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JOM reference

Create Entity Manager

• Store EntityManager as a static variable at the application level.
• Have a separate entity manager for each, keyspace.
• You can connect to SSL enabled nodes.
• Each property of createEntityManager is documented below.

   public class App{
     private static CqlEntityManager em;
     public static void init(){
       Properties props=new Properties();
       //cql.contactpoints: if you have multiple nodes, specify their ip addresses separated by comma.
       // example: 111.222.222.1,111.222.222.2,111.222.222.3"
       props.put("cql.contactpoints", "localhost");
       props.put("cql.keyspace","jom_test");

       //cql.synctableschema: If true, the table schema will be auto created, otherwise schema will be untouched.
       // Any new fields added will be synced. But, it can not delete columns.
       props.put("cql.synctableschema", "true");

       //cql.packagestoscan Specify all your packages that contain your entity objects.
       //Annotate your domain objects with @CqlEntity annotation.
       props.put("cql.packagestoscan", "org.w3cloud.jom.testmodels");
       
       //Following properties are only required if you clusters communicate using SSL.
       props.put("cql.ssl", "true");
       props.put("cql.ssl.truststorePath", "/full/path/.truststore"); //Truststore file name with full path
       props.put("cql.ssl.truststorePassword", "password");
       props.put("cql.ssl.keystorePath", "/full/path/.keystore");
       props.put("cql.ssl.keystorePassword", "yourpassword");
    
        em=CqlEntityManagerFactory.createEntityManger(props);
      }
    }

Entity Object Annotations

####@CqlEntity Annotate your domain objects with @CqlEntity annotation. JOM will create schema, if it does not exist. If the schema exists, it compares and adds the missing columns.

@CqlEntity
public class CarModel {
....
}

####@CqlId

• Partition key field is annotated with CqlId(idType=IdType.PARTITION_KEY) annotation.
• Cluster key field is annotated with CqlId(idType=IdType.CLUSTER_KEY) annotation.
• More than one field can be annotated with this annotation to make a composite key.

####@CqlAutoGen

• Any UUID field can be annotated with @CqlAutoGen
• JOM auto populates such ID fields with a GUID value.

####@CqlTransient

• Any in-memory variables that you do not want to persist in the database, mark it with @CqlTransit annotation.

####@CqlEmbed

• Do not annotate embedded (eg. Address) object with @CqlEntity.
• JOM create fields for each embedded object.
• Field naming convention: deliver_address__city.

  @CqlEntity
  public class Customer{
  .....
    @CqlEmbed
    public Address deliveryAddress;
  ...
  }

####@CqlStoreAsJson

• List or array of String can be stored as json

   @CqlStoreAsJson
   public List\ phoneNos;

• @CqlStoreAsJson does not work well with list of Objects like List of Addresses.
• For such situations, use String addressListJson to store json and Serialize and Load manually.

	@JsonIgnore
	public String addressesJson;
	@CqlTransient
	public List\
 addresses;

Supported Java Datatypes

• int, long, boolean, String.
• java.util.Date
• UUID
• java.math.BigDecimal

CqlEntityManager Interface

CqlEntityManager is the core interface that your DAO will be using to perform the CRUD operations.

	public interface CqlEntityManager {
		//Insert Methods
		void insert(Object entity);
		void insert(BatchStatement batchStatement, Object entity; //Insert in batch.
	
		//Update Methods
		void update(Object entity);
		void update(BatchStatement batchStatement, Object entity);
		void updateColumn(T entity, CqlStatement statement);
		void updateColumn(BatchStatement batchStatement, T entity, CqlStatement statement);
	
		//Delete Methods
		void delete(Object entity);
		void deleteByKey(ClassentityClass, Object...keys);
		void delete(BatchStatement batchStatement, Object entity);

		//Operations are committed only when the execute method is called
		void execute(BatchStatement batchStatement);

		// Query Methods
		 T findOne(CqlStatement statement);
		 List findAll(CqlStatement statement);
		 long count(CqlStatement statement);
		 List findAll(CqlStatement statement, CqlFilter filter);
		 Object[] findAllOneColumn(String coloumnNameToBeSelected, CqlStatement statement);
		 void findAllOneColumn(SetobjSet, String coloumnNameToBeSelected, CqlStatement statement);
	}

####Multiple updates in One transaction

• With BatchStatment, multiple Create/update/delete operations can be performed in a single transaction.
• Multiple operations are performed and at the end the operations are committed only when the execute method is called.

	BatchStatement stmt=new BatchStatement();
	CustOrder order=new CustOrder();
	//... Set required Order fields
	em.insert(stmt, order); //Still not commited.
	CustOrderIndex orderIndex=new CustOrderIndex();
	//..set the requried fields.
	em.insert(stmt, orderIndex);
	//Committed only after the execute call.
	//If an exception is encoutnered, the transaction is rolled back.
	em.execute(stmt);

####updateColumn

• In cassandra updating a single column is more faster.
• If you want to update just a column, use this method.

	em.updateColumn(restaurant, CqlBuilder.update(Customer.class).field("firstName").set("John"));

####Query Methods Examples

	@Override
	public CustOrder findById(UUID id) {
		CustOrder order=em.findOne(CqlBuilder.select(CustOrder.class).field("id").eq(id));
		return order;
	}

	@Override
	public CustOrder findByOrderNo(UUID restaurantId, String orderNo) {
		CustOrder order=null;
				
		CustOrderIndex1 i1=em.findOne(CqlBuilder.select(CustOrderIndex1.class).field("restaurantId").eq(restaurantId).field("orderNo").eq(orderNo));
		return order;
	}

	@Override
	public List findByStatusAndDateRange(UUID restaurantId,
			String status, Date dt1, Date dt2) {
		Set idSet=new HashSet();
		em.findAllOneColumn(idSet,"id",CqlBuilder.select(CustOrderLink5.class).field("restaurantId").eq(restaurantId).field("status").eq(status).field("orderDtTm").ge(dt1).field("orderDtTm").le(dt2).limit(500));
		
		List orders=em.findAll(CqlBuilder.select(CustOrder.class).field("id").in(idSet));
		return orders; 
	}