javax.servlet
Class GenericServlet
java.lang.Objectjavax.servlet.GenericServlet
- java.io.Serializable, Servlet, ServletConfig
public abstract class GenericServlet
extends java.lang.Object
Defines a generic, protocol-independent
servlet. To write an HTTP servlet for use on the
Web, extend
HttpServlet instead.
GenericServlet implements the
Servlet
and
ServletConfig interfaces.
GenericServlet
may be directly extended by a servlet, although it's more common to extend
a protocol-specific subclass such as
HttpServlet.
GenericServlet makes writing servlets
easier. It provides simple versions of the lifecycle methods
init and
destroy and of the methods
in the
ServletConfig interface.
GenericServlet
also implements the
log method, declared in the
ServletContext interface.
To write a generic servlet, you need only
override the abstract
service method.
void | destroy()- Called by the servlet container to indicate to a servlet that the
servlet is being taken out of service.
|
String | getInitParameter(String name)- Returns a
String containing the value of the named
initialization parameter, or null if the parameter does
not exist.
|
Enumeration | getInitParameterNames()- Returns the names of the servlet's initialization parameters
as an
Enumeration of String objects,
or an empty Enumeration if the servlet has no
initialization parameters.
|
ServletConfig | getServletConfig()- Returns this servlet's
ServletConfig object.
|
ServletContext | getServletContext()- Returns a reference to the
ServletContext in which this servlet
is running.
|
String | getServletInfo()- Returns information about the servlet, such as
author, version, and copyright.
|
String | getServletName()- Returns the name of this servlet instance.
|
void | init()-
A convenience method which can be overridden so that there's no need
to call
super.init(config).
|
void | init(ServletConfig config)-
Called by the servlet container to indicate to a servlet that the
servlet is being placed into service.
|
void | log(String msg)-
Writes the specified message to a servlet log file, prepended by the
servlet's name.
|
void | log(String message, Throwable t)- Writes an explanatory message and a stack trace
for a given
Throwable exception
to the servlet log file, prepended by the servlet's name.
|
abstract void | service(ServletRequest req, ServletResponse res)- Called by the servlet container to allow the servlet to respond to
a request.
|
GenericServlet
public GenericServlet()
Does nothing. All of the servlet initialization
is done by one of the init methods.
destroy
public void destroy()
Called by the servlet container to indicate to a servlet that the
servlet is being taken out of service. See
Servlet.destroy().
- destroy in interface Servlet
getInitParameter
public String getInitParameter(String name)
Returns a
String containing the value of the named
initialization parameter, or
null if the parameter does
not exist. See
ServletConfig.getInitParameter(String).
This method is supplied for convenience. It gets the
value of the named parameter from the servlet's
ServletConfig object.
- getInitParameter in interface ServletConfig
name - a String specifying the name
of the initialization parameter
- String a
String containing the value
of the initialization parameter
getInitParameterNames
public Enumeration getInitParameterNames()
Returns the names of the servlet's initialization parameters
as an
Enumeration of
String objects,
or an empty
Enumeration if the servlet has no
initialization parameters. See
ServletConfig.getInitParameterNames().
This method is supplied for convenience. It gets the
parameter names from the servlet's
ServletConfig object.
- getInitParameterNames in interface ServletConfig
- Enumeration an enumeration of
String
objects containing the names of
the servlet's initialization parameters
getServletInfo
public String getServletInfo()
Returns information about the servlet, such as
author, version, and copyright.
By default, this method returns an empty string. Override this method
to have it return a meaningful value. See
Servlet.getServletInfo().
- getServletInfo in interface Servlet
- String information about this servlet, by default an
empty string
init
public void init()
throws ServletException
A convenience method which can be overridden so that there's no need
to call
super.init(config).
Instead of overriding
init(ServletConfig), simply override
this method and it will be called by
GenericServlet.init(ServletConfig config).
The
ServletConfig object can still be retrieved via
getServletConfig().
ServletException - if an exception occurs that
interrupts the servlet's
normal operation
init
public void init(ServletConfig config)
throws ServletException
Called by the servlet container to indicate to a servlet that the
servlet is being placed into service. See
Servlet.init(ServletConfig).
This implementation stores the
ServletConfig
object it receives from the servlet container for later use.
When overriding this form of the method, call
super.init(config).
- init in interface Servlet
config - the ServletConfig object
that contains configutation
information for this servlet
ServletException - if an exception occurs that
interrupts the servlet's normal
operation
log
public void log(String msg)
msg - a String specifying
the message to be written to the log file
log
public void log(String message,
Throwable t)message - a String that describes
the error or exceptiont - the java.lang.Throwable error
or exception
service
public abstract void service(ServletRequest req,
ServletResponse res)
throws ServletException,
IOException- service in interface Servlet
req - the ServletRequest object
that contains the client's requestres - the ServletResponse object
that will contain the servlet's response
ServletException - if an exception occurs that
interferes with the servlet's
normal operation occurred
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