I'm trying to troubleshoot a GWT-based app I'm writing in Eclipse. It currently uses Spring Framework 3.1.1 and Hibernate 4.1.6 on the back-end side. I'm currently having troubles with the dreaded "javax.validation.ValidationException: Unable to find a default provider" that seems to plague a lot of folks but is caused by different problems. I've tried the various solutions of using different versions of the JSR 303 implementation (e.g. diff. versions of Hibernate Validator) but it doesn't seem to make a difference.
And after debugging, I'm seeing why. Once execution gets to javax.validation.Validation.getValidationProviders():317 (in validation-api-1.0.0.GA), the app (running on an Eclipse internal Jetty server) attempts to read the META-INF/services/javax.validation.spi.ValidationProvider resource from the classpath and comes back empty. I am absolutely certain that the different validator implementations I've put (e.g. hibernate-validator-4.3.0.Final.jar) have that resource and it does contain a value (e.g. org.hibernate.validator.HibernateValidator), but is not appearing to the classloader in question. The way I've included the JAR in the classpath is by adding it to the project's Build Path which seems to add it to the Jetty runtime when I execute the applications.
My question is: Is there a way to view the classpath in Eclipse debug mode visible to a certain classloader? Secondly, does anyone know why the Hibernate Validator's resource is not first and foremost in the classloader that Validation is using?
The webapp classpath is composed by the directory WEB-INF/classes and by all the jars in WEB-INF/lib. If you want a jar to be available at runtime, you must NOT add it to the build path, but to WEB-INF/lib.
Dropping a jar in WebContent/WEB-INF/lib in Eclipse will make it automatically part of the buid path of your webapp, and available at runtime.
Related
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?
How should I add JAR libraries to a WAR project in Eclipse without facing java.lang.ClassNotFoundException or java.lang.NoClassDefFoundError?
The CLASSPATH environment variable does not seem to work. In some cases we add JAR files to the Build Path property of Eclipse project to make the code compile. We sometimes need to put JAR files inside /WEB-INF/lib folder of the Java EE web application to make the code to run on classes inside that JAR.
I do not exactly understand why CLASSPATH does not work and in which cases we should add JARs to Build Path and when exactly those JARs should be placed in /WEB-INF/lib.
The CLASSPATH environment variable is only used by the java.exe command and even then only when the command is invoked without any of the -cp, -classpath, -jar arguments. The CLASSPATH environment variable is ignored by IDEs like Eclipse, Netbeans and IDEA. See also java.lang.ClassNotFoundException in spite of using CLASSPATH environment variable.
The Build Path is only for libraries which are required to get the project's code to compile. Manually placing JAR in /WEB-INF/lib, or setting the Deployment Assembly, or letting an external build system like Maven place the <dependency> as JAR in /WEB-INF/lib of produced WAR during the build, is only for libraries which are required to get the code to deploy and run on the target environment too. Do note that you're not supposed to create subfolders in /WEB-INF/lib. The JARs have to be placed in the root.
Some libraries are already provided by the target JEE server or servletcontainer, such as JSP, Servlet, EL, etc. So you do not need put JARs of those libraries in /WEB-INF/lib. Moreover, it would only cause classloading trouble. It's sufficient to (indirectly) specify them in Build Path only. In Eclipse, you normally do that by setting the Targeted Runtime accordingly. It will automatically end up in Build Path. You do not need to manually add them to Build Path. See also How do I import the javax.servlet / jakarta.servlet API in my Eclipse project?
Other libraries, usually 3rd party ones like Apache Commons, JDBC drivers and JEE libraries which are not provided by the target servletcontainer (e.g. Tomcat doesn't support many JEE libraries out the box such as JSF, JSTL, CDI, JPA, EJB, etc), need to end up in /WEB-INF/lib. You can just copy and paste the physical JAR files in there. You do not necessarily need to specify it in Build Path. Only perhaps when you already have it as User Library, but you should then use Deployment assembly setting for this instead. See also ClassNotFoundException when using User Libraries in Eclipse build path.
In case you're using Maven, then you need to make absolutely sure that you mark libraries as <scope>provided</scope> if those are already provided by the target runtime, such as JEE, Servlet, EL, etc in case you deploy to WildFly, TomEE, etc. This way they won't end up in /WEB-INF/lib of produced WAR (and potentially cause conflicts with server-bundled libraries), but they will end up in Eclipse's Build Path (and get the project's code to compile). See also How to properly install and configure JSF libraries via Maven?
Those JARs in the build path are referenced for the build (compile) process only. If you export your Web Application they are not included in the final WAR (give it a try).
If you need the JARs at runtime you must place them in WEB-INF/lib or the server classpath. Placing your JARs in the server classpath does only make sense if several WARs share a common code base and have the need to access shared objects (e.g. a Singleton).
If you are using Maven:
Open the project properties, and under Deployment Assembly click Add...
Then select Java Build Path Entries and select Maven Dependencies
Resolved by setting permissions.
