WebStack

Annotated tools/JavaServlet/classes/uk/org/boddie/webstack/util/PyServlet.java

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2005-11-26 paulb file changeset files shortlog [project @ 2005-11-26 01:15:51 by paulb] Fixed get_processed_virtual_path_info.
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package uk.org.boddie.webstack.util;
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import java.io.*;
 
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import java.util.*;
 
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import javax.servlet.*;
 
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import javax.servlet.http.*;
 
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import org.python.core.*;
 
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import org.python.util.PythonInterpreter;
 
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/**
 
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 * This servlet is used to re-serve JPython servlets.  It stores
 
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 * bytecode for JPython servlets and re-uses it if the underlying .py
 
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 * file has not changed.
 
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 * <p>
 
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 * Many people have been involved with this class:
 
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 * <ul>
 
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 * <li>Chris Gokey
 
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 * <li>David Syer
 
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 * <li>Finn Bock
 
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 * </ul>
 
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 * If somebody is missing from this list, let us know.
 
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 * <p>
 
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 *
 
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 * e.g. http://localhost:8080/test/hello.py
 
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 * <pre>
 
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 *
 
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 * from javax.servlet.http import HttpServlet
 
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 * class hello(HttpServlet):
 
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 *     def doGet(self, req, res):
 
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 *         res.setContentType("text/html");
 
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 *         out = res.getOutputStream()
 
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 *         print >>out, "<html>"
 
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 *         print >>out, "<head><title>Hello World, How are we?</title></head>"
 
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 *         print >>out, "<body>Hello World, how are we?"
 
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 *         print >>out, "</body>"
 
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 *         print >>out, "</html>"
 
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 *         out.close()
 
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 *         return
 
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 * </pre>
 
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 *
 
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 * in web.xml for the PyServlet context:
 
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 * <pre>
 
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 * &lt;web-app>
 
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 *     &lt;servlet>
 
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 *         &lt;servlet-name>PyServlet&lt;/servlet-name>
 
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 *         &lt;servlet-class>uk.org.boddie.webstack.util.PyServlet&lt;/servlet-class>
 
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 *         &lt;init-param>
 
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 *             &lt;param-name>python.home&lt;/param-name>
 
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 *             &lt;param-value>/usr/home/jython-2.1&lt;/param-value>
 
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 *         &lt;/init-param>
 
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 *         &lt;init-param>
 
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 *             &lt;param-name>servlet.file&lt;/param-name>
 
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 *             &lt;param-value>hello.py&lt;/param-value>
 
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 *         &lt;/init-param>
 
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 *     &lt;/servlet>
 
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 *     &lt;servlet-mapping>
 
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 *         &lt;servlet-name>PyServlet&lt;/servlet-name>
 
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 *         &lt;url-pattern>/*&lt;/url-pattern>
 
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 *     &lt;/servlet-mapping>
 
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 * &lt;/web-app>
 
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 *
 
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 * </pre>
 
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 */
 
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public class PyServlet extends HttpServlet {
 
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    private PythonInterpreter interp;
 
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    private Hashtable cache = new Hashtable();
 
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    private String rootPath;
 
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    private String servletFile = null;
 
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    public void init() {
 
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        rootPath = getServletContext().getRealPath("/");
 
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        if (!rootPath.endsWith(File.separator))
 
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            rootPath += File.separator;
 
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        Properties props = new Properties();
 
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        // Context parameters
 
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        ServletContext context = getServletContext();
 
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        Enumeration e = context.getInitParameterNames();
 
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        while (e.hasMoreElements()) {
 
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            String name = (String) e.nextElement();
 
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            props.put(name, context.getInitParameter(name));
 
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        }
 
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        // Config parameters
 
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        e = getInitParameterNames();
 
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        while (e.hasMoreElements()) {
 
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            String name = (String) e.nextElement();
 
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            props.put(name, getInitParameter(name));
 
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        }
 
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        if (props.getProperty("python.home") == null &&
 
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                                System.getProperty("python.home") == null) {
 
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            props.put("python.home", rootPath + "WEB-INF" +
 
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                                             File.separator + "lib");
 
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        }
 
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        // Define the servlet file.
 
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        servletFile = props.getProperty("servlet.file");
 
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        PythonInterpreter.initialize(System.getProperties(), props,
 
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                                     new String[0]);
 
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        reset();
 
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        PySystemState sys = Py.getSystemState();
 
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        sys.add_package("javax.servlet");
 
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        sys.add_package("javax.servlet.http");
 
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        sys.add_package("javax.servlet.jsp");
 
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        sys.add_package("javax.servlet.jsp.tagext");
 
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        sys.add_classdir(rootPath + "WEB-INF" +
 
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                          File.separator + "classes");
 
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        sys.add_extdir(rootPath + "WEB-INF" + File.separator + "lib", true);
 
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    }
 
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    /**
 
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     * Implementation of the HttpServlet main method.
 
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     * @param req the request parameter.
 
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     * @param res the response parameter.
 
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     * @exception ServletException
 
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     * @exception IOException
 
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     */
 
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    public void service(ServletRequest req, ServletResponse res)
 
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        throws ServletException, IOException
 
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    {
 
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        req.setAttribute("pyservlet", this);
 
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        String spath = (String)req.getAttribute(
 
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                                    "javax.servlet.include.servlet_path");
 
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        if (spath == null) {
 
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            spath = ((HttpServletRequest) req).getServletPath();
 
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            if (spath == null || spath.length() == 0) {
 
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                // Servlet 2.1 puts the path of an extension-matched
 
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                // servlet in PathInfo.
 
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                spath = ((HttpServletRequest) req).getPathInfo();
 
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            }
 
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        }
 
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        String rpath = getServletContext().getRealPath(spath);
 
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        interp.set("__file__", rpath);
 
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        // Instead of using the URL to find the Jython servlet, use a supplied
 
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        // property instead.
 
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        if (servletFile == null)
 
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            throw new ServletException("No servlet.file specified in configuration.");
 
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        HttpServlet servlet = getServlet(rootPath + servletFile);
 
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        if (servlet !=  null)
 
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            servlet.service(req, res);
 
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        else
 
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            throw new ServletException("No python servlet found for: " + rpath);
 
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    }
 
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    public void reset() {
 
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        destroyCache();
 
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        interp = new PythonInterpreter(null, new PySystemState());
 
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        cache.clear();
 
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        PySystemState sys = Py.getSystemState();
 
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        sys.path.append(new PyString(rootPath));
 
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        String modulesDir = rootPath + "WEB-INF" +
 
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                            File.separator + "jython";
 
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        sys.path.append(new PyString(modulesDir));
 
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    }
 
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    private synchronized HttpServlet getServlet(String path)
 
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        throws ServletException, IOException
 
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    {
 
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        CacheEntry entry = (CacheEntry) cache.get(path);
 
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        if (entry == null)
 
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            return loadServlet(path);
 
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        File file = new File(path);
 
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        if (file.lastModified() > entry.date)
 
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            return loadServlet(path);
 
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        return entry.servlet;
 
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    }
 
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    private HttpServlet loadServlet(String path)
 
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        throws ServletException, IOException
 
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    {
 
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        HttpServlet servlet = null;
 
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        File file = new File(path);
 
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        // Extract servlet name from path (strip ".../" and ".py")
 
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        int start = path.lastIndexOf(File.separator);
 
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        if (start < 0)
 
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            start = 0;
 
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        else
 
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            start++;
 
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        int end = path.lastIndexOf('.');
 
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        if ((end < 0) || (end <= start))
 
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            end = path.length();
 
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        String name = path.substring(start, end);
 
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        try {
 
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            interp.execfile(path);
 
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            PyObject cls = interp.get(name);
 
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            if (cls == null)
 
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                throw new ServletException("No callable (class or function) "+
 
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                                       "named " + name + " in " + path);
 
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            PyObject pyServlet = cls.__call__();
 
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            Object o = pyServlet.__tojava__(HttpServlet.class);
 
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            if (o == Py.NoConversion)
 
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                throw new ServletException("The value from " + name +
 
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                                       "must extend HttpServlet");
 
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            servlet = (HttpServlet)o;
 
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            servlet.init(getServletConfig());
 
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        } catch (PyException e) {
 
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            throw new ServletException("Could not create "+
 
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                                       "Jython servlet" + e.toString());
 
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        }
 
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        CacheEntry entry = new CacheEntry(servlet, file.lastModified());
 
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        cache.put(path, entry);
 
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        return servlet;
 
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    }
 
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    public void destroy() {
 
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        destroyCache();
 
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    }
 
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    private void destroyCache() {
 
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        for (Enumeration e = cache.elements(); e.hasMoreElements(); ) {
 
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            CacheEntry entry = (CacheEntry) e.nextElement();
 
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            entry.servlet.destroy();
 
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        }
 
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    }
 
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}
 
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class CacheEntry {
 
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    public long date;
 
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    public HttpServlet servlet;
 
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    CacheEntry(HttpServlet servlet, long date) {
 
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        this.servlet = servlet;
 
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        this.date = date;
 
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    }
 
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}