Question

In eclipse I’ve installed m2e plugin. I am trying to understand how do you know the names of properties for dependencies to add to pom file?

Say for instance how do you know which artifact id to use?

<dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjrt</artifactId>
        <version>${org.aspectj-version}</version>                   
</dependency>   

why here say aspectjrt in artifact id?

<dependency>
        <groupId>javax.inject</groupId>
        <artifactId>javax.inject</artifactId>
        <version>1</version>
    </dependency>

and here same as group id ??
is there any pattern?

say my project is missing

org.hibernate.Query;
org.hibernate.Session;
org.hibernate.SessionFactory;

and in maven dependencies folder I have hibernate-core-3.6.0.Final.jar which effectively contains everything except those 3.

Do you write these .pom yourself?

I am betting that for student project I will have to stick with manually adding hundreds of libraries… otherwise I will fail trying to learn it 🙂

Answer 1

1. You know what groupId:artifactId:version (we call these coordinates) to use by which artifact you want. Most often, you find out which artifact you want by reading it in the project’s documentation, especially for projects with a large number of artifacts, some of which might contain optional addons.
2. aspectjrt is short for AspectJ RunTime.
3. GroupId and artifactId are defined by the creators of the library in question. There’s no universal pattern because there’s no one central coordinator. There are some conventions that have evolved, though. Generally, the groupId is at least partly the reversed domain name, like the first part of a Java package name is: org.hibernate, org.apache, org.springframework… The artifactId distinctly identifies the role of that particular artifact in the group it belongs to, like spring-core, spring-tx, spring-jms, etc. You can get an idea of what groupId’s and artifactId’s look like by searching Maven Central for some of the libraries you know.
4. If you’re missing org.hibernate.SessionFactory, then you don’t have hibernate-core-3.6.0.Final on your classpath. If you have that on your classpath, then you’re not missing the SessionFactory class. Those three classes you mentioned are most definitely in that artifact, as you can see from searching for the class in Central. If you still doubt, do a jar -tf hibernate-core-3.6.0.Final.jar and check out the contents yourself. I promise it has those classes.