Just recently started using Eclipse and ran into an issue with exporting the plugin I'm working on. I tried to search but so far no luck - but if the answer is already here I'd be grateful if someone can point me to it.
I'm writing a n OSGi/Equinox plugin with Eclipse. The plugin is for a 3rd party system, which allows extensions: basically all jars placed in the application's plugin folder are automatically loaded into the application at startup. I have managed to put together my plugin, it's loading fine and it works.
The issue is that I rely on another plugin which is placed beside mine in the plugins folder. For obvious reasons I do not want to package that plugin into my plugin jar file. I have tried to add the dependency as an external archive, but this breaks the export: when I try to export my plugin project ant complains about missing dependencies and types. (If I actually include the other jar file in my plugin everything works, but obviously this is less then ideal.)
So: how do I set up my plugin project dependency, that it's a) an external dependency and b) doesn't need to be specified with a path or a variable - i.e. how do I tell my exporter to "don't worry, it will be there right beside you"?
Edit: Apparently there's an important detail I didn't mention. The external jar file I depend on is not an OSGi plugin, just a regular jar file with some classes in it. To the 3rd party system it seems all the same (all are under the plugins folder, all are loaded into the application), but for Eclipse the distinction seems important.
If you reference the other plug-in as a dependency in your plug-in's MANIFEST.MF the export should work without errors. The plug-in should be listed in the Require-Bundle list in the MANIFEST.MF.
You can do this in the MANIFEST.MF editor by adding to the 'Required Plug-ins' list on the 'Dependencies' tab of the editor.
Note: When referencing other plug-ins you must always use this method. Do not try adding the plug-in jar to the Java build path or anything like that.
If the jar you want to use is not an Eclipse plug-in you must should include it as part of the plug-in and list the jar in the Bundle-Classpath in the MANIFEST.MF. If you cannot do this you can reference an external jar in the Bundle-Classpath using something like:
Bundle-Classpath: .,external:$LIB_LOCATION$/lib.jar
. is the normal entry in for the plug-in code. external:$LIB_LOCATION$/lib.jar looks for lib.jar in a location defined by the environment variable LIB_LOCATION. This method can be difficult to get right.
In the end the solution to my specific problem was to add the external jar file as an Extra Classpath Entry on the build properties tab (this translated to a "jars.extra.classpath = .jar" entry in the build.properties file). I have also added the jar file to the project itself - after adding the extra class path entry that got changed into an external dependency automatically.
With these two changes I was able to successfully export my plugin, which didn't contain the external jar file, but was able to reference it when loaded into the 3rd party system.
I'm testing a web application with Eclipse + Tomcat, Eclipse deploys the web application files and launches Tomcat, and the application runs fine. But when MyBatis is trying to open it's XML configuration files, it looks for them in
C:\Program Files\Apache Software Foundation\Tomcat 7.0\lib\persistence\db\oracle.xml
instead of the correct place:
C:\workspace\mywebapp\src\persistence\db\oracle.xml
Where is MyBatis supposed to look for XML files?
EDIT:
This is where I specify the relative path:
String cfgFile = "persistence/db/oracle.xml";
Reader reader = Resources.getResourceAsReader(cfgFile);
session.put(db, new SqlSessionFactoryBuilder().build(reader));
Resources.getResourceAsReader looks files in classpath. For web application running in tomcat classpath consist of WEB-INF/classes and all jars from WEB-INF/lib and tomcat folders like $TOMCAT_HOME\lib.
The issue you encounter most probably is caused by the fact that oracle.xml file is not added to deployment. It looks like c:\workspace\myweapp\src is not among source folder of eclipse project so eclipse doesn't copy files from it to the folder which is deployed to tomcat. Depending on your existing project structure you may need to create subfolder in src and add persistence with all subfolders there. This will allow you to avoid clash if some subfolder of src is already a source folder in eclipse. I would recommend to use maven project structure:
src
main
* java
you java source code here organized by package
* resources
persistence
I marked folders which should be added as source folder to eclipse with *.
Please note that it is not correct to say that C:\workspace\mywebapp\src\persistence\db\oracle.xml is a correct place to search for it. After you create a war to deploy it on production this path most probably will not be available at your production server. What you really need is to include persistence\db\oracle.xml to the war in appropriate place (under WEB-INF/classes).
Maybe you need another class loader 1. Try this:
String cfgFile = "persistence/db/oracle.xml";
ClassLoader classloader = Thread.currentThread().getContextClassLoader()
Reader reader = Resources.getResourceAsReader(classloader, cfgFile);
Notes
See Difference between thread's context class loader and normal classloader and you may want to see the code of org.apache.ibatis.io.Resources. You find it here.
