java modules maven
java modules maven
I'd be happy to help!
Java modules are a feature introduced in Java 9 that allows for better encapsulation and reuse of code. A module is a set of related classes, interfaces, and other resources packaged together as a single unit.
In Maven, you can create modules by creating separate directories within your project's directory structure. Each directory should contain its own module-info.java
file, which defines the module's name and the packages that it contains.
Here are some basic steps to create a Java module in Maven:
Create a new directory for your module:mkdir my-module
Create a module-info.java
file within this directory:
cd my-module
touch module-info.java
In the module-info.java
file, define your module's name and the packages that it contains:
Create a separate directory for each package that you want to include in your module:@MODULE
public class MyModule {
public requires public "org.example";
public provides org.example.MyClass;
}
mkdir org/example
Place your Java source files within these directories. In your pom.xml
file, define the modules and their dependencies:
Build and run your module:
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
4.0.0
com.example
my-project
1.0-SNAPSHOT
jar
org.example
my-module
1.0-SNAPSHOT
org.apache.maven.plugins
maven-compiler-plugin
1.8
1.8
my-module
mvn package
That's it! You've successfully created a Java module in Maven.
Note that you can have multiple modules within a single project, each with its own dependencies and requirements.
java module-info
I'm happy to respond in English for you!
A Java module-info is a declaration file that specifies the details of a Java module, such as its name, requires clauses, provides clauses, and exports clauses. This file serves as a contract between the module and other modules or applications that use it.
The basic structure of a module-info file is as follows:
module {
// Module declaration
}
Let's break down the different parts of a module-info file:
Module name: This is the unique identifier for your Java module. It should match the directory name where your module's source files are stored. Requires clauses: These specify dependencies between modules. A requires clause tells other modules that your module depends on them and may also require other modules or API versions. For example:requires java.base;
requires org.example.moduleA;
This means that your module depends on the Java standard library (java.base
) and another module called org.example.moduleA
.
provides type org.example.api.MyInterface;
provides service org.example.service.MyService with org.example.impl.MyServiceImpl;
This means that your module provides an interface called MyInterface
and a service called MyService
along with its implementation.
exports org.example.api;
export org.example.service.MyService;
This means that your module exports the entire org.example.api
package and a specific service called MyService
.
uses org.example.moduleB;
uses java.time.DateTime API 1.8;
This means that your module uses another module called org.example.moduleB
and the Java Time API with version 1.8.
In summary, a module-info file is used to declare the details of a Java module, including its dependencies, provided APIs or services, exported parts, and internal usages. It serves as a contract between the module and other modules or applications that use it.
I hope this helps! Let me know if you have any further questions.