Java的Spring框架中DAO数据访问对象的使用示例

Spring DAO之JDBC
 
Spring提供的DAO(数据访问对象)支持主要的目的是便于以标准的方式使用不同的数据访问技术， 如JDBC，Hibernate或者JDO等。它不仅可以让你方便地在这些持久化技术间切换， 而且让你在编码的时候不用考虑处理各种技术中特定的异常。
为了便于以一种一致的方式使用各种数据访问技术，如JDBC、JDO和Hibernate， Spring提供了一套抽象DAO类供你扩展。这些抽象类提供了一些方法，通过它们你可以 获得与你当前使用的数据访问技术相关的数据源和其他配置信息。
Dao支持类：
JdbcDaoSupport - JDBC数据访问对象的基类。 需要一个DataSource，同时为子类提供 JdbcTemplate。
HibernateDaoSupport - Hibernate数据访问对象的基类。 需要一个SessionFactory，同时为子类提供 HibernateTemplate。也可以选择直接通过 提供一个HibernateTemplate来初始化， 这样就可以重用后者的设置，例如SessionFactory， flush模式，异常翻译器（exception translator）等等。
JdoDaoSupport - JDO数据访问对象的基类。 需要设置一个PersistenceManagerFactory， 同时为子类提供JdoTemplate。 
JpaDaoSupport - JPA数据访问对象的基类。 需要一个EntityManagerFactory，同时 为子类提供JpaTemplate。 
本节主要讨论Sping对JdbcDaoSupport的支持。
下面是个例子：

drop table if exists user; 

/*==============================================================*/
/* Table: user                         */
/*==============================================================*/
create table user
(
  id          bigint AUTO_INCREMENT not null,
  name         varchar(24),
  age         int,
  primary key (id)
);

public class User {
  private Integer id;
  private String name;
  private Integer age; 

  public Integer getId() {
    return id;
  } 

  public void setId(Integer id) {
    this.id = id;
  } 

  public String getName() {
    return name;
  } 

  public void setName(String name) {
    this.name = name;
  } 

  public Integer getAge() {
    return age;
  } 

  public void setAge(Integer age) {
    this.age = age;
  }
}

/**
* Created by IntelliJ IDEA.<br>
* <b>User</b>: leizhimin<br>
* <b>Date</b>: 2008-4-22 15:34:36<br>
* <b>Note</b>: DAO接口
*/
public interface IUserDAO {
  public void insert(User user); 

  public User find(Integer id);
}

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.SQLException; 

/**
* Created by IntelliJ IDEA.<br>
* <b>Note</b>: 基类DAO，提供了数据源注入
*/
public class BaseDAO {
  private DataSource dataSource; 

  public DataSource getDataSource() {
    return dataSource;
  } 

  public void setDataSource(DataSource dataSource) {
    this.dataSource = dataSource;
  } 

  public Connection getConnection() {
    Connection conn = null;
    try {
      conn = dataSource.getConnection();
    } catch (SQLException e) {
      e.printStackTrace();
    }
    return conn;
  }
}

/**
* Created by IntelliJ IDEA.<br>
* <b>User</b>: leizhimin<br>
* <b>Date</b>: 2008-4-22 15:36:04<br>
* <b>Note</b>: DAO实现
*/
public class UserDAO extends BaseDAO implements IUserDAO { 

  public JdbcTemplate getJdbcTemplate(){
    return new JdbcTemplate(getDataSource());
  }
  public void insert(User user) {
    String name = user.getName();
    int age = user.getAge().intValue(); 

//    jdbcTemplate.update("INSERT INTO user (name,age) "
//        + "VALUES('" + name + "'," + age + ")"); 

    String sql = "insert into user(name,age) values(?,?)";
    getJdbcTemplate().update(sql,new Object[]{name,age});
  } 

  public User find(Integer id) {
    List rows = getJdbcTemplate().queryForList(
        "SELECT * FROM user WHERE id=" + id.intValue()); 

    Iterator it = rows.iterator();
    if (it.hasNext()) {
      Map userMap = (Map) it.next();
      Integer i = new Integer(userMap.get("id").toString());
      String name = userMap.get("name").toString();
      Integer age = new Integer(userMap.get("age").toString()); 

      User user = new User(); 

      user.setId(i);
      user.setName(name);
      user.setAge(age); 

      return user;
    }
    return null;
  }
}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING/DTD BEAN/EN"
    "http://www.springframework.org/dtd/spring-beans.dtd"> 

<beans>
  <bean id="dataSource"
     class="org.apache.commons.dbcp.BasicDataSource" singleton="true">
    <property name="driverClassName">
      <value>com.mysql.jdbc.Driver</value>
    </property>
    <property name="url">
      <value>jdbc:mysql://localhost:3306/springdb</value>
    </property>
    <property name="username">
      <value>root</value>
    </property>
    <property name="password">
      <value>leizhimin</value>
    </property>
  </bean> 

  <bean id="baseDAO" class="com.lavasoft.springnote.ch05_jdbc03_temp.BaseDAO" abstract="true">
    <property name="dataSource">
      <ref bean="dataSource"/>
    </property>
  </bean> 

  <bean id="userDAO"
     class="com.lavasoft.springnote.ch05_jdbc03_temp.UserDAO" parent="baseDAO">
  </bean> 

</beans>

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.FileSystemXmlApplicationContext; 

