How to add and use a jar library in IntelliJ IDEA?

Question

I created a new Java app from scratch in IntelliJ IDEA. Now I want to use a jar library, eg OpenJPA. I added the library using Project Structure -> Libraries like this:

then I tried to use annotations from that library in my Java code, but I don't get the option to import these classes. It looks like IntelliJ IDEA is not known about my library yet:

What am I doing wrong when adding this library? Is there anything more that I have to do to get it working?

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After adding this library, it looks like it is automatically added to "Modules":

Answer 1

You have created a library, but you haven't said IntelliJ that the module must use it. Click *Modulesµ in the project structure, then select the module you want to add this library to, go to the Dependencies tab, and add the library.

EDIT:

It's simply that the annotation is not part of the jar. You need to add the jpa api jar, not only openjpa.jar

Answer 2

您必须将库添加到模块依赖项，请在此处检查： 配置模块依赖项和库