httpservlet.html

javaservlet 2.4 spec api describe javaservlet 2.4 spec api describe

<A HREF="../../../javax/servlet/GenericServlet.html#getServletConfig()">getServletConfig</A>, 
<A HREF="../../../javax/servlet/GenericServlet.html#getServletContext()">getServletContext</A>, 
<A HREF="../../../javax/servlet/GenericServlet.html#getServletInfo()">getServletInfo</A>, 
<A HREF="../../../javax/servlet/GenericServlet.html#getServletName()">getServletName</A>, 
<A HREF="../../../javax/servlet/GenericServlet.html#init()">init</A>, 
<A HREF="../../../javax/servlet/GenericServlet.html#init(javax.servlet.ServletConfig)">init</A>, 
<A HREF="../../../javax/servlet/GenericServlet.html#log(java.lang.String)">log</A>, 
<A HREF="../../../javax/servlet/GenericServlet.html#log(java.lang.String, java.lang.Throwable)">log</A></CODE></TD>
</TR>
</TABLE>
&nbsp;<A NAME="methods_inherited_from_class_java.lang.Object"><!-- --></A>
<TABLE BORDER="1" CELLPADDING="3" CELLSPACING="0" WIDTH="100%">
<TR BGCOLOR="#EEEEFF" CLASS="TableSubHeadingColor">
<TD><B>Methods inherited from class java.lang.Object</B></TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD><CODE>clone, 
equals, 
finalize, 
getClass, 
hashCode, 
notify, 
notifyAll, 
toString, 
wait, 
wait, 
wait</CODE></TD>
</TR>
</TABLE>
&nbsp;
<P>

<!-- ============ FIELD DETAIL =========== -->


<!-- ========= CONSTRUCTOR DETAIL ======== -->

<A NAME="constructor_detail"><!-- --></A>
<TABLE BORDER="1" CELLPADDING="3" CELLSPACING="0" WIDTH="100%">
<TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor">
<TD COLSPAN=1><FONT SIZE="+2">
<B>Constructor Detail</B></FONT></TD>
</TR>
</TABLE>

<A NAME="HttpServlet()"><!-- --></A><H3>
HttpServlet</H3>
<PRE>
public <B>HttpServlet</B>()</PRE>
<DL>
<DD>Does nothing, because this is an abstract class.</DL>

<!-- ============ METHOD DETAIL ========== -->

<A NAME="method_detail"><!-- --></A>
<TABLE BORDER="1" CELLPADDING="3" CELLSPACING="0" WIDTH="100%">
<TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor">
<TD COLSPAN=1><FONT SIZE="+2">
<B>Method Detail</B></FONT></TD>
</TR>
</TABLE>

<A NAME="doGet(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)"><!-- --></A><H3>
doGet</H3>
<PRE>
protected void <B>doGet</B>(<A HREF="../../../javax/servlet/http/HttpServletRequest.html">HttpServletRequest</A>&nbsp;req,
                     <A HREF="../../../javax/servlet/http/HttpServletResponse.html">HttpServletResponse</A>&nbsp;resp)
              throws <A HREF="../../../javax/servlet/ServletException.html">ServletException</A>,
                     java.io.IOException</PRE>
<DL>
<DD>Called by the server (via the <code>service</code> method) to
 allow a servlet to handle a GET request. 

 <p>Overriding this method to support a GET request also
 automatically supports an HTTP HEAD request. A HEAD
 request is a GET request that returns no body in the
 response, only the request header fields.

 <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>The GET method should be safe, that is, without
 any side effects for which users are held responsible.
 For example, most form queries have no side effects.
 If a client request is intended to change stored data,
 the request should use some other HTTP method.

 <p>The GET method should also be idempotent, meaning
 that it can be safely repeated. Sometimes making a
 method safe also makes it idempotent. For example, 
 repeating queries is both safe and idempotent, but
 buying a product online or modifying data is neither
 safe nor idempotent. 

 <p>If the request is incorrectly formatted, <code>doGet</code>
 returns an HTTP "Bad Request" message.<DD><DL>
</DL>
</DD>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>req</CODE> - an <A HREF="../../../javax/servlet/http/HttpServletRequest.html"><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"><CODE>HttpServletResponse</CODE></A> object that
			contains the response the servlet sends
			to the client<DT><B>Throws:</B><DD>java.io.IOException - if an input or output error is 
				detected when the servlet handles
				the GET request<DD><A HREF="../../../javax/servlet/ServletException.html">ServletException</A> - if the request for the GET
					could not be handled<DT><B>See Also: </B><DD><A HREF="../../../javax/servlet/ServletResponse.html#setContentType(java.lang.String)"><CODE>ServletResponse.setContentType(java.lang.String)</CODE></A></DL>
</DD>
</DL>
<HR>

<A NAME="getLastModified(javax.servlet.http.HttpServletRequest)"><!-- --></A><H3>
getLastModified</H3>
<PRE>
protected long <B>getLastModified</B>(<A HREF="../../../javax/servlet/http/HttpServletRequest.html">HttpServletRequest</A>&nbsp;req)</PRE>
<DL>
<DD>Returns the time the <code>HttpServletRequest</code>
 object was last modified,
 in milliseconds since midnight January 1, 1970 GMT.
 If the time is unknown, this method returns a negative
 number (the default).

 <p>Servlets that support HTTP GET requests and can quickly determine
 their last modification time should override this method.
 This makes browser and proxy caches work more effectively,
 reducing the load on server and network resources.<DD><DL>
</DL>
</DD>
<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">HttpServletRequest</A>&nbsp;req,
                      <A HREF="../../../javax/servlet/http/HttpServletResponse.html">HttpServletResponse</A>&nbsp;resp)
               throws <A HREF="../../../javax/servlet/ServletException.html">ServletException</A>,
                      java.io.IOException</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.<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>java.io.IOException - if an input or output error occurs<DD><A HREF="../../../javax/servlet/ServletException.html">ServletException</A> - 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">HttpServletRequest</A>&nbsp;req,
                      <A HREF="../../../javax/servlet/http/HttpServletResponse.html">HttpServletResponse</A>&nbsp;resp)
               throws <A HREF="../../../javax/servlet/ServletException.html">ServletException</A>,
                      java.io.IOException</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.<DD><DL>
</DL>
</DD>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>req</CODE> - an <A HREF="../../../javax/servlet/http/HttpServletRequest.html"><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"><CODE>HttpServletResponse</CODE></A> object that
			contains the response the servlet sends
			to the client<DT><B>Throws:</B><DD>java.io.IOException - if an input or output error is 
				detected when the servlet handles
				the request<DD><A HREF="../../../javax/servlet/ServletException.html">ServletException</A> - if the request for the POST
					could not be handled<DT><B>See Also: </B><DD><A HREF="../../../javax/servlet/ServletOutputStream.html"><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>