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XML-to-Database Mapping with Hibernate 3.1
by Deepak Vohra
Hibernate is an open source object/relational persistence and query service for Java. Hibernate's latest version, 3.x, introduces a new feature: XML-to-database mapping, which allows you to to map data representation in an XML document to a database (of which Hibernate supports several—including DB2, MySQL, Oracle, and PostgreSQL). With Hibernate, you map your XML document nodes to database columns. Only an XML mapping file is required to map an XML document to a database table; a POJO is not required. Hibernate generates the required SQL to create, update, and delete database tables. You can also use it togenerate tables from a Hibernate configuration file and add data to a database table from an XML document. You can retrieve database table data as an XML document and update it from that XML document. Further, Hibernate 3.x supports dom4j API for XML processing. Hibernate also provides classes for Ant build tasks. In this tutorial, you'll learn how to develop an XML/relational application with Hibernate 3.1.
The first thing you'll want to do is take a look at the database configuration properties, which are specified in the hibernate.properties file. These files specify the database, the JDBC driver class, and the connection URL you'll use to connect to the database. The mapping file, a hbm.xml file, specifies the XML document nodes and the corresponding database columns to which the nodes are mapped. The database table name to which a Java bean class is mapped to is also specified in the mapping file. You'll use the org.hibernate.tool.hbm2ddl.SchemaExport tool to map the mapping file to the database table. This tutorial will show you how to map an example mapping file (Catalog.hbm.xml), consisting of properties for a journal catalog, to an Oracle database table, OE.Catalog.
Preliminary Setup
You'll need the Hibernate API classes to develop a Hibernate application. Download Hibernate 3.1.2 and extract the files to an installation directory. Install the Oracle 10g database (to do so, install and create the database, refer to Oracle database documentation). Next, add the .jar files required to generate a Hibernate application to the CLASSPATH environment variable (the .jar files are listed in Table 1.
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JAR/Zip File
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Description
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<Hibernate3.1>/hibernate3.jar
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The Hibernate API classes
including the org.hibernate.tool.hbm2ddl.SchemaExport
class.
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<Hibernate3.1>/lib/dom4j-1.6.1.jar, <Hibernate3.1>/lib/commons-logging-1.0.4.jar, <Hibernate3.1>/lib/commons-collections-2.1.1.jar,
<Hibernate3.1>/lib/ehcache-1.1.jar,
<Hibernate3.1>/lib/cglib-2.1.3.jar,
<Hibernate3.1>/lib/jta.jar, <Hibernate3.1>/lib/asm.jar, <Hibernate3.1>/lib/antlr-2.7.6rc1.jar
<Hibernate3.1>/lib/jaxen-1.1-beta-7.jar
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The auxiliary Hibernate
classes.
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<Oracle10g>/jdbc/lib/classes12.jar
or ojdbc14.jar
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The Oracle database JDBC classes.
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Table 1. Hibernate JAR Files
Table 1 shows <Hibernate> as the directory, C:/Hibernate/hibernate-3.1, in which Hibernate 3.1 is installed.
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