Class Module

java.lang.Object
java.lang.Module
All Implemented Interfaces:
AnnotatedElement
public final classModuleextendsObjectimplementsAnnotatedElement
Represents a run-time module, eithernamed or unnamed.

Named modules have aname and are constructed by theJava Virtual Machine when a graph of modules is defined to the Java virtualmachine to create amodule layer.

An unnamed module does not have a name. There is an unnamed module foreachClassLoader, obtained by invoking itsgetUnnamedModule method. All types that arenot in a named module are members of their defining class loader's unnamedmodule.

The package names that are parameters or returned by methods defined inthis class are the fully-qualified names of the packages as defined insection6.5.3 ofThe Java Language Specification, forexample,"java.lang".

Unless otherwise specified, passing anull argument to a methodin this class causes aNullPointerException tobe thrown.

SeeJava Language Specification:
7.7 Module Declarations
Since:
9
See Also:

  • Method Details

    • isNamed

      public boolean isNamed()
      Returnstrue if this module is a named module.
      Returns:
      true if this is a named module
      SeeJava Language Specification:
      7.7.5 Unnamed Modules
      See Also:

    • getName

      public String getName()
      Returns the module name ornull if this module is an unnamedmodule.
      Returns:
      The module name

    • getClassLoader

      public ClassLoader getClassLoader()
      Returns theClassLoader for this module.
      Returns:
      The class loader for this module

    • getDescriptor

      public ModuleDescriptor getDescriptor()
      Returns the module descriptor for this module ornull if thismodule is an unnamed module.
      Returns:
      The module descriptor for this module

    • getLayer

      public ModuleLayer getLayer()
      Returns the module layer that contains this module ornull ifthis module is not in a module layer.A module layer contains named modules and therefore this method alwaysreturnsnull when invoked on an unnamed module.

      Dynamic modules arenamed modules that are generated at runtime. A dynamic module may or maynot be in a module layer.

      Returns:
      The module layer that contains this module
      See Also:

    • isNativeAccessEnabled

      public boolean isNativeAccessEnabled()
      Returnstrue if this module can accessrestricted methods.
      Returns:
      true if this module can accessrestricted methods.
      Since:
      22

    • canRead

      public boolean canRead(Module other)
      Indicates if this module reads the given module. This method returnstrue if invoked to test if this module reads itself. It alsoreturnstrue if invoked on an unnamed module (as unnamedmodules read all modules).
      Parameters:
      other - The other module
      Returns:
      true if this module readsother
      See Also:

    • addReads

      public Module addReads(Module other)
      If the caller's module is this module then update this module to readthe given module.This method is a no-op ifother is this module (all modules readthemselves), this module is an unnamed module (as unnamed modules readall modules), or this module already readsother.
      Implementation Note:
      Read edges added by this method areweak anddo not preventother from being GC'ed when this module isstrongly reachable.
      Parameters:
      other - The other module
      Returns:
      this module
      Throws:
      IllegalCallerException - If this is a named module and the caller's module is not this module
      See Also:

    • isExported

      public boolean isExported(String pn,Module other)
      Returnstrue if this module exports the given package to atleast the given module.

      This method returnstrue if invoked to test if a package inthis module is exported to itself. It always returnstrue wheninvoked on an unnamed module. A package that isopen tothe given module is considered exported to that module at run-time andso this method returnstrue if the package is open to the givenmodule.

      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
      See Also:

    • isOpen

      public boolean isOpen(String pn,Module other)
      Returnstrue if this module hasopened a package to atleast the given module.

      This method returnstrue if invoked to test if a package inthis module is open to itself. It returnstrue when invoked on anopen module with a package in the module.It always returnstrue when invoked on an unnamed module.

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

      API Note:
      A packagep opened to moduleM allows code inM dodeep reflection on all types in the package.Further, ifM reads this module, it can obtain aLookup object that is allowed todefine classesin packagep.
      Parameters:
      pn - The package name
      other - The other module
      Returns:
      true if this module hasopened the package to at least the given module
      See Also:

    • isExported

      public boolean isExported(String pn)
      Returnstrue if this module exports the given packageunconditionally.

      This method always returnstrue when invoked on an unnamedmodule. A package that isopened unconditionallyis considered exported unconditionally at run-time and so this methodreturnstrue if the package is opened unconditionally.

      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
      See Also:

    • isOpen

      public boolean isOpen(String pn)
      Returnstrue if this module hasopened a packageunconditionally.

      This method always returnstrue when invoked on an unnamedmodule. Additionally, it always returnstrue when invoked on anopen module with a package in themodule.

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

      API Note:
      A packagep opened to moduleM allows code inM dodeep reflection on all types in the package.Further, ifM reads this module, it can obtain aLookup object that is allowed todefine classesin packagep.
      Parameters:
      pn - The package name
      Returns:
      true if this module hasopened the package unconditionally
      See Also:

    • addExports

      public Module addExports(String pn,Module other)
      If the caller's module is this module then update this module to exportthe given package to the given module.

      This method has no effect if the package is already exported (oropen) to the given module.

