I'm doing some clean-ups in a GWT (no maven) project. It has a lot of jars added in WEB-INF/lib. I know the purpose of those jars (for example for REST service - luckily it's documented) so I wanted to put them in appropriate subfolders for nicer look.
After re-adding them to build path (as now they are in subfolders) I tried to run SuperDevMode and got multiple warnings:
Server class 'X' could not be found in the web app, but was found on the system classpath
and some errors like:
Cannot find a default implementation of the HK2 ServiceLocatorGenerator
When I put those jars back in WEB-INF/lib (without subfolders) and re-add to build path everything runs just fine.
My question is: can't/should't I use subfolders in WEB-INF/lib? If so, why?
Server class loader is programmed to look only into WEB-INF/lib, not other folder nor subfolders.
I strongly suggest to get into the maven world, it has a steep learning curve but it will assure to your project a solid foundation to grow on. Another big plus of Maven is that it can automatically pick up the latest security patch of your libraries (Equifax, anyone?).
Extract from the Apache Tomcat 7 Docs:
WebappX — A class loader is created for each web application that is deployed in a single Tomcat instance. All unpacked classes and resources in the /WEB-INF/classes directory of your web application, plus classes and resources in JAR files under the /WEB-INF/lib directory of your web application, are made visible to this web application, but not to other ones.
Related
Eclipse's Web Tools Platform (WTP) allows you to configure Tomcat to "Server modules without publishing":
Web content will be served directly from the "WebContent" folder of the Dynamic Web Project. A customized context is used to make the project's dependencies available in the Web application's classloader.
In a 5 step process (just joking, you pick the # of steps), what happens technically and where are the files that Eclipse generates? I did notice that Eclipse generated a org.eclipse.jst.server.tomcat.runtime.70.loader.jar file in the Tomcat lib directory.
The idea is to serve a web application directly from the scattered directory structure of the development workspace, without packaging modules into JARs which then end up in WEB-INF/lib in a WAR.
The main benefits are:
You don't need to build archives.
When you change a resource in your workspace, the change is reflected in the running webapp without redeploying the webapp or restarting the server.
With Servlet 3.0, web resources may also be bundled in library JARs in META-INF/resources, so classes and resources may come from multiple workspace directories.
Tomcat 7.0 supports a VirtualWebappLoader and a VirtualDirContext to configure a web application based on a collection of scattered resource and class directories.
To serve your web app directly from your Eclipse workspace, WTP generates a suitable Tomcat configuration matching your project structure
in $WORKSPACE/.metadata/.plugins/org.eclipse.wst.server.core/tmp1/conf/server.xml
For some reason, WTP does not directly use the Tomcat loader and context implementations but has its own WtpDirContext and WtpWebappLoader which are slightly different but similar. (I believe this approach is older than the current solution in Tomcat. There is some special logic for TLD scanning - I'm not sure if this is still required with the latest Tomcat versions.) These helper classes are contained in the org.eclipse.jst.server.tomcat.runtime.70.loader.jar you noticed.
Without Serve modules without publishing, when you change a web resource in META-INF/resources in a library module, this change will not be directly visible in the running application after reloading the current page in the browser.
Hullo - issue is this:
I wrote a servlet in Eclipse which requires mysql-connector-java-5.1.22-bin.jar
To compile I need to add the jar via the project's "Java Build Path"
To deploy I need to add the jar to the project's "Deployment Assembly"
To run the servlet within eclipse I need to add the jar to the servlet's Run Configuration -> Classpath
It's not the end of the world re-re-repeating myself like this, but it does seem odd.
Given that Eclipse gets a lot of other stuff correct I'm guessing / hoping that maybe I'm overlooking some feature to avoid this silliness (I cannot imagine a scenario where you'd benefit from entering this in 3 different spots ... but maybe I'm being uncreative here ...).
Insights appreciated :-)
The only thing you need to do is to drop the jar in WebContent/WEB-INF/lib.
You are developing a Java Web project, so the traditional place to put the required libs (JAR files etc) is under /WEB-INF/lib. And you do it only once.
In Eclipse, when you create Dynamic Web Project the appropriate project structure is generated for you (this is a development structure). In this case you place your JAR files in ProjectName/WebContent/WEB-INF/lib folder. And this folder is *automatically included in the project's build path.
Considering the fact that it is a Java Web project (you said you use servlets) you have to deploy your web app to some Application Server, like GlassFish, JBoss, WebLogic, WebSphere etc, or more simple Web Container like Apache Tomcat. If you do this thru Eclipse, then again your web project is automatically deployed.
NB!
There may be some additional details related to using libraries.
For instance, when it comes to using database drivers (MySql, PostgreSQL, Oracle etc) Tomcat advises the following while configuring JNDI Datasource (quote):
Before you proceed, don't forget to copy the JDBC Driver's jar into
$CATALINA_HOME/lib
In your case (MySQL) see the example here: MySQL DBCP Example
Also see my answer related to Webapp configuration file organization convention.
Hope this will help you.
P.S. Here is a step-by-step example: How do I access MySQL from a web application?
I am developing a Java EE 6 bottom-up JAX-WS to expose an EJB3.1 stateless session bean. The web service in a WAR is failing to install on deployment because it references an external jar (or shared library) which one can assume is not loaded yet.
