javolution.context

Class StorageContext

java.lang.Object

javolution.context.AbstractContext

javolution.context.StorageContext

public abstract class StorageContext
extends AbstractContext

A context for persistent storage integrated with OSGi and SecurityContext.

How the data is going to be stored (database, files) is implementation dependent. But how the resources are structured (hierarchical, semantics) is defined by the client implementing the StorageContext.Resource class.

 class SemanticResource<T> extends SemanticEntity implements Resource<T> { ... }
 ...
 StorageContext ctx = StorageContext.enter(); // Enters the current storage service.
 try {
     // Stores resource.
     SemanticResource<Image> logoId = new SemanticResource<Image>(
          "http://purl.org/goodrelations/v1#Logo|MyCompany");
     ctx.write(logoId, logoImg);  // May raise SecurityException. 
     ...
     // Retrieves resource.
     Image logoImg = ctx.read(logoId); // May raise SecurityException. 
  } finally {
     ctx.exit(); 
  }

Permission to read/write resource values may or not be granted at all or only for particular resources. Sensitive data should always be encrypted (e.g. using a SecuredStorageContext sub-class). There is no limit in the size of the data being stored (except the actual storage available). It is nonetheless recommended to split large data set in smaller resources to allow for partial/concurrent retrieval.

Version:

6.0, July 21, 2013

Author:

Jean-Marie Dautelle

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	StorageContext.Resource<T> A resource identifier.

Field Summary

Fields

Modifier and Type	Field and Description
static Configurable<File>	FILE_STORAGE_LOCATION Holds the default storage location for file based-implementations (default new File("storage")).

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	StorageContext() Default constructor.

Method Summary

Methods

Modifier and Type	Method and Description
static StorageContext	enter() Enters and returns a storage context instance.
abstract <V extends Serializable> V	read(StorageContext.Resource<V> resource) Reads the persistent value of the specified resource value.
abstract <V extends Serializable> void	write(StorageContext.Resource<V> resource, V value) Writes the persistent value of the specified resource.

Methods inherited from class javolution.context.AbstractContext

current, current, enter, enterInner, exit, getOuter, inherit, inner

Methods inherited from class java.lang.Object

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

Field Detail

FILE_STORAGE_LOCATION

public static final Configurable<File> FILE_STORAGE_LOCATION

Holds the default storage location for file based-implementations (default new File("storage")).

Constructor Detail

StorageContext

protected StorageContext()

Default constructor.

Method Detail

enter

public static StorageContext enter()

Enters and returns a storage context instance.

read

public abstract <V extends Serializable> V read(StorageContext.Resource<V> resource)
                                     throws SecurityException

Reads the persistent value of the specified resource value.

Parameters:

resource - the entity whose persistent value is returned.

Returns:

the resource value or null if none.

Throws:

SecurityException - if the permission to read the resource is not granted (new Permission<Resource<V>>(Resource.class, "read", resource)).

write

public abstract <V extends Serializable> void write(StorageContext.Resource<V> resource,
                                  V value)
                    throws SecurityException

Writes the persistent value of the specified resource.

Parameters:

resource - the entity whose persistent value is stored.

value - the persistent value.

Throws:

SecurityException - if the permission to write the resource is not granted (new Permission<Resource<V>>(Resource.class, "write", resource)).