Module java.base

Package java.lang.reflect

Class Module

java.lang.Object

java.lang.reflect.Module

public final class Module
extends Object

Represents a run-time module, either named or unnamed.

Named modules have a name and are constructed by the Java Virtual Machine when a graph of modules is defined to the Java virtual machine to create a module Layer.

An unnamed module does not have a name. There is an unnamed module per ClassLoader that is obtained by invoking the class loader's getUnnamedModule method. The getModule method of all types defined by a class loader that are not in a named module return the class loader's unnamed module.

The package names that are parameters or returned by methods defined in this class are the fully-qualified names of the packages as defined in section 6.5.3 of The Java™ Language Specification , for example, "java.lang".

Unless otherwise specified, passing a null argument to a method in this class causes a NullPointerException to be thrown.

Since:

9

See Also:

Class.getModule()

Method Summary

Modifier and Type	Method and Description
Module	addExports(String pn, Module other) If the caller's module is this module then update this module to export package pn to the given module.
Module	addReads(Module other) If the caller's module is this module then update this module to read the given module.
Module	addUses(Class<?> st) If the caller's module is this module then update this module to add a service dependence on the given service type.
boolean	canRead(Module other) Indicates if this module reads the given module.
boolean	canUse(Class<?> st) Indicates if this module has a service dependence on the given service type.
ClassLoader	getClassLoader() Returns the ClassLoader for this module.
ModuleDescriptor	getDescriptor() Returns the module descriptor for this module or null if this module is an unnamed module.
Layer	getLayer() Returns the layer that contains this module or null if this module is not in a layer.
String	getName() Returns the module name or null if this module is an unnamed module.
String[]	getPackages() Returns an array of the package names of the packages in this module.
InputStream	getResourceAsStream(String name) Returns an input stream for reading a resource in this module.
boolean	isExported(String pn) Returns true if this module exports the given package unconditionally.
boolean	isExported(String pn, Module other) Returns true if this module exports the given package to at least the given module.
boolean	isNamed() Returns true if this module is a named module.
String	toString() Returns the string representation of this module.

Methods inherited from class java.lang.Object

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

Method Detail

isNamed

public boolean isNamed()

Returns true if this module is a named module.

Returns:

true if this is a named module

See Also:

ClassLoader.getUnnamedModule()

getName

public String getName()

Returns the module name or null if this module is an unnamed module.

Returns:

The module name

getClassLoader

public ClassLoader getClassLoader()

Returns the ClassLoader for this module.

If there is a security manager then its checkPermission method if first called with a RuntimePermission("getClassLoader") permission to check that the caller is allowed to get access to the class loader.

Returns:

The class loader for this module

Throws:

SecurityException - If denied by the security manager

getDescriptor

public ModuleDescriptor getDescriptor()

Returns the module descriptor for this module or null if this module is an unnamed module.

Returns:

The module descriptor for this module

getLayer

public Layer getLayer()

Returns the layer that contains this module or null if this module is not in a layer. A module Layer contains named modules and therefore this method always returns null when invoked on an unnamed module.

Dynamic modules are named modules that are generated at runtime. A dynamic module may or may not be in a module Layer.

Returns:

The layer that contains this module

See Also:

Proxy

canRead

public boolean canRead(Module other)

Indicates if this module reads the given module. This method returns true if invoked to test if this module reads itself. It also returns true if invoked on an unnamed module (as unnamed modules read all modules).

Parameters:

other - The other module

Returns:

true if this module reads other

See Also:

addReads(Module)

addReads

public Module addReads(Module other)

If the caller's module is this module then update this module to read the given module. This method is a no-op if other is this module (all modules can read themselves) or this module is an unnamed module (as unnamed modules read all modules).

Parameters:

other - The other module

Returns:

this module

Throws:

IllegalStateException - If this is a named module and the caller is not this module

See Also:

canRead(java.lang.reflect.Module)

isExported

public boolean isExported(String pn,
                          Module other)

Returns true if this module exports the given package to at least the given module.

This method always return true when invoked on an unnamed module.

This method does not check if the given module reads this module

Parameters:

pn - The package name

other - The other module

Returns:

true if this module exports the package to at least the given module

isExported

public boolean isExported(String pn)

Returns true if this module exports the given package unconditionally.

This method always return true when invoked on an unnamed module.

This method does not check if the given module reads this module

Parameters:

pn - The package name

Returns:

true if this module exports the package unconditionally

addExports

public Module addExports(String pn,
                         Module other)

If the caller's module is this module then update this module to export package pn to the given module.

This method has no effect if the package is already exported to the given module. It also has no effect if invoked on an unnamed module (as unnamed modules export all packages).

Parameters:

pn - The package name

other - The module

Returns:

this module

Throws:

IllegalArgumentException - If pn is null, or this is a named module and the package pn is not a package in this module

IllegalStateException - If this is a named module and the caller is not this module

addUses

public Module addUses(Class<?> st)

If the caller's module is this module then update this module to add a service dependence on the given service type. This method is intended for use by frameworks that invoke ServiceLoader on behalf of other modules or where the framework is passed a reference to the service type by other code. This method is a no-op when invoked on an unnamed module.

This method does not cause resolveRequiresAndUses to be re-run.

Parameters:

st - The service type

Returns:

this module

Throws:

IllegalStateException - If this is a named module and the caller is not this module

See Also:

canUse(Class), ModuleDescriptor.uses()

canUse

public boolean canUse(Class<?> st)

Indicates if this module has a service dependence on the given service type. This method always returns true when invoked on an unnamed module.

Parameters:

st - The service type

Returns:

true if this module uses service type st

See Also:

addUses(Class)

getPackages

public String[] getPackages()

Returns an array of the package names of the packages in this module.

For named modules, the returned array contains an element for each package in the module. It may contain elements corresponding to packages added to the module, dynamic modules for example, after it was loaded.

For unnamed modules, this method is the equivalent of invoking the getDefinedPackages method of this module's class loader and returning the array of package names.

A package name appears at most once in the returned array.

API Note:

This method returns an array rather than a Set for consistency with other java.lang.reflect types.

Returns:

an array of the package names of the packages in this module

getResourceAsStream

public InputStream getResourceAsStream(String name)
                                throws IOException

Returns an input stream for reading a resource in this module. Returns null if the resource is not in this module or access to the resource is denied by the security manager. The name is a '/'-separated path name that identifies the resource.

If this module is an unnamed module, and the ClassLoader for this module is not null, then this method is equivalent to invoking the getResourceAsStream method on the class loader for this module.

Parameters:

name - The resource name

Returns:

An input stream for reading the resource or null

Throws:

IOException - If an I/O error occurs

See Also:

ModuleReader.open(String)

toString

public String toString()

Returns the string representation of this module. For a named module, the representation is the string "module", followed by a space, and then the module name. For an unnamed module, the representation is the string "unnamed module", followed by a space, and then an implementation specific string that identifies the unnamed module.

Overrides:

toString in class Object

Returns:

The string representation of this module