Package org.pipservices3.commons.refer

Class DependencyResolver

java.lang.Object

org.pipservices3.commons.refer.DependencyResolver

All Implemented Interfaces:

IConfigurable, IReconfigurable, IReferenceable

public class DependencyResolver
extends Object
implements IReferenceable, IReconfigurable

Helper class for resolving component dependencies.

The resolver is configured to resolve named dependencies by specific locator. During deployment the dependency locator can be changed.

This mechanism can be used to clarify specific dependency among several alternatives. Typically components are configured to retrieve the first dependency that matches logical group, type and version. But if container contains more than one instance and resolution has to be specific about those instances, they can be given a unique name and dependency resolvers can be reconfigured to retrieve dependencies by their name.

Configuration parameters:

• dependencies:
  • [dependency name 1]: [dependency 1 locator (descriptor)]
  • ...
  • [dependency name N]: [dependency N locator (descriptor)]
• References:
  • [references that match configured dependencies]

### Example ###

 
 class MyComponent implements IConfigurable, IReferenceable {
   private DependencyResolver _dependencyResolver = new DependencyResolver();
   private IMyPersistence _persistence;
   ...

   public MyComponent() {
     this._dependencyResolver.put("persistence", new Descriptor("mygroup", "persistence", "*", "*", "1.0"));
     }

   public void configure(ConfigParams config) {
     this._dependencyResolver.configure(config);
   }

   public void setReferences(IReferences references) {
     this._dependencyResolver.setReferences(references);
     this._persistence = (IMyPersistence)this._dependencyResolver.getOneRequired("persistence");
   }
 }

 // Create mycomponent and set specific dependency out of many
 MyComponent component = new MyComponent();
 component.configure(ConfigParams.fromTuples(
   "dependencies.persistence", "mygroup:persistence:*:persistence2:1.0" // Override default persistence dependency
 ));
 component.setReferences(References.fromTuples(
   new Descriptor("mygroup","persistence","*","persistence1","1.0"), new MyPersistence(),
   new Descriptor("mygroup","persistence","*","persistence2","1.0"), new MyPersistence()  // This dependency shall be set
 ));
 
 

See Also:

• IReferences

Constructor Summary

Constructors

Constructor	Description
DependencyResolver()	Creates a new instance of the dependency resolver.
DependencyResolver(ConfigParams config)	Creates a new instance of the dependency resolver.

Method Summary

Modifier and Type	Method	Description
void	configure(ConfigParams config)	Configures the component with specified parameters.
<T> List<T>	find(Class<T> type, String name, boolean required)	Finds all matching dependencies by their name and matching to the specified type.
List<Object>	find(String name, boolean required)	Finds all matching dependencies by their name.
static DependencyResolver	fromTuples(Object... tuples)	Creates a new DependencyResolver from a list of key-value pairs called tuples where key is dependency name and value the depedency locator (descriptor).
static DependencyResolver	fromTuples(List<Object>... tuples)	Creates a new DependencyResolver from a list of key-value pairs called tuples where key is dependency name and value the depedency locator (descriptor).
<T> T	getOneOptional(Class<T> type, String name)	Gets one optional dependency by its name and matching to the specified type.
Object	getOneOptional(String name)	Gets one optional dependency by its name.
<T> T	getOneRequired(Class<T> type, String name)	Gets one required dependency by its name and matching to the specified type.
Object	getOneRequired(String name)	Gets one required dependency by its name.
<T> List<T>	getOptional(Class<T> type, String name)	Gets all optional dependencies by their name.
List<Object>	getOptional(String name)	Gets all optional dependencies by their name.
<T> List<T>	getRequired(Class<T> type, String name)	Gets all required dependencies by their name.
List<Object>	getRequired(String name)	Gets all required dependencies by their name.
void	put(String name, Object locator)	Adds a new dependency into this resolver.
void	setReferences(IReferences references)	Sets the component references

Methods inherited from class java.lang.Object

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

Constructor Details

DependencyResolver

public DependencyResolver()

Creates a new instance of the dependency resolver.

DependencyResolver

public DependencyResolver(ConfigParams config)

Creates a new instance of the dependency resolver.

Parameters:

config - (optional) default configuration where key is dependency name and value is locator (descriptor)

See Also:

• ConfigParams
• configure(ConfigParams)
• IReferences
• setReferences(IReferences)

Method Details

configure

public void configure(ConfigParams config)
               throws ConfigException

Configures the component with specified parameters.

