Context (com.holon-platform.core:holon-root 5.0.2 API)

```
public interface Context
```
Main interface to access global platform context resources.
A context resource is an object instance identified by a String key.

Resources are organized in ContextScopes, each of them characterized by a resource data source and a resource retrieval strategy. A scope can be manageable, i.e. supporting resource addition and removal, or not.

Context scope can be registered either by using standard Java extension service loading using ContextScope class name files under META-INF/services, or by direct registration using ContextManager.registerScope(ClassLoader, ContextScope).

When asking for a context resource using resource(String, Class) and similar methods, all registered context scopes are invoked, in the order defined by ContextScope.getOrder() precedence value. The first not null resource instance obtained from a scope is the one returned to caller, if any.

Every Context resource set is bound to a ClassLoader. If not specified, the default classloader is obtained from ClassUtils.getDefaultClassLoader().
Two default context scope are registered by default:
- A ClassLoader bound scope named CLASSLOADER_SCOPE_NAME, registering and providing resources as singleton instances for the reference ClassLoader. This scope is registered with a low precedence order;
- A thread-bound scope named THREAD_SCOPE_NAME, using current Thread local data set to register and provide context resources. This scope is registered with a high precedence order.
Since:

5.0.0

Field Summary

Fields
Modifier and Type Field and Description

static String CLASSLOADER_SCOPE_NAME
Default classloader-bound scope name

static String THREAD_SCOPE_NAME
Default thread-bound scope name

Fields
Modifier and Type	Field and Description
`static String`	`CLASSLOADER_SCOPE_NAME` Default classloader-bound scope name
`static String`	`THREAD_SCOPE_NAME` Default thread-bound scope name

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method and Description
`default Optional<ContextScope>`	`classLoaderScope()` Shortcut method to obtain the thread-bound context scope, i.e. the default `ContextScope` named `CLASSLOADER_SCOPE_NAME`, using the default `ClassLoader`.
`default Optional<ContextScope>`	`classLoaderScope(ClassLoader classLoader)` Shortcut method to obtain the ClassLoader-bound context scope, i.e. the default `ContextScope` named `CLASSLOADER_SCOPE_NAME`.
`default <V> V`	`executeThreadBound(String resourceKey, Object resource, Callable<V> operation)` Execute given `Callable` `operation`, binding given `Context` resource key and value to current Thread, and removing the binding after operation execution.
`default void`	`executeThreadBound(String resourceKey, Object resource, Runnable operation)` Execute given `Runnable` `operation`, binding given `Context` resource key and value to current Thread, and removing the binding after operation execution.
`static Context`	`get()` Obtain the default `Context` implementation instance.
`default <T> Optional<T>`	`resource(Class<T> resourceType)` Shortcut method to obtain a `Context` resource using the `resourceType` class name as resource key.
`default <T> Optional<T>`	`resource(Class<T> resourceType, ClassLoader classLoader)` Shortcut method to obtain a `Context` resource using the `resourceType` class name as resource key and given `classLoader`.
`default <T> Optional<T>`	`resource(String resourceKey, Class<T> resourceType)` Lookup a context resource of `resourceType` class using given `resourceKey` and the default `ClassLoader`.
`<T> Optional<T>`	`resource(String resourceKey, Class<T> resourceType, ClassLoader classLoader)` Lookup a context resource of `resourceType` class using given `resourceKey`.
`default Optional<ContextScope>`	`scope(String name)` Gets a registered `ContextScope` with the given `name` and bound to default `ClassLoader`.
`Optional<ContextScope>`	`scope(String name, ClassLoader classLoader)` Gets a registered `ContextScope` with the given `name` and bound to given `classLoader`.
`default Optional<ContextScope>`	`threadScope()` Shortcut method to obtain the thread-bound context scope, i.e. the default `ContextScope` named `THREAD_SCOPE_NAME`, using the default `ClassLoader`.
`default Optional<ContextScope>`	`threadScope(ClassLoader classLoader)` Shortcut method to obtain the thread-bound context scope, i.e. the default `ContextScope` named `THREAD_SCOPE_NAME`.

- Field Detail
  - THREAD_SCOPE_NAME
```
static final String THREAD_SCOPE_NAME
```
    Default thread-bound scope name
    
    See Also:
    
    Constant Field Values
  - CLASSLOADER_SCOPE_NAME
```
static final String CLASSLOADER_SCOPE_NAME
```
    Default classloader-bound scope name
    
    See Also:
    
    Constant Field Values
- Method Detail
  - resource
```
<T> Optional<T> resource(String resourceKey,
                         Class<T> resourceType,
                         ClassLoader classLoader)
```
    Lookup a context resource of resourceType class using given resourceKey.
    All registered context scopes are invoked, in the order defined by ContextScope.getOrder() precedence value. The first not null resource instance obtained from a scope is the one returned to caller, if any.
    
    Type Parameters:
    
    T - Resource type
    
    Parameters:
    
    resourceKey - Resource key (not null)
    
    resourceType - Required resource type (not null)
    
    classLoader - ClassLoader to use. If null, the default ClassLoader is used.
    
