Which module should I require in Java 9 to use JPA?

问题

I'm testing Java 9 with a project which requires JPA (javax.persistence.* classes). When I add the module-info.java and declare my module, all classes under javax.persistece package become unavailable.

I searched a lot, but I couldn't find the module to require to use JPA in a Java 9 module project.

UPDATE As Alan suggested, I ran

$ jar --describe-module --file=javax.persistence-api-2.2.jar

No module descriptor found. Derived automatic module.

java.persistence@2.2 automatic
requires java.base mandated
contains javax.persistence
contains javax.persistence.criteria
contains javax.persistence.metamodel
contains javax.persistence.spi

But still with this module-info.java

module my.module {

    requires java.persistence;

}

I get "module-info.java:[3,18] module not found: java.persistence".

UPDATE 2 This is my project structure:

.
├── pom.xml
└── src
    ├── main
    │   ├── java
    │   │   ├── my
    │   │   │   └── module
    │   │   │       └── MyBean.java
    │   │   └── module-info.java
    │   └── resources
    └── test
        ├── java
        └── resources

The pom.xml has the javax.persistence-api dependency.

Testing repo: https://github.com/heruan/java9-jpa

回答1:

With maven, you can use a dependency like

<dependency>
    <groupId>javax.persistence</groupId>
    <artifactId>javax.persistence-api</artifactId>
    <version>2.2</version>
</dependency>

with maven-compiler-plugin as updated to work with jdk9 detailed here.

Similar with dependency with gradle

compile group: 'javax.persistence', name: 'javax.persistence-api', version: '2.2'

which is based out of the javaee/jpa-spec. This would facilitate the

requires java.persistence

as an automatic module as proposed to be the name intended for the module here.

Adding to the details, this is defined in the META-INF/MANIFEST.MF as :

Manifest-Version: 1.0
Bundle-Description: Java(TM) Persistence 2.2 API jar
Automatic-Module-Name: java.persistence
...

Note- The way to figure out the module name as suggested by Alan is precise, but no advertising and I still prefer using a class of some package and then let IntelliJ(2017.2.4) do that resolution for me when I say 'import class' and then 'add requires'. ;)

回答2:

I don't think that JPA has been published as a module yet but you should be able to use it as an automatic module. Can you use jar --file=<jarfile> --describe-module to see what module name is derived for the JPA JAR file.

来源：https://stackoverflow.com/questions/46471927/which-module-should-i-require-in-java-9-to-use-jpa

标签

java

jpa

java-9

module-info