Advanced Queries

Service Builder doesn’t limit you to what you can cook up with <finder /> elements in service.xml. If simple finders aren’t sufficient for getting data out of your application, you can use Liferay’s Dynamic Query API, which wraps Hibernate’s Criteria API, or your own SQL to make exactly the queries you need.

Though you can use custom SQL queries with Service Builder to retrieve data from the database, sometimes it’s more convenient to build queries dynamically at runtime. You can do this with Liferay’s Dynamic Query API, which wraps Hibernate’s Criteria API. The Dynamic Query API lets you build queries without writing any SQL. It helps you think in terms of objects and member variables instead of tables and columns. Complex queries can be significantly easier to understand and maintain than the equivalent custom SQL (or HQL) queries. While you technically don’t need to know SQL to construct Dynamic Queries, you still must take care to construct efficient queries. For information on Hibernate’s Criteria API, please see Hibernate’s manual.

Whichever way you decide to implement your custom queries, this guide shows you how. Here are the steps:

1. If using SQL, create your SQL query.

2. Define a custom finder method.

3. Implement your finder using Dynamic Query API or SQL.

4. Add a method to your *LocalServiceImpl class that invokes your finder.

Once you’ve taken these steps, you can access your custom finder as a service method. Note: You can create multiple or overloaded findBy* finder methods in your *FinderImpl class. Next, you’ll examine these steps in more detail.