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| 设置鉴别值 |
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File: AbstractProfessor.java
import javax.persistence.MappedSuperclass;
@MappedSuperclass
public abstract class AbstractProfessor extends Professor {
private int vacation;
public int getVacation() {
return vacation;
}
public void setVacation(int vacation) {
this.vacation = vacation;
}
}
File: BadProfessor.java
import javax.persistence.Column;
import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;
@Entity(name="BadEmp")
@DiscriminatorValue("BadEmp")
public class BadProfessor extends AbstractProfessor {
@Column(name="H_RATE")
private float hourlyRate;
public float getHourlyRate() {
return hourlyRate;
}
public void setHourlyRate(float hourlyRate) {
this.hourlyRate = hourlyRate;
}
public String toString() {
return "PartTimeProfessor id: " + getId() + " name: " + getName();
}
}
File: GoodProfessor.java
import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;
@Entity
@DiscriminatorValue("GoodEmp")
public class GoodProfessor extends AbstractProfessor {
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 "GoodProfessor id: " + getId() + " name: " + getName();
}
}
File: Professor.java
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.DiscriminatorColumn;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
@Entity
@Table(name="EMP")
@Inheritance
@DiscriminatorColumn(name="EMP_TYPE")
public abstract class Professor {
@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 "Professor id: " + getId() + " name: " + getName();
}
}
File: ProfessorService.java
import java.util.Collection;
import javax.persistence.EntityManager;
import javax.persistence.Query;
public class ProfessorService {
protected EntityManager em;
public ProfessorService(EntityManager em) {
this.em = em;
}
public void createProfessor(Professor emp) {
em.persist(emp);
}
public Collection<Professor> findAllProfessors() {
Query query = em.createQuery("SELECT e FROM Professor e");
return (Collection<Professor>) query.getResultList();
}
}
File: JPAUtil.java
import java.io.Reader;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class JPAUtil {
Statement st;
public JPAUtil() throws Exception{
Class.forName("org.hsqldb.jdbcDriver");
System.out.println("Driver Loaded.");
String url = "jdbc:hsqldb:data/tutorial";
Connection conn = DriverManager.getConnection(url, "sa", "");
System.out.println("Got Connection.");
st = conn.createStatement();
}
public void executeSQLCommand(String sql) throws Exception {
st.executeUpdate(sql);
}
public void checkData(String sql) throws Exception {
ResultSet rs = st.executeQuery(sql);
ResultSetMetaData metadata = rs.getMetaData();
for (int i = 0; i < metadata.getColumnCount(); i++) {
System.out.print("\t"+ metadata.getColumnLabel(i + 1));
}
System.out.println("\n----------------------------------");
while (rs.next()) {
for (int i = 0; i < metadata.getColumnCount(); i++) {
Object value = rs.getObject(i + 1);
if (value == null) {
System.out.print("\t ");
} else {
System.out.print("\t"+value.toString().trim());
}
}
System.out.println("");
}
}
}
File: Main.java
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
public class Main {
public static void main(String[] a) throws Exception {
JPAUtil util = new JPAUtil();
EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
EntityManager em = emf.createEntityManager();
ProfessorService service = new ProfessorService(em);
em.getTransaction().begin();
Professor emp = null;
emp = new GoodProfessor();
emp.setId(1);
emp.setName("good");
service.createProfessor(emp);
emp = new BadProfessor();
emp.setId(2);
emp.setName("bad");
service.createProfessor(emp);
System.out.println("Professors: ");
for (Professor emp1 : service.findAllProfessors()) {
System.out.print(emp1);
}
util.checkData("select * from EMP");
em.getTransaction().commit();
em.close();
emf.close();
}
}
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>
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 JPA-SetDiscriminatorValue.zip( 5,336 k) |
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