JpaIntegration (Smart GWT LGPL Edition API 6.1p (2024-07-30))

```
public interface JpaIntegration
```
Integration with JPA
To use JPA, set serverType="jpa" in your .ds.xml file, then set beanClassName to the fully qualified class name of the JPA entity. For example:
```
  <DataSource
      ID="countryDS"
      serverType="jpa"
      beanClassName="com.smartgwt.sample.showcase.server.jpa.Country"
  >
      <fields>
  
      </fields>
  </DataSource>
  
```
DataSource.autoDeriveSchema is supported for deriving DataSource fields from JPA entities automatically (except with JPA 1.0; see below).
Full support is provided for executing simple Criteria, with AdvancedCriteria supported if you have Power Edition or above. However, note that there are limitations with case sensitive search in MySQL since MySQL automatically uses the 'like' operator in a case-insensitive manner and JPA does not correct this. See MySQL Reference Manual :: C.5.5.1 Case Sensitivity in String Searches for more information.

If create a custom DataSource based on the built-in JPA functionality, subclass com.isomorphic.jpa.JPA2DataSource.

Beans and the DSRequest / DSResponse

In case of "pre-existing beans" approach, see com.smartgwt.client.docs.HbBeans for the information how incoming DSRequest data is used and what to expect in DSResponse.

JPA relations

For JPA integration where Java beans have been explicitly declared, JPADataSource supports automatic handling of JPA relations that don't declare a concrete field to hold ID values - see JpaHibernateRelations.

JPA configuration

JPA configuration should be specified in the persistence.xml file as usual, and placed in the /WEB-INF/classes/META-INF directory. For JPA 2.0 make sure you correctly declare its usage in persistence.xml:
```
  <persistence
      version="2.0"
      xmlns="http://java.sun.com/xml/ns/persistence"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://java.sun.com/xml/ns/persistence 
                          http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
  >
  ...
  </persistence>
```
JPADataSource supports operations with composite primary keys. Setting data source level property idClassName to fully qualified class name indicates, that entity uses composite primary key.
JPADataSource supports automatic handling of JPA relations that don't declare a concrete field to hold ID values - see JpaHibernateRelations.

JPA 1.0 compatibility

To use JPA 1.0, set serverType="jpa1" instead. JPA 1.0 does not support DataSource.autoDeriveSchema. For JPA 1.0, the concrete implementation class (for subclassing to create a custom DataSource) is com.isomorphic.jpa.JPADataSource.

