Interacting with data in a transaction for Java applications

Use sessions to interact with data, including insert and update operations.

About this task

The ObjectMap interface has the typical Map operations such as put, get, and remove. However, use the more specific operation names such as: get, getForUpdate, insert, update, and remove. These method names convey the intent more precisely than the traditional Map APIs.

Note: The upsert and upsertAll methods replace the ObjectMap put and putAll methods. Use the upsert method to tell the BackingMap and loader that an entry in the data grid needs to place the key and value into the grid. The BackingMap and loader does either an insert or an update to place the value into the grid and loader . If you run the upsert API within your applications, then the loader gets an UPSERT LogElement type, which allows loaders to do database merge or upsert calls instead of using insert or update.

You can also use the indexing support, which is flexible.

• Insert data.
  After you obtain a session, you can use the following code fragment to use the Map API for inserting data.

  Session session = ...;
  ObjectMap personMap = session.getMap("PERSON");
  session.begin();
  Person p = new Person();
  p.name = "John Doe";
  personMap.insert(p.name, p);
  session.commit();

  The same example using the EntityManager API follows. This code sample assumes that the Person object is mapped to an Entity.

  Session session = ...;
  EntityManager em = session.getEntityManager();
  session.begin();
  Person p = new Person();
  p.name = "John Doe";
  em.persist(p);
  session.commit();
  

  The pattern is designed to obtain references to the ObjectMaps for the Maps that the thread works with, start a transaction, work with the data, then commit the transaction.

• Update data.

  Use the following code fragment to use the Map API for updating data.

  session.begin();
  Person p = (Person)personMap.getForUpdate("John Doe");
  p.name = "John Doe";
  p.age = 30;
  personMap.update(p.name, p);
  session.commit();

  The application normally uses the getForUpdate method rather than a simple get to lock the record. The update method must be called to actually provide the updated value to the Map. If update is not called then the Map is unchanged. The following code is the same fragment using the EntityManager API:

  session.begin();
  Person p = (Person)em.findForUpdate(Person.class, "John Doe");
  p.age = 30;
  session.commit();

  The EntityManager API is simpler than the Map approach. In this case, eXtreme Scale finds the Entity and returns a managed object to the application. The application modifies the object and commits the transaction, and eXtreme Scale tracks changes to managed objects automatically at commit time and performs the necessary updates.

• Insert data with the two-phase commitment protocol by calling the following method: session.setTxCommitProtocol(Session.TxCommitProtocol.TWOPHASE); session.begin(); The following code snippet illustrates how to create, retrieve, update, and delete operations in a grid with a two-phase commit protocol.

  Session session = og.getSession();
  Objectmap map1 = session.getMap("Map1");
  Objectmap map2 = session.getMap("Map2");
  Objectmap map3 = session.getMap("Map3");
  session.setTxCommitProtocol(Session.TxCommitProtocol.TWOPHASE);
  session.begin();
  map1.insert("randKey345", "HelloMap1");
  map2.insert("randKey58901", "HelloMap2");
  map3.insert("randKey58", "HelloMap3");
  session.commit();