Had related issue using PySpark and Oracle jdbc. The error does not state that the file cannot be accessed, just that the class cannot be loaded.
So if anyone still struggles, check the permissions. Some might find it obvious tho'.
I want to give the answer for the folowing link question ClassNotFoundException oracle.jdbc.driver.OracleDriver only in servlet, using Eclipse
Ans: In Myeclipse go to Server-->left click on Myeclipse Tomcat7-->Configure Server Connector-->(Expand)Myeclipse Tomcat7--> Paths-->Prepend to classpath-->Add jar (add oracle14 jar)-->ok
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 am struggling with the configuration of the Eclipse Dali plugin and Hibernate. The version I'm using is as recommended:
Eclipse 3.6.1 (Helios SR1) IDE for Java EE Developers (including Dali 2.3)
JBoss Tools 3.2 (for the Hibernate Tools plugin)
When configuring the Java Persistence properties for my project, I created a user library named "Hibernate JPA" and included the following JARs:
hibernate-distribution-3.6.1.Final\hibernate3.jar
hibernate-distribution-3.6.1.Final\lib\jpa\hibernate-jpa-2.0-api-1.0.0.Final.jar
hibernate-distribution-3.6.1.Final\lib\required\dom4j-1.6.1.jar
hibernate-distribution-3.6.1.Final\lib\required\slf4j-api-1.6.1.jar
hibernate-distribution-3.6.1.Final\lib\required\javassist-3.12.0.GA.jar
hibernate-distribution-3.6.1.Final\lib\required\commons-collections-3.1.jar
hibernate-distribution-3.6.1.Final\lib\required\antlr-2.7.6.jar
hibernate-distribution-3.6.1.Final\lib\required\jta-1.1.jar
As long as the hibernate-distribution-3.6.1.Final folder is outside of my project directory, everything works fine. However, if I put the Hibernate folder into the project directory, I get an error saying "Required class org.hibernate.SessionFactory does not exist in selected libraries":
The error text is wrong, the required class is definitely included in hibernate3.jar, and everything works as expected when I move the JARs outside of my project directory.
I have two questions about that:
I do not understand why the User Library behaves differently depending on whether the JARs are placed inside or outside of my project directory. Could anybody explain what's happening here?
I would like to have my project in SVN, including all the required libraries. Is there any way to configure Dali to accept User Libraries within the project directory?
Thank you very much.
I was having the same problem cos I forgot to add hibernate-jpa-2.0-api-1.0.0.Final.jar.
The only difference is that I'm using 3.5.1-Final cos 3.6.x seems not stable at the moment.
Actually, I'd prefer EclipseLink: everything works fine as a charm. I've wasted many hours with environment configuration :( Last time I've used Hibernate was years ago and looks like troubles to configure still are the same :(
Does anyone know any sane reason for such bundling decision? Google engineers act wisely in most cases, so this kinda surprized me.
This would cause collisions with other versions of servlet API pulled via Maven dependencies:
webapp classpath will likely contain
version which is bundled with GWT;
container may refuse to load the GWT
jar as it contains the javax.servlet
package;
in most cases this will
likely deviate classpaths across your
IDE's debugger and the really
executing VM.
Link to the jar in question (just so you see the same thing after unzipping as I do, if you don't believe that GWT contains servlet API classes in the same jar):
http://repo1.maven.org/maven2/com/google/gwt/gwt-user/1.7.0/gwt-user-1.7.0.jar
You shouldn't be including gwt-dev.jar or gwt-user.jar in your war file. You only need gwt-servlet.jar in your war, and that too only if you are using RPC. If you notice, gwt-servlet.jar (ironically) does not contain any of the servlet classes.
gwt-dev.jar contains the compilers and linkers. Your code will never need this to compile.
gwt-user.jar contains the gwt framework that ultimately gets translated to javascript. You only need this during development mode.
gwt-servlet.jar contains the server side code that is needed if you use RPC framework. This is the only jar that should be present in your war file.
The reason the classes are in the package is to provide a full working solution for users who only use the gwt-user file in development. Without it GWT RPC wouldn't compile. This is/was the general view of the GWT team as can be found in this lively discussion on the GWT issue tracker: http://code.google.com/p/google-web-toolkit/issues/detail?id=3851
However, GWT 1.7 also contains the javax source files, which can cause additional problems. For example for maven and probably also for the points you mention. This was addressed in the GWT issue and in later version of GWT the javax source files have been removed from the gwt-user jar file.
For deployment you should use the gwt-servlet jar, which doesn't contain the javax classes or any other third party libraries. In the past several it could happen GWT files designed for client side use also used on the server side were missing from the gwt-servlet jar file. Losts of these issues have been addressed and classes were added to the servlet jar file. If you still find a GWT class you need is missing from the gwt-servlet you should file an issue report. In your case, assuming you're using 1.7, it might mean to upgrade to a newer version of GWT.