Advanced Queries Using Criteria CHAPTER 1 0 n (Linux web host)
Advanced Queries Using Criteria CHAPTER 1 0 n n n Advanced Queries Using Criteria CHAPTER 1 0 n n n Hibernate provides three different ways to retrieve data. We have already discussed HQL and the use of native SQL queries now we add criteria. The Criteria Query API lets you build nested, structured query expressions in Java, providing a compile-time syntax-checking that is not possible with a query language like HQL or SQL. The Criteria API also includes query by example (QBE) functionality this lets you supply example objects that contain the properties you would like to retrieve instead of having to spell the components of the query out step by step. It also includes projection and aggregation methods, including counts. In this chapter, we explore the use of the Criteria API using the sample database established in the previous chapter. Using the Criteria API The Criteria API allows you to build up a criteria query object programmatically the org.hibernate.Criteria interface defines the available methods for one of these objects. The Hibernate Session interface contains several createCriteria() methods. Pass the persistent object s class or its entity name to the createCriteria()method, and Hibernate will create a Criteria object that returns instances of the persistence object s class when your application executes a criteria query. The simplest example of a criteria query is one with no optional parameters or restrictions the criteria query will simply return every object that corresponds to the class. Criteria crit = session.createCriteria(Product.class); List results = crit.list(); When you run this example with our sample data, you will get all objects that are instances of the Product class note that this includes any instances of the Software class because they are derived from Product. Moving on from this simple example, we will add constraints to our criteria queries so we can winnow down the result set.
If you are searching for cheap webhost for your web application, please visit MySQL5 Web Hosting services.