ExistClient

Introduction

The ExistClient is a Java library implementing the ISClient interface defined in the gCoreFramework. Therefore it can be plugged in a gCore distribution to interface the gCube Information System. This ExistClient implementation reduces possible range of queries (statically implemented), each of them has a template as more generic as possible. This has been thought for covering all the main cases, enabling the user to create dynamically the query as he/she likes better enriching the query with the parameters he/she needs. There are three kinds of queries to execute on the IS:

• GCUBEResourceQuery, to query the GCUBEResources' profiles
• WSResourceQuery, to query WS-ResourceProperty documents
• and GCUBEGenericQuery, to make custom queries

The name of the component derives from the XQuery dialect supported, which is the one offered by the eXist XML Database on top of which it is built the gCube Information Collector component.

Implementation Overview

The ExistClient implements all the queries defined in the ISClient Interface (to obtain the ExistClient implementation see ):

How to query over GCUBEResource profiles

Queries over GCUBEResource:

• GCUBECollectionQuery
• GCUBECSInstanceQuery
• GCUBECSQuery
• GCUBEExternalRIQuery
• GCUBEGenericResourceQuery
• GCUBEGHNQuery
• GCUBEMCollectionQuery
• GCUBERIQuery
• GCUBEServiceQuery
• GCUBETPQuery
• GCUBEVREQuery

This queries returns a List of specialized GCUBEResource.

Usage Examples

ISClient client = GHNContext.getImplementation(ISClient.class);
GCUBERIQuery RIquery = client.getQuery(GCUBERIQuery.class);
RIquery.addAtomicConditions(new AtomicCondition("//Endpoint@EntryName","gcube/annotationmanagement/abe/factory"),new AtomicCondition("//ServiceName","ABE"));
for (GCUBERunningInstance instance : client.execute(RIquery,GCUBEScope.getScope("/gcube/devsec")))
logger.debug(instance.getServiceName()+"("+instance.getID()+")");

ISClient client = GHNContext.getImplementation(ISClient.class);
GCUBEGHNQuery GHNquery = client.getQuery(GCUBEGHNQuery.class);
for (GCUBEHostingNode node : client.execute(GHNquery,GCUBEScope.getScope("/gcube/devsec"))) l
logger.debug(node.getID()+"("+node.getNodeDescription().getName()+")");

ISClient client = GHNContext.getImplementation(ISClient.class);
GCUBERIQuery RIquery = client.getQuery(GCUBERIQuery.class);
RIquery.addGenericCondition("$result/Profile/ServiceName/string() eq 'GHNManager' or $result/Profile/ServiceName/string() eq 'SoftwareRepository'");
for (GCUBERunningInstance instance : client.execute(RIquery,GCUBEScope.getScope("/gcube/devsec")))
                      logger.debug(instance.getServiceName()+"("+instance.getID()+")");

How to query over resource property documents

Queries over GCUBEWSResource:

• WSResourceQuery

This query returns a List of RPDocument. The RPDocument object allows developer to retrieve the informations on WSResourceProperties or to exceute XPath .

To get one of GCUBEResource or GCUBEWSResource queries:

 ... 
 [GCUBE...Query] query = client.getQuery([GCUBE...Query].class);    
 ... 

On this kind of queries the developer can reduce the number of results inserting a filter. The supported filters are:

• AtomicCondition
  • with the atomic conditions can be specified that a node with a determined path *MUST* have a specified value

 ...   new AtomicCondition("//Endpoint@EntryName","gcube/annotationmanagement/abe/factory")

• GenericCondition
  • with the generic conditions can be specified a entire condition string (using $result as starter node of every used path)

  ....addGenericCondition("$result/[path] eq '[something]' or $result/[another path] eq '[something else]'");

