EJB实体Bean开发的复合主键映射

复合主键的映射：在Hibernate中是通过一个主键类来完成复合主键的映射，主键类复写了equals和hashCode方法，用来完成比较功能，以便判断主键值是否重复。

EJB3中也使用该方式完成映射，只是改为通过Annotation来配置关系。

 

1、在JBoss中配置数据源

方法见四、EJB实体Bean开发

并且保证JBoss中有该数据库连接jar包，例如：

2、建立项目

 

 

 

 

 

注意在这里配置数据源连接和选择要连接的数据库。

Driver处选择的数据源同样是在MyEclipse中配置的，方法同Hibernate之前的准备工作相同

3、在persitence.xml中配置数据源连接

配置完成后会在EJB端项目中创建一个persitence.xml文件，在该文件中进行连接等配置

（1）配置数据源

<?xml version="1.0" encoding="UTF-8"?>

<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_1_0.xsd" version="1.0">

   

    <persistence-unit name="mysql" transaction-type="JTA">

        <jta-data-source>java:jdbc/mysql</jta-data-source>

    </persistence-unit>

 

</persistence>

（2）打开show_sql

<?xml version="1.0" encoding="UTF-8"?>

<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_1_0.xsd" version="1.0">

   

    <persistence-unit name="mysql" transaction-type="JTA">

        <jta-data-source>java:jdbc/mysql</jta-data-source>

        <properties>

           <property name="hibernate.show_sql" value="true"/>

        </properties>

    </persistence-unit>

 

</persistence>

 

4、生成EntityBean映射

 

 

 

 

 

映射生成了两个实体Bean

一个主键类、一个实体类

package org.mldn.lin.entity;

 

import javax.persistence.Column;

import javax.persistence.Embeddable;

 

//@Embeddable表示该类是一个复合主键类，该类同样覆写了equals和hashcode方法

@Embeddable

public class UserCourseId implements java.io.Serializable {

 

    private String userid;

 

    private Integer cid;

 

    public UserCourseId() {

    }

 

    public UserCourseId(String userid, Integer cid) {

       this.userid = userid;

       this.cid = cid;

    }

 

    @Column(name = "userid", unique = false, nullable = false, insertable = true, updatable = true, length = 20)

    public String getUserid() {

       return this.userid;

    }

 

    public void setUserid(String userid) {

       this.userid = userid;

    }

 

    @Column(name = "cid", unique = false, nullable = false, insertable = true, updatable = true)

    public Integer getCid() {

       return this.cid;

    }

 

    public void setCid(Integer cid) {

       this.cid = cid;

    }

 

    public boolean equals(Object other) {

       if ((this == other))

           return true;

       if ((other == null))

           return false;

       if (!(other instanceof UserCourseId))

           return false;

       UserCourseId castOther = (UserCourseId) other;

 

       return ((this.getUserid() == castOther.getUserid()) || (this

              .getUserid() != null

              && castOther.getUserid() != null && this.getUserid().equals(

              castOther.getUserid())))

              && ((this.getCid() == castOther.getCid()) || (this.getCid() != null

                     && castOther.getCid() != null && this.getCid().equals(

                     castOther.getCid())));

    }

 

    public int hashCode() {

       int result = 17;

 

       result = 37 * result

              + (getUserid() == null ? 0 : this.getUserid().hashCode());

       result = 37 * result

              + (getCid() == null ? 0 : this.getCid().hashCode());

       return result;

    }

 

}

package org.mldn.lin.entity;

 

import javax.persistence.AttributeOverride;

import javax.persistence.AttributeOverrides;

import javax.persistence.Column;

import javax.persistence.EmbeddedId;

import javax.persistence.Entity;

import javax.persistence.Table;

 

@Entity

@Table(name = "user_course", catalog = "testdb", uniqueConstraints = {})

public class UserCourse implements java.io.Serializable {

 

    private UserCourseId id;

 

    private Integer status;

 

    public UserCourse() {

    }

 

    public UserCourse(UserCourseId id) {

       this.id = id;

    }

 

    public UserCourse(UserCourseId id, Integer status) {

       this.id = id;

       this.status = status;

    }

 