I am trying to use an external jar in a Google Web Toolkit project.
The jar is for use only on the server side. For reference it is the jbcrypt jar packaged as org.mindrot.jbcrypt.
I have included the jar in my project's build path, and eclipse finds it and resolves the BCrypt class in my project.
When I try to use the service that relies on this jar (a login service that extends RemoteServiceServlet), I get a com.google.gwt.user.server.rpc.UnexpectedException which is caused by a NoClassDefFoundError for org.mindrot.jbcrypt.BCrypt.
Does the development server need the jar to be somewhere else? What should I do? Thanks.
Turns out, it goes in project/war/WEB-INF/lib
I am trying to use MatlabCotrol (http://code.google.com/p/matlabcontrol/) from a Netbeans application.
In order to use Matlabcontrol from a Java application (e.g. no Netbeans modules), the only thing needed is to add the matlabcontrol-4.0.jar file to the project and everything works nicely.
When I try to do the same from the Netbeans application, I include the jar file using a "Library Wrapper Module", which in principle, should enable the use of the jar file as a Netbeans module. However, Matlabcontrol does not like that way. The project compiles properly, indicating that the Wrapper Module does indeed exposes the class definitions in the matlabcontrol jar file. However, I get the following exception when the program runs:
java.lang.NullPointerException
at java.io.File.<init>(File.java:222)
at matlabcontrol.Configuration.getSupportCodeLocation(Configuration.java:227)
at matlabcontrol.RemoteMatlabProxyFactory.createProcess(RemoteMatlabProxyFactory.java:278)
at matlabcontrol.RemoteMatlabProxyFactory.requestProxy(RemoteMatlabProxyFactory.java:116)
at matlabcontrol.RemoteMatlabProxyFactory.getProxy(RemoteMatlabProxyFactory.java:134)
at matlabcontrol.MatlabProxyFactory.getProxy(MatlabProxyFactory.java:81)
The problem seems to be that the matlabcontrol code in the jar file, needs to know the location of the code. In the Java application case, the jar file is in a specific directory that Matlabcontrol seems to expect. Inside netbeans, that is not the case. The error happens exactly in these lines of code:
URL url = Configuration.class.getProtectionDomain().getCodeSource().getLocation();
File file = new File(url.toURI().getPath()).getCanonicalFile();
The exception is being triggered by the File constructor, because the Configuration class function is returning a null url.
Does anybody have a clue about how to fix this problem?
In any case, thanks for reading my question!
There is a VERY similar question to mine but in my case I don't have any duplicate jars in my build path, so the solution does not work for me. I've searched google for a couple of hours now, but none of the solutions I've found there actually resolve my issue. I'm creating a web site with some database connectivity for a homework. I'm using a MySQL database, developing in Eclipse and running on Windows.
I keep getting java.lang.ClassNotFoundException: com.mysql.jdbc.Driver with the following code:
import java.sql.*;
//...
public void someMethodInMyServlet(PrintWriter out)
{
Connection connection = null;
PreparedStatement query = null;
try {
out.println("Create the driver instance.<br>");
Class.forName("com.mysql.jdbc.Driver").newInstance();
out.println("Get the connection.<br>");
connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "secret");
query = connection.prepareStatement( "SELECT * FROM customers");
//...
} catch (Exception e)
{
out.println(e.toString()+"<br>");
}
}
//...
When I run the above code I get the following output:
Create the driver instance.
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
It doesn't get past the Class.forName... line and I can't figure out why! Here is what I did:
Download mysql-connector.
Put it in my MySQL folder C:\Program Files\MySQL\mysql-connector-java-5.1.12\mysql-connector-java-5.1.12-bin.jar.
Opened the project properties in Eclipse.
Add External Jar to my Build Path and I selected mysql-connector-java-5.1.12-bin.jar.
Every time I attempt to use the servlet I get the same error regardless if I have the jar in there or if I don't. Could you help me figure this out?
As for every "3rd-party" library in flavor of a JAR file which is to be used by the webapp, just copy/drop the physical JAR file in webapp's /WEB-INF/lib. It will then be available in webapp's default classpath. Also, Eclipse is smart enough to notice that. No need to hassle with buildpath. However, make sure to remove all unnecessary references you added before, else it might collide.
An alternative is to install it in the server itself by dropping the physical JAR file in server's own /lib folder. This is required when you're using server-provided JDBC connection pool data source which in turn needs the MySQL JDBC driver.
