Package javax.servlet

Interface RequestDispatcher

public interface 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. The servlet container creates the RequestDispatcher object, which is used as a wrapper around a server resource located at a particular path or given by a particular name.

This interface is intended to wrap servlets, but a servlet container can create RequestDispatcher objects to wrap any type of resource.

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  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final String
    ERROR_EXCEPTION
    The name of the request attribute under which the exception object is propagated during an error dispatch
    static final String
    ERROR_EXCEPTION_TYPE
    The name of the request attribute under which the type of the exception object is propagated during an error dispatch
    static final String
    ERROR_MESSAGE
    The name of the request attribute under which the exception message is propagated during an error dispatch
    static final String
    ERROR_REQUEST_URI
    The name of the request attribute under which the request URI whose processing caused the error is propagated during an error dispatch
    static final String
    ERROR_SERVLET_NAME
    The name of the request attribute under which the name of the servlet in which the error occurred is propagated during an error dispatch
    static final String
    ERROR_STATUS_CODE
    The name of the request attribute under which the response status is propagated during an error dispatch
    static final String
    FORWARD_CONTEXT_PATH
    The name of the request attribute under which the original context path is made available to the target of a forward
    static final String
    FORWARD_PATH_INFO
    The name of the request attribute under which the original path info is made available to the target of a forward
    static final String
    FORWARD_QUERY_STRING
    The name of the request attribute under which the original query string is made available to the target of a forward
    static final String
    FORWARD_REQUEST_URI
    The name of the request attribute under which the original request URI is made available to the target of a forward
    static final String
    FORWARD_SERVLET_PATH
    The name of the request attribute under which the original servlet path is made available to the target of a forward
    static final String
    INCLUDE_CONTEXT_PATH
    The name of the request attribute under which the context path of the target of an include is stored
    static final String
    INCLUDE_PATH_INFO
    The name of the request attribute under which the path info of the target of an include is stored
    static final String
    INCLUDE_QUERY_STRING
    The name of the request attribute under which the query string of the target of an include is stored
    static final String
    INCLUDE_REQUEST_URI
    The name of the request attribute under which the request URI of the target of an include is stored
    static final String
    INCLUDE_SERVLET_PATH
    The name of the request attribute under which the servlet path of the target of an include is stored

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    forward(ServletRequest request, ServletResponse response)
    Forwards a request from a servlet to another resource (servlet, JSP file, or HTML file) on the server.
    void
    include(ServletRequest request, ServletResponse response)
    Includes the content of a resource (servlet, JSP page, HTML file) in the response.

  • Field Details

    • FORWARD_REQUEST_URI

      static final String FORWARD_REQUEST_URI
      The name of the request attribute under which the original request URI is made available to the target of a forward
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    • FORWARD_CONTEXT_PATH

      static final String FORWARD_CONTEXT_PATH
      The name of the request attribute under which the original context path is made available to the target of a forward
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    • FORWARD_PATH_INFO

      static final String FORWARD_PATH_INFO
      The name of the request attribute under which the original path info is made available to the target of a forward
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    • FORWARD_SERVLET_PATH

      static final String FORWARD_SERVLET_PATH
      The name of the request attribute under which the original servlet path is made available to the target of a forward
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    • FORWARD_QUERY_STRING

      static final String FORWARD_QUERY_STRING
      The name of the request attribute under which the original query string is made available to the target of a forward
      See Also:

    • INCLUDE_REQUEST_URI

      static final String INCLUDE_REQUEST_URI
      The name of the request attribute under which the request URI of the target of an include is stored
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    • INCLUDE_CONTEXT_PATH

      static final String INCLUDE_CONTEXT_PATH
      The name of the request attribute under which the context path of the target of an include is stored
      See Also:

    • INCLUDE_PATH_INFO

      static final String INCLUDE_PATH_INFO
      The name of the request attribute under which the path info of the target of an include is stored
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    • INCLUDE_SERVLET_PATH

      static final String INCLUDE_SERVLET_PATH
      The name of the request attribute under which the servlet path of the target of an include is stored
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    • INCLUDE_QUERY_STRING

      static final String INCLUDE_QUERY_STRING
      The name of the request attribute under which the query string of the target of an include is stored
      See Also:

    • ERROR_EXCEPTION

      static final String ERROR_EXCEPTION
      The name of the request attribute under which the exception object is propagated during an error dispatch
      See Also:

    • ERROR_EXCEPTION_TYPE

      static final String ERROR_EXCEPTION_TYPE
      The name of the request attribute under which the type of the exception object is propagated during an error dispatch
      See Also:

    • ERROR_MESSAGE

      static final String ERROR_MESSAGE
      The name of the request attribute under which the exception message is propagated during an error dispatch
      See Also:

    • ERROR_REQUEST_URI

      static final String ERROR_REQUEST_URI
      The name of the request attribute under which the request URI whose processing caused the error is propagated during an error dispatch
      See Also:

    • ERROR_SERVLET_NAME

      static final String ERROR_SERVLET_NAME
      The name of the request attribute under which the name of the servlet in which the error occurred is propagated during an error dispatch
      See Also:

    • ERROR_STATUS_CODE

      static final String ERROR_STATUS_CODE
      The name of the request attribute under which the response status is propagated during an error dispatch
      See Also:

  • Method Details

    • forward

      void forward(ServletRequest request, ServletResponse response) throws ServletException, IOException
      Forwards a request from a servlet to another resource (servlet, JSP file, or HTML file) on the server. This method allows one servlet to do preliminary processing of a request and another resource to generate the response.

      For a RequestDispatcher obtained via getRequestDispatcher(), the ServletRequest object has its path elements and parameters adjusted to match the path of the target resource.

      forward should be called before the response has been committed to the client (before response body output has been flushed). If the response already has been committed, this method throws an IllegalStateException. Uncommitted output in the response buffer is automatically cleared before the forward.

      The request and response parameters must be either the same objects as were passed to the calling servlet's service method or be subclasses of the ServletRequestWrapper or ServletResponseWrapper classes that wrap them.

      This method sets the dispatcher type of the given request to DispatcherType.FORWARD.

      Parameters:
      request - a ServletRequest object that represents the request the client makes of the servlet
      response - a ServletResponse object that represents the response the servlet returns to the client
      Throws:
      ServletException - if the target resource throws this exception
      IOException - if the target resource throws this exception
      IllegalStateException - if the response was already committed
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    • include

      void include(ServletRequest request, ServletResponse response) throws ServletException, IOException
      Includes the content of a resource (servlet, JSP page, HTML file) in the response. In essence, this method enables programmatic server-side includes.

      The ServletResponse object has its path elements and parameters remain unchanged from the caller's. The included servlet cannot change the response status code or set headers; any attempt to make a change is ignored.

      The request and response parameters must be either the same objects as were passed to the calling servlet's service method or be subclasses of the ServletRequestWrapper or ServletResponseWrapper classes that wrap them.

      This method sets the dispatcher type of the given request to DispatcherType.INCLUDE.

      Parameters:
      request - a ServletRequest object that contains the client's request
      response - a ServletResponse object that contains the servlet's response
      Throws:
      ServletException - if the included resource throws this exception
      IOException - if the included resource throws this exception
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