httpservlet.html

j2ee帮助文档软件设计/软件工程 文件格式

<DD><DL>
<DT><B>Parameters:</B><DD><CODE>req</CODE> - the <code>HttpServletRequest</code> 
                        object that is sent to the servlet
<DT><B>Returns:</B><DD>a <code>long</code> integer specifying
                        the time the <code>HttpServletRequest</code>
                        object was last modified, in milliseconds
                        since midnight, January 1, 1970 GMT, or
                        -1 if the time is not known</DL>
</DD>
</DL>
<HR>

<A NAME="doHead(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)"><!-- --></A><H3>
doHead</H3>
<PRE>
protected void <B>doHead</B>(<A HREF="../../../javax/servlet/http/HttpServletRequest.html" title="interface in javax.servlet.http">HttpServletRequest</A>&nbsp;req,
                      <A HREF="../../../javax/servlet/http/HttpServletResponse.html" title="interface in javax.servlet.http">HttpServletResponse</A>&nbsp;resp)
               throws <A HREF="../../../javax/servlet/ServletException.html" title="class in javax.servlet">ServletException</A>,
                      <A HREF="http://java.sun.com/j2se/1.5/docs/api/java/io/IOException.html" title="class or interface in java.io">IOException</A></PRE>
<DL>
<DD><p>Receives an HTTP HEAD request from the protected
 <code>service</code> method and handles the
 request.
 The client sends a HEAD request when it wants
 to see only the headers of a response, such as
 Content-Type or Content-Length. The HTTP HEAD
 method counts the output bytes in the response
 to set the Content-Length header accurately.

 <p>If you override this method, you can avoid computing
 the response body and just set the response headers
 directly to improve performance. Make sure that the
 <code>doHead</code> method you write is both safe
 and idempotent (that is, protects itself from being
 called multiple times for one HTTP HEAD request).

 <p>If the HTTP HEAD request is incorrectly formatted,
 <code>doHead</code> returns an HTTP "Bad Request"
 message.
<P>
<DD><DL>
</DL>
</DD>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>req</CODE> - the request object that is passed
                        to the servlet<DD><CODE>resp</CODE> - the response object that the servlet
                        uses to return the headers to the clien
<DT><B>Throws:</B>
<DD><CODE><A HREF="http://java.sun.com/j2se/1.5/docs/api/java/io/IOException.html" title="class or interface in java.io">IOException</A></CODE> - if an input or output error occurs
<DD><CODE><A HREF="../../../javax/servlet/ServletException.html" title="class in javax.servlet">ServletException</A></CODE> - if the request for the HEAD
                                        could not be handled</DL>
</DD>
</DL>
<HR>

<A NAME="doPost(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)"><!-- --></A><H3>
doPost</H3>
<PRE>
protected void <B>doPost</B>(<A HREF="../../../javax/servlet/http/HttpServletRequest.html" title="interface in javax.servlet.http">HttpServletRequest</A>&nbsp;req,
                      <A HREF="../../../javax/servlet/http/HttpServletResponse.html" title="interface in javax.servlet.http">HttpServletResponse</A>&nbsp;resp)
               throws <A HREF="../../../javax/servlet/ServletException.html" title="class in javax.servlet">ServletException</A>,
                      <A HREF="http://java.sun.com/j2se/1.5/docs/api/java/io/IOException.html" title="class or interface in java.io">IOException</A></PRE>
<DL>
<DD>Called by the server (via the <code>service</code> method)
 to allow a servlet to handle a POST request.

 The HTTP POST method allows the client to send
 data of unlimited length to the Web server a single time
 and is useful when posting information such as
 credit card numbers.

 <p>When overriding this method, read the request data,
 write the response headers, get the response's writer or output
 stream object, and finally, write the response data. It's best 
 to include content type and encoding. When using a
 <code>PrintWriter</code> object to return the response, set the 
 content type before accessing the <code>PrintWriter</code> object. 

 <p>The servlet container must write the headers before committing the
 response, because in HTTP the headers must be sent before the 
 response body.

 <p>Where possible, set the Content-Length header (with the
 <A HREF="../../../javax/servlet/ServletResponse.html#setContentLength(int)"><CODE>ServletResponse.setContentLength(int)</CODE></A> method),
 to allow the servlet container to use a persistent connection 
 to return its response to the client, improving performance.
 The content length is automatically set if the entire response fits
 inside the response buffer.  

 <p>When using HTTP 1.1 chunked encoding (which means that the response
 has a Transfer-Encoding header), do not set the Content-Length header. 

 <p>This method does not need to be either safe or idempotent.
 Operations requested through POST can have side effects for
 which the user can be held accountable, for example, 
 updating stored data or buying items online.

 <p>If the HTTP POST request is incorrectly formatted,
 <code>doPost</code> returns an HTTP "Bad Request" message.
<P>
<DD><DL>
</DL>
</DD>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>req</CODE> - an <A HREF="../../../javax/servlet/http/HttpServletRequest.html" title="interface in javax.servlet.http"><CODE>HttpServletRequest</CODE></A> object that
                        contains the request the client has made
                        of the servlet<DD><CODE>resp</CODE> - an <A HREF="../../../javax/servlet/http/HttpServletResponse.html" title="interface in javax.servlet.http"><CODE>HttpServletResponse</CODE></A> object that
                        contains the response the servlet sends
                        to the client
<DT><B>Throws:</B>
<DD><CODE><A HREF="http://java.sun.com/j2se/1.5/docs/api/java/io/IOException.html" title="class or interface in java.io">IOException</A></CODE> - if an input or output error is 
                                detected when the servlet handles
                                the request
<DD><CODE><A HREF="../../../javax/servlet/ServletException.html" title="class in javax.servlet">ServletException</A></CODE> - if the request for the POST
                                        could not be handled<DT><B>See Also:</B><DD><A HREF="../../../javax/servlet/ServletOutputStream.html" title="class in javax.servlet"><CODE>ServletOutputStream</CODE></A>, 
<A HREF="../../../javax/servlet/ServletResponse.html#setContentType(java.lang.String)"><CODE>ServletResponse.setContentType(java.lang.String)</CODE></A></DL>
</DD>
</DL>
<HR>

