org.osgi.service.dmt.spi.ReadableDataSession Maven / Gradle / Ivy
/*
* Copyright (c) OSGi Alliance (2004, 2013). All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.osgi.service.dmt.spi;
import java.util.Date;
import org.osgi.service.dmt.DmtData;
import org.osgi.service.dmt.DmtException;
import org.osgi.service.dmt.MetaNode;
/**
* Provides read-only access to the part of the tree handled by the plugin that
* created this session.
*
* Since the {@link ReadWriteDataSession} and {@link TransactionalDataSession}
* interfaces inherit from this interface, some of the method descriptions do
* not apply for an instance that is only a {@code ReadableDataSession}. For
* example, the {@link #close()} method description also contains information
* about its behaviour when invoked as part of a transactional session.
*
* The {@code nodePath} parameters appearing in this interface always contain an
* array of path segments identifying a node in the subtree of this plugin. This
* parameter contains an absolute path, so the first segment is always
* ".". Special characters appear escaped in the segments.
*
* Error handling
*
* When a tree access command is called on the DmtAdmin service, it must perform
* an extensive set of checks on the parameters and the authority of the caller
* before delegating the call to a plugin. Therefore plugins can take certain
* circumstances for granted: that the path is valid and is within the subtree
* of the plugin and the session, the command can be applied to the given node
* (e.g. the target of {@code getChildNodeNames} is an interior node), etc. All
* errors described by the error codes {@link DmtException#INVALID_URI},
* {@link DmtException#URI_TOO_LONG}, {@link DmtException#PERMISSION_DENIED},
* {@link DmtException#COMMAND_NOT_ALLOWED} and
* {@link DmtException#TRANSACTION_ERROR} are fully filtered out before control
* reaches the plugin.
*
* If the plugin provides meta-data for a node, the DmtAdmin service must also
* check the constraints specified by it, as described in {@link MetaNode}. If
* the plugin does not provide meta-data, it must perform the necessary checks
* for itself and use the {@link DmtException#METADATA_MISMATCH} error code to
* indicate such discrepancies.
*
* The DmtAdmin does not check that the targeted node exists before calling the
* plugin. It is the responsibility of the plugin to perform this check and to
* throw a {@link DmtException#NODE_NOT_FOUND} if needed. In this case the
* DmtAdmin must pass through this exception to the caller of the corresponding
* DmtSession method.
*
* The plugin can use the remaining error codes as needed. If an error does not
* fit into any other category, the {@link DmtException#COMMAND_FAILED} code
* should be used.
*
* @author $Id: 127f2bfbfa19d4bafbddfb1c8c6b8fb76138ef5f $
*/
public interface ReadableDataSession {
/**
* Notifies the plugin that the given node has changed outside the scope of
* the plugin, therefore the Version and Timestamp properties must be
* updated (if supported). This method is needed because the ACL property of
* a node is managed by the DmtAdmin instead of the plugin. The DmtAdmin
* must call this method whenever the ACL property of a node changes.
*
* @param nodePath the absolute path of the node that has changed
* @throws DmtException with the following possible error codes:
*
* - {@code NODE_NOT_FOUND} if {@code nodePath} points to a
* non-existing node
* - {@code DATA_STORE_FAILURE} if an error occurred while
* accessing the data store
* - {@code COMMAND_FAILED} if some unspecified error is
* encountered while attempting to complete the command
*
*/
void nodeChanged(String[] nodePath) throws DmtException;
/**
* Closes a session. This method is always called when the session ends for
* any reason: if the session is closed, if a fatal error occurs in any
* method, or if any error occurs during commit or rollback. In case the
* session was invalidated due to an exception during commit or rollback, it
* is guaranteed that no methods are called on the plugin until it is
* closed. In case the session was invalidated due to a fatal exception in
* one of the tree manipulation methods, only the rollback method is called
* before this (and only in atomic sessions).
*
* This method should not perform any data manipulation, only cleanup
* operations. In non-atomic read-write sessions the data manipulation
* should be done instantly during each tree operation, while in atomic
* sessions the {@code DmtAdmin} always calls
* {@link TransactionalDataSession#commit()} automatically before the
* session is actually closed.
*
* @throws DmtException with the error code {@code COMMAND_FAILED} if the
* plugin failed to close for any reason
*/
void close() throws DmtException;
/**
* Get the list of children names of a node. The returned array contains the
* names - not the URIs - of the immediate children nodes of the given node.
