Spring提供的DAO(數據訪問對象)支持主要的目的是便于以標準的方式使用不同的數據訪問技術， 如JDBC，Hibernate或者JDO等。它不僅可以讓你方便地在這些持久化技術間切換， 而且讓你在編碼的時候不用考慮處理各種技術中特定的異常。

為了便于以一種一致的方式使用各種數據訪問技術，如JDBC、JDO和Hibernate， Spring提供了一套抽象DAO類供你擴展。這些抽象類提供了一些方法，通過它們你可以 獲得與你當前使用的數據訪問技術相關的數據源和其他配置信息。

Dao支持類：

JdbcDaoSupport - JDBC數據訪問對象的基類。 需要一個DataSource，同時為子類提供 JdbcTemplate。

HibernateDaoSupport - Hibernate數據訪問對象的基類。 需要一個SessionFactory，同時為子類提供 HibernateTemplate。也可以選擇直接通過 提供一個HibernateTemplate來初始化， 這樣就可以重用后者的設置，例如SessionFactory， flush模式，異常翻譯器（exception translator）等等。

JdoDaoSupport - JDO數據訪問對象的基類。 需要設置一個PersistenceManagerFactory， 同時為子類提供JdoTemplate。

JpaDaoSupport - JPA數據訪問對象的基類。 需要一個EntityManagerFactory，同時 為子類提供JpaTemplate。

本節主要討論Sping對JdbcDaoSupport的支持。

下面是個例子：

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>User</b>: leizhimin<br>?
* <b>Date</b>: 2008-4-22 13:53:56<br>?
* <b>Note</b>: 基類DAO，提供了數據源注入?
*/?
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實現?
*/?
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>: 測試類，客戶端?
*/?
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());?
????}?
}

運行結果：

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