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The purpose of Hibernate is to allow you to treat your database as if it stores Java objects. However, in practice, relational databases do not store objects – they store data in tables and columns. Unfortunately, there is no simple way to correlate the data stored in a relational database with the data represented by Java objects.

Hibernate provides three different ways to retrieve data. We have already discussed HQL and the use of native SQL queries; now we add criteria.

In this chapter, you’ll take another look at some of the steps necessary to get the example from Chapter 1 up and running. You’ll also build a somewhat larger application from scratch. All of the code in this book is available for download from the Apress site (www.apress.com).

Integrating Hibernate into a Java application is easy. The designers of Hibernate avoided some of the more common pitfalls and problems with the existing Java persistence solutions, and created a clean but powerful architecture. In practice, this means that you do not have to run Hibernate inside any particular Java EE container or framework. As of Hibernate 5.2, Java 8 or later is required, thanks to the integration of the date and time API and other such useful features.

In addition to annotations, Hibernate supports the use of XML mapping files to describe the relationship between the object model and the database. A mapping file can map a single class or multiple classes to the database. The mapping can also describe standard queries (in HQL and SQL) and filters.

This book is for software developers and designers who develop Java applications for portals. We cover version 1.0 of the Java portlet API, also known as Java Specification Request (JSR) 168. Portlets are the individual components that provide content for a portal. Portals aggregate one or more portlets into web pages, which are usually personalized or customized for individual users or groups of users. Some portals also support mobile devices and voice support.

The portlet application can use servlets and JavaServer Pages (JSP) in addition to portlets. These Java 2 Enterprise Edition (J2EE) resources can be created especially for the portlet application, or they can be part of a port of an existing J2EE application. Existing servlets and JSP will probably need to be edited to conform to the portlet markup rules for a content fragment. In this chapter, we discuss using servlets and JSP with a portlet. Most portlets will use JSP or another page display technology such as Apache Velocity to render content. Rendering content directly from a portlet is just as awkward as displaying HTML output from a servlet.

This book will demonstrate the use of freely available Java Open Source (JOS) development frameworks for building and deploying applications. Specifically, we will focus on the JOS development frameworks available from the Apache Software Foundation’s Jakarta group (http://jakarta.apache.org).