Interface RequestDispatcher
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public interface RequestDispatcherDefines 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 theRequestDispatcherobject, 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
RequestDispatcherobjects to wrap any type of resource.
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Field Summary
Fields Modifier and Type Field Description static java.lang.StringERROR_EXCEPTIONThe name of the request attribute that should be set by the container when custom error-handling servlet or JSP page is invoked.static java.lang.StringERROR_EXCEPTION_TYPEThe name of the request attribute that should be set by the container when custom error-handling servlet or JSP page is invoked.static java.lang.StringERROR_MESSAGEThe name of the request attribute that should be set by the container when custom error-handling servlet or JSP page is invoked.static java.lang.StringERROR_REQUEST_URIThe name of the request attribute that should be set by the container when custom error-handling servlet or JSP page is invoked.static java.lang.StringERROR_SERVLET_NAMEThe name of the request attribute that should be set by the container when custom error-handling servlet or JSP page is invoked.static java.lang.StringERROR_STATUS_CODEThe name of the request attribute that should be set by the container when custom error-handling servlet or JSP page is invoked.static java.lang.StringFORWARD_CONTEXT_PATHThe name of the request attribute that should be set by the container when theforward(ServletRequest, ServletResponse)method is called.static java.lang.StringFORWARD_PATH_INFOThe name of the request attribute that should be set by the container when theforward(ServletRequest, ServletResponse)method is called.static java.lang.StringFORWARD_QUERY_STRINGThe name of the request attribute that should be set by the container when theforward(ServletRequest, ServletResponse)method is called.static java.lang.StringFORWARD_REQUEST_URIThe name of the request attribute that should be set by the container when theforward(ServletRequest, ServletResponse)method is called.static java.lang.StringFORWARD_SERVLET_PATHThe name of the request attribute that should be set by the container when theforward(ServletRequest, ServletResponse)method is called.static java.lang.StringINCLUDE_CONTEXT_PATHThe name of the request attribute that should be set by the container when theinclude(ServletRequest, ServletResponse)method is called on theRequestDispatcherobtained by a path and not by a name.static java.lang.StringINCLUDE_PATH_INFOThe name of the request attribute that should be set by the container when theinclude(ServletRequest, ServletResponse)method is called on theRequestDispatcherobtained by a path and not by a name.static java.lang.StringINCLUDE_QUERY_STRINGThe name of the request attribute that should be set by the container when theinclude(ServletRequest, ServletResponse)method is called on theRequestDispatcherobtained by a path and not by a name.static java.lang.StringINCLUDE_REQUEST_URIThe name of the request attribute that should be set by the container when theinclude(ServletRequest, ServletResponse)method is called on theRequestDispatcherobtained by a path and not by a name.static java.lang.StringINCLUDE_SERVLET_PATHThe name of the request attribute that should be set by the container when theinclude(ServletRequest, ServletResponse)method is called on theRequestDispatcherobtained by a path and not by a name.
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description voidforward(ServletRequest request, ServletResponse response)Forwards a request from a servlet to another resource (servlet, JSP file, or HTML file) on the server.voidinclude(ServletRequest request, ServletResponse response)Includes the content of a resource (servlet, JSP page, HTML file) in the response.
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Field Detail
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FORWARD_REQUEST_URI
static final java.lang.String FORWARD_REQUEST_URI
The name of the request attribute that should be set by the container when theforward(ServletRequest, ServletResponse)method is called. It provides the original value of a path-related property of the request. See the chapter "Forwarded Request Parameters" in the Servlet Specification for details.- Since:
- Servlet 3.0
- See Also:
- Constant Field Values
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FORWARD_CONTEXT_PATH
static final java.lang.String FORWARD_CONTEXT_PATH
The name of the request attribute that should be set by the container when theforward(ServletRequest, ServletResponse)method is called. It provides the original value of a path-related property of the request. See the chapter "Forwarded Request Parameters" in the Servlet Specification for details.- Since:
- Servlet 3.0
- See Also:
- Constant Field Values
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FORWARD_PATH_INFO
static final java.lang.String FORWARD_PATH_INFO
The name of the request attribute that should be set by the container when theforward(ServletRequest, ServletResponse)method is called. It provides the original value of a path-related property of the request. See the chapter "Forwarded Request Parameters" in the Servlet Specification for details.- Since:
- Servlet 3.0
- See Also:
- Constant Field Values
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FORWARD_SERVLET_PATH
static final java.lang.String FORWARD_SERVLET_PATH
The name of the request attribute that should be set by the container when theforward(ServletRequest, ServletResponse)method is called. It provides the original value of a path-related property of the request. See the chapter "Forwarded Request Parameters" in the Servlet Specification for details.- Since:
- Servlet 3.0
- See Also:
- Constant Field Values
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FORWARD_QUERY_STRING
static final java.lang.String FORWARD_QUERY_STRING
The name of the request attribute that should be set by the container when theforward(ServletRequest, ServletResponse)method is called. It provides the original value of a path-related property of the request. See the chapter "Forwarded Request Parameters" in the Servlet Specification for details.- Since:
- Servlet 3.0
- See Also:
- Constant Field Values
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INCLUDE_REQUEST_URI
static final java.lang.String INCLUDE_REQUEST_URI
The name of the request attribute that should be set by the container when theinclude(ServletRequest, ServletResponse)method is called on theRequestDispatcherobtained by a path and not by a name. It provides information on the path that was used to obtain theRequestDispatcherinstance for this include call. See the chapter "Included Request Parameters" in the Servlet Specification for details.- Since:
