javax.servlet
Class GenericServlet

java.lang.Object
  javax.servlet.GenericServlet

All Implemented Interfaces:

java.io.Serializable, Servlet, ServletConfig

Direct Known Subclasses:

HttpServlet

public abstract class GenericServlet
extends java.lang.Object
implements Servlet, ServletConfig, java.io.Serializable

Abstract base class for all servlets.

Since:

Servlet API 1.0

Version:

Servlet API 2.2

See Also:

Serialized Form

Constructor Summary

GenericServlet()
Does nothing.

Method Summary

void	destroy() Called by the server when it no longer needs the servlet.
java.lang.String	getInitParameter(java.lang.String name) Gets a servlet's initialization parameter
java.util.Enumeration	getInitParameterNames() Gets all the initialization parameters
ServletConfig	getServletConfig() Gets the servlet servletConfig class
ServletContext	getServletContext() Returns the servlets context
java.lang.String	getServletInfo() The servlet programmer can put other additional info (version number, etc) here.
java.lang.String	getServletName() Gets you the name of this servlet's instance.
void	init() Automatically called by init(ServletConfig servletConfig).
void	init(ServletConfig servletConfig) Initializes the servlet.
void	log(java.lang.String message) Writes the class name and a message to the log.
void	log(java.lang.String message, java.lang.Throwable th) Writes the class name, a message and a stack trace to the log.
abstract void	service(ServletRequest request, ServletResponse response) Called by the server every time it wants the servlet to handle a request.

Methods inherited from class java.lang.Object

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

Constructor Detail

GenericServlet

public GenericServlet()

Does nothing.

Since:

Servlet API 1.0

Method Detail

init

public void init(ServletConfig servletConfig)
          throws ServletException

Initializes the servlet. Called by the server exactly once during the lifetime of the servlet. This method can be used to setup resources (connections to a database for example) for this servlet.

This version saves the ServletConfig and calls init(). This means that a servlet can just override init(). Note that if a servlet overrides this method it should call super.init(servletConfig) otherwise the other methods in GenericServlet are not garanteed to work.

Specified by:

init in interface Servlet

Parameters:

servletConfig - This servlet configuration class

Throws:

ServletException - If an error occurs

Since:

Servlet API 1.0

See Also:

UnavailableException

init

public void init()
          throws ServletException

Automatically called by init(ServletConfig servletConfig). This version does nothing.

Throws:

ServletException - If an error occurs

Since:

Servlet API 2.1

getServletContext

public ServletContext getServletContext()

Returns the servlets context

Specified by:

getServletContext in interface ServletConfig

Returns:

The context

Since:

Servlet API 1.0

getInitParameter

public java.lang.String getInitParameter(java.lang.String name)

Gets a servlet's initialization parameter

Specified by:

getInitParameter in interface ServletConfig

Parameters:

name - the name of the wanted parameter

Returns:

the value of the wanted parameter. null if the named parameter is not present.

Since:

Servlet API 1.0

getInitParameterNames

public java.util.Enumeration getInitParameterNames()

Gets all the initialization parameters

Specified by:

getInitParameterNames in interface ServletConfig

Returns:

an Enumeration of all the parameters

Since:

Servlet API 1.0

log

public void log(java.lang.String message)

Writes the class name and a message to the log. Calls getServletContext().log().

Parameters:

message - the message to write

Since:

Servlet API 1.0

log

public void log(java.lang.String message,
                java.lang.Throwable th)

Writes the class name, a message and a stack trace to the log. Calls getServletContext().log().

Parameters:

message - the message to write

th - the object that was thrown to cause this log

Since:

Servlet API 2.1

getServletInfo

public java.lang.String getServletInfo()

The servlet programmer can put other additional info (version number, etc) here.

The Servlet 2.1 Spec says that this should return an empty string. The Servlet 2.1 API says that this should return null unless overridden. This version returns the servlet's class name which seems more usefull.

Specified by:

getServletInfo in interface Servlet

Returns:

The String holding the information

Since:

Servlet API 1.0

getServletConfig

public ServletConfig getServletConfig()

Gets the servlet servletConfig class

Specified by:

getServletConfig in interface Servlet

Returns:

The servletConfig class

Since:

Servlet API 1.0

service

public abstract void service(ServletRequest request,
                             ServletResponse response)
                      throws ServletException,
                             java.io.IOException

Called by the server every time it wants the servlet to handle a request.

Specified by:

service in interface Servlet

Parameters:

request - all the request information

response - class to write all the response data to

Throws:

ServletException - If an error occurs

java.io.IOException - If an error occurs

Since:

Servlet API 1.0

See Also:

SingleThreadModel

destroy

public void destroy()

Called by the server when it no longer needs the servlet. The servlet programmer should use this method to free all the resources the servlet is holding.

This version does nothing because it has nothing to clean up.

Note that the the 2.1 Spec says that this should do nothing, but the 2.1 API Doc says that it logs the destroy action.

Specified by:

destroy in interface Servlet

Since:

Servlet API 1.0

getServletName

public java.lang.String getServletName()

Gets you the name of this servlet's instance. Calls its servletConfig's getServletName.

Specified by:

getServletName in interface ServletConfig