JPA transactions

JPA provides three mechanisms for transactions: for JEE applications JPA provides integration with JTA (Bean Managed Transactions and Container Managed Transactions); for JSE applications JPA has a native EntityTransaction implementation (Locally Managed Transactions). Spring framework is another popular way for declaring transactions in application. The transaction mechanism should be configured in the server.properties file by setting property jpa.emfProvider to the fully qualified class name of the provider (implementation of com.isomorphic.jpa.EMFProviderInterface). Smart GWT comes with five implementations:
- com.isomorphic.jpa.EMFProviderLMT - for Locally Managed Transactions. Every fetch or DML operation starts a new transaction and commits after successful execution.
  This implementation reads the jpa.persistenceUnitName property from the server.properties file. The value of this property needs to be set to the name of the persistence unit configured in persistence.xml file. For example:
```
  jpa.persistenceUnitName: PERSISTENCE_UNIT_NAME
       
```
- com.isomorphic.jpa.EMFProviderBMT - for Bean Managed Transactions. Every fetch or DML operation acquires the transaction object from the container and starts it.
  This implementation reads two properties from the server.properties file: jpa.entityManager and jpa.entityManagerFactory containing appropriate resource name references configured in /WEB-INF/web.xml. Configuration example:
```
  
  <persistence-context-ref>
     <persistence-context-ref-name>persistence/em</persistence-context-ref-name>
     <persistence-unit-name>PERSISTENCE_UNIT_NAME</persistence-unit-name>
  </persistence-context-ref>
 
  
   <persistence-unit-ref>
       <persistence-unit-ref-name>persistence/emf</persistence-unit-ref-name>
       <persistence-unit-name>PERSISTENCE_UNIT_NAME</persistence-unit-name>
   </persistence-unit-ref>
 
  #Property values for sample references:
  jpa.entityManager: persistence/em
  jpa.entityManagerFactory: persistence/emf
       
```
- com.isomorphic.jpa.EMFProviderCMT - for Container Managed Transactions. Every fetch or DML operation acquires the transaction object from the JEE container. After successful method execution the container commits the transaction. In case of execution failure tx.setRollbackOnly() is used to notify container to rollback the transaction.
  This implementation reads two properties from the server.properties file: jpa.entityManager and jpa.entityManagerFactory containing appropriate resource name references configured in /META-INF/ejb-jar.xml. Configuration example:
```
  <?xml version="1.0" encoding="UTF-8"?>
  <ejb-jar
       version = "3.0"
       xmlns = "http://java.sun.com/xml/ns/javaee"
       xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation = "http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/ejb-jar_3_0.xsd">
       <enterprise-beans>
           <session>
               <ejb-name>TestEJB</ejb-name>
               <persistence-context-ref>
                   <persistence-context-ref-name>persistence/em</persistence-context-ref-name>
                   <persistence-unit-name>PERSISTENCE_UNIT_NAME</persistence-unit-name>
               </persistence-context-ref>
               <persistence-unit-ref>
                   <persistence-unit-ref-name>persistence/emf</persistence-unit-ref-name>
                   <persistence-unit-name>PERSISTENCE_UNIT_NAME</persistence-unit-name>
               </persistence-unit-ref>
          </session>
      </enterprise-beans>
  </ejb-jar>
 
  #Property values for sample references:
  jpa.entityManager: persistence/em
  jpa.entityManagerFactory: persistence/emf
       
```
- com.isomorphic.jpa.EMFProviderNoTransactions - transactions are not used.
  From the server.properties file this implementation reads the jpa.persistenceUnitName property which must containt the name of persistence unit configured in persistence.xml file. For example:
```
  jpa.persistenceUnitName: PERSISTENCE_UNIT_NAME
       
```
- com.isomorphic.jpa.EMFProviderSpring - for Spring Framework managed Transactions. Every fetch or DML operation acquires the transaction object from the Spring Application Context.
  This implementation reads two properties from the server.properties file: jpa.entityManagerFactory and jpa.transaction containing appropriate bean names configured in Spring Application Context. You have to declare additional bean in your Spring Application Context to allow Smart GWT to acquire reference to context. Configuration example:
```
  
  <bean id="springApplicationContextProvider" class="com.isomorphic.spring.SpringApplicationContextProvider" />
 
  
  <bean id="dataSource"
       class="org.springframework.jdbc.datasource.DriverManagerDataSource"
       p:driverClassName="DRIVER_CLASS"
       p:url="CONNECTION_URL"
       p:username="DB_USER_NAME"
       p:password="DB_USER_PASSWORD" />
 
  
  <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
      <property name="dataSource" ref="dataSource" />
      <property name="jpaVendorAdapter">
         <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
             <property name="database" value="DB_TYPE" />
         </bean>
      </property>
      <property name="persistenceUnitName" value="PERSISTENCE_UNIT_NAME" />
  </bean>
 
  
  <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
      <property name="entityManagerFactory" ref="entityManagerFactory" />
  </bean>
 
  #Property values for sample bean names:
  jpa.entityManagerFactory: entityManagerFactory
  jpa.transaction: transactionManager
       
```
You can set jpa.emfProvider to your own implementation of com.isomorphic.jpa.EMFProviderInterface if you have specific requirements for transaction handling. EMF will instantiate provided implementation on initialization (static) and will use same instance every time. By using own implementation you can have complete control over creating/using EntityManagerFactory and EntityManager instances.
Additional configurations:
In case you have several persistence units defined in your persistence.xml you can have additional configurations in server.properties file. Additional configurations (prefixed with jpa.) should have name, emfProvider property and other properties required by specified EMF provider implementation. For example:
```
  jpa.configName.emfProvider: com.isomorphic.jpa.EMFProviderLMT
  jpa.configName.persistenceUnitName: ANOTHER_PERSISTENCE_UNIT_NAME
```
To use additional JPA configuration you have to set jpaConfig property in data source definition:
```
  <DataSource
      ID="countryDS"
      serverType="jpa"
      beanClassName="com.smartgwt.sample.showcase.server.jpa.Country"
      jpaConfig="configName"
  >
```
Transaction management:
- Operating under RPCManager (DSRequest has reference to RPCManager):
  - If participating in automatic transactions:
    - retrieves existing transaction from RPCManager (if available);
    - starts new transaction (if not found in RPCManager);
  - If one transaction per operation is used - starts new transaction;
  - Registers itself to DSRequest.registerCallback() for onSuccess()/ onFailure() execution to commit/roll back transaction;
  - Sets DSRequest.setFreeOnExecute() to false to postpone releasing of EntityManager avoiding lazy loading exceptions when creating JS response and traversing through persistent object tree;
  - Registers itself to RPCManager.registerFreeResourcesHandler() for freeResources() execution to release EntityManager.
  If you want to use same EntityManager and transaction in your custom data source implementation you can acquire it by
```
JPAConnectionHolder holder = DataSource.getTransactionObject(req, EMF.TRANSACTION_ATTR);
```
  JPAConnectionHolder instance contains references to entity manager and transaction object used by JPADataSource. You should never commit/rollback automatic transaction. Overall commit/rollback will be issued by RPCManager and will be handled by JPADataSource object which started transaction.
- Operating without RPCManager:
  - starts new transaction;
  - commits/rolls back transaction and releases EntityManager if DSRequest.setFreeOnExecute() is set to true (defalut);
  - relies on calling code to call onSuccess()/onFailure() to commit/roll back transaction and to call freeResources() to release EntityManager.
    Example code for data source operation execution with manual transaction handling:
```
               DSRequest req = new DSRequest("myDS", "fetch");
               req.setFreeOnExecute(false);
               DSResponse resp = req.execute();
               List dataList = resp.getDataList();
               //... traverse through persistent object tree
               // Commit current transaction.
               ((JPADataSource) r.getDataSource()).onSuccess();
               // Release entity manager.
               ((JPADataSource) r.getDataSource()).freeResources(req);
           
```
Inbound DSRequest data will use numeric field types from your bean

For fields with numeric types, the record data in DSRequests will automatically be converted to the type of the target field, before the request is received in a DMI. For details, see DsRequestBeanTypes.

Manual JPA Integration

In some cases you may not be able to immediately use the built-in JPADataSource - in this case take a look at manual Hibernate integration.
See Also:

SqlConnectionPooling

Interface JpaIntegration

Integration with JPA

Beans and the DSRequest / DSResponse

JPA relations

JPA configuration

JPA 1.0 compatibility

JPA transactions

Inbound DSRequest data will use numeric field types from your bean

Manual JPA Integration