    Returns:
    
    Optional resource instance, empty if not available from context
    
    Throws:
    
    TypeMismatchException - If a context resource with given key was found but it is not of required type
  - resource
```
default <T> Optional<T> resource(String resourceKey,
                                 Class<T> resourceType)
```
    Lookup a context resource of resourceType class using given resourceKey and the default ClassLoader.
    All registered context scopes are invoked, in the order defined by ContextScope.getOrder() precedence value. The first not null resource instance obtained from a scope is the one returned to caller, if any.
    
    Type Parameters:
    
    T - Resource type
    
    Parameters:
    
    resourceKey - Resource key (not null)
    
    resourceType - Required resource type (not null)
    
    Returns:
    
    Optional resource instance, empty if not available from context
    
    Throws:
    
    TypeMismatchException - If a context resource with given key was found but it is not of required type
  - resource
```
default <T> Optional<T> resource(Class<T> resourceType)
```
    Shortcut method to obtain a Context resource using the resourceType class name as resource key.
    
    Type Parameters:
    
    T - Resource type
    
    Parameters:
    
    resourceType - Resource type (not null)
    
    Returns:
    
    Optional resource instance, empty if not available from context
  - resource
```
default <T> Optional<T> resource(Class<T> resourceType,
                                 ClassLoader classLoader)
```
    Shortcut method to obtain a Context resource using the resourceType class name as resource key and given classLoader.
    
    Type Parameters:
    
    T - Resource type
    
    Parameters:
    
    resourceType - Resource type (not null)
    
    classLoader - ClassLoader to use. If null, the default ClassLoader is used.
    
    Returns:
    
    Optional resource instance, empty if not available from context
  - scope
```
Optional<ContextScope> scope(String name,
                             ClassLoader classLoader)
```
    Gets a registered ContextScope with the given name and bound to given classLoader.
    
    Parameters:
    
    name - Scope name (not null)
    
    classLoader - ClassLoader, if null, the default ClassLoader is used
    
    Returns:
    
    The registered ContextScope with given name, or an empty Optional if a scope with such name is not registered in context
  - scope
```
default Optional<ContextScope> scope(String name)
```
    Gets a registered ContextScope with the given name and bound to default ClassLoader.
    
    Parameters:
    
    name - Scope name (not null)
    
    Returns:
    
    The registered ContextScope with given name, or an empty Optional if a scope with such name is not registered in context
  - classLoaderScope
```
default Optional<ContextScope> classLoaderScope(ClassLoader classLoader)
```
    Shortcut method to obtain the ClassLoader-bound context scope, i.e. the default ContextScope named CLASSLOADER_SCOPE_NAME.
    
    Parameters:
    
    classLoader - ClassLoader, if null, the default ClassLoader is used
    
    Returns:
    
    The ClassLoader-bound context scope, or an empty Optional if scope is not registered
  - classLoaderScope
```
default Optional<ContextScope> classLoaderScope()
```
    Shortcut method to obtain the thread-bound context scope, i.e. the default ContextScope named CLASSLOADER_SCOPE_NAME, using the default ClassLoader.
    
    Returns:
    
    The ClassLoader-bound context scope, or an empty Optional if scope is not registered
  - threadScope
```
default Optional<ContextScope> threadScope(ClassLoader classLoader)
```
    Shortcut method to obtain the thread-bound context scope, i.e. the default ContextScope named THREAD_SCOPE_NAME.
    
    Parameters:
    
    classLoader - ClassLoader, if null, the default ClassLoader is used
    
    Returns:
    
    The thread-bound context scope, or an empty Optional if scope is not registered
  - threadScope
```
default Optional<ContextScope> threadScope()
```
    Shortcut method to obtain the thread-bound context scope, i.e. the default ContextScope named THREAD_SCOPE_NAME, using the default ClassLoader.
    
    Returns:
    
    The thread-bound context scope, or an empty Optional if scope is not registered
  - executeThreadBound
```
default void executeThreadBound(String resourceKey,
                                Object resource,
                                Runnable operation)
                         throws RuntimeException
```
    Execute given Runnable operation, binding given Context resource key and value to current Thread, and removing the binding after operation execution.
    The THREAD_SCOPE_NAME context scope is used.
    
    Parameters:
    
    resourceKey - Context resource key (not null)
    
    resource - Context resource value to bind to current Thread (not null)
    
    operation - Operation to execute (not null)
    
    Throws:
    
    RuntimeException - Exception during operation execution
  - executeThreadBound
```
default <V> V executeThreadBound(String resourceKey,
                                 Object resource,
                                 Callable<V> operation)
                          throws RuntimeException
```
    Execute given Callable operation, binding given Context resource key and value to current Thread, and removing the binding after operation execution.
    The THREAD_SCOPE_NAME context scope is used.
    
    Type Parameters:
    
    V - Operation result type
    
    Parameters:
    
    resourceKey - Context resource key (not null)
    
    resource - Context resource value to bind to current Thread (not null)
    
    operation - Operation to execute
    
    Returns:
    
    Operation result
    
    Throws:
    
    RuntimeException - Exception during operation execution
  - get
```
static Context get()
```
    Obtain the default Context implementation instance.
    
    Returns:
    
    Default Context

Interface Context

Field Summary

Method Summary

Field Detail

THREAD_SCOPE_NAME

CLASSLOADER_SCOPE_NAME

Method Detail

resource

resource

resource

resource

scope

scope

classLoaderScope

classLoaderScope

threadScope

threadScope

executeThreadBound

executeThreadBound

get