check Tomcat version when webapp is deployed

[vladak]

We can check Tomcat version in WebappListener#contextInitialized() with application.getServerInfo() (http://stackoverflow.com/questions/14925073/how-to-find-out-running-tomcat-version)

Granted, this will not help for issues like #1303 where Tomcat's JSP compiler is instructed to compile with older Java version but better than nothing and complements the recently added check for Java version in cset 4b511ed.

[vladak]

The method lives in org.apache.catalina.util.ServerInfo in Tomcat 8 so it can be used like this:

--- a/src/org/opensolaris/opengrok/web/WebappListener.java
+++ b/src/org/opensolaris/opengrok/web/WebappListener.java
@@ -66,6 +66,19 @@ public final class WebappListener
         ServletContext context = servletContextEvent.getServletContext();
         RuntimeEnvironment env = RuntimeEnvironment.getInstance();
 
+        // Check Tomcat version.
+        String serverInfo = context.getServerInfo();
+        if (serverInfo.contains("Tomcat")) {
+            int idx;
+            if ((idx = serverInfo.indexOf('/')) > 0) {
+                String version = serverInfo.substring(idx + 1);
+                if (!version.startsWith("8.")) {
+                    // XXX make webapp return error page for all requests
+                    LOGGER.severe("Tomcat version not 8");
+                }
+            }
+        }
+        
         String config = context.getInitParameter("CONFIGURATION");
         if (config == null) {
             LOGGER.severe("CONFIGURATION section missing in web.xml");

[vladak]

Possibly the JSP compiler config could be somehow verified with org.apache.jasper.compiler

[vladak]

The net result of the check should be error page displayed for all OpenGrok JSPs.

[vladak]

The web.xml configuration (which includes the JSP compiler settings) seems to be stored in object returned by http://docs.oracle.com/javaee/6/api/javax/servlet/ServletContext.html#getJspConfigDescriptor%28%29 however that seems to be supported only since servlet 3.0 and OpenGrok currently uses version 2.5.

[vladak]

OpenGrok now actually requires Servlet API 3.0 so this can be revisited.

[vladak]

Instead of checking specific container flavor/version the web app should check context.getEffectiveMajorVersion() and/or JspFactory.getDefaultFactory().getEngineInfo().getSpecificationVersion()

[vladak]

This might be worthwhile to revisit given #4075 that basically prohibits using Tomcat 10.1.