Package javax.servlet

Class 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
    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.

    See Also:
    Serialized Form
    • Constructor Summary

      Constructors 
      Constructor Description
      GenericServlet()
      Does nothing.
    • Method Summary

      All Methods Instance Methods Abstract Methods Concrete Methods 
      Modifier and Type Method Description
      void destroy()
      Called by the servlet container to indicate to a servlet that the servlet is being taken out of service.
      java.lang.String getInitParameter​(java.lang.String name)
      Returns a String containing the value of the named initialization parameter, or null if the parameter does not exist.
      java.util.Enumeration<java.lang.String> 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.
      java.lang.String getServletInfo()
      Returns information about the servlet, such as author, version, and copyright.
      java.lang.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​(java.lang.String message)
      Writes the specified message to a servlet log file, prepended by the servlet's name.
      void log​(java.lang.String message, java.lang.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.
      • 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. All of the servlet initialization is done by one of the init methods.
    • Method Detail

      • 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().
        Specified by:
        destroy in interface Servlet
      • getInitParameter

        public java.lang.String getInitParameter​(java.lang.String name)
        Returns a String containing the value of the named initialization parameter, or null if the parameter does not exist. See ServletConfig.getInitParameter(java.lang.String).

        This method is supplied for convenience. It gets the value of the named parameter from the servlet's ServletConfig object.

        Specified by:
        getInitParameter in interface ServletConfig
        Parameters:
        name - a String specifying the name of the initialization parameter
        Returns:
        String a String containing the value of the initialization parameter
      • getInitParameterNames

        public java.util.Enumeration<java.lang.String> 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.

        Specified by:
        getInitParameterNames in interface ServletConfig
        Returns:
        Enumeration an enumeration of String objects containing the names of the servlet's initialization parameters
      • getServletInfo

        public java.lang.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().
        Specified by:
        getServletInfo in interface Servlet
        Returns:
        String information about this servlet, by default an empty string
      • 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(javax.servlet.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).

        Specified by:
        init in interface Servlet
        Parameters:
        config - the ServletConfig object that contains configuration information for this servlet
        Throws:
        ServletException - if an exception occurs that interrupts the servlet's normal operation
        See Also:
        UnavailableException
      • 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().

        Throws:
        ServletException - if an exception occurs that interrupts the servlet's normal operation
      • log

        public void log​(java.lang.String message)
        Writes the specified message to a servlet log file, prepended by the servlet's name. See ServletContext.log(String).
        Parameters:
        message - a String specifying the message to be written to the log file
      • log

        public void log​(java.lang.String message,
                        java.lang.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. See ServletContext.log(String, Throwable).
        Parameters:
        message - a String that describes the error or exception
        t - the java.lang.Throwable error or exception