Package org.springframework.core.io.support

Class SpringFactoriesLoader

java.lang.Object

org.springframework.core.io.support.SpringFactoriesLoader

Direct Known Subclasses:

MockSpringFactoriesLoader

public class SpringFactoriesLoader
extends Object

General purpose factory loading mechanism for internal use within the framework.

SpringFactoriesLoader loads and instantiates factories of a given type from "META-INF/spring.factories" files which may be present in multiple JAR files in the classpath. The spring.factories file must be in Properties format, where the key is the fully qualified name of the interface or abstract class, and the value is a comma-separated list of implementation class names. For example:

example.MyService=example.MyServiceImpl1,example.MyServiceImpl2

where example.MyService is the name of the interface, and MyServiceImpl1 and MyServiceImpl2 are two implementations.

Implementation classes must have a single resolvable constructor that will be used to create the instance, either:

• a primary or single constructor
• a single public constructor
• the default constructor

If the resolvable constructor has arguments, a suitable ArgumentResolver should be provided. To customize how instantiation failures are handled, consider providing a FailureHandler.

Since:

3.2

Author:

Arjen Poutsma, Juergen Hoeller, Sam Brannen, Andy Wilkinson, Madhura Bhave, Phillip Webb

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	SpringFactoriesLoader.ArgumentResolver	Strategy for resolving constructor arguments based on their type.
static interface	SpringFactoriesLoader.FailureHandler	Strategy for handling a failure that occurs when instantiating a factory.

Field Summary

Fields

Modifier and Type	Field	Description
static final String	FACTORIES_RESOURCE_LOCATION	The location to look for factories.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	SpringFactoriesLoader(ClassLoader classLoader, Map<String,List<String>> factories)	Create a new SpringFactoriesLoader instance.

Method Summary

Modifier and Type	Method	Description
static SpringFactoriesLoader	forDefaultResourceLocation()	Create a SpringFactoriesLoader instance that will load and instantiate the factory implementations from "META-INF/spring.factories", using the default class loader.
static SpringFactoriesLoader	forDefaultResourceLocation(ClassLoader classLoader)	Create a SpringFactoriesLoader instance that will load and instantiate the factory implementations from "META-INF/spring.factories", using the given class loader.
static SpringFactoriesLoader	forResourceLocation(String resourceLocation)	Create a SpringFactoriesLoader instance that will load and instantiate the factory implementations from the given location, using the default class loader.
static SpringFactoriesLoader	forResourceLocation(String resourceLocation, ClassLoader classLoader)	Create a SpringFactoriesLoader instance that will load and instantiate the factory implementations from the given location, using the given class loader.
protected <T> T	instantiateFactory(String implementationName, Class<T> type, SpringFactoriesLoader.ArgumentResolver argumentResolver, SpringFactoriesLoader.FailureHandler failureHandler)
<T> List<T>	load(Class<T> factoryType)	Load and instantiate the factory implementations of the given type from "META-INF/spring.factories", using the configured class loader and a default argument resolver that expects a no-arg constructor.
<T> List<T>	load(Class<T> factoryType, SpringFactoriesLoader.ArgumentResolver argumentResolver)	Load and instantiate the factory implementations of the given type from "META-INF/spring.factories", using the configured class loader and the given argument resolver.
<T> List<T>	load(Class<T> factoryType, SpringFactoriesLoader.ArgumentResolver argumentResolver, SpringFactoriesLoader.FailureHandler failureHandler)	Load and instantiate the factory implementations of the given type from "META-INF/spring.factories", using the configured class loader, the given argument resolver, and custom failure handling provided by the given failure handler.
<T> List<T>	load(Class<T> factoryType, SpringFactoriesLoader.FailureHandler failureHandler)	Load and instantiate the factory implementations of the given type from "META-INF/spring.factories", using the configured class loader with custom failure handling provided by the given failure handler.
static <T> List<T>	loadFactories(Class<T> factoryType, ClassLoader classLoader)	Load and instantiate the factory implementations of the given type from "META-INF/spring.factories", using the given class loader.
protected static Map<String,List<String>>	loadFactoriesResource(ClassLoader classLoader, String resourceLocation)
static List<String>	loadFactoryNames(Class<?> factoryType, ClassLoader classLoader)	Load the fully qualified class names of factory implementations of the given type from "META-INF/spring.factories", using the given class loader.

