Java的Spring框架中DAO數據訪問對象的使用示例

Spring DAO之JDBC

Spring提供的DAO(數據訪問對象)支持主要的目的是便於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。
為了便於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。這些抽像類提供了一些方法，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， 這樣就可以重用後者的設置，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>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" 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" abstract="true"> <property name="dataSource"> <ref bean="dataSource"/> </property> </bean> <bean id="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

Spring DAO之Hibernate

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， 這樣就可以重用後者的設置，例如SessionFactory， flush模式，異常翻譯器（exception translator）等等。

本節主要討論Sping對HibernateTemplate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) );

 /** * Created by IntelliJ IDEA.<br> * <b>Note</b>: Hiberante實體類*/ 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/> </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實現*/ 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對象的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" > <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" 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"> <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>: 測試類、客戶端*/ 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()); } }

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. 所保存的User對象的ID:18 name: jdbctemplate Process finished with exit code 0