Class ModuleDescriptor

java.lang.Object
java.lang.module.ModuleDescriptor
All Implemented Interfaces:
Comparable<ModuleDescriptor>
public classModuleDescriptorextendsObjectimplementsComparable<ModuleDescriptor>
A module descriptor.

A module descriptor describes a named module and defines methods to obtain each of its components. The module descriptor for a named module in the Java virtual machine is obtained by invoking theModule'sgetDescriptor method. Module descriptors can also be created using theModuleDescriptor.Builder class or by reading the binary form of a module declaration (module-info.class) using theread methods defined here.

A module descriptor describes anormal, open, or automatic module.Normal modules and open modules describe theirdependences,exported-packages, the services that theyuse orprovide, and other components.Normal modules mayopen specific packages. The module descriptor for an open module does not declare any open packages (itsopens method returns an empty set) but when instantiated in the Java virtual machine then it is treated as if all packages are open. The module descriptor for an automatic module does not declare any dependences (except for the mandatory dependency on java.base), and does not declare any exported or open packages. Automatic modules receive special treatment during resolution so that they read all other modules in the configuration. When an automatic module is instantiated in the Java virtual machine then it reads every unnamed module and is treated as if all packages are exported and open.

ModuleDescriptor objects are immutable and safe for use by multiple concurrent threads.

Since:
9
See Also:

  • Method Details

    • name

      public String name()

      Returns the module name.

      Returns:
      The module name

    • modifiers

      public Set<ModuleDescriptor.Modifier> modifiers()

      Returns the set of module modifiers.

      Returns:
      A possibly-empty unmodifiable set of modifiers

    • accessFlags

      public Set<AccessFlag> accessFlags()
      Returns the set of themodule flags.
      Returns:
      A possibly-empty unmodifiable set of module flags
      SeeJava Virtual Machine Specification:
      4.7.25 The Module Attribute
      Since:
      20
      See Also:

    • isOpen

      public boolean isOpen()

      Returnstrue if this is an open module.

      This method is equivalent to testing if the set ofmodifiers contains theOPEN modifier.

      Returns:
      true if this is an open module

    • isAutomatic

      public boolean isAutomatic()

      Returnstrue if this is an automatic module.

      This method is equivalent to testing if the set ofmodifiers contains theAUTOMATIC modifier.

      Returns:
      true if this is an automatic module

    • requires

      public Set<ModuleDescriptor.Requires> requires()

      Returns the set ofRequires objects representing the module dependences.

      The set includes a dependency on "java.base" when this module is not named "java.base". If this module is an automatic module then it does not have a dependency on any module other than "java.base".

      Returns:
      A possibly-empty unmodifiable set ofModuleDescriptor.Requires objects

    • exports

      public Set<ModuleDescriptor.Exports> exports()

      Returns the set ofExports objects representing the exported packages.

      If this module is an automatic module then the set of exports is empty.

      Returns:
      A possibly-empty unmodifiable set of exported packages

    • opens

      public Set<ModuleDescriptor.Opens> opens()

      Returns the set ofOpens objects representing the open packages.

      If this module is an open module or an automatic module then the set of open packages is empty.

      Returns:
      A possibly-empty unmodifiable set of open packages

    • uses

      public Set<String> uses()

      Returns the set of service dependences.

      If this module is an automatic module then the set of service dependences is empty.

      Returns:
      A possibly-empty unmodifiable set of thebinary names of the service types used

    • provides

      public Set<ModuleDescriptor.Provides> provides()

      Returns the set ofProvides objects representing the services that the module provides.

      Returns:
      The possibly-empty unmodifiable set of the services that this module provides

    • version

      Returns the module version.

      Returns:
      This module's version, or an emptyOptional if the module does not have a version or the version isunparseable

    • rawVersion

      public Optional<String> rawVersion()

      Returns the string with the possibly-unparseable version of the module.

      Returns:
      The string containing the version of the module or an emptyOptional if the module does not have a version
      See Also:

    • toNameAndVersion

      public String toNameAndVersion()

      Returns a string containing the module name and, if present, its version.