Methods inherited from class java.lang.Object

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

Field Details

FACTORIES_RESOURCE_LOCATION

public static final String FACTORIES_RESOURCE_LOCATION

The location to look for factories.

Can be present in multiple JAR files.

See Also:

• Constant Field Values

Constructor Details

SpringFactoriesLoader

protected SpringFactoriesLoader(@Nullable
 ClassLoader classLoader,
 Map<String,List<String>> factories)

Create a new SpringFactoriesLoader instance.

Parameters:

classLoader - the classloader used to instantiate the factories

factories - a map of factory class name to implementation class names

Since:

6.0

Method Details

load

public <T> List<T> load(Class<T> factoryType)

Load and instantiate the factory implementations of the given type from "META-INF/spring.factories", using the configured class loader and a default argument resolver that expects a no-arg constructor.

The returned factories are sorted through AnnotationAwareOrderComparator.

If a custom instantiation strategy is required, use load(...) with a custom ArgumentResolver and/or FailureHandler.

As of Spring Framework 5.3, if duplicate implementation class names are discovered for a given factory type, only one instance of the duplicated implementation type will be instantiated.

Parameters:

factoryType - the interface or abstract class representing the factory

Throws:

IllegalArgumentException - if any factory implementation class cannot be loaded or if an error occurs while instantiating any factory

Since:

6.0

load

public <T> List<T> load(Class<T> factoryType,
 @Nullable
 SpringFactoriesLoader.ArgumentResolver argumentResolver)

Load and instantiate the factory implementations of the given type from "META-INF/spring.factories", using the configured class loader and the given argument resolver.

The returned factories are sorted through AnnotationAwareOrderComparator.

As of Spring Framework 5.3, if duplicate implementation class names are discovered for a given factory type, only one instance of the duplicated implementation type will be instantiated.

Parameters:

factoryType - the interface or abstract class representing the factory

argumentResolver - strategy used to resolve constructor arguments by their type

Throws:

IllegalArgumentException - if any factory implementation class cannot be loaded or if an error occurs while instantiating any factory

Since:

6.0

load

public <T> List<T> load(Class<T> factoryType,
 @Nullable
 SpringFactoriesLoader.FailureHandler failureHandler)

Load and instantiate the factory implementations of the given type from "META-INF/spring.factories", using the configured class loader with custom failure handling provided by the given failure handler.

The returned factories are sorted through AnnotationAwareOrderComparator.

As of Spring Framework 5.3, if duplicate implementation class names are discovered for a given factory type, only one instance of the duplicated implementation type will be instantiated.

For any factory implementation class that cannot be loaded or error that occurs while instantiating it, the given failure handler is called.

Parameters:

factoryType - the interface or abstract class representing the factory

failureHandler - strategy used to handle factory instantiation failures

Since:

6.0

load

public <T> List<T> load(Class<T> factoryType,
 @Nullable
 SpringFactoriesLoader.ArgumentResolver argumentResolver,
 @Nullable
 SpringFactoriesLoader.FailureHandler failureHandler)

Load and instantiate the factory implementations of the given type from "META-INF/spring.factories", using the configured class loader, the given argument resolver, and custom failure handling provided by the given failure handler.

The returned factories are sorted through AnnotationAwareOrderComparator.

As of Spring Framework 5.3, if duplicate implementation class names are discovered for a given factory type, only one instance of the duplicated implementation type will be instantiated.

For any factory implementation class that cannot be loaded or error that occurs while instantiating it, the given failure handler is called.

