Class GenericServlet
- java.lang.Object
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- javax.servlet.GenericServlet
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- 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, extendHttpServletinstead.GenericServletimplements theServletandServletConfiginterfaces.GenericServletmay be directly extended by a servlet, although it's more common to extend a protocol-specific subclass such asHttpServlet.GenericServletmakes writing servlets easier. It provides simple versions of the lifecycle methodsinitanddestroyand of the methods in theServletConfiginterface.GenericServletalso implements thelogmethod, declared in theServletContextinterface.To write a generic servlet, you need only override the abstract
servicemethod.- See Also:
- Serialized Form
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Constructor Summary
Constructors Constructor Description GenericServlet()Does nothing.
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description voiddestroy()Called by the servlet container to indicate to a servlet that the servlet is being taken out of service.java.lang.StringgetInitParameter(java.lang.String name)Returns aStringcontaining the value of the named initialization parameter, ornullif the parameter does not exist.java.util.Enumeration<java.lang.String>getInitParameterNames()Returns the names of the servlet's initialization parameters as anEnumerationofStringobjects, or an emptyEnumerationif the servlet has no initialization parameters.ServletConfiggetServletConfig()Returns this servlet'sServletConfigobject.ServletContextgetServletContext()Returns a reference to theServletContextin which this servlet is running.java.lang.StringgetServletInfo()Returns information about the servlet, such as author, version, and copyright.java.lang.StringgetServletName()Returns the name of this servlet instance.voidinit()A convenience method which can be overridden so that there's no need to callsuper.init(config).voidinit(ServletConfig config)Called by the servlet container to indicate to a servlet that the servlet is being placed into service.voidlog(java.lang.String message)Writes the specified message to a servlet log file, prepended by the servlet's name.voidlog(java.lang.String message, java.lang.Throwable t)Writes an explanatory message and a stack trace for a givenThrowableexception to the servlet log file, prepended by the servlet's name.abstract voidservice(ServletRequest req, ServletResponse res)Called by the servlet container to allow the servlet to respond to a request.
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Method Detail
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destroy
public void destroy()
Called by the servlet container to indicate to a servlet that the servlet is being taken out of service. SeeServlet.destroy().
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getInitParameter
public java.lang.String getInitParameter(java.lang.String name)
Returns aStringcontaining the value of the named initialization parameter, ornullif the parameter does not exist. SeeServletConfig.getInitParameter(java.lang.String).This method is supplied for convenience. It gets the value of the named parameter from the servlet's
ServletConfigobject.- Specified by:
getInitParameterin interfaceServletConfig- Parameters:
name- aStringspecifying the name of the initialization parameter- Returns:
- String a
Stringcontaining the value of the initialization parameter
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getInitParameterNames
public java.util.Enumeration<java.lang.String> getInitParameterNames()
Returns the names of the servlet's initialization parameters as anEnumerationofStringobjects, or an emptyEnumerationif the servlet has no initialization parameters. SeeServletConfig.getInitParameterNames().This method is supplied for convenience. It gets the parameter names from the servlet's
ServletConfigobject.- Specified by:
getInitParameterNamesin interfaceServletConfig- Returns:
- Enumeration an enumeration of
Stringobjects containing the names of the servlet's initialization parameters
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getServletConfig
public ServletConfig getServletConfig()
Returns this servlet'sServletConfigobject.- Specified by:
getServletConfigin interfaceServlet- Returns:
- ServletConfig the
ServletConfigobject that initialized this servlet - See Also:
Servlet.init(javax.servlet.ServletConfig)
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getServletContext
public ServletContext getServletContext()
Returns a reference to theServletContextin which this servlet is running. SeeServletConfig.getServletContext().This method is supplied for convenience. It gets the context from the servlet's
ServletConfigobject.- Specified by:
getServletContextin interfaceServletConfig- Returns:
- ServletContext the
ServletContextobject passed to this servlet by theinitmethod - See Also:
ServletContext
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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. SeeServlet.getServletInfo().- Specified by:
getServletInfoin interfaceServlet- Returns:
- String information about this servlet, by default an empty string
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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. SeeServlet.init(javax.servlet.ServletConfig).This implementation stores the
ServletConfigobject it receives from the servlet container for later use. When overriding this form of the method, callsuper.init(config).- Specified by:
initin interfaceServlet- Parameters:
config- theServletConfigobject that contains configuration information for this servlet- Throws:
ServletException- if an exception occurs that interrupts the servlet's normal operation- See Also:
UnavailableException
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init
public void init() throws ServletExceptionA convenience method which can be overridden so that there's no need to callsuper.init(config).Instead of overriding
init(ServletConfig), simply override this method and it will be called byGenericServlet.init(ServletConfig config). TheServletConfigobject can still be retrieved viagetServletConfig().- Throws:
ServletException- if an exception occurs that interrupts the servlet's normal operation
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log
public void log(java.lang.String message)
Writes the specified message to a servlet log file, prepended by the servlet's name. SeeServletContext.log(String).- Parameters:
message- aStringspecifying the message to be written to the log file
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log
public void log(java.lang.String message, java.lang.Throwable t)Writes an explanatory message and a stack trace for a givenThrowableexception to the servlet log file, prepended by the servlet's name. SeeServletContext.log(String, Throwable).- Parameters:
message- aStringthat describes the error or exceptiont- thejava.lang.Throwableerror or exception
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service
public abstract void service(ServletRequest req, ServletResponse res) throws ServletException, java.io.IOException
Called by the servlet container to allow the servlet to respond to a request. SeeServlet.service(javax.servlet.ServletRequest, javax.servlet.ServletResponse).This method is declared abstract so subclasses, such as
HttpServlet, must override it.- Specified by:
servicein interfaceServlet- Parameters:
req- theServletRequestobject that contains the client's requestres- theServletResponseobject that will contain the servlet's response- Throws:
ServletException- if an exception occurs that interferes with the servlet's normal operation occurredjava.io.IOException- if an input or output exception occurs
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getServletName
public java.lang.String getServletName()
Returns the name of this servlet instance. SeeServletConfig.getServletName().- Specified by:
getServletNamein interfaceServletConfig- Returns:
- the name of this servlet instance
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