javax.servlet.Filter, and
+ * to insert them in your servlet container's filter chain, like any Java Filter.
+ *
+ * + * Example: + * + *
+ * /WEB-INF/filters/HeaderFilter.py: + * + *
+ * from javax.servlet import Filter
+ *
+ * # Module must contain a class with the same name as the module
+ * # which in turn must implement javax.servlet.Filter
+ * class HeaderFilter (Filter):
+ * def init(self, config): self.header = config.getInitParameter('header')
+ *
+ * def destroy(self): pass
+ *
+ * def doFilter(self, request, response, chain):
+ * response.setHeader(self.header, "Yup")
+ * chain.doFilter(request, response)
+ *
+ *
+ * + * web.xml: + *
+ * + *+ * <!-- PyFilter depends on PyServlet --> + * <servlet> + * <servlet-name>PyServlet</servlet-name> + * <servlet-class>org.python.util.PyServlet</servlet-class> + * <load-on-startup>1</load-on-startup> + * </servlet> + * + * <!-- Declare a uniquely-named PyFilter --> + * <filter> + * <filter-name>HeaderFilter</filter-name> + * <filter-class>org.jython.util.PyFilter</filter-class> + * + * <!-- The special param __filter__ gives the context-relative path to the Jython source file --> + * <init-param> + * <param-name>__filter__</param-name> + * <param-value>/WEB-INF/pyfilter/HeaderFilter.py</param-value> + * </init-param> + * + * <!-- Other params are passed on the the Jython filter --> + * <init-param> + * <param-name>header</param-name> + * <param-value>X-LookMaNoJava</param-value> + * </init-param> + * </filter> + * <filter-mapping> + * <filter-name>HeaderFilter</filter-name> + * <url-pattern>/*</url-pattern> + * </filter-mapping> + *+ * + *
+ * PyFilter depends on initialization code from PyServlet being run. If PyServlet is used to serve + * pages, this code will be executed and PyFilter will work properly. However, if you aren't using + * PyServlet, and wouldn't like to include it as a servlet that isn't serving pages, PyServlet's + * initialization code can be invoked as a ServletContextListener instead of as an HttpServlet. Use + * the following in web.xml instead of a servlet tag: + * + *
+ * <listener> + * <listener-class>org.python.util.PyServlet</listener-class> + * <load-on-startup>1</load-on-startup> + * </listener> + *+ * + */ +public class PyFilter implements Filter { + + private static final String FILTER_PATH_PARAM = "__filter__"; + + private PythonInterpreter interp; + + FilterConfig filterConfig; + + private File filterSource; + + Filter cachedFilter; + + long timeLoaded = -1; + + public void doFilter(final ServletRequest request, + final ServletResponse response, + final FilterChain chain) throws IOException, ServletException { + request.setAttribute("pyfilter", this); + getFilter().doFilter(request, response, chain); + } + + public void init(final FilterConfig filterConfig) throws ServletException { + this.filterConfig = filterConfig; + final String filterPath = filterConfig.getInitParameter(FILTER_PATH_PARAM); + if (filterPath == null) { + throw new ServletException("Missing required param '" + + FILTER_PATH_PARAM + "'"); + } + filterSource = new File(getRealPath(filterConfig.getServletContext(), filterPath)); + if (!filterSource.exists()) { + throw new ServletException(filterSource.getAbsolutePath() + " does not exist."); + } + interp = new PythonInterpreter(null, new PySystemState()); + interp.set("__file__", filterSource.getAbsolutePath()); + interp.exec("import sys; sys.path.append('" + + getRealPath(filterConfig.getServletContext(), "/WEB-INF/jython/") + "')\n"); + } + + private String getRealPath(ServletContext context, final String appPath) { + final String realPath = context.getRealPath(appPath); + // This madness seems to be necessary on Windows + return realPath.replaceAll("\\\\", "/"); + } + + private Filter getFilter() throws ServletException, IOException { + if (cachedFilter == null || filterSource.lastModified() > timeLoaded) { + return loadFilter(); + } + return cachedFilter; + } + + private static final Pattern FIND_NAME = Pattern.compile("([^/]+)\\.py$"); + + private Filter loadFilter() throws ServletException, IOException { + cachedFilter = null; + try { + interp.execfile(filterSource.getAbsolutePath()); + final Matcher m = FIND_NAME.matcher(filterSource.getName()); + if (!m.find()) { + throw new ServletException("I can't guess the name of the filter class from " + + filterSource); + } + final String className = m.group(1); + final PyObject cls = interp.get(className); + if (cls == null) { + throw new ServletException("No class " + className + " in " + filterSource); + } + final Object pythonFilter = cls.__call__().__tojava__(Filter.class); + if (pythonFilter == Py.NoConversion) { + throw new ServletException(cls + " must extend javax.servlet.Filter"); + } + cachedFilter = (Filter)pythonFilter; + cachedFilter.init(filterConfig); + timeLoaded = new Date().getTime(); + } catch (final PyException e) { + throw new ServletException(e); + } + return cachedFilter; + } + + public void destroy() { + if (cachedFilter != null) { + cachedFilter.destroy(); + } + cachedFilter = null; + if (interp != null) { + interp.cleanup(); + } + interp = null; + filterSource = null; + } +}