* The returned array may contain {@code null} entries, but these are
* removed by the DmtAdmin before returning it to the client.
*
* @param nodePath the absolute path of the node
* @return the list of child node names as a string array or an empty string
* array if the node has no children
* @throws DmtException with the following possible error codes:
*
* - {@code NODE_NOT_FOUND} if {@code nodePath} points to a
* non-existing node
* - {@code METADATA_MISMATCH} if the information could not be
* retrieved because of meta-data restrictions
* - {@code DATA_STORE_FAILURE} if an error occurred while
* accessing the data store
* - {@code COMMAND_FAILED} if some unspecified error is
* encountered while attempting to complete the command
*
* @throws SecurityException if the caller does not have the necessary
* permissions to execute the underlying management operation
*/
String[] getChildNodeNames(String[] nodePath) throws DmtException;
/**
* Get the meta data which describes a given node. Meta data can be only
* inspected, it can not be changed.
*
* Meta data support by plugins is an optional feature. It can be used, for
* example, when a data plugin is implemented on top of a data store or
* another API that has their own metadata, such as a relational database,
* in order to avoid metadata duplication and inconsistency. The meta data
* specific to the plugin returned by this method is complemented by meta
* data from the DmtAdmin before returning it to the client. If there are
* differences in the meta data elements known by the plugin and the
* {@code DmtAdmin} then the plugin specific elements take precedence.
*
* Note, that a node does not have to exist for having meta-data associated
* with it. This method may provide meta-data for any node that can possibly
* exist in the tree (any node defined by the Management Object provided by
* the plugin). For nodes that are not defined, a {@code DmtException} may
* be thrown with the {@code NODE_NOT_FOUND} error code. To allow easier
* implementation of plugins that do not provide meta-data, it is allowed to
* return {@code null} for any node, regardless of whether it is defined or
* not.
*
* @param nodePath the absolute path of the node
* @return a MetaNode which describes meta data information, can be
* {@code null} if there is no meta data available for the given
* node
* @throws DmtException with the following possible error codes:
*
* - {@code NODE_NOT_FOUND} if {@code nodeUri} points to a node
* that is not defined in the tree (see above)
-
* {@code DATA_STORE_FAILURE} if an error occurred while accessing
* the data store
- {@code COMMAND_FAILED} if some unspecified
* error is encountered while attempting to complete the command
*
*
* @throws SecurityException if the caller does not have the necessary
* permissions to execute the underlying management operation
*/
MetaNode getMetaNode(String[] nodePath) throws DmtException;
/**
* Get the size of the data in a leaf node. The value to return depends on
* the format of the data in the node, see the description of the
* {@link DmtData#getSize()} method for the definition of node size for each
* format.
*
* @param nodePath the absolute path of the leaf node
* @return the size of the data in the node
* @throws DmtException with the following possible error codes:
*
* - {@code NODE_NOT_FOUND} if {@code nodePath} points to a
* non-existing node
* - {@code METADATA_MISMATCH} if the information could not be
* retrieved because of meta-data restrictions
* - {@code FEATURE_NOT_SUPPORTED} if the Size property is not
* supported by the plugin
* - {@code DATA_STORE_FAILURE} if an error occurred while
* accessing the data store
* - {@code COMMAND_FAILED} if some unspecified error is
* encountered while attempting to complete the command
*
* @throws SecurityException if the caller does not have the necessary
* permissions to execute the underlying management operation
* @see DmtData#getSize()
*/
int getNodeSize(String[] nodePath) throws DmtException;
/**
* Get the timestamp when the node was last modified.
*
* @param nodePath the absolute path of the node
* @return the timestamp of the last modification
* @throws DmtException with the following possible error codes:
*
* - {@code NODE_NOT_FOUND} if {@code nodePath} points to a
* non-existing node
* - {@code METADATA_MISMATCH} if the information could not be
* retrieved because of meta-data restrictions
* - {@code FEATURE_NOT_SUPPORTED} if the Timestamp property is
* not supported by the plugin
* - {@code DATA_STORE_FAILURE} if an error occurred while
* accessing the data store
* - {@code COMMAND_FAILED} if some unspecified error is
* encountered while attempting to complete the command
*
* @throws SecurityException if the caller does not have the necessary
* permissions to execute the underlying management operation
*/
Date getNodeTimestamp(String[] nodePath) throws DmtException;
/**
* Get the title of a node. There might be no title property set for a node.