Parameters:

factoryType - the interface or abstract class representing the factory

argumentResolver - strategy used to resolve constructor arguments by their type

failureHandler - strategy used to handle factory instantiation failures

Since:

6.0

instantiateFactory

@Nullable
protected <T> T instantiateFactory(String implementationName,
 Class<T> type,
 @Nullable
 SpringFactoriesLoader.ArgumentResolver argumentResolver,
 SpringFactoriesLoader.FailureHandler failureHandler)

loadFactories

public static <T> List<T> loadFactories(Class<T> factoryType,
 @Nullable
 ClassLoader classLoader)

Load and instantiate the factory implementations of the given type from "META-INF/spring.factories", using the given class loader.

The returned factories are sorted through AnnotationAwareOrderComparator.

As of Spring Framework 5.3, if duplicate implementation class names are discovered for a given factory type, only one instance of the duplicated implementation type will be instantiated.

For more advanced factory loading with SpringFactoriesLoader.ArgumentResolver or SpringFactoriesLoader.FailureHandler support use forDefaultResourceLocation(ClassLoader) to obtain a SpringFactoriesLoader instance.

Parameters:

factoryType - the interface or abstract class representing the factory

classLoader - the ClassLoader to use for loading (can be null to use the default)

Throws:

IllegalArgumentException - if any factory implementation class cannot be loaded or if an error occurs while instantiating any factory

loadFactoryNames

public static List<String> loadFactoryNames(Class<?> factoryType,
 @Nullable
 ClassLoader classLoader)

Load the fully qualified class names of factory implementations of the given type from "META-INF/spring.factories", using the given class loader.

As of Spring Framework 5.3, if a particular implementation class name is discovered more than once for the given factory type, duplicates will be ignored.

Parameters:

factoryType - the interface or abstract class representing the factory

classLoader - the ClassLoader to use for loading resources; can be null to use the default

Throws:

IllegalArgumentException - if an error occurs while loading factory names

See Also:

• loadFactories(java.lang.Class<T>, java.lang.ClassLoader)

forDefaultResourceLocation

public static SpringFactoriesLoader forDefaultResourceLocation()

Create a SpringFactoriesLoader instance that will load and instantiate the factory implementations from "META-INF/spring.factories", using the default class loader.

Returns:

a SpringFactoriesLoader instance

Since:

6.0

See Also:

• forDefaultResourceLocation(ClassLoader)

forDefaultResourceLocation

public static SpringFactoriesLoader forDefaultResourceLocation(@Nullable
 ClassLoader classLoader)

Create a SpringFactoriesLoader instance that will load and instantiate the factory implementations from "META-INF/spring.factories", using the given class loader.

Parameters:

classLoader - the ClassLoader to use for loading resources; can be null to use the default

Returns:

a SpringFactoriesLoader instance

Since:

6.0

See Also:

• forDefaultResourceLocation()

forResourceLocation

public static SpringFactoriesLoader forResourceLocation(String resourceLocation)

Create a SpringFactoriesLoader instance that will load and instantiate the factory implementations from the given location, using the default class loader.

Parameters:

resourceLocation - the resource location to look for factories

Returns:

a SpringFactoriesLoader instance

Since:

6.0

See Also:

• forResourceLocation(String, ClassLoader)

forResourceLocation

public static SpringFactoriesLoader forResourceLocation(String resourceLocation,
 @Nullable
 ClassLoader classLoader)

Create a SpringFactoriesLoader instance that will load and instantiate the factory implementations from the given location, using the given class loader.

Parameters:

resourceLocation - the resource location to look for factories

classLoader - the ClassLoader to use for loading resources; can be null to use the default

Returns:

a SpringFactoriesLoader instance

Since:

6.0

See Also:

• forResourceLocation(String)

loadFactoriesResource

protected static Map<String,List<String>> loadFactoriesResource(ClassLoader classLoader,
 String resourceLocation)