I am trying to do a log4j migration for a legacy application. I made the changes to the configuration files and tested it locally with Tomcat, where the logs were displayed correctly. However when I deploy on WAS, the logging stops.
I checked a lot of pages about the necessary dependencies and the possible problems, but now I feel I'm stuck. Here is what I already tried:
Added the log4j jars manually to the lib/ext directory in WAS (together with commons-logging, I read an article where it helped, although all these jar-s were already present in the ear)
Double checked, that the configuration file is on the classpath and that it's syntax is correct
Added logj42-web dependency
Added the necessary filters in web.xml (Spring version is 3.8, so also the config listener with the config name context-param)
Checked classloader in WAS - it's parent first
Am I missing something?
Any ideas are appreciated. Thank you in advance!
WAS includes its own commons-logging API (that does not utilize Log4j), so bringing your own logger requires a bit of extra class-loader-related config. Typically, that would go something like this:
Put your commons-logging and log4j jars, along with your logging properties files, in some directory (not WAS_HOME/lib/ext) readable by the user running the server.
Create a shared library on the server, with that directory as its class path, and select the "use an isolated class loader" option. Associate that shared library with your application or web module.
Ideally, that should be it. Isolated shared libraries search themselves before delegating to the server's loaders, so your application will "see" the commons-logging/log4j classes in the shared library instead of in the server, and likewise, it should pick up the configuration files from that directory instead of the ones found in the server.
You can also accomplish this same basic thing by leaving all the logging stuff in your WAR or EAR and setting its class loader to parent-last (which causes the class loader to search locally before delegating to the server-level loaders), but that is a bit riskier configuration - if your application includes APIs that are also provided by the server, parent-last class loading increases the possibility of ClassCastExceptions or LinkageErrors.
Related
The project artifact structure is:
test.ear
--lib - has all log4j2 jars core, web, bridge and JCL
--META-INF -- has app.xml, JBoss specific deployment XML, and manifest file
--a.war -- each war has web.xml with log4jConfiguration and Log4jServletContextListener specified.
--b.war
--c.war
The war creates context with log4jConfiguration, which is "classpath:test.xml". I can see each war creating the context with log4jContextName I have provided in web.xml.I have a few crons, too, which run based on configured time intervals. When crons run, and many of the JMS process run, I observed the log files are not populated with logs(From project-specific classes). While going through the log4j2 code, I understood that log4j2 creates a context for each classloader. And in my case, it creates a context for "test.ear", which is defaulted to error(DefaultContext) as it is not able to find a default log4j2.xml since I have a custom named(test.xml) on in the classpath. The Log4jServletContextListener does not catch the "test.ear" event.
How to inject my "classpath:test.xml" while log4j2 creates a context for the ear file? Since my project can be both deployed to WebSphere and JBoss, I am looking forward to suggestions that are not server-specific. Or is there a way to create a single context for all the war and ear somehow? I have different apps outside this ear in same server so I cannot give an environmental config of -Dlog4j.configurationFile as other apps have there own log4j2 xml's.
One approach that I can think of is to place your log4j config file test.xml in a shared library and configure your application to use the shared library.
The following link describes how to configure a shared library for a server or an enterprise application on WebSphere.
https://www.ibm.com/support/pages/how-create-shared-library-and-associate-it-application-server-or-enterprise-application-websphere-application-server
The shared library should be a generic function for modern Java app servers, so JBoss should also be able to configure this.
I am creating a library using spring-boot (v2.1.6.RELEASE) as a starter project that will facilitate as base extension jar responsible for configuring and starting up some of the components based on client project properties file.
The issue I am facing is that if the client project's SpringBoot Application class contains the same package path as library everything works like charm! but when client project contains different package path and includes ComponentScan, it is not able to load or start components from the library.
Did anyone encounter this issue? how to make client application to auto-configure some of the components from library jar?
Note: I am following the library creation example from here: https://www.baeldung.com/spring-boot-custom-starter
There are many things that can go wrong here, without seeing relevant parts of actual code its hard to tell something concrete. Out of my head, here are a couple of points for consideration that can hopefully lead to the solution:
Since we use starters in our applications (and sometimes people use explicit component scanning in there spring applications) and this obviously works, probably the issue is with the starter module itself. Don't think that the fact that the component scan is used alone prevents the starter from being loaded ;)
Make sure the starter is a: regular library and not packaged as a spring boot application (read you don't use spring boot plugin) and have <packaging>jar</packaging> in your pom.xml or whatever you use to build.
