Jpa Datadescriptor

JPA DataDescriptors are used to describe the data structure in an SQL database. A JPA DataDescriptor has access to the data through the JPA layer, so a DataDescriptor must use entity classes. JPA DataDescriptors enable you to read and write data in an SQL database.

The JPA DataDescriptor is the default data descriptor type in the JBStrap framework. If you don't specify the connectorType attribute in the data descriptor, the framework creates a JPA DataDescriptor from an XML descriptor.

Creating a JPA DataDescriptor in an XML structure:

         <?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE xml>
<datadescriptor name="Example" dataClass="com.jbstrap.sample.domain.Example">
 <access>
   <type>Public</type>
 </access>
 <column name="supplierId" datatype="NUMBER" primaryKey="true" nullable="false" />
 <column name="supplierName" datatype="VARCHAR2" length="255" />
 <column name="supplierCountry" datatype="VARCHAR2" length="40" />
</datadescriptor>
        

Programmatically creating a JPA DataDescriptor that corresponds to the above XML:

         JPADataDescriptor dataDescriptor = new JPADataDescriptor("Example", "com.jbstrap.sample.domain.Example")
.setAccess(AccessType.PUBLIC)
.addColumn(new DataDescriptorColumn("supplierId", DataDescriptorColumnType.LONG), "Example")
.setPrimaryKey(true)
.setNullable(false)
)
.addColumn(new DataDescriptorColumn("supplierName", DataDescriptorColumnType.TEXT), "Example")
.setLength(255)
)
.addColumn(new DataDescriptorColumn("supplierCountry", DataDescriptorColumnType.LONG), "Example")
.setLength(40)
);
        

The JPA DataDescriptor enables you to perform any data handling operation: reading data from the database, updating and deleting data.

Fetches all records from the database by using the data descriptor:

Fetches all records satisfying the specified criteria using the data descriptor:

         List<DataRecord> result = dataDescriptor.find(new Criteria("supplierCountry", OperatorType.EQUALS, "USA"));
        

Fetching a record using its primary key:

Saving a record to the database using the data descriptor:

Removing a record using the data descriptor:

DataDescriptors also support transaction handling. To handle transactions, you must specify an SQLTransaction for the DataDescriptor.

Fetching a record, then modifying and saving it within a single transaction:

         // Start new transaction
SQLTransaction transaction = new SQLTransaction();
// Read record from the database
DataRecord supplier = dataDescriptor.findById(transaction, null, 25L);
// Modify the record value
supplier.setValue("supplierName", "New Supplier Name");
// Save the modified record to the database
dataDescriptor.save(supplier, null, transaction);
// Commit the changes in the database
transaction.commit();
        