<A NAME="doPut(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)"><!-- --></A><H3>
doPut</H3>
<PRE>
protected void <B>doPut</B>(<A HREF="../../../javax/servlet/http/HttpServletRequest.html" title="interface in javax.servlet.http">HttpServletRequest</A>&nbsp;req,
                     <A HREF="../../../javax/servlet/http/HttpServletResponse.html" title="interface in javax.servlet.http">HttpServletResponse</A>&nbsp;resp)
              throws <A HREF="../../../javax/servlet/ServletException.html" title="class in javax.servlet">ServletException</A>,
                     <A HREF="http://java.sun.com/j2se/1.5/docs/api/java/io/IOException.html" title="class or interface in java.io">IOException</A></PRE>
<DL>
<DD>Called by the server (via the <code>service</code> method)
 to allow a servlet to handle a PUT request.

 The PUT operation allows a client to 
 place a file on the server and is similar to 
 sending a file by FTP.

 <p>When overriding this method, leave intact
 any content headers sent with the request (including
 Content-Length, Content-Type, Content-Transfer-Encoding,
 Content-Encoding, Content-Base, Content-Language, Content-Location,
 Content-MD5, and Content-Range). If your method cannot
 handle a content header, it must issue an error message
 (HTTP 501 - Not Implemented) and discard the request.
 For more information on HTTP 1.1, see RFC 2616
 <a href="http://www.ietf.org/rfc/rfc2616.txt"></a>.

 <p>This method does not need to be either safe or idempotent.
 Operations that <code>doPut</code> performs can have side
 effects for which the user can be held accountable. When using
 this method, it may be useful to save a copy of the
 affected URL in temporary storage.

 <p>If the HTTP PUT request is incorrectly formatted,
 <code>doPut</code> returns an HTTP "Bad Request" message.
<P>
<DD><DL>
</DL>
</DD>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>req</CODE> - the <A HREF="../../../javax/servlet/http/HttpServletRequest.html" title="interface in javax.servlet.http"><CODE>HttpServletRequest</CODE></A> object that
                        contains the request the client made of
                        the servlet<DD><CODE>resp</CODE> - the <A HREF="../../../javax/servlet/http/HttpServletResponse.html" title="interface in javax.servlet.http"><CODE>HttpServletResponse</CODE></A> object that
                        contains the response the servlet returns
                        to the client
<DT><B>Throws:</B>
<DD><CODE><A HREF="http://java.sun.com/j2se/1.5/docs/api/java/io/IOException.html" title="class or interface in java.io">IOException</A></CODE> - if an input or output error occurs
                                while the servlet is handling the
                                PUT request
<DD><CODE><A HREF="../../../javax/servlet/ServletException.html" title="class in javax.servlet">ServletException</A></CODE> - if the request for the PUT
                                        cannot be handled</DL>
</DD>
</DL>
<HR>

<A NAME="doDelete(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)"><!-- --></A><H3>
doDelete</H3>
<PRE>
protected void <B>doDelete</B>(<A HREF="../../../javax/servlet/http/HttpServletRequest.html" title="interface in javax.servlet.http">HttpServletRequest</A>&nbsp;req,
                        <A HREF="../../../javax/servlet/http/HttpServletResponse.html" title="interface in javax.servlet.http">HttpServletResponse</A>&nbsp;resp)
                 throws <A HREF="../../../javax/servlet/ServletException.html" title="class in javax.servlet">ServletException</A>,
                        <A HREF="http://java.sun.com/j2se/1.5/docs/api/java/io/IOException.html" title="class or interface in java.io">IOException</A></PRE>
<DL>
<DD>Called by the server (via the <code>service</code> method)
 to allow a servlet to handle a DELETE request.

 The DELETE operation allows a client to remove a document
 or Web page from the server.
 
 <p>This method does not need to be either safe
 or idempotent. Operations requested through
 DELETE can have side effects for which users
 can be held accountable. When using
 this method, it may be useful to save a copy of the
 affected URL in temporary storage.

 <p>If the HTTP DELETE request is incorrectly formatted,
 <code>doDelete</code> returns an HTTP "Bad Request"
 message.
<P>
<DD><DL>
</DL>
</DD>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>req</CODE> - the <A HREF="../../../javax/servlet/http/HttpServletRequest.html" title="interface in javax.servlet.http"><CODE>HttpServletRequest</CODE></A> object that
                        contains the request the client made of
                        the servlet<DD><CODE>resp</CODE> - the <A HREF="../../../javax/servlet/http/HttpServletResponse.html" title="interface in javax.servlet.http"><CODE>HttpServletResponse</CODE></A> object that
                        contains the response the servlet returns
                        to the client
<DT><B>Throws:</B>
<DD><CODE><A HREF="http://java.sun.com/j2se/1.5/docs/api/java/io/IOException.html" title="class or interface in java.io">IOException</A></CODE> - if an input or output error occurs
                                while the servlet is handling the