Make sure you have: src/main/resources/META-INF/spring.factories file
(case sensitive and everything)
Make sure that this spring.factories file indeed contains a valid reference on your configuration (java class annotated with #Configuration). If you use component scanning in the same package, it will find and load this configuration even without spring factories, in this case, its just kind of another portion of your code just packaged as a separate jar. So this looks especially "suspicious" to me.
Make sure that #Configuration doesn't have #Conditional-something - maybe this condition is not obeyed and the configuration doesn't start. For debugging purposes maybe you even should remove these #Conditional annotations just to ensure that the Configuration starts. You can also provide some logging inside the #Configuration class, like: "loading my cool library".
I'm working on a project that uses two maven projects (named core and webapp); core is built with JAR packaging and used for two different purposes: as a stand-alone app (essentially an executable JAR), and also embedded into webapp.
For its purpose as a stand-alone app, core needs to have its own logback configuration (a logback.xml file) that needs to be included on the classpath. Normal Maven convention would have me put it in src/main/resources/logback.xml. That works fine, but causes a problem when the core JAR is included in webapp. webapp needs to have its own logback configuration, but the container (tc Server or Jetty) is picking up the one from core.jar first.
I realize that logback can be told about a custom config location via a system property (-D on the command line) but that's not viable in a app container like Tomcat or Jetty.
I've read some other people asking about this situation, but none of the solutions I've seen sits well with me. One solution involved setting up a context listener that runs early in the webapp initialization and explicitly configures logback based on a <context-param>. That's a bit brutish in my opinion, and probably a hard sell to my fellow dev team when log4j "just works" in this situation.
I'm far from a Maven expert, so I'm hoping there is some elegant way to get Maven to help me here. Or perhaps some logback extension or add-on that makes it more web-app friendly. Or even a clever idea that I haven't thought of.
There are a number of possible solutions, but the easiest is to put the file in its own module and mark the dependency as provided. The, conspire to have it on the classpath when running the standalone version of the app.
The solution that we ended up using was to leave only the common "non-app" pieces (code and configuration) in core and then extract the other "app" pieces into a new module (batch-app).
The logging configuration only lives in the 2 app projects (webapp and batch-app) that depend on core. core has a logback-test.xml configuration in it, but that's excluded from the JAR that maven builds (since it's in the src/test/resources folder).
Is there a way to make the Websphere Application Server use the jar places inside the application's WEB-INF/libs folder and ignore the one that available within the server's plugin folder.
I am using EMF in my application and the version provided in the server doesn't include support for EMF GenericType, so I want to make the application use the jar file inside the libs folder.
Thanks for any help
This is quite possible. You need to change the classloading order from parent first to parent last. This will cause it to consult the server runtimes version of the code after your application. This is documented in the infocenter.
Another approach you might want to consider is to use an isolated shared library. There is a good introduction for those in IBM Education Assistant. These are more complex to setup, but using parent last classloading order can sometimes cause unexpected side effects that don't occur with isolated shared libraries.
I am working on a custom session manager for Tomcat and I got it working with one caveat, I have to put the jar(and all the associated jars) in the CATALINA_HOME/lib directory or I get a noclassdef found exception, even though the classes are in the WEB-INF/lib directory.
Is there any way to force tomcat to look in the web apps lib directory when it is loading a session manager? Putting it in the lib directory is error-prone(as you have to remember to copy the jar over when upgrading and/or installing on a new system) and makes development of the jar more difficult.
As of Tomcat 7.0.27, the <Manager> element in your META-INF/context.xml file is processed by the commons-digester and the effective ClassLoader is set to that which loaded the ContextConfig class -- one which firmly resides in Tomcat's server ClassLoader, which is outside of the ClassLoading chain of anything with access to the webapp's classes.
So, without modifying the Tomcat source, there will be no way to load your Manager from within your webapp. Consider joining the Tomcat users' mailing list to discuss such a feature.
EDIT 2015-067-01
If you want to specify a ClassLoader for your web application, you'll need to use the <Loader> element within your <Context>: http://tomcat.apache.org/tomcat-8.0-doc/config/loader.html