e1044. processing a head request in a servlet.txt

这里面包含了一百多个JAVA源文件

By default, a HEAD request is automatically processed by the HttpServlet.doGet() method using a modified response object that simply counts and discards any characters written to the buffer. If it is necessary to improve the performance of a servlet that is frequently accessed with a HEAD request method, you can override the HttServlet.doHead() method and implement a more efficient algorithm. Typically, a doHead() implementation sets the content length and type, as demonstrated by this example. 
Note: In the JWSDP 1.0, calling resetBuffer() does nothing in a HEAD request. Therefore, if resetBuffer() is used during servlet processing, a GET and HEAD request may return different content lengths. 

    // See also e1035 The Quintessential Servlet
    
    // This method is called by the servlet container to process a HEAD request.
    // There may be many threads calling this method simultaneously.
    public void doHead(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        // Set the content length and type
        resp.setContentLength(123);
        resp.setContentType("text/html");
    }

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