休眠中的COMPOSITE-ID

Question

從

https://docs.jboss.org/hibernate/orm/3.3/reference/zh/html/mapping.html

我不知道如何在沒有“ class”參數的情況下使用“ composite-id”標記，以及我設法使Google變得更加混亂的那幾個例子。

所以我的例子

<class name="mainPack.Point" table="POINT">
    <composite-id>
        <key-property name="x" type="int">
            <column name="X" />
        </key-property>
        <key-property name="y" type="int">
            <column name="Y" />
        </key-property>
    </composite-id>
    <property name="str" type="java.lang.String">
        <column name="STR" />
    </property>
</class>

能行嗎

將列

 <column name="X" />
 <column name="Y" /> 

出現在桌子上嗎？

並且將創建另一個包含新的“ id class”，兩個參數“ X”，“ Y”的映射表嗎？

Answer 1

1. 能行嗎

是。 我用hibernate-update創建了一個表，結果如下：

CREATE TABLE point
(
  x integer NOT NULL,
  y integer NOT NULL,
  str character varying(255),
  CONSTRAINT point_pkey PRIMARY KEY (x, y)
)

2. 表格中是否會出現列？

是。 您可以在上方看到它。

3. 並且將創建另一個包含新的“ id class”，兩個參數“ X”，“ Y”的映射表嗎？

沒有。

---

這是java類：

 public class Point implements Serializable { private int x; private int y; private String str; public int getX() { return this.x; } public void setX(int x) { this.x = x; } public int getY() { return this.y; } public void setY(int y) { this.y = y; } public String getStr() { return this.str; } public void setStr(String str) { this.str = str; } @Override public int hashCode() { return new HashCodeBuilder().append(this.x).append(this.y).toHashCode(); } @Override public boolean equals(Object obj) { if (this == obj) { return true; } if (!(obj instanceof Point)) { return false; } Point other = (Point) obj; return (this.getX() == other.getX()) && (this.getY() == other.getY()); } 

}

Answer 2

// Composite primary key bean

import java.io.Serializable;

public class CoursePk implements Serializable {

private static final long serialVersionUID = 1L;
private String title;
private String tutor;

public CoursePk(){

}
public String getTitle() {
    return title;
}
public void setTitle(String title) {
    this.title = title;
}
public String getTutor() {
    return tutor;
}
public void setTutor(String tutor) {
    this.tutor = tutor;
}
}


// Course class for composite primary key
@Entity
@Table(name="course")
public class Course implements Serializable {
private static final long serialVersionUID = 1L;

@EmbeddedId                    // composite key
private CoursePk id=null;

private int totalStudents;

public int getTotalStudents() {
    return totalStudents;
}

public void setTotalStudents(int totalStudents) {
    this.totalStudents = totalStudents;
}

public CoursePk getId() {
    return id;
}
public void setId(CoursePk id) {
    this.id = id;
}
}


 // Hibernate Util to get Session factory
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
public class HibernateUtil {
private HibernateUtil(){

}
 private static SessionFactory sessionFactory ;
 static {
    Configuration configuration = new Configuration();

    configuration.addAnnotatedClass (Course.class);
    configuration.setProperty("connection.driver_class","com.mysql.jdbc.Driver");
    configuration.setProperty("hibernate.connection.url", "jdbc:mysql://localhost:3306/hibernate");                                
    configuration.setProperty("hibernate.connection.username", "root");     
    configuration.setProperty("hibernate.connection.password", "root");
    configuration.setProperty("dialect", "org.hibernate.dialect.MySQLDialect");
    configuration.setProperty("hibernate.hbm2ddl.auto", "update");
    configuration.setProperty("hibernate.show_sql", "true");
    configuration.setProperty(" hibernate.connection.pool_size", "10");

    StandardServiceRegistryBuilder builder = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties());
    sessionFactory = configuration.buildSessionFactory(builder.build());
 }
public  SessionFactory getSessionFactory() {
    return sessionFactory;
}

public static HibernateUtil getInstance(){
    return new HibernateUtil();
}
} 

// Main Class for testing composite primary key
public class CompositePrimaryKeyTest {
public static void main(String[] args) {
    CoursePk pk=new CoursePk();
    pk.setTitle("Java Book");
    pk.setTutor("Deepak");

    Course course=new Course();
    course.setTotalStudents(100);
    course.setId(pk);
    Session   session=HibernateUtil.getInstance().getSessionFactory().openSession();
    session.beginTransaction();

    session.save(course);

    session.getTransaction().commit();
}
}