EJB实例教程笔记(四)

EJB实例教程笔记(四)

电子书EJB3实例教程byLiHuoming.pdf笔记

第三章 实体Bean(Entity Bean)
在EJB的早期版本中，持久化是EJB平台的一部分。从EJB3.0开始，持久化已经自成规范，被称为Java Persistence API。

POJO通过Java Persistence元数据映射到数据库后，我们称entity bean。
创建一个Entity Bean对象相当于新建一条记录
删除一个Entity Bean会同时从数据库中删除对应记录
修改一个Entity Bean，容器会自动将Entity Bean的状态同步到数据库。

Java Persistence API还定义了一种查询语言（JPQL）。

3.1 JBOSS数据源的配置
取名格式为xxx-ds.xml
3.1.1 MySql数据源的配置
sample-ds.xml如下：
<?xml version="1.0" encoding="UTF-8"?>
<datasources>
<local-tx-datasource>
<jndi-name>demoDS</jndi-name>
<connection-url>jdbc:mysql://localhost:3307/demo?useUnicode=true&amp;characterEncoding=GBK</connection-url>
<driver-class>com.mysql.jdbc.Driver</driver-class>
<user-name>root</user-name>
<password></password>
<min-pool-size>1</min-pool-size>
<max-pool-size>4</max-pool-size>
<!--  抛出异常前最大的等待链接时间  -->
<blocking-timeout-millis>30000</blocking-timeout-millis>
            <!-- 关闭连接前链接空闲的最大时间 -->
<idel-timeout-minutes>5</idel-timeout-minutes>
            <exception-sorter-class-name>org.jboss.resource.adapter.jdbc.vendor.MySQLExceptionSorter</exception-sorter-class-name>
<metadata>
<type-mapping>mySQL</type-mapping>
</metadata>
</local-tx-datasource>
</datasources>

3.1.2 Ms Sql Server2000数据源的配置

3.1.3 Oracle9i数据源的配置

3.2 单表映射的实体Bean
JSP Engine                        --------->     EntityBeanTest.jsp

SessionBean EJB Container   --------->     PersonDAOBean.class

Java Persistence API           ---------->     Person.class(EJB annotated POJOs)

create database table:

CREATE TABLE `test`.`person` (
  `id` INTEGER UNSIGNED NOT NULL AUTO_INCREMENT,
  `name` VARCHAR(32) NOT NULL,
  `sex` TINYINT(1) UNSIGNED NOT NULL,
  `age` SMALLINT(6) UNSIGNED NOT NULL,
  `birthday` DATETIME,
  PRIMARY KEY (`id`)
)
ENGINE = InnoDB;

POJO annotation class Person.java:
package com.sillycat.ejb3.model;

import java.io.Serializable;
import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

@Entity
@Table(name = "person")
public class Person implements Serializable
{
    private static final long serialVersionUID = 7290155616161659440L;
    private Integer           id;
    private String            name;
    private boolean           sex;
    private Short             age;
    private Date              birthday;
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    public Integer getId()
    {
        return id;
    }
    public void setId(Integer id)
    {
        this.id = id;
    }
    @Column(nullable=false,length=32)
    public String getName()
    {
        return name;
    }
    public void setName(String name)
    {
        this.name = name;
    }
    @Column(nullable=false)
    public boolean getSex()
    {
        return sex;
    }
    public void setSex(boolean sex)
    {
        this.sex = sex;
    }
    @Column(nullable=false)
    public Short getAge()
    {
        return age;
    }
    @Temporal(value=TemporalType.DATE)
    public void setAge(Short age)
    {
        this.age = age;
    }
    public Date getBirthday()
    {
        return birthday;
    }
    public void setBirthday(Date birthday)
    {
        this.birthday = birthday;
    }
}

实体Bean不直接与客户端打交道。而是被session bean或message-driven bean使用。
接口类PersonDAO.java:
package com.sillycat.ejb3.dao;
import java.util.List;
import com.sillycat.ejb3.model.Person;
public interface PersonDAO
{
    public void insert(Person person);
    public void updateName(String name,Integer id);
    public void update(Person person);
    public void delete(Integer id);
    public Person get(Integer id);
    public List<Person> getAll();
}
实现类PersonDAOBean.java:
package com.sillycat.ejb3.dao;
import java.util.List;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.Query;
import com.sillycat.ejb3.model.Person;

public class PersonDAOBean implements PersonDAO
{
    @PersistenceContext(unitName = "demoTest")
    protected EntityManager em;
    public PersonDAOBean(EntityManager em)
    {
        this.em = em;
    }
    public void delete(Integer id)
    {
        Person person = em.find(Person.class, id);
        if (person != null)
        {
            em.remove(person);
        }
    }
    public Person get(Integer id)
    {
        return em.find(Person.class, id);
    }
    @SuppressWarnings("unchecked")
    public List<Person> getAll()
    {
        Query query = em.createQuery("select o from Person o order by o.id asc");
        return (List<Person>) query.getResultList();
    }
    public void insert(Person person)
    {
        em.persist(person);
    }
    public void update(Person person)
    {
        em.merge(person);
    }
    public void updateName(String name, Integer id)
    {
        Person person = em.find(Person.class, id);
        if (person != null)
        {
            person.setName(name);
        }
    }
}
JPA的配置文件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_1_0.xsd"
version="1.0">
<persistence-unit name="demoTest" transaction-type="RESOURCE_LOCAL">
<properties>
<property name="hibernate.hbm2ddl.auto" value="update" />
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect" />
<property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver" />
<property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/test" />
<property name="hibernate.connection.username" value="root" />
<property name="hibernate.connection.password" value="kaishi" />
<property name="hibernate.connection.autocommit" value="true"/>
</properties>
</persistence-unit>
</persistence>

如果发布给jboss使用，应该是persistence.xml：
<?xml version="1.0" ?>
<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="demoTest" transaction-type="JTA">
    <jta-data-source>java:/DefaultDemoTestDS</jta-data-source>
    <properties>
    <property name="hibernate.hbm2ddl.auto" value="update"/>
    <property name="hibernate.jdbc.fetch_size" value="18"/>
    <property name="hibernate.jdbc.batch_size" value="10" />
    <property name="hibernate.show_sql" value="true" />
    <property name="hibernate.format_sql" value="true" />
    </properties>
    </persistence-unit>
</persistence>
里面的DefaultDemoTestDS就是jboss下面配置的数据库链接的文件了。