Sql ResultSet Mapping For Hierarchical Entity : ResultSet Mapping « JPA « Java Tutorial

1. Java Tutorial
2. JPA
3. ResultSet Mapping

File: Employee.java

import java.util.Date;

import javax.persistence.Column;
import javax.persistence.DiscriminatorColumn;
import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;
import javax.persistence.EntityResult;
import javax.persistence.FieldResult;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.SqlResultSetMapping;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

@Entity 
@Table(name="EMPLOYEE_STAGE")
@Inheritance
@DiscriminatorColumn(name="EMP_TYPE")
@SqlResultSetMapping(
    name="EmployeeStageMapping",
    entities=
        @EntityResult(
            entityClass=Employee.class,
            discriminatorColumn="TYPE",
            fields={
                @FieldResult(name="startDate", column="START_DATE"),
                @FieldResult(name="dailyRate", column="DAILY_RATE"),
                @FieldResult(name="hourlyRate", column="HOURLY_RATE")
            }
        )
)
public abstract class Employee {
    @Id private int id;
    private String name;
    @Temporal(TemporalType.DATE)
    @Column(name="START_DATE")
    private Date startDate;

    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 Date getStartDate() {
        return startDate;
    }

    public void setStartDate(Date startDate) {
        this.startDate = startDate;
    }

    public String toString() {
        return "Employee id: " + getId() + " name: " + getName();
    }
}

@Entity
class ContractEmployee extends Employee {
    @Column(name="DAILY_RATE")
    private int dailyRate;
    private int term;
    
    public int getDailyRate() {
        return dailyRate;
    }
    
    public void setDailyRate(int dailyRate) {
        this.dailyRate = dailyRate;
    }
    
    public int getTerm() {
        return term;
    }
    
    public void setTerm(int term) {
        this.term = term;
    }

    public String toString() {
        return "ContractEmployee id: " + getId() + " name: " + getName();
    }
}



@Entity(name="PTEmp")
@DiscriminatorValue("PTEmp")
class PartTimeEmployee extends Employee {
    @Column(name="HOURLY_RATE")
    private float hourlyRate;

    public float getHourlyRate() {
        return hourlyRate;
    }

    public void setHourlyRate(float hourlyRate) {
        this.hourlyRate = hourlyRate;
    }

    public String toString() {
        return "PartTimeEmployee id: " + getId() + " name: " + getName();
    }
}

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: Main.java

import java.util.List;

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();

    



    em.getTransaction().commit();
    em.close();
    emf.close();

    Helper.checkData();
  }
}

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>

22.30.ResultSet Mapping
	22.30.1.	Single Table ResultSet Mapping
	22.30.2.	Sql ResultSet Mapping With Entity Result And Field Result
	22.30.3.	Sql ResultSet Mapping For Hierarchical Entity
	22.30.4.	Sql ResultSet Mapping With Entity And Column
	22.30.5.	Resultset Mapping With Two Entities
	22.30.6.	ID Class ResultSet Mapping
	22.30.7.	Alias Column In Resultset Mapping