BC4J: How get Connection from Application Module

Question

I've written a custom method for my Application Module for using by the client tier. In this method I call a JPUblisher created class, that accesses a PL/SQL procedure. For this JPublisher created class I need a connection context. The class calls DefaultContext.getDefaultContext() but that seems to be null.
How can I get the current Connection of the Application Module, so that I can create a DefaultContext?
Unfortunately Transaction has no getConnection method.
Thanks,
Robert

Answer 1

We don't make the Connection directly available because in some sense it's a rope on which you can hang yourself if you are not careful. Since BC4J AppModules are most often used from a pool, and you might be using connection pooling in addition to application module pooling, in general it is not safe to get hold of the raw JDBC connection and "hang onto it".
If you make careful use to always get the current JDBC connection before you use it, and not try to cache it, then you should be ok. Often, you can avoid the need to get the raw JDBC connection by calling getDBTransaction().createPreparedStatement(...) or the analogous createCallableStatement() or createStatement() that are also on the DBTransaction interface.
Here is a little function you can add to your application module impl class to retrieve the Connection:
  private Connection getCurrentConnection() {
    Statement st = null;
    try {
      st = getDBTransaction().createStatement(0);
      return st.getConnection();
    catch (SQLException s) {
      s.printStackTrace();
      return null;
    finally {
      if (st != null) try { st.close(); } catch (SQLException s2) {}
  }It basically creates a (dummy) statement, gets the current connection from the statement, then closes the statement.
I tried using this in a custom method in an AppModuleImpl class that invoked a JPublisher-create package-wrapper class like this:
  public void callStoredProc() {
    try {
      // Empservice is package wrapper class created by JPublisher
      Empservice e = new Empservice(getCurrentConnection());
      BigDecimal sal = e.lookupsalary(new BigDecimal(7369));
      System.out.println(sal);
    catch (SQLException s) {
      s.printStackTrace();
  }and it works for me.