# Package javax.servlet

package javax.servlet
The javax.servlet package contains a number of classes and interfaces that describe and define the contracts between a servlet class and the runtime environment provided for an instance of such a class by a conforming servlet container.

- Related Packages
  Package
  Description
  javax.servlet.annotation
  javax.servlet.descriptor
  javax.servlet.http
  The javax.servlet.http package contains a number of classes and interfaces that describe and define the contracts between a servlet class running under the HTTP protocol and the runtime environment provided for an instance of such a class by a conforming servlet container.
- Class
  Description
  AsyncContext
  Provides the context for asynchronous request handling
  AsyncEvent
  Used to pass data to the methods of `AsyncListener`.
  AsyncListener
  Listener for events associated with an `AsyncContext`.
  DispatcherType
  Enumeration of dispatcher types.
  Filter
  A filter is an object that performs filtering tasks on either the request to a resource (a servlet or static content), or on the response from a resource, or both.
  FilterChain
  A FilterChain is an object provided by the servlet container to the developer giving a view into the invocation chain of a filtered request for a resource.
  FilterConfig
  A filter configuration object used by a servlet container to pass information to a filter during initialization.
  FilterRegistration
  Interface through which a Filter may be further configured.
  FilterRegistration.Dynamic
  Interface through which a Filter registered via one of the addFilter methods on ServletContext may be further configured.
  GenericServlet
  Defines a generic, protocol-independent servlet.
  HttpConstraintElement
  Equivalent of `HttpConstraint` for programmatic configuration of security constraints.
  HttpMethodConstraintElement
  Programmatic equivalent of a security constraint defined for a single HTTP method.
  MultipartConfigElement
  The programmatic equivalent of `MultipartConfig` used to configure multi-part handling for a Servlet when registering a Servlet via code.
  ReadListener
  Receives notification of read events when using non-blocking IO.
  Registration
  Common interface for the registration of Filters and Servlets.
  Registration.Dynamic
  Interface through which a Servlet or Filter registered via one of the addServlet or addFilter methods, respectively, on ServletContext may be further configured.
  RequestDispatcher
  Defines an object that receives requests from the client and sends them to any resource (such as a servlet, HTML file, or JSP file) on the server.
  Servlet
  Defines methods that all servlets must implement.
  ServletConfig
  A servlet configuration object used by a servlet container to pass information to a servlet during initialization.
  ServletContainerInitializer
  ServletContainerInitializers (SCIs) are registered via an entry in the file META-INF/services/javax.servlet.ServletContainerInitializer that must be included in the JAR file that contains the SCI implementation.
  ServletContext
  Defines a set of methods that a servlet uses to communicate with its servlet container, for example, to get the MIME type of a file, dispatch requests, or write to a log file.
  ServletContextAttributeEvent
  This is the event class for notifications about changes to the attributes of the servlet context of a web application.
  ServletContextAttributeListener
  Implementations of this interface receive notifications of changes to the attribute list on the servlet context of a web application.
  ServletContextEvent
  This is the event class for notifications about changes to the servlet context of a web application.
  ServletContextListener
  Implementations of this interface receive notifications about changes to the servlet context of the web application they are part of.
  ServletException
  Defines a general exception a servlet can throw when it encounters difficulty.
  ServletInputStream
  Provides an input stream for reading binary data from a client request, including an efficient `readLine` method for reading data one line at a time.
  ServletOutputStream
  Provides an output stream for sending binary data to the client.
  ServletRegistration
  Interface through which a Servlet may be further configured.
  ServletRegistration.Dynamic
  Interface through which a Servlet registered via one of the addServlet methods on ServletContext may be further configured.
  ServletRequest
  Defines an object to provide client request information to a servlet.
  ServletRequestAttributeEvent
  This is the event class for notifications of changes to the attributes of the servlet request in an application.
  ServletRequestAttributeListener
  A ServletRequestAttributeListener can be implemented by the developer interested in being notified of request attribute changes.
  ServletRequestEvent
  Events of this kind indicate lifecycle events for a ServletRequest.
  ServletRequestListener
  A ServletRequestListener can be implemented by the developer interested in being notified of requests coming in and out of scope in a web component.
  ServletRequestWrapper
  Provides a convenient implementation of the ServletRequest interface that can be subclassed by developers wishing to adapt the request to a Servlet.
  ServletResponse
  Defines an object to assist a servlet in sending a response to the client.
  ServletResponseWrapper
  Provides a convenient implementation of the ServletResponse interface that can be subclassed by developers wishing to adapt the response from a Servlet.
  ServletSecurityElement
  The programmatic equivalent of `ServletSecurity` used to configre security constraints for a Servlet.
  SessionCookieConfig
  Configures the session cookies used by the web application associated with the ServletContext from which this SessionCookieConfig was obtained.
  SessionTrackingMode
  Defines the permitted options for configuring the session tracking mode.
  SingleThreadModel
  Deprecated.
  As of Java Servlet API 2.4, with no direct replacement.
  UnavailableException
  Defines an exception that a servlet or filter throws to indicate that it is permanently or temporarily unavailable.
  WriteListener
  Receives notification of write events when using non-blocking IO.