• oracle.jsql.BinaryStream—An InputStream-derived class whose bytes should be interpreted as binary.
• oracle.jsql.BooleanInOut—A holder class used to pass an argument of type BOOLEAN as an in-out parameter to a J/SQL operation.
• oracle.jsql.byteArrayInOut—A holder class used to pass an argument of type byte[] as an in-out parameter to a J/SQL operation.
• oracle.jsql.DateInOut—A holder class used to pass an argument of type java.sql.Date as an in-out parameter to a J/SQL operation.
• oracle.jsql.DateOut—A holder class used to pass an argument of type java.sql.Date as an out parameter to a J/SQL operation.
• oracle.jsql.ExecStatus—ExecStatus defines the status of the last successfully executed SQL.exec() operation on a particular instance of JSQLntext.
• oracle.jsql.IntegerInOut—A holder class used to pass an argument of type Integer as an in-out parameter to a J/SQL operation.
• oracle.jsql.JSQLContext—JSQLContext manages a set of SQL operations performed during a session with a specific database. JSQLContext implements the JDBC connection interface, and as such it can be used as an entry point for performing dynamic SQL operations in the same way you would use any other JDBC connection.
• oracle.jsql.JSQLException ()—A constructor without an associated error message.
• oracle.jsql.JSQLException (string)—A constructor with an associated error message.
• n oracle.jsql.ObjectInOut—A holder class used to pass an argument of type Object as an in-out parameter to a J/SQL operation.
• oracle.jsql.StreamWrapper—This class wraps a particular instance of InputStream. It also extends the InputStream class by providing direct call-throughs to the wrapped InputStream instance for all methods.
• oracle.jsql.StringInOut—A holder class used to pass an argument of type String as an in-out parameter to a J/SQL operation.
• oracle.jsql.TimeInOut—A holder class used to pass an argument of type java.sql.Time as an in-out parameter to a J/SQL operation.
• oracle.jsql.TimestampInOut—A holder class used to pass an argument of type java.sql.Timestamp as an in-out parameter to a J/SQL operation.
• oracle.jsql.UnicodeStream—An InputStream-derived class whose bytes should be interpreted as Unicode. When passing InputStream as an input parameter to a SQL.exec() operation, you must specify both the length of InputStream and the way to interpret its bytes.

JDBC

As mentioned earlier, JDBC provides the standard interface between Java and the database. At this point, I would like to take a brief minute and discuss JDBC.

JDBC (Java Database Connectivity) is a standard relational database access interface. It's somewhat analogous to Microsoft's ODBC (Open Database Connectivity) in that JDBC is driver based and database independent. JDBC is widely supported by third-party tool vendors and many popular databases. As such, JDBC will remain the main database access mechanism for Java for the near future.

JDBC requires an operating system driver to access the relational database. Several company vendors provide generic JDBC-ODBC bridge drivers that allow any ODBC driver to be used with JDBC. With these bridge drivers, the JDBC API acts as a wrapper for the underlying ODBC calls. To use the drivers, place JDBC calls within your Java source code.

Unfortunately, being driver based is also the main disadvantage of JDBC. JDBC requires the drivers to be installed on the same platform as the JDBC application, which means that Java and the drivers must be installed with the Internet browser. This adds to the complexity of the overall application architecture. This is a limitation you must endure to have the Java-relational database connectivity. Another limitation of JDBC is that it provides access to the standard SQL types only and does not support the Oracle-specific types such as ROWID.

Even though JDBC has these few limitations, it does offer the following benefits:

• Oracle supports the entire JDBC standards. Some RDBMSs support only a partial JDBC standard.
• Oracle's JDBC drivers are portable to several other environments.
• Oracle has designed a special version of JDBC that is stored inside the Oracle database. This dramatically improves access performance.

PL/SQL Versus Java

PL/SQL and Java have many similarities and common strengths that make them both outstanding programming languages. Likewise, they have some differences that are attributable to their purposes and origins. PL/SQL and Java compare and contrast as follows:

• One of PL/SQL's main strengths is its ability to manipulate data. Structures such as cursors, loops, and arrays offer an advantage over Java.
• Both Java and PL/SQL allow SQL to be embedded within them for standard data access routines. PL/SQL allows native SQL code within it while Java source code requires J/SQL or a similar language to incorporate SQL.

• PL/SQL is very integrated and operates almost seamlessly with the Oracle database. To access Oracle through Java, you need to use J/SQL or some other means.
• PL/SQL and Java both have the capability to process data locally, without regard for execution location and networking aspects.
• Java enables you to take advantage of several object orientation (OO) features such as classes and inheritance. PL/SQL doesn't support these two OO features. However, both languages incorporate OO encapsulation—PL/SQL through packages and Java through classes.
• Java tends to be more "wordy" than PL/SQL. In other words, Java requires more definitions and lacks the capability to use logical pointers.

The World Wide Web and SQL

Over the past several years, the primary user interface to the Internet and the World Wide Web (WWW) has been the browser. Internet browsers from companies such as Oracle, Microsoft, and Netscape primarily access Web pages, which are written in Hypertext Markup Language (HTML) and Java.

You learned earlier in this chapter that Java and J/SQL can be integrated to give Java access to an RDBMS. J/SQL opens the door and allows Web pages that use Java to access Oracle databases. This RDBMS access from a Web browser is the architecture of the future. In fact, it has already begun. Internet applications such as E-COMMERCE (Electronic Commerce) would not be possible without this Web-page-to-database connectivity. E-COMMERCE is the applications that allow you to perform sales and purchasing activities over the Internet. Figure 21.2 illustrates typical scenarios for the processing of SQL statements through a Web page or a Web server.

At this point, I want to share with you several options, other than J/SQL and JDBC, that enable you to have Java-to-RDBMS connectivity. Although I prefer and recommend J/SQL, it's important and reasonable for me to review alternatives with you:

• Oracle provides a Java cartridge that includes classes for calling stored procedures directly from a Java application. This is accomplished by Oracle using class wrappers around the PL/SQL packages, functions, and procedures.
• One vendor, WebLogic Inc., offers APIs for database access from Java. These APIs are classes that treat Oracle tables as arrays and records to automatically generate the necessary DML statements.
• Various vendors offer their own, nonstandard interfaces that use JDBC, ODBC, or their own proprietary database drivers. Exercise some caution here to ensure driver compatibility. For information about JDBC interfaces and drivers, check out the site at http://splash.javasoft.com/jdbc.