As mentioned earlier in this chapter, HQL lets you go beyond the use of JDBC-style query placeholders to get parameters conveniently into your queries. You can use named parameters and named queries to make your programs much easier to read and maintain.
Named parameters make code easier to understand because the purpose of the parameter is clear both within the query itself and within the Java code that is setting it up. This self-documenting nature is valuable in itself, but it also reduces the potential for error by freeing you from counting commas and question marks, and it can modestly improve efficiency by letting you use the same parameter more than once in a single query.
Named queries let you move the queries completely out of the Java code. Keeping queries out of your Java source makes them much easier to read and edit because they aren’t giant concatenated series of Java strings spread across multiple lines and interwoven with extraneous quotation marks, backslashes, and other Java punctuation. Typing them the first time is bad enough, but if you’ve ever had to perform significant surgery on a query embedded in a program in this way, you will have had your fill of moving quotation marks and plus signs around to try to get the lines to break in nice places again.
The key to both of these capabilities in Hibernate is
Query interface. We already began
using this interface in Example 3-7 because, starting with Hibernate ...