/**
 * Implementation of a request processor which delegates the processing to a
 * Coyote processor.
 *
 * @author Craig R. McClanahan
 * @author Remy Maucherat
 * @version $Revision: 1.26 $ $Date: 2004/05/14 11:00:25 $
 */

public class CoyoteAdapter
    implements Adapter 
 {
    private static Log log = LogFactory.getLog(CoyoteAdapter.class);

    /**
     * The match string for identifying a session ID parameter.
     */
    private static final String match =
        ";" + Globals.SESSION_PARAMETER_NAME + "=";

    /**
     * Parse session id in URL.
     */
    protected void parseSessionId(Request req, CoyoteRequest request) {

        CharChunk uriCC = req.decodedURI().getCharChunk();
        int semicolon = uriCC.indexOf(match, 0, match.length(), 0);

        if (semicolon > 0) {

            // Parse session ID, and extract it from the decoded request URI
            int start = uriCC.getStart();
            int end = uriCC.getEnd();

            int sessionIdStart = start + semicolon + match.length();
            int semicolon2 = uriCC.indexOf(';', sessionIdStart);
            if (semicolon2 >= 0) {
                request.setRequestedSessionId
                    (new String(uriCC.getBuffer(), sessionIdStart, 
                                semicolon2 - semicolon - match.length()));
            } else {
                request.setRequestedSessionId
                    (new String(uriCC.getBuffer(), sessionIdStart, 
                                end - sessionIdStart));
            }
            request.setRequestedSessionURL(true);

            // Extract session ID from request URI
            ByteChunk uriBC = req.requestURI().getByteChunk();
            start = uriBC.getStart();
            end = uriBC.getEnd();
            semicolon = uriBC.indexOf(match, 0, match.length(), 0);

            if (semicolon > 0) {
                sessionIdStart = start + semicolon;
                semicolon2 = uriCC.indexOf
                    (';', start + semicolon + match.length());
                uriBC.setEnd(start + semicolon);
                byte[] buf = uriBC.getBuffer();
                if (semicolon2 >= 0) {
                    for (int i = 0; i < end - start - semicolon2; i++) {
                        buf[start + semicolon + i] 
                            = buf[start + i + semicolon2];
                    }
                    uriBC.setBytes(buf, start, semicolon 
                                   + (end - start - semicolon2));
                }
            }

        } else {
            request.setRequestedSessionId(null);
            request.setRequestedSessionURL(false);
        }

    }


    /**
     * Parse session id in URL.
     */
    protected void parseSessionCookiesId(Request req, CoyoteRequest request) {

        // Parse session id from cookies
        Cookies serverCookies = req.getCookies();
        int count = serverCookies.getCookieCount();
        if (count <= 0)
            return;

        for (int i = 0; i < count; i++) {
            ServerCookie scookie = serverCookies.getCookie(i);
            if (scookie.getName().equals(Globals.SESSION_COOKIE_NAME)) {
                // Override anything requested in the URL
                if (!request.isRequestedSessionIdFromCookie()) {
                    // Accept only the first session id cookie
                    request.setRequestedSessionId
                        (scookie.getValue().toString());
                    request.setRequestedSessionCookie(true);
                    request.setRequestedSessionURL(false);
                    if (log.isDebugEnabled())
                        log.debug(" Requested cookie session id is " +
                            ((HttpServletRequest) request.getRequest())
                            .getRequestedSessionId());
                } else {
                    if (!request.isRequestedSessionIdValid()) {
                        // Replace the session id until one is valid
                        request.setRequestedSessionId
                            (scookie.getValue().toString());
                    }
                }
            }
        }

    }
}

public final class Globals {
    /**
     * The name of the cookie used to pass the session identifier back
     * and forth with the client.
     */
    public static final String SESSION_COOKIE_NAME = "JSESSIONID";


    /**
     * The name of the path parameter used to pass the session identifier
     * back and forth with the client.
     */
    public static final String SESSION_PARAMETER_NAME = "jsessionid";

}

3.3，response.encodeURL做了什么

public class CoyoteResponse
    implements HttpResponse, HttpServletResponse {
	protected CoyoteRequest request = null; 
	/*******************在此隐藏N行******/
    /**
     * Encode the session identifier associated with this response
     * into the specified URL, if necessary.
     *
     * @param url URL to be encoded
     */
    public String encodeURL(String url) {
        
        String absolute = toAbsolute(url);
        if (isEncodeable(absolute)) {
            HttpServletRequest hreq =
                (HttpServletRequest) request.getRequest();
            
            // W3c spec clearly said 
            if (url.equalsIgnoreCase("")){
                url = absolute;
            }
            return (toEncoded(url, hreq.getSession().getId()));
        } else {
            return (url);
        }

    }

    /**
     * Return the specified URL with the specified session identifier
     * suitably encoded.
     *
     * @param url URL to be encoded with the session id
     * @param sessionId Session id to be included in the encoded URL
     */
    private String toEncoded(String url, String sessionId) {

        if ((url == null) || (sessionId == null))
            return (url);

        String path = url;
        String query = "";
        String anchor = "";
        int question = url.indexOf('?');
        if (question >= 0) {
            path = url.substring(0, question);
            query = url.substring(question);
        }
        int pound = path.indexOf('#');
        if (pound >= 0) {
            anchor = path.substring(pound);
            path = path.substring(0, pound);
        }
        StringBuffer sb = new StringBuffer(path);
        if( sb.length() > 0 ) { // jsessionid can't be first.
            sb.append(";jsessionid=");
            sb.append(sessionId);
        }
        sb.append(anchor);
        sb.append(query);
        return (sb.toString());

    }

}