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The "HowTo/FasterStartUp" page has been changed by KonstantinKolinko: https://wiki.apache.org/tomcat/HowTo/FasterStartUp?action=diff&rev1=16&rev2=17 Comment: Correction: TLD scanning does occur at startup. I was confused that there are two TLD scans and the first one happens silently. These features require scanning the JAR files. The worst is scanning for annotated classes. There are a lot of class files to process and parsing a class file takes noticeable time. - It is possible to configure a web application to omit most of the scanning. It is also possible to configure which JARs Tomcat should skip in its scanning. + It is possible to configure a web application to omit most of the scanning. It is also possible to configure which JARs Tomcat should skip. Other features that require scanning are: - * Discovery of tag libraries (`META-INF/**/*.tld`) (shortened as TLD scanning) + * Discovery of tag libraries — scanning for Tag Library Descriptor files (`META-INF/**/*.tld`) (shortened as TLD scanning) - The TLD scanning happens when Tomcat needs to compile a JSP page. It does not affect the startup time, but does affect the access time for the first not-yet-compiled JSP page in the web application. + The TLD scanning is done at startup, because a library can define a `Listener` in its TLD file. + + A note: in Tomcat 7 and earlier the TLD scanning happens twice, (1) by servlet engine to discover the listeners, (2) by JSP engine when compiling a JSP page. The first scanning happens at startup time (in `TldConfig`), the second one happens when Tomcat needs to compile a JSP page (in `TldLocationsCache`). The second scanning is more noticeable, because it prints a diagnostic message about scanned JARs that contained no TLDs. In Tomcat 8 the TLD scanning happens only once at startup time (in `JasperInitializer`). + == Remove unnecessary JARs == @@ -37, +40 @@ 1. `metadata-complete="true"` attribute on the `<web-app>` element. 2. an empty `<absolute-ordering />` element. - "`metadata-complete="true"`" disables scanning your web application and its libraries for classes that use annotations to define components of a web application (Servlets etc.). This option is not enough to disable all of annotation scanning. If there is a SCI with a @HandlesTypes annotation, Tomcat has to scan your application for classes that use annotations or interfaces specified in that @HandlesTypes annotation and provide the list of such classes to the SCI. + Setting `metadata-complete="true"` disables scanning your web application and its libraries for classes that use annotations to define components of a web application (Servlets etc.). - An example of such SCI is in the WebSocket API implementation jar (`tomcat-websocket.jar`, `tomcat7-websocket.jar`) which is included with Tomcat 7 starting with 7.0.47. + The `metadata-complete` option is not enough to disable all of annotation scanning. If there is a SCI with a !HandlesTypes annotation, Tomcat has to scan your application for classes that use annotations or interfaces specified in that annotation. - The "`<absolute-ordering>`" element specifies which web fragment JARs (according to the names in their `WEB-INF/web-fragment.xml` files) have to be scanned for SCIs, fragments and annotations. If you specify an empty "`<absolute-ordering/>`" it means that none of that scanning will occur. This feature does not affect scanning for web application resources. + The `<absolute-ordering>` element specifies which web fragment JARs (according to the names in their `WEB-INF/web-fragment.xml` files) have to be scanned for SCIs, fragments and annotations. An empty `<absolute-ordering/>` element configures that none are to be scanned. + + Note: in Tomcat 8 the container-provided SCIs are always discovered, regardless of `absolute-ordering`. + + An example of a SCI is in the WebSocket API implementation jar (`tomcat-websocket.jar`, `tomcat7-websocket.jar`) which is included with Tomcat 7 starting with 7.0.47. + + Scanning for web application resources and TLD scanning are not affected by these options. == Exclude JARs from scanning == --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@tomcat.apache.org For additional commands, e-mail: dev-h...@tomcat.apache.org
