Ecommerce web host - Querying with criteria and example We think both
Querying with criteria and example We think both these options are ugly, even after spending five minutes trying to format them for maximum readability. JDK 5.0 static imports can help improve readability considerably, but even so, unless you re constructing a query on the fly, the HQL or JPA QL string is much easier to understand. You may have noticed that many standard comparison operators (less than, greater than, equals, and so on) are built into the Criteria API, but certain operators are missing. For example, any arithmetic operators such as addition and division aren t supported directly. Another issue is function calls. Criteria has built-in functions only for the most common cases such as string case-insensitive matching. HQL, on the other hand, allows you to call arbitrary SQL functions in the WHERE clause. The Criteria API has a similar facility: You can add an arbitrary SQL expression as a Criterion. Adding arbitrary SQL expressions Let s assume you want to test a string for its length and restrict your query result accordingly. The Criteria API has no equivalent to the LENGTH() function in SQL, HQL, or JPA QL. You can, however, add a plain SQL function expression to your Criteria: session.createCriteria(User.class) .add( Restrictions.sqlRestriction( “length({alias}.PASSWORD) < ?", 5, Hibernate.INTEGER ) ); This query returns all User objects that have a password with less than 5 characters. The {alias} placeholder is needed to prefix any table alias in the final SQL; it always refers to the table the root entity is mapped to (USERS in this case). You also use a position parameter (named parameters aren t supported by this API) and specify its type as Hibernate.INTEGER. Instead of a single bind argument and type, you can also use an overloaded version of the sqlRestriction() method that supports arrays of arguments and types. This facility is powerful for example, you can add an SQL WHERE clause subselect with quantification: session.createCriteria(Item.class) .add( Restrictions.sqlRestriction( "'100' > all” + ” ( select b.AMOUNT from BID b” +
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