How can I use classes from other project with maven? (ClassNotFoundException and NoClassDefFoundError is thrown)

Question

I have two Vaadin projects (I will name them A and B). Both are using Maven for resolving the dependencies and are in the same workspace. I'm working with Eclipse and I'm using the m2e-plugin. I want to use some classes of B in project A. In Eclipse I can instatiate them without errors/warnings but when I try to run A I get a ClassNotFoundException and a NoClassDefFoundError caused by instatiating a class of B.

The .class files of A are located in ...\workspace\A\target\classes and the for project B they are in ...\workspace\B\target\classes. I've been trying to solve this problem but I didn't find a solution. What I tried so far:

• Configure build path -> Libaries -> add Class Folder -> B\target
• Configure build path -> Libaries -> add External Class Folder -> B\target
• Configure build path -> Projects -> add -> B

I think adding the project is necessary because when I remove it, Eclipse gives me error messages when I try to use the classes from B in A

I don't have any idea what else to do. Maybe I have to configure my pom.xml file but I don't know what I must do there.

Edit: In pom.xml of project B:

<groupId>de.qufis</groupId>
<artifactId>CentwertApp</artifactId>
<packaging>war</packaging>
<version>0.0.1-SNAPSHOT</version>
<name>CentwertApp</name>

In pom.xml of project A:

    <dependency>
        <groupId>de.qufis</groupId>
        <artifactId>CentwertApp</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <type>war</type>
        <scope>import</scope>
    </dependency>

I did clean compile for project B with maven build. Then I tried to do the same with project A but then I get error message: Could not find artifact de.qufis:CentwertApp:war:0.0.1-SNAPSHOT in vaadin-addons (http://maven.vaadin.com/vaadin-addons)

When I run the Application normally I still get the ClassNotFoundException and NoClassDefError.

Edit 2: I have added

<scope>compile</scope>

When I run Maven build (clean compile), part of my building process looks like this:

[INFO] Building centwertAdmin 0.0.1-SNAPSHOT

[INFO] ------------------------------------------------------------------------

[WARNING] The POM for de.qufis:CentwertApp:war:0.0.1-SNAPSHOT is missing, no dependency information available

[INFO] ------------------------------------------------------------------------

[INFO] BUILD FAILURE

Then there is the errormessage:

[ERROR] Failed to execute goal on project centwertAdmin: Could not resolve dependencies for project de.qufis:centwertAdmin:war:0.0.1-SNAPSHOT: Failure to find de.qufis:CentwertApp:war:0.0.1-SNAPSHOT in http://maven.vaadin.com/vaadin-addons was cached in the local repository, resolution will not be reattempted until the update interval of vaadin-addons has elapsed or updates are forced -> [Help 1]

Answer 1

can u try to remove <packaging>war</packaging> from B? Maven's default packaging is jar, and this is what you need for B.

Plus, add B to the dependencies of A.

• Build B project. use mvn clean install, that would install B's JAR+POM in your local repository (.m2).
• Verify it is there... Then Maven will be able to find it, so you will not get the error "Could not find artifact de.qufis:CentwertApp"
• Build A.

Usually, dependencies are of type JAR. If B must be a WAR, see this.