Package jakarta.servlet

Class GenericFilter

java.lang.Object

jakarta.servlet.GenericFilter

All Implemented Interfaces:

Filter, FilterConfig, Serializable

Direct Known Subclasses:

HttpFilter

public abstract class GenericFilter
extends Object
implements Filter, FilterConfig, Serializable

Provides a base class that implements the Filter and FilterConfig interfaces to reduce boilerplate when writing new filters.

Since:

Servlet 4.0

See Also:

• Filter
• FilterConfig
• Serialized Form

Constructor Summary

Constructors

Constructor	Description
GenericFilter()

Method Summary

Modifier and Type	Method	Description
FilterConfig	getFilterConfig()	Obtain the FilterConfig used to initialise this Filter instance.
String	getFilterName()	Get the name of the filter.
String	getInitParameter(String name)	Returns a String containing the value of the named initialization parameter, or null if the parameter does not exist.
Enumeration<String>	getInitParameterNames()	Returns the names of the filter's initialization parameters as an Enumeration of String objects, or an empty Enumeration if the filter has no initialization parameters.
ServletContext	getServletContext()	Returns a reference to the ServletContext in which the caller is executing.
void	init()	Convenience method for sub-classes to save them having to call super.init(config).
void	init(FilterConfig filterConfig)	Called by the web container to indicate to a filter that it is being placed into service.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface jakarta.servlet.Filter

destroy, doFilter

Constructor Details

GenericFilter

public GenericFilter()

Method Details

getInitParameter

public String getInitParameter(String name)

Description copied from interface: FilterConfig

Returns a String containing the value of the named initialization parameter, or null if the parameter does not exist.

Specified by:

getInitParameter in interface FilterConfig

Parameters:

name - String specifying the name of the initialization parameter

Returns:

String containing the value of the initialization parameter

getInitParameterNames

public Enumeration<String> getInitParameterNames()

Description copied from interface: FilterConfig

Returns the names of the filter's initialization parameters as an Enumeration of String objects, or an empty Enumeration if the filter has no initialization parameters.

Specified by:

getInitParameterNames in interface FilterConfig

Returns:

Enumeration of String objects containing the names of the filter's initialization parameters

getFilterConfig

public FilterConfig getFilterConfig()

Obtain the FilterConfig used to initialise this Filter instance.

Returns:

The config previously passed to the init(FilterConfig) method

getServletContext

public ServletContext getServletContext()

Description copied from interface: FilterConfig

Returns a reference to the ServletContext in which the caller is executing.

Specified by:

getServletContext in interface FilterConfig

Returns:

ServletContext object, used by the caller to interact with its servlet container

See Also:

• ServletContext

init

public void init(FilterConfig filterConfig)
          throws ServletException

Description copied from interface: Filter

Called by the web container to indicate to a filter that it is being placed into service. The servlet container calls the init method exactly once after instantiating the filter. The init method must complete successfully before the filter is asked to do any filtering work.

The web container cannot place the filter into service if the init method either:

• Throws a ServletException
• Does not return within a time period defined by the web container

The default implementation is a NO-OP.

Specified by:

init in interface Filter

Parameters:

filterConfig - The configuration information associated with the filter instance being initialised

Throws:

ServletException - if the initialisation fails

init

public void init()
          throws ServletException

Convenience method for sub-classes to save them having to call super.init(config). This is a NO-OP by default.

Throws:

ServletException - If an exception occurs that interrupts the Filter's normal operation

getFilterName

public String getFilterName()

Description copied from interface: FilterConfig

Get the name of the filter.

Specified by:

getFilterName in interface FilterConfig

Returns:

The filter-name of this filter as defined in the deployment descriptor.