*
* @param nodePath the absolute path of the node
* @return the title of the node, or {@code null} if the node has no title
* @throws DmtException with the following possible error codes:
*
* - {@code NODE_NOT_FOUND} if {@code nodePath} points to a
* non-existing node
* - {@code METADATA_MISMATCH} if the information could not be
* retrieved because of meta-data restrictions
* - {@code FEATURE_NOT_SUPPORTED} if the Title property is not
* supported by the plugin
* - {@code DATA_STORE_FAILURE} if an error occurred while
* accessing the data store
* - {@code COMMAND_FAILED} if some unspecified error is
* encountered while attempting to complete the command
*
* @throws SecurityException if the caller does not have the necessary
* permissions to execute the underlying management operation
*/
String getNodeTitle(String[] nodePath) throws DmtException;
/**
* Get the type of a node. The type of leaf node is the MIME type of the
* data it contains. The type of an interior node is a URI identifying a DDF
* document; a {@code null} type means that there is no DDF document
* overriding the tree structure defined by the ancestors.
*
* @param nodePath the absolute path of the node
* @return the type of the node, can be {@code null}
* @throws DmtException with the following possible error codes:
*
* - {@code NODE_NOT_FOUND} if {@code nodePath} points to a
* non-existing node
* - {@code METADATA_MISMATCH} if the information could not be
* retrieved because of meta-data restrictions
* - {@code DATA_STORE_FAILURE} if an error occurred while
* accessing the data store
* - {@code COMMAND_FAILED} if some unspecified error is
* encountered while attempting to complete the command
*
* @throws SecurityException if the caller does not have the necessary
* permissions to execute the underlying management operation
*/
String getNodeType(String[] nodePath) throws DmtException;
/**
* Check whether the specified path corresponds to a valid node in the DMT.
*
* @param nodePath the absolute path to check
* @return true if the given node exists in the DMT
*/
boolean isNodeUri(String[] nodePath);
/**
* Tells whether a node is a leaf or an interior node of the DMT.
*
* @param nodePath the absolute path of the node
* @return true if the given node is a leaf node
* @throws DmtException with the following possible error codes:
*
* - {@code NODE_NOT_FOUND} if {@code nodePath} points to a
* non-existing node
* - {@code METADATA_MISMATCH} if the information could not be
* retrieved because of meta-data restrictions
* - {@code DATA_STORE_FAILURE} if an error occurred while
* accessing the data store
* - {@code COMMAND_FAILED} if some unspecified error is
* encountered while attempting to complete the command
*
* @throws SecurityException if the caller does not have the necessary
* permissions to execute the underlying management operation
*/
boolean isLeafNode(String[] nodePath) throws DmtException;
/**
* Get the data contained in a leaf or interior node.
*
* @param nodePath the absolute path of the node to retrieve
* @return the data of the leaf node, must not be {@code null}
* @throws DmtException with the following possible error codes:
*
* - {@code NODE_NOT_FOUND} if {@code nodePath} points to a
* non-existing node
* - {@code METADATA_MISMATCH} if the information could not be
* retrieved because of meta-data restrictions
* - {@code FEATURE_NOT_SUPPORTED} if the specified node is an
* interior node and does not support Java object values
* - {@code DATA_STORE_FAILURE} if an error occurred while
* accessing the data store
* - {@code COMMAND_FAILED} if some unspecified error is
* encountered while attempting to complete the command
*
* @throws SecurityException if the caller does not have the necessary
* permissions to execute the underlying management operation
*/
DmtData getNodeValue(String[] nodePath) throws DmtException;
/**
* Get the version of a node. The version can not be set, it is calculated
* automatically by the device. It is incremented modulo 0x10000 at every
* modification of the value or any other property of the node, for both
* leaf and interior nodes. When a node is created the initial value is 0.
*
* @param nodePath the absolute path of the node
* @return the version of the node
* @throws DmtException with the following possible error codes:
*
* - {@code NODE_NOT_FOUND} if {@code nodePath} points to a
* non-existing node
* - {@code METADATA_MISMATCH} if the information could not be
* retrieved because of meta-data restrictions
* - {@code FEATURE_NOT_SUPPORTED} if the Version property is not
* supported by the plugin
* - {@code DATA_STORE_FAILURE} if an error occurred while
* accessing the data store
* - {@code COMMAND_FAILED} if some unspecified error is
* encountered while attempting to complete the command
*
* @throws SecurityException if the caller does not have the necessary
* permissions to execute the underlying management operation
*/
int getNodeVersion(String[] nodePath) throws DmtException;
}