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接下來我們要注意的是，由於Spring的宣告事務管理是基於Spring AOP機制實現，
而Spring AOP是使用動態代理（dynamic proxy），所以要求代理的對象必須實作介面，所以我們不能直接如下生成bean：
代碼:
ApplicationContext context = new FileSystemXmlApplicationContext("bean.xml");
UserDAO userDAO = (UserDAO) context.getBean("userDAOProxy");
這會發生ClassCastException
總之，我們要定義一個介面，讓UserDAO實現介面：
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一个组件，需要来个bean组成，一个目标bean，一个事务代理。
这种配置方式还有一个坏处：目标bean直接暴露在Spring容器中，可以直接引用，如果目标bean被误引用，将导致业务操作不具备事务性。
为了避免这种现象，可将目标bean配置成嵌套bean，下面是目标bean和事务代理的配置：
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CustomersDAO.java
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package db;
import java.util.List;
import java.util.Set;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.LockMode;
import org.springframework.context.ApplicationContext;
import org.springframework.orm.hibernate3.support.HibernateDaoSupport;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.TransactionDefinition;
import org.springframework.transaction.TransactionStatus;
import org.springframework.transaction.support.TransactionCallbackWithoutResult;
import org.springframework.transaction.support.TransactionTemplate;
import test.IUserDAO;
public class CustomersDAO extends HibernateDaoSupport implements IUserDAO {
private static final Log log = LogFactory.getLog(CustomersDAO.class);
protected void initDao() {
// do nothing
}
private TransactionTemplate transactionTemplate;
public void setTransactionManager(
PlatformTransactionManager transactionManager) {
this.transactionTemplate = new TransactionTemplate(transactionManager);
}
public void insertUser(Customers transientInstance) {
getHibernateTemplate().saveOrUpdate(transientInstance);
}
}
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applicationContext.xml
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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd">
<bean
>
<property
value="com.mysql.jdbc.Driver">
</property>
<property
value="jdbc:mysql://localhost:3306/sampledb">
</property>
<property value="root"></property>
</bean>
<bean
>
<property >
<ref bean="localMysql" />
</property>
<property >
<props>
<prop key="hibernate.dialect">
org.hibernate.dialect.MySQLDialect
</prop>
<prop key="hibernate.hbm2ddl.auto">update</prop>
<prop key="hibernate.show_sql">true</prop>
</props>
</property>
<property >
<list>
<value>db/Orders.hbm.xml</value>
<value>db/Customers.hbm.xml</value>
</list>
</property>
</bean>
<!-- 定义事务管理器，使用适用于Hibernte的事务管理器-->
<bean
>
<property >
<ref bean="localSessionFactory" />
</property>
</bean>
<!-- 定义DAO bean的事务代理-->
<bean
>
<!-- 为事务代理bean注入事务管理器-->
<property >
<ref bean="transactionManager" />
</property>
<!-- 设置事务属性-->
<property >
<props>
<prop key="inserUser">PROPAGATION_REQUIRED</prop>
</props>
</property>
<!-- 为事务代理bean设置目标bean -->
<property >
<!-- 采用嵌套bean配置目标bean-->
<bean >
<!-- 为DAO bean注入SessionFactory引用-->
<property >
<ref local="localSessionFactory" />
</property>
</bean>
</property>
</bean>
</beans>
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Demo .java
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package test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import db.Customers;
import db.CustomersDAO;
public class Demo {
public static void main(String[] args) {
ApplicationContext ctx = new ClassPathXmlApplicationContext(
"applicationContext.xml");
test.IUserDAO dao = (test.IUserDAO) ctx.getBean("userDAOTarget");
Customers c = new Customers();
c.setId(3l);
c.setName("xxx");
dao.insertUser(c);
System.out.println("END");
}
}
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IUserDAO .java
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package test;
import db.Customers;
public interface IUserDAO {
public void insertUser(Customers c);
}
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