PrecompileAllJspsFilter.java

/**
 * http://pukkaone.github.com/2010/12/22/jsp-precompile-application-start.html
 * <p/>
 * Allows for all JSPs to be compiled with a single request to
 * http://localhost:8080/actrack/index.html?jsp_precompile_all
 * <p/>
 * Use a locking flag to make sure that this operation can only be run once (to prevent possible DoS attacks)
 *
 * @author barry
 * @since 2013/01/25 11:46 AM
 */
public class PrecompileAllJspsFilter implements Filter {

    private static final String PRECOMPILE_ALL_PARAMETER = "jsp_precompile_all";
    private ServletContextResourcePatternResolver resolver;
    private final AtomicBoolean hasRun = new AtomicBoolean(false);
    private static final Logger LOG = LoggerFactory.getLogger(PrecompileAllJspsFilter.class);

    public void init(FilterConfig config) throws ServletException {
        resolver = new ServletContextResourcePatternResolver(config.getServletContext());
    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) resp;

        if (request.getParameter(PRECOMPILE_ALL_PARAMETER) != null) {
            compileAllJsps(request, response);
            return;
        }
        chain.doFilter(req, resp);
    }

    private void compileAllJsps(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
        if (hasRun.getAndSet(true)) {
            LOG.warn("Skipping JSP compilation - already run once!");
            response.setStatus(200);
            return;
        }

        Resource[] jsps = resolver.getResources("/**/*.jsp");
        compile(request, response, jsps);
    }

    private void compile(HttpServletRequest request, HttpServletResponse response, Resource[] jsps) throws ServletException, IOException {
        LOG.info("Precompiling " + jsps.length + " JSPs");
        boolean anyErrors = false;
        for (Resource jsp : jsps) {
            try {
                String path = ((ServletContextResource) jsp).getPathWithinContext();
                LOG.info("Compiling " + path);
                request.getRequestDispatcher(path).include(new RequestWrapper(request), response);
            } catch (Exception e) {
                anyErrors = true;
                LOG.error(e.getMessage());
            }
        }
        response.setStatus(anyErrors ? 500 : 200);
    }

    public void destroy() {
    }

    private static class RequestWrapper extends HttpServletRequestWrapper {
        public RequestWrapper(HttpServletRequest request) {super(request);}

        @Override
        public String getQueryString() {
            return "jsp_precompile";
        }
    }
}