      Returns:
      A string containing the module name and, if present, its version

    • mainClass

      public Optional<String> mainClass()

      Returns the module main class.

      Returns:
      Thebinary name of the module's main class

    • packages

      public Set<String> packages()
      Returns the set of packages in the module.

      The set of packages includes all exported and open packages, as well as the packages of any service providers, and the package for the main class.

      Returns:
      A possibly-empty unmodifiable set of the packages in the module

    • compareTo

      public int compareTo(ModuleDescriptor that)
      Compares this module descriptor to another.

      TwoModuleDescriptor objects are compared by comparing their module names lexicographically. Where the module names are equal then the module versions are compared. When comparing the module versions then a module descriptor with a version is considered to succeed a module descriptor that does not have a version. If both versions areunparseable then theraw version strings are compared lexicographically. Where the module names are equal and the versions are equal (or not present in both), then the set of modifiers are compared. Sets of modifiers are compared by comparing abinary value computed for each set. If a modifier is present in the set then the bit at the position of its ordinal is1 in the binary value, otherwise0. If the two set of modifiers are also equal then the other components of the module descriptors are compared in a manner that is consistent withequals.

      Specified by:
      compareTo in interface Comparable<ModuleDescriptor>
      Parameters:
      that - The module descriptor to compare
      Returns:
      A negative integer, zero, or a positive integer if this module descriptor is less than, equal to, or greater than the given module descriptor

    • equals

      public boolean equals(Object ob)
      Tests this module descriptor for equality with the given object.

      If the given object is not aModuleDescriptor then this method returnsfalse. Two module descriptors are equal if each of their corresponding components is equal.

      This method satisfies the general contract of theObject.equals method.

      Overrides:
      equals in class Object
      Parameters:
      ob - the object to which this object is to be compared
      Returns:
      true if, and only if, the given object is a module descriptor that is equal to this module descriptor
      See Also:

    • hashCode

      public int hashCode()
      Computes a hash code for this module descriptor.

      The hash code is based upon the components of the module descriptor, and satisfies the general contract of theObject.hashCode method.

      Overrides:
      hashCode in class Object
      Returns:
      The hash-code value for this module descriptor
      See Also:

    • toString

      public String toString()

      Returns a string describing the module.

      Overrides:
      toString in class Object
      Returns:
      A string describing the module

    • newModule

      public static ModuleDescriptor.Builder newModule(String name,Set<ModuleDescriptor.Modifier> ms)
      Instantiates a builder to build a module descriptor.
      Parameters:
      name - The module name
      ms - The set of module modifiers
      Returns:
      A new builder
      Throws:
      IllegalArgumentException - If the module name isnull or is not a legal module name, or the set of modifiers containsAUTOMATIC with other modifiers

    • newModule

      public static ModuleDescriptor.Builder newModule(String name)
      Instantiates a builder to build a module descriptor for anormal module. This method is equivalent to invokingnewModule with an empty set ofmodifiers.
      Parameters:
      name - The module name
      Returns:
      A new builder
      Throws:
      IllegalArgumentException - If the module name isnull or is not a legal module name

    • newOpenModule

      public static ModuleDescriptor.Builder newOpenModule(String name)
      Instantiates a builder to build a module descriptor for an open module. This method is equivalent to invokingnewModule with theOPEN modifier.

      The builder for an open module cannot be used to declare any open packages.

      Parameters:
      name - The module name
      Returns:
      A new builder that builds an open module
      Throws:
      IllegalArgumentException - If the module name isnull or is not a legal module name

    • newAutomaticModule

      public static ModuleDescriptor.Builder newAutomaticModule(String name)
      Instantiates a builder to build a module descriptor for an automatic module. This method is equivalent to invokingnewModule with theAUTOMATIC modifier.

      The builder for an automatic module cannot be used to declare module or service dependences. It also cannot be used to declare any exported or open packages.

