Module jakarta.servlet

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

Defines a generic, protocol-independent filter. To write an HTTP filter for use on the Web, extend HttpFilter instead.

GenericFilter implements the Filter and FilterConfig interfaces. GenericFilter may be directly extended by a filter, although it's more common to extend a protocol-specific subclass such as HttpFilter.

GenericFilter makes writing filters easier. It provides simple versions of the lifecycle methods init and destroy and of the methods in the FilterConfig interface.

To write a generic filter, you need only override the abstract doFilter method.

Since:

Servlet 4.0

See Also:

• Serialized Form

Constructor Summary

Constructors

Constructor	Description
GenericFilter()	Does nothing.

Method Summary

Modifier and Type	Method	Description
FilterConfig	getFilterConfig()	Returns this servlet's ServletConfig object.
String	getFilterName()	Returns the name of this filter instance.
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 this filter is running.
void	init()	A convenience method which can be overridden so that there's no need to call super.init(config).
void	init(FilterConfig config)	Called by the servlet 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()

Does nothing. All of the filter initialization is done by one of the init methods.

Since:

Servlet 4.0

Method Details

getInitParameter

public String getInitParameter(String name)

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

Parameters:

name - a String specifying the name of the initialization parameter

Returns:

String a String containing the value of the initialization parameter

Since:

Servlet 4.0

getInitParameterNames

public 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. See FilterConfig.getInitParameterNames().

This method is supplied for convenience. It gets the parameter names from the filter's FilterConfig object.

Specified by:

getInitParameterNames in interface FilterConfig

Returns:

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

Since:

Servlet 4.0

getFilterConfig

public FilterConfig getFilterConfig()

Returns this servlet's ServletConfig object.

Returns:

FilterConfig the FilterConfig object that initialized this filter

Since:

Servlet 4.0

getServletContext

public ServletContext getServletContext()

Returns a reference to the ServletContext in which this filter is running. See FilterConfig.getServletContext().

This method is supplied for convenience. It gets the context from the filter's FilterConfig object.

Specified by:

getServletContext in interface FilterConfig

Returns:

ServletContext the ServletContext object passed to this filter by the init method

Since:

Servlet 4.0

See Also:

• ServletContext

init

public void init(FilterConfig config)
          throws ServletException

Called by the servlet container to indicate to a filter that it is being placed into service. See Filter.init(jakarta.servlet.FilterConfig).

This implementation stores the FilterConfig 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 Filter

Parameters:

config - the FilterConfig object that contains configuration information for this filter

Throws:

ServletException - if an exception occurs that interrupts the servlet's normal operation

Since:

Servlet 4.0

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(FilterConfig), simply override this method and it will be called by GenericFilter.init(FilterConfig config). The FilterConfig object can still be retrieved via getFilterConfig().

Throws:

ServletException - if an exception occurs that interrupts the servlet's normal operation

Since:

Servlet 4.0

getFilterName

public String getFilterName()

Returns the name of this filter instance. See FilterConfig.getFilterName().

Specified by:

getFilterName in interface FilterConfig

Returns:

the name of this filter instance

Since:

Servlet 4.0