Specified by:

configure in interface IConfigurable

Parameters:

config - configuration parameters to set.

Throws:

ConfigException - when configuration is wrong.

See Also:

• ConfigParams

setReferences

public void setReferences(IReferences references)
                   throws ReferenceException

Sets the component references

Specified by:

setReferences in interface IReferenceable

Parameters:

references - references to set.

Throws:

ReferenceException - when no references found.

See Also:

• IReferences

put

public void put(String name,
 Object locator)

Adds a new dependency into this resolver.

Parameters:

name - the dependency's name.

locator - the locator to find the dependency by.

getOptional

public List<Object> getOptional(String name)

Gets all optional dependencies by their name.

Parameters:

name - the dependency name to locate.

Returns:

a list with found dependencies or empty list of no dependencies was found.

getOptional

public <T> List<T> getOptional(Class<T> type,
 String name)

Gets all optional dependencies by their name.

Parameters:

type - the Class type that defined the type of the result.

name - the dependency name to locate.

Returns:

a list with found dependencies or empty list of no dependencies was found.

getRequired

public List<Object> getRequired(String name)
                         throws ReferenceException

Gets all required dependencies by their name. At least one dependency must present. If no dependencies was found it throws a ReferenceException

Parameters:

name - the dependency name to locate.

Returns:

a list with found dependencies.

Throws:

ReferenceException - when no single component reference is found

getRequired

public <T> List<T> getRequired(Class<T> type,
 String name)
                        throws ReferenceException

Gets all required dependencies by their name. At least one dependency must present. If no dependencies was found it throws a ReferenceException

Parameters:

type - the Class type that defined the type of the result.

name - the dependency name to locate.

Returns:

a list with found dependencies.

Throws:

ReferenceException - when no single component reference is found

getOneOptional

public Object getOneOptional(String name)

Gets one optional dependency by its name.

Parameters:

name - the dependency name to locate.

Returns:

a dependency reference or null of the dependency was not found

getOneOptional

public <T> T getOneOptional(Class<T> type,
 String name)

Gets one optional dependency by its name and matching to the specified type.

Parameters:

type - the Class type that defined the type of the result.

name - the dependency name to locate.

Returns:

a dependency reference or null of the dependency was not found

getOneRequired

public Object getOneRequired(String name)
                      throws ReferenceException

Gets one required dependency by its name. At least one dependency must present. If the dependency was found it throws a ReferenceException

Parameters:

name - the dependency name to locate.

Returns:

a dependency reference

Throws:

ReferenceException - if dependency was not found.

getOneRequired

public <T> T getOneRequired(Class<T> type,
 String name)
                     throws ReferenceException

Gets one required dependency by its name and matching to the specified type. At least one dependency must present. If the dependency was found it throws a ReferenceException

Parameters:

type - the Class type that defined the type of the result.

name - the dependency name to locate.

Returns:

a dependency reference

Throws:

ReferenceException - if dependency was not found.

find

public List<Object> find(String name,
 boolean required)
                  throws ReferenceException

Finds all matching dependencies by their name.

Parameters:

name - the dependency name to locate.

required - true to raise an exception when no dependencies are found.

Returns:

a list of found dependencies

Throws:

ReferenceException - of required is true and no dependencies found.

find

public <T> List<T> find(Class<T> type,
 String name,
 boolean required)
                 throws ReferenceException

Finds all matching dependencies by their name and matching to the specified type.

Parameters:

type - the Class type that defined the type of the result.

name - the dependency name to locate.

required - true to raise an exception when no dependencies are found.

Returns:

a list of found dependencies

Throws:

ReferenceException - of required is true and no dependencies found.

fromTuples

public static DependencyResolver fromTuples(Object... tuples)

Creates a new DependencyResolver from a list of key-value pairs called tuples where key is dependency name and value the depedency locator (descriptor).

Parameters:

tuples - a list of values where odd elements are dependency name and the following even elements are dependency locator (descriptor)

Returns:

a newly created DependencyResolver.

fromTuples

@SafeVarargs
public static DependencyResolver fromTuples(List<Object>... tuples)

Creates a new DependencyResolver from a list of key-value pairs called tuples where key is dependency name and value the depedency locator (descriptor).

Parameters:

tuples - a list of values where odd elements are dependency name and the following even elements are dependency locator (descriptor)

Returns:

a newly created DependencyResolver.