pc-hi

V1.0.0 - CRUD Example with JDBC

<dependency>
  <groupId>mysql</groupId>
  <artifactId>mysql-connector-java</artifactId>
  <version>8.0.31</version>
</dependency>

Need to use a singleton pattern to the database connection

v2.0.0 - CRUD Example with JPA

 <dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.31</version>
  </dependency>

  <dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-core</artifactId>
    <version>5.5.7.Final</version>
  </dependency>

src/main/resources/META-INF/persistence.xml

<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence
    http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
    <persistence-unit name="laptop_persist">
    <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
        <properties>
        <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
        <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/device_store"/>
        <property name="hibernate.connection.autocommit" value="false"/>
        <property name="hibernate.connection.username" value="root"/>
        <property name="hibernate.connection.password" value="19940306"/>
        <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect"/>
        <property name="hibernate.connection.CharSet" value="utf8"/>
        <property name="hibernate.connection.characterEncoding" value="utf8"/>
        <property name="hibernate.connection.useUnicode" value="true"/>
        <property name="hibernate.show_sql" value="false"/>
        <property name="hibernate.hbm2ddl.auto" value="update"/>
        </properties>
    </persistence-unit>
</persistence>

EntityManager...

EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("laptop_persist");
EntityManager entityManager = entityManagerFactory.createEntityManager();
entityManager.getTransaction().begin();
entityManager.persist(laptop);
entityManager.getTransaction().commit();
entityManager.close();
entityManagerFactory.close();

Need to use class name(Laptop) in the queries as follows.

@Entity
@Table(name = "laptop")
@NamedQueries({
    @NamedQuery(name = "Laptop.getAllLaptopDetails", query = "SELECT lap FROM Laptop lap"),
    @NamedQuery(name = "Laptop.deleteGivenLaptop", query = "DELETE FROM Laptop lap WHERE lap.lapId= :id"),
    @NamedQuery(name = "Laptop.updateGivenLaptop", query = "UPDATE Laptop lap SET lap.brandName = :brand, lap.modelName = :model, lap.serialNumber =           :serial  WHERE lap.lapId= :id")
 })

cascade type will helps to sync the dependency objects with the dependent objects. Otherwise needs to mannually update, delete and create the dependencies

 @ManyToOne(cascade = CascadeType.ALL)

To maintain the ManyToMany relationship, we can use jointable for it

@ManyToMany(cascade = CascadeType.ALL)
@JoinTable(name = "laptop_printer", joinColumns = @JoinColumn(name = "lap_id"), inverseJoinColumns = @JoinColumn(name = "printer_id"))
private Set<Printer> printers;  

@ManyToMany(mappedBy = "printers")
private Set<Laptop> laptops;

mappedBy will help to handover the ownership