- Servlet 3.0
- See Also:
- Constant Field Values
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INCLUDE_CONTEXT_PATH
static final java.lang.String INCLUDE_CONTEXT_PATH
The name of the request attribute that should be set by the container when theinclude(ServletRequest, ServletResponse)method is called on theRequestDispatcherobtained by a path and not by a name. It provides information on the path that was used to obtain theRequestDispatcherinstance for this include call. See the chapter "Included Request Parameters" in the Servlet Specification for details.- Since:
- Servlet 3.0
- See Also:
- Constant Field Values
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INCLUDE_PATH_INFO
static final java.lang.String INCLUDE_PATH_INFO
The name of the request attribute that should be set by the container when theinclude(ServletRequest, ServletResponse)method is called on theRequestDispatcherobtained by a path and not by a name. It provides information on the path that was used to obtain theRequestDispatcherinstance for this include call. See the chapter "Included Request Parameters" in the Servlet Specification for details.- Since:
- Servlet 3.0
- See Also:
- Constant Field Values
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INCLUDE_SERVLET_PATH
static final java.lang.String INCLUDE_SERVLET_PATH
The name of the request attribute that should be set by the container when theinclude(ServletRequest, ServletResponse)method is called on theRequestDispatcherobtained by a path and not by a name. It provides information on the path that was used to obtain theRequestDispatcherinstance for this include call. See the chapter "Included Request Parameters" in the Servlet Specification for details.- Since:
- Servlet 3.0
- See Also:
- Constant Field Values
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INCLUDE_QUERY_STRING
static final java.lang.String INCLUDE_QUERY_STRING
The name of the request attribute that should be set by the container when theinclude(ServletRequest, ServletResponse)method is called on theRequestDispatcherobtained by a path and not by a name. It provides information on the path that was used to obtain theRequestDispatcherinstance for this include call. See the chapter "Included Request Parameters" in the Servlet Specification for details.- Since:
- Servlet 3.0
- See Also:
- Constant Field Values
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ERROR_EXCEPTION
static final java.lang.String ERROR_EXCEPTION
The name of the request attribute that should be set by the container when custom error-handling servlet or JSP page is invoked. The value of the attribute is of typejava.lang.Throwable. See the chapter "Error Handling" in the Servlet Specification for details.- Since:
- Servlet 3.0
- See Also:
- Constant Field Values
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ERROR_EXCEPTION_TYPE
static final java.lang.String ERROR_EXCEPTION_TYPE
The name of the request attribute that should be set by the container when custom error-handling servlet or JSP page is invoked. The value of the attribute is of typejava.lang.Class. See the chapter "Error Handling" in the Servlet Specification for details.- Since:
- Servlet 3.0
- See Also:
- Constant Field Values
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ERROR_MESSAGE
static final java.lang.String ERROR_MESSAGE
The name of the request attribute that should be set by the container when custom error-handling servlet or JSP page is invoked. The value of the attribute is of typejava.lang.String. See the chapter "Error Handling" in the Servlet Specification for details.- Since:
- Servlet 3.0
- See Also:
- Constant Field Values
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ERROR_REQUEST_URI
static final java.lang.String ERROR_REQUEST_URI
The name of the request attribute that should be set by the container when custom error-handling servlet or JSP page is invoked. The value of the attribute is of typejava.lang.String. See the chapter "Error Handling" in the Servlet Specification for details.- Since:
- Servlet 3.0
- See Also:
- Constant Field Values
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ERROR_SERVLET_NAME
static final java.lang.String ERROR_SERVLET_NAME
The name of the request attribute that should be set by the container when custom error-handling servlet or JSP page is invoked. The value of the attribute is of typejava.lang.String. See the chapter "Error Handling" in the Servlet Specification for details.- Since:
- Servlet 3.0
- See Also:
- Constant Field Values
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ERROR_STATUS_CODE
static final java.lang.String ERROR_STATUS_CODE
The name of the request attribute that should be set by the container when custom error-handling servlet or JSP page is invoked. The value of the attribute is of typejava.lang.Integer. See the chapter "Error Handling" in the Servlet Specification for details.- Since:
- Servlet 3.0
- See Also:
- Constant Field Values
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Method Detail
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forward
void forward(ServletRequest request, ServletResponse response) throws ServletException, java.io.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
RequestDispatcherobtained viagetRequestDispatcher(), theServletRequestobject has its path elements and parameters adjusted to match the path of the target resource.forwardshould 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 anIllegalStateException. 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
ServletRequestWrapperorServletResponseWrapperclasses that wrap them.- Parameters:
request- aServletRequestobject that represents the request the client makes of the servletresponse- aServletResponseobject that represents the response the servlet returns to the client- Throws:
ServletException- if the target resource throws this exceptionjava.io.IOException- if the target resource throws this exceptionjava.lang.IllegalStateException- if the response was already committed
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include
void include(ServletRequest request, ServletResponse response) throws ServletException, java.io.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
ServletResponseobject 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
ServletRequestWrapperorServletResponseWrapperclasses that wrap them.- Parameters:
request- aServletRequestobject that contains the client's requestresponse- aServletResponseobject that contains the servlet's response- Throws:
ServletException- if the included resource throws this exceptionjava.io.IOException- if the included resource throws this exception
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