Class Configuration
A configuration encapsulates the readability graph that is the
output of resolution. A readability graph is a directed graph whose vertices
are of type ResolvedModule
and the edges represent the readability
amongst the modules. Configuration
defines the modules()
method to get the set of resolved modules in the graph.
ResolvedModule
defines the reads()
method to
get the set of modules that a resolved module reads. The modules that are
read may be in the same configuration or may be in parent
configurations.
Configuration defines the resolve
method to resolve a collection of root modules, and the resolveAndBind
method to do resolution with service binding. There are instance and
static variants of both methods. The instance methods create a configuration
with the receiver as the parent configuration. The static methods are for
more advanced cases where there can be more than one parent configuration.
Each layer
of modules in the Java virtual
machine is created from a configuration. The configuration for the boot
layer is obtained by invoking
ModuleLayer.boot().configuration()
. The configuration for the boot layer
will often be the parent when creating new configurations.
Example
The following example uses the resolve
method to resolve a
module named myapp with the configuration for the boot layer as the
parent configuration. It prints the name of each resolved module and the
names of the modules that each module reads.
Path dir1 = ..., dir2 = ..., dir3 = ...;
ModuleFinder finder = ModuleFinder.of(dir1, dir2, dir3);
Configuration parent = ModuleLayer.boot().configuration();
Configuration cf = parent.resolve(finder, ModuleFinder.of(), Set.of("myapp"));
cf.modules().forEach(m -> {
System.out.format("%s -> %s%n",
m.name(),
m.reads().stream()
.map(ResolvedModule::name)
.collect(Collectors.joining(", ")));
});
- Since:
- 9
- See Also:
-
Method Summary
Modifier and TypeMethodDescriptionstatic Configuration
empty()
Returns the empty configuration.findModule
(String name) Finds a resolved module in this configuration, or if not in this configuration, the parent configurations.modules()
Returns an unmodifiable set of the resolved modules in this configuration.parents()
Returns an unmodifiable list of this configuration's parents, in search order.resolve
(ModuleFinder before, ModuleFinder after, Collection<String> roots) Resolves a collection of root modules, with this configuration as its parent, to create a new configuration.static Configuration
resolve
(ModuleFinder before, List<Configuration> parents, ModuleFinder after, Collection<String> roots) Resolves a collection of root modules to create a configuration.resolveAndBind
(ModuleFinder before, ModuleFinder after, Collection<String> roots) Resolves a collection of root modules, with service binding, and with this configuration as its parent, to create a new configuration.static Configuration
resolveAndBind
(ModuleFinder before, List<Configuration> parents, ModuleFinder after, Collection<String> roots) Resolves a collection of root modules, with service binding, to create configuration.toString()
Returns a string describing this configuration.
-
Method Details
-
resolve
Resolves a collection of root modules, with this configuration as its parent, to create a new configuration. This method works exactly as specified by the staticresolve
method when invoked with this configuration as the parent. In other words, if this configuration iscf
then this method is equivalent to invoking:Configuration.resolve(before, List.of(cf), after, roots);
- Parameters:
before
- The before module finder to find modulesafter
- The after module finder to locate modules when not located by thebefore
module finder or in parent configurationsroots
- The possibly-empty collection of module names of the modules to resolve- Returns:
- The configuration that is the result of resolving the given root modules
- Throws:
FindException
- If resolution fails for any of the observability-related reasons specified by the staticresolve
methodResolutionException
- If resolution fails any of the consistency checks specified by the staticresolve
methodSecurityException
- If locating a module is denied by the security manager
-
resolveAndBind
public Configuration resolveAndBind(ModuleFinder before, ModuleFinder after, Collection<String> roots) Resolves a collection of root modules, with service binding, and with this configuration as its parent, to create a new configuration. This method works exactly as specified by the staticresolveAndBind
method when invoked with this configuration as the parent. In other words, if this configuration iscf
then this method is equivalent to invoking:Configuration.resolveAndBind(before, List.of(cf), after, roots);
- Parameters:
before
- The before module finder to find modulesafter
- The after module finder to locate modules when not located by thebefore
module finder or in parent configurationsroots
- The possibly-empty collection of module names of the modules to resolve- Returns:
- The configuration that is the result of resolving, with service binding, the given root modules
- Throws:
FindException
- If resolution fails for any of the observability-related reasons specified by the staticresolve
methodResolutionException
- If resolution fails any of the consistency checks specified by the staticresolve
methodSecurityException
- If locating a module is denied by the security manager
-
resolve
public static Configuration resolve(ModuleFinder before, List<Configuration> parents, ModuleFinder after, Collection<String> roots) Resolves a collection of root modules to create a configuration.Each root module is located using the given
before
module finder. If a module is not found then it is located in the parent configuration as if by invoking thefindModule
method on each parent in iteration order. If not found then the module is located using the givenafter
module finder. The same search order is used to locate transitive dependences. Root modules or dependences that are located in a parent configuration are resolved no further and are not included in the resulting configuration.When all modules have been enumerated then a readability graph is computed, and in conjunction with the module exports and service use, checked for consistency.
