Package org.springframework.core.io.support

Class SpringFactoriesLoader

java.lang.Object
org.springframework.core.io.support.SpringFactoriesLoader
public final 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

  • 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:

  • Method Details

    • 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 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 loadFactories 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
      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

    • loadFactories

      public static <T> List<T> loadFactories(Class<T> factoryType, @Nullable ClassLoader classLoader, @Nullable SpringFactoriesLoader.ArgumentResolver argumentResolver)
      Load and instantiate the factory implementations of the given type from "META-INF/spring.factories", using the given class loader and 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
      classLoader - the ClassLoader to use for loading (can be null to use the default)
      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

    • loadFactories

      public static <T> List<T> loadFactories(Class<T> factoryType, @Nullable ClassLoader classLoader, @Nullable SpringFactoriesLoader.FailureHandler failureHandler)
      Load and instantiate the factory implementations of the given type from "META-INF/spring.factories", using the given 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
      classLoader - the ClassLoader to use for loading (can be null to use the default)
      failureHandler - strategy used to handle factory instantiation failures
      Since:
      6.0

    • loadFactories

      public static <T> List<T> loadFactories(Class<T> factoryType, @Nullable ClassLoader classLoader, @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 given class loader, 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
      classLoader - the ClassLoader to use for loading (can be null to use the default)
      argumentResolver - strategy used to resolve constructor arguments by their type
      failureHandler - strategy used to handle factory instantiation failures
      Since:
      6.0

    • 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: