Bean实例化的三种方式

1.无参构造实例化

在配置文件中配置

<bean id="userDao" class="Wss.dao.impl.UserDaoImpl" scope="singleton" init-method="init" destroy-method="destory"></bean>

测试代码：

public class SpringTest {
    public static void test1(){
//        ApplicationContext app =new ClassPathXmlApplicationContext("applicationContext.xml");
        ClassPathXmlApplicationContext app =new ClassPathXmlApplicationContext("applicationContext.xml");
        UserDao userDao1 = (UserDao) app.getBean("userDao");
//        UserDao userDao2 = (UserDao) app.getBean("userDao");
        System.out.println(userDao1);
//        System.out.println(userDao2);
//        app.close();
    }

运行结果：

2.工厂静态方法实例化

同1：

 <bean id="userDao" class="Wss.factory.StaticFactory" factory-method="getUserDao"> </bean>

package Wss.factory;

import Wss.dao.UserDao;
import Wss.dao.impl.UserDaoImpl;

public class StaticFactory {
    public static UserDao getUserDao(){
        return new UserDaoImpl();
    }

测试与结果同1

3.工厂实例方法实例化

<bean id="factory" class="Wss.factory.DynamicFactory" > </bean>
<bean id="userDao" factory-bean="factory" factory-method="getUserDao"> </bean>

package Wss.factory;

import Wss.dao.UserDao;
import Wss.dao.impl.UserDaoImpl;

public class DynamicFactory {
    public  UserDao getUserDao(){
        return new UserDaoImpl();
    }
}

测试及结果同上

总结：

 测试代码: