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Jython is an implementation of the high-level, dynamic, object-oriented
language Python written in 100% Pure Java, and seamlessly integrated with
the Java platform. It thus allows you to run Python on any Java platform.
package org.python.util;
import java.io.File;
import java.io.IOException;
import java.util.Enumeration;
import java.util.Map;
import java.util.Properties;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import org.python.core.PrePy;
import org.python.core.Py;
import org.python.core.PyException;
import org.python.core.PyObject;
import org.python.core.PyString;
import org.python.core.PyStringMap;
import org.python.core.PySystemState;
/**
* This servlet is used to re-serve Jython servlets. It stores bytecode for Jython servlets and
* re-uses it if the underlying .py file has not changed.
*
* e.g. {@code http://localhost:8080/test/hello.py}
*
{@literal
*
* from javax.servlet.http import HttpServlet
* class hello(HttpServlet):
* def doGet(self, req, res):
* res.setContentType("text/html");
* out = res.getOutputStream()
* print >>out, ""
* print >>out, "Hello World, How are we? "
* print >>out, "Hello World, how are we?"
* print >>out, ""
* print >>out, ""
* out.close()
* }
*
* in web.xml for the PyServlet context:
* {@literal
*
*
* PyServlet
* org.python.util.PyServlet
*
* python.home
* /usr/home/jython-2.5
*
*
*
* PyServlet
* *.py
*
*
* }
*/
public class PyServlet extends HttpServlet {
public static final String SKIP_INIT_NAME = "skip_jython_initialization";
protected static final String INIT_ATTR = "__jython_initialized__";
@Override
public void init() {
Properties props = new Properties();
// Config parameters
Enumeration e = getInitParameterNames();
while (e.hasMoreElements()) {
String name = (String)e.nextElement();
props.put(name, getInitParameter(name));
}
boolean initialize = getServletConfig().getInitParameter(SKIP_INIT_NAME) != null;
if (getServletContext().getAttribute(INIT_ATTR) != null) {
if (initialize) {
System.err.println("Jython has already been initialized in this context, not "
+ "initializing for " + getServletName() + ". Add " + SKIP_INIT_NAME
+ " to as an init param to this servlet's configuration to indicate this "
+ "is expected.");
}
} else if (initialize) {
init(props, getServletContext());
}
reset();
}
/**
* PyServlet's initialization can be performed as a ServletContextListener or as a regular
* servlet, and this is the shared init code. If both initializations are used in a single
* context, the system state initialization code only runs once.
*/
protected static void init(Properties props, ServletContext context) {
String rootPath = getRootPath(context);
context.setAttribute(INIT_ATTR, true);
Properties baseProps = PrePy.getSystemProperties();
// Context parameters
Enumeration e = context.getInitParameterNames();
while (e.hasMoreElements()) {
String name = (String)e.nextElement();
props.put(name, context.getInitParameter(name));
}
if (props.getProperty("python.home") == null
&& baseProps.getProperty("python.home") == null) {
props.put("python.home", rootPath + "WEB-INF" + File.separator + "lib");
}
PySystemState.initialize(baseProps, props, new String[0]);
PySystemState.add_package("javax.servlet");
PySystemState.add_package("javax.servlet.http");
PySystemState.add_package("javax.servlet.jsp");
PySystemState.add_package("javax.servlet.jsp.tagext");
PySystemState.add_classdir(rootPath + "WEB-INF" + File.separator + "classes");
PySystemState.add_extdir(rootPath + "WEB-INF" + File.separator + "lib", true);
}
protected static PythonInterpreter createInterpreter(ServletContext servletContext) {
String rootPath = getRootPath(servletContext);
PySystemState sys = new PySystemState();
PythonInterpreter interp = new PythonInterpreter(Py.newStringMap(), sys);
sys.path.append(new PyString(rootPath));
String modulesDir = rootPath + "WEB-INF" + File.separator + "jython";
sys.path.append(new PyString(modulesDir));
return interp;
}
protected static String getRootPath(ServletContext context) {
String rootPath = context.getRealPath("/");
if (!rootPath.endsWith(File.separator)) {
rootPath += File.separator;
}
return rootPath;
}
@Override
public void service(ServletRequest req, ServletResponse res)
throws ServletException, IOException
{
req.setAttribute("pyservlet", this);
String spath = (String) req.getAttribute("javax.servlet.include.servlet_path");
if (spath == null) {
spath = ((HttpServletRequest)req).getServletPath();
if (spath == null || spath.length() == 0) {
// Servlet 2.1 puts the path of an extension-matched servlet in PathInfo.
spath = ((HttpServletRequest)req).getPathInfo();
}
}
String rpath = getServletContext().getRealPath(spath);
getServlet(rpath).service(req, res);
}
@Override
public void destroy() {
super.destroy();
destroyCache();
}
/**
* Clears the cache of loaded servlets and makes a new PythonInterpreter to service further
* requests.
*/
public void reset() {
destroyCache();
interp = createInterpreter(getServletContext());
}
private synchronized HttpServlet getServlet(String path)
throws ServletException, IOException
{
CacheEntry entry = cache.get(path);
if (entry == null || new File(path).lastModified() > entry.date) {
return loadServlet(path);
}
return entry.servlet;
}
private HttpServlet loadServlet(String path)
throws ServletException, IOException
{
File file = new File(path);
HttpServlet servlet = createInstance(interp, file, HttpServlet.class);
try {
servlet.init(getServletConfig());
} catch (PyException e) {
throw new ServletException(e);
}
cache.put(path, new CacheEntry(servlet, file.lastModified()));
return servlet;
}
protected static T createInstance(PythonInterpreter interp, File file, Class type)
throws ServletException {
Matcher m = FIND_NAME.matcher(file.getName());
if (!m.find()) {
throw new ServletException("I can't guess the name of the class from "
+ file.getAbsolutePath());
}
String name = m.group(1);
try {
interp.set("__file__", file.getAbsolutePath());
interp.execfile(file.getAbsolutePath());
PyObject cls = interp.get(name);
if (cls == null) {
throw new ServletException("No callable (class or function) named " + name + " in "
+ file.getAbsolutePath());
}
PyObject pyServlet = cls.__call__();
Object o = pyServlet.__tojava__(type);
if (o == Py.NoConversion) {
throw new ServletException("The value from " + name + " must extend "
+ type.getSimpleName());
}
@SuppressWarnings("unchecked")
T asT = (T)o;
return asT;
} catch (PyException e) {
throw new ServletException(e);
}
}
private void destroyCache() {
for (CacheEntry entry : cache.values()) {
entry.servlet.destroy();
}
cache.clear();
}
private static class CacheEntry {
public long date;
public HttpServlet servlet;
CacheEntry(HttpServlet servlet, long date) {
this.servlet= servlet;
this.date = date;
}
}
private static final Pattern FIND_NAME = Pattern.compile("([^/]+)\\.py$");
private PythonInterpreter interp;
private Map cache = Generic.map();
}