Module java.base
Package java.lang.module

## Class ModuleReference

- java.lang.Object
- - java.lang.module.ModuleReference

-     public abstract class ModuleReference
      extends Object

  A reference to a module's content.

  A module reference is a concrete implementation of this class that implements the abstract methods defined by this class. It contains the module's descriptor and its location, if known. It also has the ability to create a `ModuleReader` in order to access the module's content, which may be inside the Java run-time system itself or in an artifact such as a modular JAR file.

  Since:
    9
  See Also:
    `ModuleFinder`, `ModuleReader`

- - ### Constructor Summary

    Constructors
    Modifier | Constructor | Description
    --- | --- | ---
    `protected` | `ModuleReference​(ModuleDescriptor descriptor, URI location)` | Constructs a new instance of this class.

  - ### Method Summary

    All Methods Instance Methods Abstract Methods Concrete Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `ModuleDescriptor` | `descriptor​()` | Returns the module descriptor.
    `Optional<URI>` | `location​()` | Returns the location of this module's content, if known.
    `abstract ModuleReader` | `open​()` | Opens the module content for reading.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### ModuleReference

          protected ModuleReference​(ModuleDescriptor descriptor,
                                    URI location)

      Constructs a new instance of this class.
      Parameters:
        `descriptor` - The module descriptor
        `location` - The module location or `null` if not known

  - ### Method Detail

    - #### descriptor

          public final ModuleDescriptor descriptor​()

      Returns the module descriptor.
      Returns:
        The module descriptor

    - #### location

          public final Optional<URI> location​()

      Returns the location of this module's content, if known.

      This URI, when present, can be used as the location value of a `CodeSource` so that a module's classes can be granted specific permissions when loaded by a `SecureClassLoader`.

      Returns:
        The location or an empty `Optional` if not known

    - #### open

          public abstract ModuleReader open​()
                                     throws IOException

      Opens the module content for reading.
      Returns:
        A `ModuleReader` to read the module
      Throws:
        `IOException` - If an I/O error occurs
        `SecurityException` - If denied by the security manager