| javax.servlet.Servlet
All known Subclasses: javax.servlet.GenericServlet,
| Servlet | | public interface Servlet (Code) | | Defines methods that all servlets must implement.
A servlet is a small Java program that runs within a Web server.
Servlets receive and respond to requests from Web clients,
usually across HTTP, the HyperText Transfer Protocol.
To implement this interface, you can write a generic servlet
that extends
javax.servlet.GenericServlet or an HTTP servlet that
extends javax.servlet.http.HttpServlet.
This interface defines methods to initialize a servlet,
to service requests, and to remove a servlet from the server.
These are known as life-cycle methods and are called in the
following sequence:
- The servlet is constructed, then initialized with the
init method.
- Any calls from clients to the
service method are handled.
- The servlet is taken out of service, then destroyed with the
destroy method, then garbage collected and finalized.
In addition to the life-cycle methods, this interface
provides the getServletConfig method, which the servlet
can use to get any startup information, and the getServletInfo
method, which allows the servlet to return basic information about itself,
such as author, version, and copyright.
author:
Various
version:
$Version$
See Also: GenericServlet
See Also: javax.servlet.http.HttpServlet |
| Method Summary | |
| public void | destroy()
Called by the servlet container to indicate to a servlet that the
servlet is being taken out of service. | | public ServletConfig | getServletConfig()
Returns a
ServletConfig object, which contains
initialization and startup parameters for this servlet.
The ServletConfig object returned is the one
passed to the init method. | | public String | getServletInfo()
Returns information about the servlet, such
as author, version, and copyright. | | public void | init(ServletConfig config)
Called by the servlet container to indicate to a servlet that the
servlet is being placed into service. | | public void | service(ServletRequest req, ServletResponse res)
Called by the servlet container to allow the servlet to respond to
a request.
This method is only called after the servlet's init()
method has completed successfully.
The status code of the response always should be set for a servlet
that throws or sends an error.
Servlets typically run inside multithreaded servlet containers
that can handle multiple requests concurrently. |
| destroy | | public void destroy()(Code) | | Called by the servlet container to indicate to a servlet that the
servlet is being taken out of service. This method is
only called once all threads within the servlet's
service method have exited or after a timeout
period has passed. After the servlet container calls this
method, it will not call the service method again
on this servlet.
This method gives the servlet an opportunity
to clean up any resources that are being held (for example, memory,
file handles, threads) and make sure that any persistent state is
synchronized with the servlet's current state in memory.
|
| getServletConfig | | public ServletConfig getServletConfig()(Code) | | Returns a
ServletConfig object, which contains
initialization and startup parameters for this servlet.
The ServletConfig object returned is the one
passed to the init method.
Implementations of this interface are responsible for storing the
ServletConfig object so that this
method can return it. The
GenericServlet class, which implements this interface, already does this.
the ServletConfig objectthat initializes this servlet
See Also: Servlet.init |
| getServletInfo | | public String getServletInfo()(Code) | | Returns information about the servlet, such
as author, version, and copyright.
The string that this method returns should
be plain text and not markup of any kind (such as HTML, XML,
etc.).
a String containing servlet information |
| init | | public void init(ServletConfig config) throws ServletException(Code) | | Called by the servlet container to indicate to a servlet that the
servlet is being placed into service.
The servlet container calls the init
method exactly once after instantiating the servlet.
The init method must complete successfully
before the servlet can receive any requests.
The servlet container cannot place the servlet into service
if the init method
- Throws a
ServletException
- Does not return within a time period defined by the Web server
Parameters:
config - a ServletConfig object containing the servlet'sconfiguration and initialization parameters
exception:
ServletException - if an exception has occurred thatinterferes with the servlet's normaloperation
See Also: UnavailableException
See Also: Servlet.getServletConfig |
| service | | public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException(Code) | | Called by the servlet container to allow the servlet to respond to
a request.
This method is only called after the servlet's init()
method has completed successfully.
The status code of the response always should be set for a servlet
that throws or sends an error.
Servlets typically run inside multithreaded servlet containers
that can handle multiple requests concurrently. Developers must
be aware to synchronize access to any shared resources such as files,
network connections, and as well as the servlet's class and instance
variables.
More information on multithreaded programming in Java is available in
the Java tutorial on multi-threaded programming.
Parameters:
req - the ServletRequest object that containsthe client's request
Parameters:
res - the ServletResponse object that containsthe servlet's response
exception:
ServletException - if an exception occurs that interfereswith the servlet's normal operation
exception:
IOException - if an input or output exception occurs |
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