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 SummaryConstructors Constructor Description GenericServlet()Does nothing.
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Method SummaryAll 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- 
destroypublic 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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getInitParameterpublic 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 interface- ServletConfig
- Parameters:
- name- a- Stringspecifying the name of the initialization parameter
- Returns:
- String a Stringcontaining the value of the initialization parameter
 
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getInitParameterNamespublic 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 interface- ServletConfig
- Returns:
- Enumeration an enumeration of Stringobjects containing the names of the servlet's initialization parameters
 
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getServletConfigpublic ServletConfig getServletConfig() Returns this servlet'sServletConfigobject.- Specified by:
- getServletConfigin interface- Servlet
- Returns:
- ServletConfig the ServletConfigobject that initialized this servlet
- See Also:
- Servlet.init(javax.servlet.ServletConfig)
 
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getServletContextpublic 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 interface- ServletConfig
- Returns:
- ServletContext the ServletContextobject passed to this servlet by theinitmethod
- See Also:
- ServletContext
 
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getServletInfopublic 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 interface- Servlet
- Returns:
- String information about this servlet, by default an empty string
 
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initpublic 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 interface- Servlet
- Parameters:
- config- the- ServletConfigobject 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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initpublic 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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logpublic 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- a- Stringspecifying the message to be written to the log file
 
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logpublic 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- a- Stringthat describes the error or exception
- t- the- java.lang.Throwableerror or exception
 
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servicepublic 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 interface- Servlet
- Parameters:
- req- the- ServletRequestobject that contains the client's request
- res- the- ServletResponseobject that will contain the servlet's response
- Throws:
- ServletException- if an exception occurs that interferes with the servlet's normal operation occurred
- java.io.IOException- if an input or output exception occurs
 
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getServletNamepublic java.lang.String getServletName() Returns the name of this servlet instance. SeeServletConfig.getServletName().- Specified by:
- getServletNamein interface- ServletConfig
- Returns:
- the name of this servlet instance
 
 
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