See also:
How to add JAR libraries to WAR project without facing java.lang.ClassNotFoundException? Classpath vs Build Path vs /WEB-INF/lib
How should I connect to JDBC database / datasource in a servlet based application?
Where do I have to place the JDBC driver for Tomcat's connection pool?
JDBC CLASSPATH Not Working
Since you are running it in servlet, you need to have the jar accessible by the servlet container. You either include the connector as part of your application war or put it as part of the servlet container's extended library and datasource management stuff, if it has one. The second part is totally depend on the container that you have.
The others are right about making the driver JAR available to your servlet container. My comment was meant to suggest that you verify from the command line whether the driver itself is intact.
Rather than an empty main(), try something like this, adapted from the included documentation:
public class LoadDriver {
public static void main(String[] args) throws Exception {
Class.forName("com.mysql.jdbc.Driver");
}
}
On my platform, I'd do this:
$ ls mysql-connector-java-5.1.12-bin.jar
mysql-connector-java-5.1.12-bin.jar
$ javac LoadDriver.java
$ java -cp mysql-connector-java-5.1.12-bin.jar:. LoadDriver
On your platform, you need to use ; as the path separator, as discussed here and here.
Place mysql-connector-java-5.1.6-bin.jar to the \Apache Tomcat 6.0.18\lib folder. Your problem will be solved.
What you should not do do (especially when working on a shared project)
Ok, after had the same issue and after reading some answers here and other places. it seems that putting external lib into WEB-INF/lib is not that good idea as it pollute webapp/JRE libs with server-specific libraries - for more information check this answer"
Another solution that i do NOT recommend is: to copy it into tomcat/lib folder. although this may work, it will be hard to manage dependency for a shared(git for example) project.
Good solution 1
Create vendor folder. put there all your external lib. then, map this folder as dependency to your project. in eclipse you need to
add your folder to the build path
Project Properties -> Java build path
Libraries -> add external lib or any other solution to add your files/folder
add your build path to deployment Assembly (reference)
Project Properties -> Deployment Assembly
Add -> Java Build Path Entries
You should now see the list of libraries on your build path that you can specify for inclusion into your finished WAR.
Select the ones you want and hit Finish.
Good solution 2
Use maven (or any alternative) to manage project dependency
Just follow these steps:
1) Install eclipse
2) Import Apache to eclipse
3) Install mysql
4) Download mysqlconnector/J
5) Unzip the zipped file navigate through it until you get the bin file in it. Then place all files that are present in the folder containing bin to C:\Program Files\mysql\mysql server5.1/
then give the same path as the address while defining the driver in eclipse.
That's all very easy guys.
If the problem still persists,
Put the-
mysql-connector-java-5.0.8-bin jar in a place inside your Tomcat->lib->folder (No matter where you've installed your Tomcat). And change your environmental variable (Done by clicking Properties of Mycomputer -Advanced system settings- Environmental variables-And set a new variable name & variable values as the place where your lib file resides.Dont forget to enter a ; at the end of the path)
If still problem persists
Try downloading commons-collections-2.0.jar (http://www.docjar.com/jar_detail/commons-collections-2.0.jar.html) and paste the jar in the same place where your mysql jar resides (ie) inside Tomcat-lib.
Clean your project-Stop your server- Finally try to run.
Many times I have been facing this problem, I have experienced ClassNotFoundException.
if jar is not at physical location.
So make sure .jar file(mysql connector) in the physical location of WEB-INF lib folder. and
make sure restarting Tomcat by using shutdown command in cmd.
it should work.
The only solution worked for me is putting the .jar file under WEB-INF/lib . Hope this will help.
assuming your project is maven based, add it to your POM:
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.26</version>
</dependency>
Save > Build > and test connection again. It works! Your actual mysql java connector version may vary.
Put mysql-connector-java-5.1.38-bin.jar to the C:\Program Files\Apache Software Foundation\Tomcat 7.0\lib folder.by doing this program with execute
My issue was a little different. Instead of jdbc:oracle:thin:#server:port/service i had it as server:port/service.
Missing was jdbc:oracle:thin:# in url attribute in GlobalNamingResources.Resource. But I overlooked tomcat exception's
java.sql.SQLException: Cannot create JDBC driver of class 'oracle.jdbc.driver.OracleDriver' for connect URL 'server:port/service'
for this error:
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
you need to:
Import java.sql.*;
Import com.mysql.jdbc.Driver;
even if its not used till app running.