Java Database Connectivity (JDBC) API
Using this API, you can fetch the data from databases, Flat files or Spread sheet.
Remote Method Invocation (RMI)
Using this API, you can create distributed java application which can remote communicate between different programs.
Java IDL (CORBA)
Common Object Request Broker Architecture also known as CORBA is the Java IDL technology which allows us connectivity and standards-based interoperability.
Using RMI-IIOP you can develop your application using other CORBA-compliant programming languages by utilizing the Internet InterORB Protocol (IIOP).
Scripting for the Java Platform
Using JSR 223 (actually a framework)which is the Java API script (included in J2SE 6), Java Applications can able to "host" script engines.
Java Naming and Directory Interface(JNDI) API
This API allows us for naming and directory functionality for the Java Applications.
Recommend the tutorial