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Articles by Manu
5 articles
What are various Inheritance mapping strategies available in Hibernate?
There are three types of inheritance mapping strategies − Table per class hierarchy Table per concrete class Table per subclassIn this article, we will discuss table per class hierarchy. Table per class hierarchy In this, only a single table is created for inheritance mapping. Disadvantages of this approach is that a lot of null values gets stored in the table. @Inheritance(strategy=InheritanceType.SINGLE_TABLE), @DiscriminatorColumn and @DiscriminatorValue are the annotations used in this strategy. @DiscriminatorColumn is used to create an additional column which is used to identify the hierarchy classes. Consider the following example to understand this − Steps ...
Read MoreHow to Execute Batch Insert Update in Hibernate?
In this article, we will see how we can execute batch insert/update in hibernate. Whenever we execute a sql statement, we do it by making a network call to the database. Now, if we have to insert 10 entries to our database table, then we have to make 10 network calls. Instead we can optimize our network calls by using batching. Batching allows us to execute a group of SQL statements in a single network call. To understand and implement this, let us define our entities − @Entity public class Parent { @Id @GeneratedValue(strategy ...
Read MoreHow to customize the Result of JPA Queries with Aggregation Functions?
Most of the time when we use JPA queries, the result obtained is mapped to an object/particular data type. But When we use aggregate function in queries, handling the result sometimes require us to customize our JPA query. Let’s understand this with help of an example (Department, Employee) − Dept.java @Entity public class Dept { @Id private Long id; private String name; @OneToMany(mappedBy = "dep") private List emp; //Getters //Setters } A department can have one or more ...
Read MoreHow to connect hibernate with MySQL Database?
In this article, we will see how we can connect to MySQL database using an ORM (object relational mapping) framework like hibernate. First of all, we need to add maven dependency for hibernate in our pom.xml file − org.hibernate hibernate-core 5.6.2.Final Now, let us define an entity class that will be mapped to a database table using hibernate. @Entity @Table( name = " Employee") public class Employee { @Id @GeneratedValue(strategy = GenerationType.AUTO) Long id; @Column(name = ...
Read MoreHow does Hibernate Second Level Cache Works?
Caching helps to reduce database network call, for executing queries. First level cache is linked with a session. It is implemented implicitly. First level cache exist only till the session object is there. Once session object is terminated/closed, there will be no cache objects. Second level cache works across multiple sessions objects. It is linked with a session factory. Second level cache objects are available to all the session in a single session factory. These cache objects are terminated when that particular session factory is closed. Implementing second level caching We need to add the following dependencies in order to ...
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