module‑info.java

module-info.java is the module descriptor file placed in the root of a module’s source directory. It defines the module’s name, dependencies, and exported packages.

Basic structure:

module module.name {
    // directives
}

Common directives:

Directive	Description	Example
requires	Declares a dependency on another module	requires java.base; (java.base is implicit)
requires transitive	Dependency that is also readable by modules that require this one	requires transitive java.sql;
exports	Makes a package available to all other modules	exports com.example.api;
exports ... to	Exports package to specific modules only	exports com.example.internal to com.example.test;
opens	Allows deep reflection on a package (used by frameworks like Spring)	opens com.example.entities;
uses	Declares a service that this module consumes	uses com.example.spi.Service;
provides ... with	Registers a service implementation	provides com.example.spi.Service with com.example.impl.ServiceImpl;

Example:

module com.example.myapp {
    requires java.sql;
    requires transitive java.logging;
    exports com.example.myapp.api;
    exports com.example.myapp.model;
    opens com.example.myapp.internal to com.example.test;
    uses com.example.spi.Plugin;
    provides com.example.spi.Plugin with com.example.plugins.MyPlugin;
}

java.base is implicitly required – no need to declare it.

File location:

src/
└── com.example.myapp/
    ├── module-info.java
    └── com/
        └── example/
            └── myapp/
                ├── api/
                └── internal/

Compilation:

javac -d mods/com.example.myapp src/com.example.myapp/module-info.java src/com.example.myapp/...