    // Property accessors

    //表示使用复合主键

    @EmbeddedId

    // 复合主键中包含以下两个属性

    @AttributeOverrides( {

           @AttributeOverride(name = "userid", column = @Column(name = "userid", unique = false, nullable = false, insertable = true, updatable = true, length = 20)),

           @AttributeOverride(name = "cid", column = @Column(name = "cid", unique = false, nullable = false, insertable = true, updatable = true)) })

    public UserCourseId getId() {

       return this.id;

    }

 

    public void setId(UserCourseId id) {

       this.id = id;

    }

 

    @Column(name = "status", unique = false, nullable = true, insertable = true, updatable = true)

    public Integer getStatus() {

       return this.status;

    }

 

    public void setStatus(Integer status) {

       this.status = status;

    }

 

}

 

5、新建SessionBean操作EntityBean

srcànewàEJB3 SessionBean

 

package org.mldn.lin.session;

 

import java.util.List;

 

import javax.ejb.Remote;

 

import org.mldn.lin.entity.UserCourseId;

 

@Remote

public interface UserCourseDAORemote {

    public boolean doCreate(UserCourseDAO uc) throws Exception;

 

    public UserCourseDAO findById(UserCourseId id) throws Exception;

 

    public List<UserCourseDAO> findByCid(int cid) throws Exception;

 

}

 

package org.mldn.lin.session;

 

import java.util.List;

 

import javax.ejb.Stateless;

import javax.persistence.EntityManager;

import javax.persistence.PersistenceContext;

import javax.persistence.Query;

 

import org.mldn.lin.entity.UserCourseId;

 

@Stateless

public class UserCourseDAO implements UserCourseDAORemote {

   

    @PersistenceContext

    private EntityManager em;

 

    public boolean doCreate(UserCourseDAO uc) throws Exception {

       // TODO Auto-generated method stub

       this.em.persist(uc);

       return true;

    }

 

    public List<UserCourseDAO> findByCid(int cid) throws Exception {

       // TODO Auto-generated method stub

       String jpql="FROM UserCourse WHERE id.cid=?";

       Query q=this.em.createQuery(jpql);

       q.setParameter(1, cid);

       return q.getResultList();

    }

 

    public UserCourseDAO findById(UserCourseId id) throws Exception {

       // TODO Auto-generated method stub

       UserCourseDAO uc=this.em.find(UserCourseDAO.class, id);

       return uc;

    }

 

}

 

 

6、EJB端项目发布

 

发布成功

 

7、在Web端建立测试类测试

通过测试类进行测试，需要将 拷贝到lib下即可

package org.mldn.lin.test;

 

import java.util.Properties;

 

import javax.naming.Context;

import javax.naming.InitialContext;

import javax.naming.NamingException;

 

import org.mldn.lin.entity.UserCourse;

import org.mldn.lin.entity.UserCourseId;

import org.mldn.lin.session.UserCourseDAORemote;

 

public class Test {

 

    public static void main(String[] args) {

        // 定义查找参数,通过定义这些参数找到该公共空间

       Properties pro = new Properties();

        pro.setProperty("java.naming.factory.initial","org.jnp.interfaces.NamingContextFactory");

       pro.setProperty("java.naming.provider.url", "192.168.1.187:1099");

       pro.setProperty("java.naming.factory.url.pkgs", "org.jboss.naming");

       // 通过JNDI查找发布的接口

       try {

           Context ctx = new InitialContext(pro);

 

           // 开始查找接口

           UserCourseDAORemote dao = (UserCourseDAORemote) ctx.lookup("UserCourseDAO/remote");

 

           UserCourse uc = new UserCourse();

           uc.setId(new UserCourseId());

           uc.getId().setCid(1);

           uc.getId().setUserid("mldn");

           uc.setStatus(1);

 

           // 打印结果

           //System.out.println(dao.doCreate(uc));

           //System.out.println(dao.findById(uc.getId()));

           System.out.println(dao.findByCid(1).size());

 

       } catch (NamingException e) {

           // TODO Auto-generated catch block

           e.printStackTrace();

       } catch (Exception e) {

           // TODO Auto-generated catch block

           e.printStackTrace();

       }

    }

}