Implementing dynamic paged queries - POJOs in Action: Developing Enterprise Applications with Lightweight Frameworks - page 446

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The doInJdo() method creates the criteria query and calls a helper method to
add the search criteria, specify the ordering and range, and to create the
PagedQueryResult .
The addCriteria() method adds criteria to the query based on what search crite-
ria are specified in the OrderSearchCriteria object. One notable feature of this
method is that if the restaurant name is not one of the search criteria, then
addCriteria() adds a fetch join for Restaurant .
The addSortBy() method specifies how to sort the results.
The addRange() method specifies the range of rows to retrieve.
The makePagedQueryResult() method constructs the PagedQueryResult .
The Hibernate version of the repository contains some conditional logic, but it's a
lot simpler than the JDO version because using criteria queries eliminates the
need to concatenate query fragments.

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11.6 Using JDO and Hibernate native SQL queries

In an ideal world, we would use object queries for all database queries and rely on
the persistence framework to generate optimal SQL statements. But as you might
expect, in the real world this isn't always possible and sometimes we must use SQL
queries that use vendor-specific features such as optimizer hints to achieve the
necessary performance. Both JDO and Hibernate support native SQL queries.
They give you complete control over the SQL while taking care of the potentially
tedious task of constructing Java objects. The only drawback is that neither Hiber-
nate nor JDO provides any support for dynamically generating SQL queries. Con-
sequently, you might want to consider using i BATIS if you are only going to display
the results of the query and do not need to manipulate the objects. Let's look at
how to use JDO and Hibernate SQL queries.

11.6.1 Using JDO native SQL queries

A JDO native SQL query is executed using the JDO Query interface but is written in
SQL instead of JDOQL . It can return either persistent objects or DTO s. SQL que-
ries that return persistent objects are useful if the application needs to manipulate
the persistent objects. However, they are somewhat restrictive because the col-
umns of the result set must map to the fields of a single persistent class. A SQL
query cannot, for example, eagerly load related objects such as an order and its
restaurant, which makes it impossible to implement the View Orders query.