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<TITLE>Getting a Request Header in a Servlet
(Java Developers Almanac Example)
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<META CONTENT="Patrick Chan" NAME="AUTHOR">
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<B><A HREF="../javax.servlet/pkg.html">javax.servlet</A></B><font color="#666666" SIZE="-2">
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<B><A HREF="../javax.servlet/pkg.html#Requests">Requests</A></B><font color="#666666" SIZE="-2">
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<h3>
e1042.
Getting a Request Header in a Servlet</h3>
This example demonstrates how to get the value of a request header
in either a GET or POST request.
<pre>
// See also <a href="../javax.servlet/com_mycompany_MyServlet.html" class="eglink"><font size="-1"><b>e1034</b> The Quintessential Servlet</font></a>
// This method is called by the servlet container to process a GET request.
public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
doGetOrPost(req, resp);
}
// This method is called by the servlet container to process a POST request.
public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
doGetOrPost(req, resp);
}
// This method handles both GET and POST requests.
private void doGetOrPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
PrintWriter out = resp.getWriter();
resp.setContentType("text/plain");
// Get the value of a request header; the name is case-insensitive
String name = <font color="#0066ff"><i>"user-agent"</i></font>;
String value = req.getHeader(name);
if (value == null) {
// The request header was not present
}
// Get all request headers
Enumeration enum = req.getHeaderNames();
for (; enum.hasMoreElements(); ) {
// Get the name of the request header
name = (String)enum.nextElement();
out.println(name);
// Get a value of the request header
value = req.getHeader(name);
// If the request header can appear more than once, get all values
Enumeration valuesEnum = req.getHeaders(name);
for (; valuesEnum.hasMoreElements(); ) {
// Get a value of the request header
value = (String)valuesEnum.nextElement();
out.println(" "+value);
}
}
out.close();
}
</pre>
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Related Examples
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e1039. <a class="eglink" href="GetReqParam.html?l=rel">
Getting a Request Parameter in a Servlet
</a>
<br>
e1040. <a class="eglink" href="NoMulti.html?l=rel">
Preventing Concurrent Requests to a Servlet
</a>
<br>
e1041. <a class="eglink" href="GetReqUrl.html?l=rel">
Getting the Requesting URL in a Servlet
</a>
<br>
e1043. <a class="eglink" href="DoHead.html?l=rel">
Processing a HEAD Request in a Servlet
</a>
<br>
e1044. <a class="eglink" href="GetClientInfo.html?l=rel">
Getting the Client's Address in a Servlet
</a>
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