ModuleReference (Java SE 17 & JDK 17)
Description: declaration: module: java.base, package: java.lang.module, class: ModuleReference
Keywords: java.lang.module.ModuleReference class

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

  Modifier and Type
  Method
  Description
  `final ModuleDescriptor`
  `descriptor()`
  Returns the module descriptor.
  `final Optional<URI>`
  `location()`
  Returns the location of this module's content, if known.
  `abstract ModuleReader`
  `open()`
  Opens the module content for reading.

  ### Methods declared in class java.lang.Object

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

- ## Constructor Details

  - ### 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 Details

  - ### 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