Data filtering and interception directly to the database (Web design tools)
Data filtering and interception directly to the database system, so you can use any SQL operator or function. It must evaluate to true if a record should pass the filter. In this example, you use a subquery to obtain the rank of the seller of the item. Unqualified columns, such as SELLER_ID, refer to the table to which the entity class is mapped. If the currently logged-in user s rank isn t greater than or equal than the rank returned by the subquery, the Item instance is filtered out. Here is the same in annotations on the Item entity: @Entity @Table(name = “ITEM”) @org.hibernate.annotations.Filter( name = “limitItemsByUserRank”, condition=”:currentUserRank >= ” + “(select u.RANK from USER u” + ” where u.USER_ID = SELLER_ID)” ) public class Item implements { … } You can apply several filters by grouping them within a @org.hibernate.annotations.Filters annotation. A defined and applied filter, if enabled for a particular unit of work, filters out any Item instance that doesn t pass the condition. Let s enable it. Enabling the filter You ve defined a data filter and applied it to a persistent class. It s still not filtering anything; it must be enabled and parameterized in the application for a particular Session (the EntityManager doesn t support this API you have to fall back to Hibernate interfaces for this functionality): Filter filter = session.enableFilter(”limitItemsByUserRank”); filter.setParameter(”currentUserRank”, loggedInUser.getRanking()); You enable the filter by name; this method returns a Filter instance. This object accepts the runtime arguments. You must set the parameters you have defined. Other useful methods of the Filter are getFilterDefinition() (which allows you to iterate through the parameter names and types) and validate() (which throws a HibernateException if you forgot to set a parameter). You can also set a list of arguments with setParameterList(), this is mostly useful if your SQL condition contains an expression with a quantifier operator (the IN operator, for example). Now every HQL or Criteria query that is executed on the filtered Session restricts the returned Item instances:
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