The common suggestion is to include the jars in the /lib folder, which does fix the issue, however the jars need to remain in this external shared library location and NOT in the ear file, because they amount to 30MB.
What are some techniques to get around this issue in a Websphere (WAS v.8) environment or any server environment.
Some suggestions I have found include:
1. define classpath in META-INF file.
2. define the resources in deployment.xml
3. alter class loading order
4. (from ibm) In the case where the jars are part of a Shared Library configured on WebSphere Application Server, then a User Library must be used to configure the project for development before generating the WebService.
However, I have been unsuccessful to find any help online in these areas. Is there another technique or does anyone know anything about accomplishing this? Thanks in advance.
EDIT: If I specify the libraries in the META-INF using class-path, they are loaded before extensions, shared libraries..etc, but they are still loaded after the WAR which is not good. Again, this isn't a runtime issue because the web services are created at deployment on the fly.
I submitted a ticket to IBM. The libraries referenced by the web service are needed during deployment and must be bundled into the Ear in some fashion. I threw them in the web-inf/lib folder. However, if the referenced libraries then depend on additional libraries, these can be placed in the Shared Libraries. Seems odd to me too, but let's all just admit "shared libraries" are a hack anyways.
If you still have issues, just make sure your class loading is set to parent_last.
I'm having a hard time getting JRebel to work in my current development environment.
I have multi module maven projects. Currently, the Tomcat instance is controlled via service (tomcat monitor) and the deployed web apps are configured with a XML located at ${catalina.home}/conf/Catalina/localhost where the docBase attribute points ${absolute maven project path}/target/app (and the attribute reloadable is true). So every time I do a maven build I only have to manually restart tomcat if there any classes changed. If the modifications occurred in the static resources (JSP, HTML, JS,
etc..) a page refresh will do it.
On my first attempt, I configured the web apps to run on a tomcat server running inside Eclipse. The maven plugin provided was also configured with success: all my sub-modules inherited the plugin configuration and I can saw in the tomcat startup the output messages from JRebel indicating the absolute project paths that were been listen. The only problem is that Eclipse WTP / Tomcat plugins don't go weel with War overlay feature in eclipse. After starting the server, only the resources present in the last web app (the module that have other War as dependencies) were deployed.
So, I returned to my original configuration development and introduced JRebel to it. I passed the JRebel java options to the Tomcat Vm, all maven modules had the rebel.xml (listening to the correct resource folders), but nothing happens. I can't see the usual JRebel messages and I experimented changing a JSP in the source folder and do a page refresh but the file ins't automatically redeployed (in this case a simple copy from the source folder the the ${maven.projec}/target/app will do the trick).
My two questions are:
It's possible to over come that eclipse WTP issue?
What is a funcional development environment involving maven eclipse and a external tomcat?
Any help would be much appreciated!
UPDATE 1
So, I got it. Kind of...I'm still struggling with the war modules overlaying. I have a main web app module that depends on several webapps modules. Because the rebel.xml it's generated dynamically via jrebel maven plugin when the main webapp build occurs, only the it's jrebel.xml prevail. All the other are squashed. The rebel.xml for the jars modules are at the right places (inside the jar file).
I can get it work if I create a custom rebel.xml for the main webapp that points to all the absolute directories containing the source files (static files such as JSP, HTML, JS, CSS, images, etc.) of the depending web apps. But this is worthless for my team development environments. I'm using maven properties but we've have two different maven multi-module hierarchy that don't know about each other and I can't use a root pom to connect them. So these kind of properties will not be enough to guarantee that the absolute paths generated on each developer machine in the rebel.xml are correct.
For now, I'm trying to tackle using some kind of maven plugin to do the rebel.xml merge. For the record without success yet.
This is becoming another issue a bit different of the original question :) Maybe I should through another question.
UPDATE 2
I got it working!..finally.
I used the XSLT Generator Maven Plugin to help me merge the various rebel.xml files. Also had to use the fabulous Maven Copy Plugin because the xslt transformation occurred after the final war packaging and I had to add the resulting rebel.xml to that WAR.
If someone needs the configuration files details down't hesitate asking.
Hope's this helps someone out there.
I got it working!..finally. I used the XSLT Generator Maven Plugin to help me merge the various rebel.xml files. Also had to use the fabulous Maven Copy Plugin because the xslt transformation occurred after the final war packaging and I had to add the resulting rebel.xml to that WAR.
I have a jruby rails app that has some jar dependencies in rails lib/java. I prefer this to just putting them straight in lib as it separates my java libs from ruby libs. Works locally using jruby. Problem is, on deploy, tomcat is looking for a bunch of these jars (such as jruby) in WEB-INF/lib, not WEB-INF/lib/java.
I think i need to put some config in the web.xml that tells tomcat to also look in lib/java, but i can't find ANY docs on the matter.
I don't want to modify tomcat's system wide classpath, I just want to tell its class loader to check a directory other than WEB-INF/lib for this particular app only
Can anyone enlighten me on how to do this?
you can't change this directory, j2ee spec says that all libs go in WEB-INF/lib. That is where they are supposed to go.
Just stay with your two directories in your project folder, but join them, when creating your .war file. This should be pretty easy with apache ant and other build tools.