Resolution may fail with
FindException
for the following observability-related reasons:A root module, or a direct or transitive dependency, is not found.
An error occurs when attempting to find a module. Possible errors include I/O errors, errors detected parsing a module descriptor (
module-info.class
) or two versions of the same module are found in the same directory.
Resolution may fail with
ResolutionException
if any of the following consistency checks fail:A cycle is detected, say where module
m1
requires modulem2
andm2
requiresm1
.A module reads two or more modules with the same name. This includes the case where a module reads another with the same name as itself.
Two or more modules in the configuration export the same package to a module that reads both. This includes the case where a module
M
containing packagep
reads another module that exportsp
toM
.A module
M
declares that it "uses p.S
" or "provides p.S with ...
" but packagep
is neither in moduleM
nor exported toM
by any module thatM
reads.
- Implementation Note:
- In the implementation then observability of modules may depend on referential integrity or other checks that ensure different builds of tightly coupled modules or modules for specific operating systems or architectures are not combined in the same configuration.
- Parameters:
before
- The before module finder to find modulesparents
- The list parent configurations in search orderafter
- The after module finder to locate modules when not located by thebefore
module finder or in parent configurationsroots
- The possibly-empty collection of module names of the modules to resolve- Returns:
- The configuration that is the result of resolving the given root modules
- Throws:
FindException
- If resolution fails for any of observability-related reasons specified aboveResolutionException
- If resolution fails for any of the consistency checks specified aboveIllegalArgumentException
- If the list of parents is empty, or the list has two or more parents with modules for different target operating systems, architectures, or versionsSecurityException
- If locating a module is denied by the security manager
-
resolveAndBind
public static Configuration resolveAndBind(ModuleFinder before, List<Configuration> parents, ModuleFinder after, Collection<String> roots) Resolves a collection of root modules, with service binding, to create configuration.This method works exactly as specified by
resolve
except that the graph of resolved modules is augmented with modules induced by the service-use dependence relation.More specifically, the root modules are resolved as if by calling
resolve
. The resolved modules, and all modules in the parent configurations, withservice dependences
are then examined. All modules found by the given module finders thatprovide
an implementation of one or more of the service types are added to the module graph and then resolved as if by calling theresolve
method. Adding modules to the module graph may introduce new service-use dependences and so the process works iteratively until no more modules are added.As service binding involves resolution then it may fail with
FindException
orResolutionException
for exactly the same reasons specified inresolve
.- Parameters:
before
- The before module finder to find modulesparents
- The list parent configurations in search orderafter
- The after module finder to locate modules when not located by thebefore
module finder or in parent configurationsroots
- The possibly-empty collection of module names of the modules to resolve- Returns:
- The configuration that is the result of resolving, with service binding, the given root modules
- Throws:
FindException
- If resolution fails for any of the observability-related reasons specified by the staticresolve
methodResolutionException
- If resolution fails any of the consistency checks specified by the staticresolve
methodIllegalArgumentException
- If the list of parents is empty, or the list has two or more parents with modules for different target operating systems, architectures, or versionsSecurityException
- If locating a module is denied by the security manager
-
empty
Returns the empty configuration. There are no modules in the empty configuration. It has no parents.- Returns:
- The empty configuration
-
parents
Returns an unmodifiable list of this configuration's parents, in search order. If this is the empty configuration then an empty list is returned.- Returns:
- A possibly-empty unmodifiable list of this parent configurations
-
modules
Returns an unmodifiable set of the resolved modules in this configuration.- Returns:
- A possibly-empty unmodifiable set of the resolved modules in this configuration
-
findModule
Finds a resolved module in this configuration, or if not in this configuration, the parent configurations. Finding a module in parent configurations is equivalent to invokingfindModule
on each parent, in search order, until the module is found or all parents have been searched. In a tree of configurations then this is equivalent to a depth-first search.- Parameters:
name
- The module name of the resolved module to find- Returns:
- The resolved module with the given name or an empty
Optional
if there isn't a module with this name in this configuration or any parent configurations
-
toString
-