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From de...@apache.org
Subject svn commit: r1606981 - /olingo/site/trunk/content/doc/tutorials/DeltaQuerySupport.mdtext
Date Tue, 01 Jul 2014 05:43:58 GMT
Author: deepa
Date: Tue Jul  1 05:43:58 2014
New Revision: 1606981

URL: http://svn.apache.org/r1606981
Log:
CMS commit to olingo by deepa

Added:
    olingo/site/trunk/content/doc/tutorials/DeltaQuerySupport.mdtext   (with props)

Added: olingo/site/trunk/content/doc/tutorials/DeltaQuerySupport.mdtext
URL: http://svn.apache.org/viewvc/olingo/site/trunk/content/doc/tutorials/DeltaQuerySupport.mdtext?rev=1606981&view=auto
==============================================================================
--- olingo/site/trunk/content/doc/tutorials/DeltaQuerySupport.mdtext (added)
+++ olingo/site/trunk/content/doc/tutorials/DeltaQuerySupport.mdtext Tue Jul  1 05:43:58 2014
@@ -0,0 +1,104 @@
+Title:
+Notice:    Licensed to the Apache Software Foundation (ASF) under one
+           or more contributor license agreements.  See the NOTICE file
+           distributed with this work for additional information
+           regarding copyright ownership.  The ASF licenses this file
+           to you 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.
+
+# Delta Query Support 
+
+Delta Query retrieves the changes done to a service. It is supported in OData JPA Processor
Library from version 1.4.0. The data returned by the feed for the query would look exactly
like any other dataset for an OData query but with delta link at the end. 
+
+There are two approaches you can follow to generate delta token.
+
+
+## Generating Delta Token
+##### First Approach
+
+1. Create a Java class by extending 'ODataJPATombstoneEntityListener.java'.
+2. Implement the abstract method 'getQuery'. In the method, implement the logic to generate
a 'javax.persistence.Query'. The Query object can be created as shown below in the code snippet.

+		
+         if (!resultsView.getStartEntitySet().getName().equals(resultsView.getTargetEntitySet().getName()))
{    
+		   contextType = JPQLContextType.JOIN;
+		 } else {    
+		   contextType = JPQLContextType.SELECT;  
+		 }   
+		 
+		 JPQLContext jpqlContext = JPQLContext.createBuilder(contextType, resultsView).build();
 
+		 JPQLStatement jpqlStatement = JPQLStatement.createBuilder(jpqlContext).build();   
+		 
+		 Query query = em.createQuery(jpqlStatement);
+		 
+ The JPQLStatement is generated based on the OData request (resultsView). The generated JPQLStatement
can be enhanced to introduce conditions that filters and fetches delta JPA Entities. To enhance
the JPQLStatement and add a condition to the WHERE Clause, refer to the following code snippet.
+
+ *Note*: It is up to the JPA application developers to come up with a logic suitable for
their use case.
+
+		String deltaToken = ODataJPATombstoneContext.getDeltaToken(); 
+		
+		Query query = null;
+		if (deltaToken != null) {  
+		  String statement = jpqlStatement.toString();  
+		  String[] statementParts = statement.split(JPQLStatement.KEYWORD.WHERE);  
+		  String deltaCondition = jpqlContext.getJPAEntityAlias() + ".creationDate >= {ts '"
+ deltaToken + "'}";  
+		  if (statementParts.length > 1)  
+		  {    
+		  statement = statementParts[0] + JPQLStatement.DELIMITER.SPACE + JPQLStatement.KEYWORD.WHERE
+ JPQLStatement.DELIMITER.SPACE + deltaCondition + JPQLStatement.DELIMITER.SPACE + JPQLStatement.Operator.AND
+ statementParts[1];  
+		  }  
+		  else {    
+		    statement = statementParts[0] + JPQLStatement.DELIMITER.SPACE + JPQLStatement.KEYWORD.WHERE
+ JPQLStatement.DELIMITER.SPACE + deltaCondition;  
+		  }   
+		  
+		  query = em.createQuery(statement);
+		 }
+		 else  
+		   query = em.createQuery(jpqlStatement.toString()); 
+
+3. Implement the method 'generateDeltaToken' to generate a string representation of the delta
token. The delta token generated shall be used by the client applications to fetch delta in
their subsequent OData requests.
+		    
+            SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.000");;
   
+			Date date = new Date(System.currentTimeMillis());    
+			dateFormat.format(date);    
+			return dateFormat.format(date);
+4. Register the class (created above) as an Entity Listener in JPA Entity.
+		
+        @Entity
+		@Table(name = "T_SALESORDERHEADER")
+		@EntityListeners(com.sap.core.odata.processor.ref.jpa.listners.SalesOrderTombstoneListner.class)
+		public class SalesOrderHeader { 
+
+##### Second Approach
+ 
+The OData JPA Processor Library also provides support so that the JPA application developer
can write a call back method in the Entity Listener class and annotate them with 'javax.persistence.PostLoad'.
Such call back methods are executed by JPA providers in a stateless manner for every record
fetched from the database table. In the call back method, logic can be provided to decide
whether a JPA entity fetched from the database table is a delta or not as shown below:
+
+		@PostLoad  
+		public void handleDelta(Object entity) {    
+		  SalesOrderHeader so = (SalesOrderHeader) entity;    
+		  if (so.getCreationDate().getTime() < ODataJPATombstoneContext.getDeltaTokenUTCTimeStamp())
     
+		    return;    
+		  else      
+		    addToDelta(entity,ENTITY_NAME);  
+		} 
+
+
+
+
+
+
+
+
+
+
+
+
+

Propchange: olingo/site/trunk/content/doc/tutorials/DeltaQuerySupport.mdtext
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