Mapping with Annotations CHAPTER 6 n n n
Mapping with Annotations CHAPTER 6 n n n Mapping with Annotations CHAPTER 6 n n n In Chapter 5, we discussed the need to create mappings between the database model and the object model. Mappings can be created as separate XML files, or as Java 5 annotations inline with the source code for your POJOs. In this chapter, we discuss the use of annotations, and in the next chapter, we will discuss the use of XML files. Java 5 Features Java 5 was introduced in late 2004 as a major new release of the language. Annotations are not supported by versions of Java prior to this, so while core Hibernate 3 is compatible with earlier versions, you will not be able to take advantage of the features described in this chapter unless your development, compilation, and runtime tools support at least version 5 of the language (version 6 of Java, codenamed Mustang, is expected some time in late 2006). Since we must perforce assume that you have a Java 5 environment available to you, the examples in this chapter will also take advantage of some of the other enhanced language features introduced in Java 5, as follows: Generics Enhanced for loops Static imports Enumerations Autoboxing Variable parameter lists Using these features will make the source code for this chapter noticeably more compact. Similarly, annotation-based mappings are significantly terser than their XML-based counterparts. Creating Hibernate Mappings with Annotations Prior to annotations, the only way to create mappings was through XML files although tools from Hibernate and third-party projects allowed part or all of these to be generated from Java source code. Although using annotations is the newest way to define mappings, it is not automatically the best way to do so. We will briefly discuss the drawbacks and benefits of annotations before discussing when and how to apply them.
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