Usage Example

ISClient client = GHNContext.getImplementation(ISClient.class);
WSResourceQuery wsquery = client.getQuery(WSResourceQuery.class);
wsquery.addAtomicConditions(new AtomicCondition("//ServiceClass","Samples"));
for (RPDocument d : client.execute(wsquery,GCUBEScope.getScope("/gcube/devsec"))) 
logger.(d.getEndpoint()+":+d.getVO()+":"d.evaluate("//MyRP").get(0));

Custom queries

The ExistClient also offers the possibility to execute custom queries: GCUBEGenericQuery. GCUBEGenericQuery allows the developer to set the query expression to execute and to use a predefined set of queries which he should set some parameters on listed below:

• GCUBEResourceQuery:
  • TYPE
  • FILTER
  • RESULT (the default value returns Ids)
• GCUBEWSResourceQuery:
  • FILTER
  • RESULT (the default value is the entire Properties Document Data)
• RIEndpoint:
  • NAME (Service name)
  • CLASS (Service class)
  • ENTRY (the entry point)
• RIOnGHN:
  • ID (the GHN id)
• RISpecificData:
  • NAME (Service name)
  • CLASS (Service class)
  • ENTRY (the entry point)
• GHNIDFromHostName:
  • NAME (GHN name)
  • RESULT (the default value returns Ids)
• InternalCollections
• InternalCollectionIDs
• UserCollectionIDsFromSchemaURI
  • URI (the schema uri)
• MCollectionIDForCollection
  • ID (related collection ID)
• MCollectionFormatsForCollection
  • ID (related collection ID)
• MCollectionIDFromCollectionIDAndRole
  • ID (related collection ID)
  • ROLE (secondary role)
• MCollectionIDFromMFLanguage
  • LANGUAGE (metadata format language)
• MCollectionIDFromName
  • NAME (metadata collection name)
• MCollectionIDFromSchemaURI
  • URI (schema uri)

This kind of queries returns a List of XMLResult. The XMLResult object allows the developer to explore the contained document with XPaths. To get a predefined generic query:

 ... 
 GCUBEGenericQuery query = client.getQuery("[one of the listed queries]");    
 ... 

to set the parameters:

 ... 
 query.addParameters(new QueryParameter("[parameter to set]","[value]"), new QueryParameter("[parameter to set]","[value ...]"));
 ...

Usage Example

GCUBEGenericQuery query = client.getQuery(GCUBEGenericQuery.class);
query.setExpression("for $Profile in collection(\"/db/Profiles\")//Document/Data/child::*[local-name()='Profile']/Resource return $Profile/UniqueID");
List<XMLResult> result =client.execute(query, scope);
for (String resultItem :result ) {
logger.debug(resultItem.evaluate("an XPath ... ")); 
logger.debug(resultItem.toString());
}

Predefined generic query examples:

GCUBEGenericQuery query = client.getQuery("GCUBEResourceQuery");
for (XMLResult result : client.execute(query,scope)) logger.debug(result.evaluate("/ID/text()"));//displays a singleton list
//a bit of customisation goes a long way whilst keeping the previous abstractions
query.addParameters(new QueryParameter("RESULT","$result/Type"));
for (XMLResult result : client.execute(query, scope)) logger.debug(result.evaluate("/Type/text()"));

//specialise to GCUBE Running Instances (NB. queries can be composed incrementally, possibly by different objects in different methods)
query.addParameters(new QueryParameter("TYPE",GCUBERunningInstance.TYPE)); 
for (XMLResult result : client.execute(query,scope)) logger.debug(result.evaluate("/Type/text()"));
//introduce a filter (NB. parameters can be added in batches) 
query.addParameters(new QueryParameter("TYPE",GCUBERunningInstance.TYPE), //ovverride previous setting
     new QueryParameter("FILTER","$result/Profile/ServiceClass/string() eq 'Annotation'"),
     new QueryParameter ("RESULT", "$result/Profile/Description")); //any Xquery condition on $result would do
for (XMLResult result : client.execute(query,scope)) logger.debug(result.evaluate("//Description")); //displays a singleton list