      API Note:
      As specified in section5.4.3 of theThe JavaVirtual Machine Specification, if an attempt to resolve asymbolic reference fails because of a linkage error, then subsequentattempts to resolve the reference always fail with the same error thatwas thrown as a result of the initial resolution attempt.
      Parameters:
      pn - The package name
      other - The module
      Returns:
      this module
      Throws:
      IllegalArgumentException - Ifpn isnull, or this is a named module and the packagepn is not a package in this module
      IllegalCallerException - If this is a named module and the caller's module is not this module
      SeeJava Virtual Machine Specification:
      5.4.3 Resolution
      See Also:

    • addOpens

      public Module addOpens(String pn,Module other)
      If this module hasopened a package to at least the callermodule then update this module to open the package to the given module.Opening a package with this method allows all types in the package,and all their members, not just public types and their public members,to be reflected on by the given module when using APIs that supportprivate access or a way to bypass or suppress default Java languageaccess control checks.

      This method has no effect if the package is alreadyopento the given module.

      API Note:
      This method can be used for cases where aconsumermodule uses a qualified opens to open a package to anAPImodule but where the reflective access to the members of classes inthe consumer module is delegated to code in another module. Code in theAPI module can use this method to open the package in the consumer moduleto the other module.
      Parameters:
      pn - The package name
      other - The module
      Returns:
      this module
      Throws:
      IllegalArgumentException - Ifpn isnull, or this is a named module and the packagepn is not a package in this module
      IllegalCallerException - If this is a named module and this module has not opened the package to at least the caller's module
      See Also:

    • addUses

      public Module addUses(Class<?> service)
      If the caller's module is this module then update this module to add aservice dependence on the given service type. This method is intendedfor use by frameworks that invokeServiceLoader on behalf of other modules or where the framework ispassed a reference to the service type by other code. This method isa no-op when invoked on an unnamed module or an automatic module.

      This method does not causeresolveAndBind to be re-run.

      Parameters:
      service - The service type
      Returns:
      this module
      Throws:
      IllegalCallerException - If this is a named module and the caller's module is not this module
      See Also:

    • canUse

      public boolean canUse(Class<?> service)
      Indicates if this module has a service dependence on the given servicetype. This method always returnstrue when invoked on an unnamedmodule or an automatic module.
      Parameters:
      service - The service type
      Returns:
      true if this module uses service typest
      See Also:

    • getPackages

      public Set<String> getPackages()
      Returns the set of package names for the packages in this module.

      For named modules, the returned set contains an element for eachpackage in the module.

      For unnamed modules, the returned set contains an element foreach package thathas been definedin the unnamed module.

      Returns:
      the set of the package names of the packages in this module

    • getAnnotation

      public <T extendsAnnotation> T getAnnotation(Class<T> annotationClass)
      Returns this element's annotation for the specified type ifsuch an annotation ispresent, else null.This method returnsnull when invoked on an unnamed module.

      Note that any annotation returned by this method is adeclaration annotation.

      Specified by:
      getAnnotation in interface AnnotatedElement
      Type Parameters:
      T - the type of the annotation to query for and return if present
      Parameters:
      annotationClass - the Class object corresponding to the annotation type
      Returns:
      this element's annotation for the specified annotation type if present on this element, else null

    • getAnnotations

      public Annotation[] getAnnotations()
      Returns annotations that arepresent on this element.If there are no annotationspresent on this element, the returnvalue is an array of length 0.The caller of this method is free to modify the returned array; it willhave no effect on the arrays returned to other callers.This method returns an empty array when invoked on an unnamed module.

      Note that any annotations returned by this method aredeclaration annotations.

      Specified by:
      getAnnotations in interface AnnotatedElement
      Returns:
      annotations present on this element

    • getDeclaredAnnotations

      public Annotation[] getDeclaredAnnotations()
      Returns annotations that aredirectly present on this element.This method ignores inherited annotations.If there are no annotationsdirectly present on this element,the return value is an array of length 0.The caller of this method is free to modify the returned array; it willhave no effect on the arrays returned to other callers.This method returns an empty array when invoked on an unnamed module.

      Note that any annotations returned by this method aredeclaration annotations.

      Specified by:
      getDeclaredAnnotations in interface AnnotatedElement
      Returns:
      annotations directly present on this element

    • getResourceAsStream

      public InputStream getResourceAsStream(String name) throwsIOException
      Returns an input stream for reading a resource in this module.Thename parameter is a'/'-separated path name thatidentifies the resource. As withClass.getResourceAsStream, this method delegates to the module's classloaderfindResource(String,String) method, invoking it with the module name(ornull when the module is unnamed) and the name of theresource. If the resource name has a leading slash then it is droppedbefore delegation.

      A resource in a named module may beencapsulated so thatit cannot be located by code in other modules. Whether a resource can belocated or not is determined as follows:

      • If the resource name ends with ".class" then it is not encapsulated.
      • Apackage name is derived from the resource name. If the package name is apackage in the module then the resource can only be located by the caller of this method when the package isopen to at least the caller's module. If the resource is not in a package in the module then the resource is not encapsulated.

      In the above, thepackage name for a resource is derivedfrom the subsequence of characters that precedes the last'/' inthe name and then replacing each'/' character in the subsequencewith'.'. A leading slash is ignored when deriving the packagename. As an example, the package name derived for a resource named"a/b/c/foo.properties" is "a.b.c". A resource namewith the name "META-INF/MANIFEST.MF" is never encapsulatedbecause "META-INF" is not a legal package name.

      This method returnsnull if the resource is not in this moduleor the resource is encapsulated and cannot be located by the caller.

      Parameters:
      name - The resource name
      Returns:
      An input stream for reading the resource ornull
      Throws:
      IOException - If an I/O error occurs
      See Also:

    • 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 isthe string"unnamed module", followed by a space, and then animplementation specific string that identifies the unnamed module.
      Overrides:
      toString in class Object
      Returns:
      The string representation of this module