/**
* Created by IntelliJ IDEA.<br>
* <b>User</b>: leizhimin<br>
* <b>Date</b>: 2008-4-22 15:59:18<br>
* <b>Note</b>: 测试类，客户端
*/
public class SpringDAODemo {
  public static void main(String[] args) {
    ApplicationContext context = new FileSystemXmlApplicationContext("D:\\_spring\\src\\com\\lavasoft\\springnote\\ch05_jdbc03_temp\\bean-jdbc-temp.xml");
    User user = new User();
    user.setName("hahhahah");
    user.setAge(new Integer(22));
    IUserDAO userDAO = (IUserDAO) context.getBean("userDAO");
    userDAO.insert(user);
    user = userDAO.find(new Integer(1));
    System.out.println("name: " + user.getName());
  }
}

运行结果：

log4j:WARN No appenders could be found for logger (org.springframework.core.CollectionFactory).
log4j:WARN Please initialize the log4j system properly.
name: jdbctemplate 

Process finished with exit code 0

Spring DAO之Hibernate
 
HibernateDaoSupport - Hibernate数据访问对象的基类。 需要一个SessionFactory，同时为子类提供 HibernateTemplate。也可以选择直接通过 提供一个HibernateTemplate来初始化， 这样就可以重用后者的设置，例如SessionFactory， flush模式，异常翻译器（exception translator）等等。

本节主要讨论Sping对HibernateTemplate的支持。

下面是个例子：

drop table if exists user; 

/*==============================================================*/
/* Table: user                         */
/*==============================================================*/
create table user
(
  id          bigint AUTO_INCREMENT not null,
  name         varchar(24),
  age         int,
  primary key (id)
);

/**
* Created by IntelliJ IDEA.<br>
* <b>Note</b>: Hiberante实体类
*/
public class User {
  private Integer id;
  private String name;
  private Integer age; 

  public Integer getId() {
    return id;
  } 

  public void setId(Integer id) {
    this.id = id;
  } 

  public String getName() {
    return name;
  } 

  public void setName(String name) {
    this.name = name;
  } 

  public Integer getAge() {
    return age;
  } 

  public void setAge(Integer age) {
    this.age = age;
  }
}

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping
  PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
  "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> 

<hibernate-mapping> 

  <class name="com.lavasoft.springnote.ch06_hbm_02deTx.User"
      table="user"> 

    <id name="id" column="id">
      <generator class="native"/>
    </id> 

    <property name="name" column="name"/> 

    <property name="age" column="age"/> 

  </class> 

</hibernate-mapping>

/**
* Created by IntelliJ IDEA.<br>
* <b>User</b>: leizhimin<br>
* <b>Date</b>: 2008-4-23 15:37:43<br>
* <b>Note</b>: DAO接口
*/
public interface IUserDAO {
  public void insert(User user);
  public User find(Integer id);
} 

import org.hibernate.SessionFactory;
import org.springframework.orm.hibernate3.HibernateTemplate; 

/**
* Created by IntelliJ IDEA.<br>
* <b>User</b>: leizhimin<br>
* <b>Date</b>: 2008-4-23 15:15:55<br>
* <b>Note</b>: DAO实现
*/
public class UserDAO implements IUserDAO {
  private HibernateTemplate hibernateTemplate; 

  public void setSessionFactory(SessionFactory sessionFactory) {
    this.hibernateTemplate =new HibernateTemplate(sessionFactory);
  } 

  public void insert(User user) {
    hibernateTemplate.save(user);
    System.out.println("所保存的User对象的ID:"+user.getId());
  } 

  public User find(Integer id) {
    User user =(User) hibernateTemplate.get(User.class, id);
    return user;
  }
}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING/DTD BEAN/EN"
"http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
  <bean id="dataSource"
     class="org.springframework.jdbc.datasource.DriverManagerDataSource">
    <property name="driverClassName">
      <value>com.mysql.jdbc.Driver</value>
    </property>
    <property name="url">
      <value>jdbc:mysql://localhost:3306/springdb</value>
    </property>
    <property name="username">
      <value>root</value>
    </property>
    <property name="password">
      <value>leizhimin</value>
    </property>
  </bean> 

  <bean id="sessionFactory"
     class="org.springframework.orm.hibernate3.LocalSessionFactoryBean"
     destroy-method="close">
    <property name="dataSource">
      <ref bean="dataSource"/>
    </property>
    <property name="mappingResources">
      <list>
        <value>com/lavasoft/springnote/ch06_hbm_02proTx/User.hbm.xml</value>
      </list>
    </property>
    <property name="hibernateProperties">
      <props>
        <prop key="hibernate.dialect">
          org.hibernate.dialect.MySQLDialect
        </prop>
      </props>
    </property>
  </bean> 

  <bean id="userDAO" class="com.lavasoft.springnote.ch06_hbm_02proTx.UserDAO">
    <property name="sessionFactory">
      <ref bean="sessionFactory"/>
    </property>
  </bean>
</beans>

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.FileSystemXmlApplicationContext; 

/**
* Created by IntelliJ IDEA.<br>
* <b>Note</b>: 测试类、客户端
*/
public class SpringHibernateDemo {
  public static void main(String[] args) {
    ApplicationContext context =new FileSystemXmlApplicationContext("D:\\_spring\\src\\com\\lavasoft\\springnote\\ch06_hbm_02proTx\\bean-hbm_tx.xml"); 

    // 建立DAO物件
    IUserDAO userDAO = (IUserDAO) context.getBean("userDAO"); 

    User user = new User();
    user.setName("caterpillar");
    user.setAge(new Integer(30)); 

    userDAO.insert(user); 

    user = userDAO.find(new Integer(1)); 

    System.out.println("name: " + user.getName());
  }
}

运行结果：

log4j:WARN No appenders could be found for logger (org.springframework.core.CollectionFactory).
log4j:WARN Please initialize the log4j system properly.
所保存的User对象的ID:18
name: jdbctemplate 

Process finished with exit code 0