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| 22. 16. 3. 设置子类值 |
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File: Employee.java |
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import java.util.Date;
import javax.persistence.Column;
import javax.persistence.DiscriminatorColumn;
import javax.persistence.DiscriminatorType;
import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
@Entity
@Table(name="EMP")
@Inheritance(strategy=InheritanceType.JOINED)
@DiscriminatorColumn(name="EMP_TYPE", discriminatorType=DiscriminatorType.INTEGER)
public abstract class Employee {
@Id private int id;
private String name;
@Temporal(TemporalType.DATE)
@Column(name="S_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
@Table(name="PT_EMP")
@DiscriminatorValue("3")
class PartTimeEmployee extends Employee {
@Column(name="H_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();
}
}
@Entity
@Table(name="FT_EMP")
@DiscriminatorValue("2")
class FullTimeEmployee extends Employee {
private long salary;
private long pension;
public long getPension() {
return pension;
}
public void setPension(long pension) {
this.pension = pension;
}
public long getSalary() {
return salary;
}
public void setSalary(long salary) {
this.salary = salary;
}
public String toString() {
return "FullTimeEmployee id: " + getId() + " name: " + getName();
}
}
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File: Helper.java |
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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");
}
}
}
}
}
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File: Main.java |
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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();
PartTimeEmployee emp = new PartTimeEmployee();
emp.setId(1);
emp.setName("Tom");
emp.setStartDate(new java.util.Date());
emp.setHourlyRate(12);
em.persist(emp);
FullTimeEmployee emp1 = new FullTimeEmployee();
emp1.setId(2);
emp1.setName("Tom");
emp1.setStartDate(new java.util.Date());
emp1.setSalary(123);
em.persist(emp1);
em.getTransaction().commit();
em.close();
emf.close();
Helper.checkData();
}
}
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File: persistence.xml |
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<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>
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 Download: JPA-SetDiscriminatorValueInSubclass.zip( 5,290 k) |
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