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.

Author:
Various
Since:
Servlet 4.0
See Also:
Serialized Form

  • 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