      Parameters:
      name - The module name
      Returns:
      A new builder that builds an automatic module
      Throws:
      IllegalArgumentException - If the module name isnull or is not a legal module name
      See Also:

    • read

      public static ModuleDescriptor read(InputStream in,Supplier<Set<String>> packageFinder) throwsIOException
      Reads the binary form of a module declaration from an input stream as a module descriptor.

      If the descriptor encoded in the input stream does not indicate a set of packages in the module then thepackageFinder will be invoked. The set of packages that thepackageFinder returns must include all the packages that the module exports, opens, as well as the packages of the service implementations that the module provides, and the package of the main class (if the module has a main class). If thepackageFinder throws anUncheckedIOException thenIOException cause will be re-thrown.

      If there are bytes following the module descriptor then it is implementation specific as to whether those bytes are read, ignored, or reported as anInvalidModuleDescriptorException. If this method fails with anInvalidModuleDescriptorException or IOException then it may do so after some, but not all, bytes have been read from the input stream. It is strongly recommended that the stream be promptly closed and discarded if an exception occurs.

      API Note:
      ThepackageFinder parameter is for use when reading module descriptors from legacy module-artifact formats that do not record the set of packages in the descriptor itself.
      Parameters:
      in - The input stream
      packageFinder - A supplier that can produce the set of packages
      Returns:
      The module descriptor
      Throws:
      InvalidModuleDescriptorException - If an invalid module descriptor is detected or the set of packages returned by thepackageFinder does not include all of the packages obtained from the module descriptor
      IOException - If an I/O error occurs reading from the input stream or UncheckedIOException is thrown by the package finder

    • read

      public static ModuleDescriptor read(InputStream in) throwsIOException
      Reads the binary form of a module declaration from an input stream as a module descriptor. This method works exactly as specified by the 2-argread method with the exception that a package finder is not used to find additional packages when the module descriptor read from the stream does not indicate the set of packages.
      Parameters:
      in - The input stream
      Returns:
      The module descriptor
      Throws:
      InvalidModuleDescriptorException - If an invalid module descriptor is detected
      IOException - If an I/O error occurs reading from the input stream

    • read

      public static ModuleDescriptor read(ByteBuffer bb,Supplier<Set<String>> packageFinder)
      Reads the binary form of a module declaration from a byte buffer as a module descriptor.

      If the descriptor encoded in the byte buffer does not indicate a set of packages in the module then thepackageFinder will be invoked. The set of packages that thepackageFinder returns must include all the packages that the module exports, opens, as well as the packages of the service implementations that the module provides, and the package of the main class (if the module has a main class). If thepackageFinder throws anUncheckedIOException thenIOException cause will be re-thrown.

      The module descriptor is read from the buffer starting at indexp, wherep is the buffer'sposition when this method is invoked. Upon return the buffer's position will be equal top + n wheren is the number of bytes read from the buffer.

      If there are bytes following the module descriptor then it is implementation specific as to whether those bytes are read, ignored, or reported as anInvalidModuleDescriptorException. If this method fails with anInvalidModuleDescriptorException then it may do so after some, but not all, bytes have been read.

      API Note:
      ThepackageFinder parameter is for use when reading module descriptors from legacy module-artifact formats that do not record the set of packages in the descriptor itself.
      Parameters:
      bb - The byte buffer
      packageFinder - A supplier that can produce the set of packages
      Returns:
      The module descriptor
      Throws:
      InvalidModuleDescriptorException - If an invalid module descriptor is detected or the set of packages returned by thepackageFinder does not include all of the packages obtained from the module descriptor

    • read

      public static ModuleDescriptor read(ByteBuffer bb)
      Reads the binary form of a module declaration from a byte buffer as a module descriptor. This method works exactly as specified by the 2-argread method with the exception that a package finder is not used to find additional packages when the module descriptor encoded in the buffer does not indicate the set of packages.
      Parameters:
      bb - The byte buffer
      Returns:
      The module descriptor
      Throws:
      InvalidModuleDescriptorException - If an invalid module descriptor is detected