Retrieve One To One Mapped Entity : One to One Mapping « JPA « Java

1. Java
2. JPA
3. One to One Mapping

Retrieve One To One Mapped Entity

File: Address.java

import javax.persistence.Entity;
import javax.persistence.Id;

@Entity
public class Address {
  @Id
  private int id;

  private String street;

  private String city;

  private String state;

  private String zip;

  public int getId() {
    return id;
  }

  public void setId(int id) {
    this.id = id;
  }

  public String getStreet() {
    return street;
  }

  public void setStreet(String address) {
    this.street = address;
  }

  public String getCity() {
    return city;
  }

  public void setCity(String city) {
    this.city = city;
  }

  public String getState() {
    return state;
  }

  public void setState(String state) {
    this.state = state;
  }

  public String getZip() {
    return zip;
  }

  public void setZip(String zip) {
    this.zip = zip;
  }

  public String toString() {
    return "Address id: " + getId() + ", street: " + getStreet() + ", city: " + getCity()
        + ", state: " + getState() + ", zip: " + getZip();
  }

}


File: Student.java

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.OneToOne;

@Entity
public class Student {
  @Id
  private int id;

  private String name;

  @OneToOne
  private Address address;

  public int getId() {
    return id;
  }

  public void setId(int id) {
    this.id = id;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public Address getAddress() {
    return address;
  }

  public void setAddress(Address address) {
    this.address = address;
  }

  public String toString() {
    return "\n\nID:" + id + "\nName:" + name + "\n\n";
  }
}


File: Main.java

import java.sql.Timestamp;
import java.util.List;
import java.util.UUID;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;

public class Main {
  static EntityManagerFactory emf = Persistence.createEntityManagerFactory("JPAService");
  static EntityManager em = emf.createEntityManager();

  public static void main(String[] a) throws Exception {
    em.getTransaction().begin();
    
    
    Student student = new Student();
    student.setName("Joe");
    Address address = new Address();
    em.persist(address);
    
    student.setAddress(address);
      
    em.persist(student);
    em.flush();
    em.getTransaction().commit();

    
    
    
    Query query = em.createQuery("SELECT e FROM Student e");
    List<Student> list = (List<Student>) query.getResultList();
    System.out.println(list.get(0).getAddress());
    
    
    em.close();
    emf.close();
    
    Helper.checkData();
  }
}


File: Helper.java

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;

public class Helper {
  public static void checkData() throws Exception {
    Class.forName("org.hsqldb.jdbcDriver");
    Connection conn = DriverManager.getConnection("jdbc:hsqldb:data/tutorial", "sa", "");
    Statement st = conn.createStatement();

    ResultSet mrs = conn.getMetaData().getTables(null, null, null, new String[] { "TABLE" });
    while (mrs.next()) {
      String tableName = mrs.getString(3);
      System.out.println("\n\n\n\nTable Name: "+ tableName);

      ResultSet rs = st.executeQuery("select * from " + tableName);
      ResultSetMetaData metadata = rs.getMetaData();
      while (rs.next()) {
        System.out.println(" Row:");
        for (int i = 0; i < metadata.getColumnCount(); i++) {
          System.out.println("    Column Name: "+ metadata.getColumnLabel(i + 1)+ ",  ");
          System.out.println("    Column Type: "+ metadata.getColumnTypeName(i + 1)+ ":  ");
          Object value = rs.getObject(i + 1);
          System.out.println("    Column Value: "+value+"\n");
        }
      }
    }
  }
}





File: persistence.xml

<persistence xmlns="http://java.sun.com/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence" version="1.0">
  <persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
      <property name="hibernate.hbm2ddl.auto" value="update"/>
      <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
      <property name="hibernate.connection.username" value="sa"/>
      <property name="hibernate.connection.password" value=""/>
      <property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>
    </properties>
  </persistence-unit>
</persistence>

           
       

JPA-RetrieveOneToOneMappedEntity.zip( 5,289 k)

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