in the log file.
    
    Parameters:
    
    message - Text of message
  - createLogEntry
```
protected void createLogEntry(String message,
                              int serviceNumber)
```
    Place a record in the log file.
    
    Parameters:
    
    message - Text of message
    
    serviceNumber - Sequence number for servlet instance
  - createLogEntry
```
protected void createLogEntry(String message,
                              Throwable e,
                              int serviceNumber)
```
    Place a message in the log file.
    
    Parameters:
    
    message - Text of message
    
    e - Exception for which message is generated
    
    serviceNumber - Sequence number for servlet instance
  - 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

Class GetFile

Field Summary

Constructor Summary

Method Summary

Methods inherited from class javax.servlet.http.HttpServlet

Methods inherited from class javax.servlet.GenericServlet

Methods inherited from class java.lang.Object

Field Detail

runningInstanceNumber

instanceNumber

runningServiceNumber

config

context

fileRootParameter

fileRoot

logFile

logFileActive

lineSeparator

valid

Constructor Detail

GetFile

Method Detail

init

destroy

createLogEntry

createLogEntry

createLogEntry

service

main