This project cannot be added because it does not produce a JAR file using an Ant script

Question

Following my question here I now came up to this problem. I'm using NetBeans 8.

I've created a Maven Project, let's call it MyLibMaven, (I used New Project -> Maven -> Java Aplication) and I moved my library, let's call it MyLib, into this Maven Project.

Now when I go to my normal Java Project (let's call it MyProject) and I try to add MyLibMaven as a library to MyProject I get this popup in Netbeans saying:

This project cannot be added because it does not produce a JAR file using an Ant script

What am I doing wrong here?

Here's my pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.dwnz.my.lib</groupId>
    <artifactId>MyLib</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.7</maven.compiler.source>
        <maven.compiler.target>1.7</maven.compiler.target>
    </properties>
    <name>MyLib</name>

    <dependencies>
        <dependency>
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>
            <version>17.0</version>
        </dependency>
    </dependencies>
</project>

///////////////////////// EDIT //////////////////////////////

I moved my project to a maven project and added the MyLibMaven as a dependency. But now when I try to run my project I get this failed error:

--- exec-maven-plugin:1.2.1:exec (default-cli) @ TeseMaven ---
Could not load the icon: /view/images/enable-server-icon.png
Exception in thread "main" java.lang.NullPointerException
    at javax.swing.ImageIcon.<init>(ImageIcon.java:217)
    at view.toolbar.ToolBar.createIcon(ToolBar.java:171)
    at view.toolbar.ToolBar.<init>(ToolBar.java:53)
    at view.MainFrame.<init>(MainFrame.java:98)
    at view.MainFrame.newInstance(MainFrame.java:586)
    at view.Main.main(Main.java:98)
------------------------------------------------------------------------

------------------------------------------------------------------------
BUILD FAILURE
------------------------------------------------------------------------
Total time: 2.382s
Finished at: Wed Jul 23 02:13:22 BST 2014
Final Memory: 5M/126M
------------------------------------------------------------------------
Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.2.1:exec (default-cli) on project MyProjectMaven: Command execution failed. Process exited with an error: 1 (Exit value: 1) -> [Help 1]

To see the full stack trace of the errors, re-run Maven with the -e switch.
Re-run Maven using the -X switch to enable full debug logging.

For more information about the errors and possible solutions, please read the following articles:
[Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException

Answer 1

The main problems you are having is...

1. Adding a Netbeans project as a library to an existing Netbeans project only works for "Netbeans Project" (ant) project types.
2. You need to add the resulting Jar from the Maven project AND all it's dependencies to your "Netbeans" project. Because a "Netbeans (Ant) Project" has no means for resolving dependencies, you must manually resolve these dependencies and add each Jar file as a library entry.
3. You Maven project is only producing the Jar for your project, it is not including the classes/jars from your projects dependencies.

You have at least two basic options...

You could...

Instruct Maven to include all the dependencies as part of the build process. There are (at least) two ways to achieve this. You can include all the classes into a single Jar or have Maven copy all the dependencies to a specified location and update the class-path manifest entry.

I, personally, prefer the second option, but that's a personal thing. As part of my Maven build process, I include the following...

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-dependency-plugin</artifactId>
            <version>2.1</version>
            <executions>
                <execution>
                    <id>copy-dependencies</id>
                    <phase>package</phase>
                    <goals>
                        <goal>copy-dependencies</goal>
                    </goals>
                    <configuration>
                        <outputDirectory>${project.build.directory}/lib</outputDirectory>
                        <overWriteReleases>false</overWriteReleases>
                        <overWriteSnapshots>false</overWriteSnapshots>
                        <overWriteIfNewer>true</overWriteIfNewer>
                    </configuration>
                </execution>
            </executions>
        </plugin>
        <plugin>
            <artifactId>maven-jar-plugin</artifactId>
            <version>2.4</version>
            <configuration>
                <archive>
                    <manifest>
                        <addClasspath>true</addClasspath>
                        <classpathPrefix>lib/</classpathPrefix>
                        <!--mainClass>com.acme.MainClass</mainClass-->
                    </manifest>
                </archive>
            </configuration>
        </plugin>        

Basically, the first plugin copies all the dependency Jars to the lib directory in the ${project.build.directory}. This is a personal thing, but I don't like merging the contents of the Jar into a single "master" Jar, as I tend to have resources with the same name which I uses as lookups in my project...

The second plugin includes the class-path element within the manifest file, this ensures that the dependent jars are included in the class loader lookup path at run time...

If you want to create a "single" Jar, take a look at Including dependencies in a jar with Maven

You could...

Make your second project a Maven project and include your first project as a dependency to it. Maven will then resolve all the dependencies automatically for you. That's kind of the point...