| Package | Description | 
|---|---|
| org.springframework.core | Provides basic classes for exception handling and version detection,
 and other core helpers that are not specific to any part of the framework. | 
| org.springframework.core.annotation | Core support package for annotations, meta-annotations, and composed
 annotations with attribute overrides. | 
| org.springframework.core.codec | |
| org.springframework.core.convert | Type conversion system API. | 
| org.springframework.core.serializer.support | Support classes for Spring's serializer abstraction. | 
| Class and Description | 
|---|
| AliasRegistry Common interface for managing aliases. | 
| AttributeAccessor Interface defining a generic contract for attaching and accessing metadata
 to/from arbitrary objects. | 
| Constants.ConstantException Exception thrown when the  Constantsclass is asked for
 an invalid constant name. | 
| DecoratingClassLoader Base class for decorating ClassLoaders such as  OverridingClassLoaderandorg.springframework.instrument.classloading.ShadowingClassLoader,
 providing common handling of excluded packages and classes. | 
| MethodClassKey A common key class for a method against a specific target class,
 including  MethodClassKey.toString()representation andComparablesupport (as suggested for customHashMapkeys as of Java 8). | 
| MethodIntrospector.MetadataLookup A callback interface for metadata lookup on a given method. | 
| MethodParameter Helper class that encapsulates the specification of a method parameter, i.e. | 
| OrderComparator Comparatorimplementation forOrderedobjects, sorting
 by order value ascending, respectively by priority descending. | 
| OrderComparator.OrderSourceProvider Strategy interface to provide an order source for a given object. | 
| Ordered Orderedis an interface that can be implemented by objects that
 should be orderable, for example in aCollection. | 
| ParameterizedTypeReference The purpose of this class is to enable capturing and passing a generic
  Type. | 
| ParameterNameDiscoverer Interface to discover parameter names for methods and constructors. | 
| PrioritizedParameterNameDiscoverer ParameterNameDiscovererimplementation that tries several discoverer
 delegates in succession. | 
| ReactiveAdapter Adapter for a Reactive Streams  Publisherto and from an async/reactive
 type such asCompletableFuture, RxJavaObservable, and others. | 
| ReactiveAdapterRegistry A registry of adapters to adapt Reactive Streams  Publisherto/from
 various async/reactive types such asCompletableFuture, RxJavaObservable, and others. | 
| ReactiveTypeDescriptor Describes the semantics of a reactive type including boolean checks for
  ReactiveTypeDescriptor.isMultiValue(),ReactiveTypeDescriptor.isNoValue(), andReactiveTypeDescriptor.supportsEmpty(). | 
| ResolvableType Encapsulates a Java  Type, providing access tosupertypes,interfaces, andgeneric parametersalong with the ability to ultimatelyresolveto aClass. | 
| Class and Description | 
|---|
| MethodParameter Helper class that encapsulates the specification of a method parameter, i.e. | 
| NestedRuntimeException Handy class for wrapping runtime  Exceptionswith a root cause. | 
| OrderComparator Comparatorimplementation forOrderedobjects, sorting
 by order value ascending, respectively by priority descending. | 
| Class and Description | 
|---|
| NestedRuntimeException Handy class for wrapping runtime  Exceptionswith a root cause. | 
| ResolvableType Encapsulates a Java  Type, providing access tosupertypes,interfaces, andgeneric parametersalong with the ability to ultimatelyresolveto aClass. | 
| Class and Description | 
|---|
| MethodParameter Helper class that encapsulates the specification of a method parameter, i.e. | 
| NestedRuntimeException Handy class for wrapping runtime  Exceptionswith a root cause. | 
| ResolvableType Encapsulates a Java  Type, providing access tosupertypes,interfaces, andgeneric parametersalong with the ability to ultimatelyresolveto aClass. | 
| Class and Description | 
|---|
| NestedRuntimeException Handy class for wrapping runtime  Exceptionswith a root cause. |