The most important features of Java in database application development are:

• Designing data-bound procedures and functions using Java SE APIs and JDBC.

• Extending the reach and capabilities of the database with standard and third-party Java libraries. For example, accessing third-party databases using their drivers in the database and accessing Hadoop/HDFS.

• Providing flexible partitioning of Java2 Platform, Standard Edition (J2SE) applications for symmetric data access at the JDBC level.

• Bridging SQL and the Java2 Platform, Enterprise Edition (J2EE) world by:

  • Calling out Web components, such as JSP and servlet

  • Bridging SQL and Web Services using Web Service Callouts

• Using an Oracle JVM as ERP Integration Hub.

• Invalidating cache.

In addition to the Oracle JVM, the Java programming environment provides:

• Java stored procedures as the Java equivalent and companion for PL/SQL. Java stored procedures are tightly integrated with PL/SQL. You can call Java stored procedures from PL/SQL packages and PL/SQL procedures from Java stored procedures.

• The JDBC and SQLJ programming interfaces for accessing SQL data.

• Tools and scripts that assist in developing, loading, and managing classes.

The following table helps you decide when to use which Java API:

Java stored procedures are Java programs written and deployed on a server and run from the server, exactly like a PL/SQL stored procedure. You invoke it directly with products like SQL*Plus, or indirectly with a trigger. You can access it from any Oracle Net client, such as OCI and PRO*, or JDBC or SQLJ.

In addition, you can use Java to develop powerful, server-side programs, which can be independent of PL/SQL. Oracle Database provides a complete implementation of the standard Java programming language and a fully compliant JVM.

You can call existing PL/SQL programs from Java and Java programs from PL/SQL. This solution protects and leverages your PL/SQL and Java code and opens up the advantages and opportunities of Java-based Internet computing.

Oracle Database offers two different Java APIs for accessing SQL data, JDBC and SQLJ. Both these APIs are available on the client, and the JDBC API is also available on the server. As a result, you can deploy your applications on the client and server.

The following topics introduce the Java APIs provided by Oracle Database:

• JDBC Drivers

• SQLJ

The introduction of Java in Oracle Database enables you to use several Java IDEs. The adherence of Oracle Database to the Java standards and specifications and the open Internet standards and protocols ensures that your Java programs work successfully, when you deploy them on Oracle Database. Oracle provides many tools or utilities that are written in Java making development and deployment of Java server applications easier. Oracle JDeveloper, a Java IDE provided by Oracle, has many features designed specifically to make deployment of Java stored procedures and EJBs easier. You can download JDeveloper from

http://www.oracle.com/technetwork/developer-tools/jdev/overview/index.html

Starting from Oracle Database 11g Release 2, Oracle JVM supports Internet Protocol Version 6 (IPv6) addresses in the URL and machine names of the Java code in the database, which resolve to IPv6 addresses. IPv6 is a new Network layer protocol designed by the Internet Engineering Task Force (IETF) to replace the current version of Internet Protocol, Internet Protocol Version 4 (IPv4). The primary benefit of IPv6 is a large address space, derived from the use of 128-bit addresses. IPv6 also improves upon IPv4 in areas such as routing, network autoconfiguration, security, quality of service, and so on.

The following system properties enable you to configure IPv6 preferences:

java.net.preferIPv4Stack

If IPv6 is available on the operating system, then the underlying native socket will be an IPv6 socket. This enables Java applications to connect to, and accept connections from both IPv4 and IPv6 hosts. If you have an application that has a preference to use only IPv4 sockets, then you can set this property to true. If you set the property to true, then it implies that the application will not be able to communicate with IPv6 hosts.

java.net.preferIPv6Addresses

Even if IPv6 is available on the operating system, then for backward compatibility reasons, the addresses are mapped to IPv4. For example, applications that depend on access to only an IPv4 service, benefit from this type of mapping. If you want to change the preferences to use IPv6 addresses over IPv4 addresses, then you can set the java.net.preferIPv6Addresses property to true. This allows applications to be tested and deployed in environments, where the application is expected to connect to IPv6 services.