Posts - Page 121 (page 121)
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6 min readTo set a parameter to null value in Java with Hibernate, you can use the setParameter method on the Query interface. When setting a parameter to null, you can simply pass null as the value for the parameter. For example, if you have a query that requires a parameter called "name" to be null, you can set it like this: Query query = session.createQuery("FROM User WHERE name = :name"); query.setParameter("name", null); List<User> users = query.
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7 min readTo remove entities from a many-to-many relationship in Hibernate, you need to first load the entities from the database and then remove the association between them. This involves removing the association records from the join table that links the two entities together.You can do this by getting the entities from their respective repositories, removing the association from one side of the relationship (e.g.
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3 min readTo save a timestamp in a single column using Hibernate, you can map the timestamp attribute of your entity class to a single column in the database table. This can be achieved by using the @Column annotation on the timestamp attribute with the specified column name as its parameter. Hibernate will map the timestamp value to that column in the table.
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7 min readTo map only a single column with Hibernate, you can use the @Column annotation on the specific field in your entity class. This annotation allows you to specify the name of the column in the database that the field should be mapped to. By default, Hibernate will map the field to a column with the same name as the field itself, but you can override this behavior by specifying a different column name in the @Column annotation.
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5 min readTo add a WHERE clause on a custom type in Hibernate, you can use the @Where annotation. This annotation allows you to specify conditions that should be added to the SQL WHERE clause when querying for entities of a specific type.First, you need to define a custom type for your entity, if you haven't already. Then, you can add the @Where annotation to your entity class, specifying the condition that should be applied.
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5 min readOne way to enforce table creation order in Hibernate is by specifying the order in which tables should be created using the @OrderColumn annotation. This annotation can be applied to a list or a map attribute in an entity class to define the order in which the elements should be stored in the database.Another approach is to use the hibernate.hbm2ddl.auto property in the Hibernate configuration file to specify the order in which tables should be created.
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6 min readWhen working with Hibernate, we may encounter situations where there are columns in a database table that are not defined in the Hibernate entity class. In such cases, Hibernate provides a way to handle these unknown columns using a feature called "Dynamic Models."With Dynamic Models, we can use a Map to represent the unknown columns in the entity class.
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5 min readHibernate cache properties can be set through the hibernate.cfg.xml configuration file or programmatically using the SessionFactory object.To set cache properties in the hibernate.cfg.xml file, you need to specify the cache provider class, cache region prefix, and cache configuration properties such as the cache mode, cache provider, and cache region.
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4 min readTo implement a custom datatype in Hibernate, you need to create a custom UserType class that implements the org.hibernate.usertype.UserType interface. This UserType class should define the mapping between your custom datatype and the database column type.In the UserType implementation, you need to override methods such as nullSafeGet(), nullSafeSet(), and returnedClass().
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4 min readIn Hibernate, caching for many-to-one mapping works by storing multiple instances of a related entity in the cache for quicker access and retrieval. When a many-to-one relationship is established between two entities, Hibernate stores the related entity object in the cache based on the foreign key of the relationship.
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7 min readTo get the insert and delete count with Hibernate, you can use the Session interface methods getStatistics() and getSessionFactory().First, obtain the statistics of the session by calling getStatistics() on the Session object. Then, you can get the insert count and delete count by using the getEntityInsertCount() and getEntityDeleteCount() methods on the Statistics object.Alternatively, you can also access the insert and delete count using the StatisticsFactory interface.
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5 min readTo add values in a single column of multiple rows in PostgreSQL, you can use the UPDATE statement along with the SET clause to modify the values in the specified column. You can use various conditions to identify the rows that you want to update and then perform the addition operation on the values in the column. Additionally, you can also use functions like SUM() or aggregate functions to calculate the sum of values in the column across multiple rows.