Bean的实例化

Bean实例化

一. 构造方法进行实例化

bookDaoImpl

package dang.dao.impl;

import dang.dao.BookDao;

public class BookDaoImpl implements BookDao {

    public BookDaoImpl() {
        System.out.println("book dao constructor is running ....");
    }

    public void save() {
        System.out.println("book dao save ...");
    }

}

配置

<!--方式一：构造方法实例化bean-->
    <bean id="bookDao" class="dang.dao.impl.BookDaoImpl"/>

---

二. 静态工厂实例化Bean（了解）

AppForInstanceOrder

package dang;

import dang.dao.OrderDao;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class AppForInstanceOrder {
    public static void main(String[] args) {
        //通过静态工厂创建对象
//        OrderDao orderDao = OrderDaoFactory.getOrderDao();
//        orderDao.save();


        ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");

        OrderDao orderDao = (OrderDao) ctx.getBean("orderDao");

        orderDao.save();

    }
}

ordeDaoFactory

package dang.factory;

import dang.dao.OrderDao;
import dang.dao.impl.OrderDaoImpl;

//静态工厂创建对象
public class OrderDaoFactory {
    public static OrderDao getOrderDao(){
        System.out.println("factory setup....");
        return new OrderDaoImpl();
    }
}

配置

<bean id="orderDao" class="dang.factory.OrderDaoFactory" factory-method="getOrderDao"/>

---

三. 使用实例工厂实例化Bean

AppForInstanceUser

package dang;

import dang.dao.UserDao;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class AppForInstanceUser {
    public static void main(String[] args) {
//        //创建实例工厂对象
//        UserDaoFactory userDaoFactory = new UserDaoFactory();
//        //通过实例工厂对象创建对象
//        UserDao userDao = userDaoFactory.getUserDao();
//        userDao.save();


        ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserDao userDao=(UserDao)ctx.getBean("userDao");
        userDao.save();

    }
}

UserDaoFactory

package dang.factory;

import dang.dao.UserDao;
import dang.dao.impl.UserDaoImpl;

//实例工厂创建对象
public class UserDaoFactory {
    public UserDao getUserDao(){
        return new UserDaoImpl();
    }
}

配置

<bean id="userFactory" class="dang.factory.UserDaoFactory"/>

<bean id="userDao" factory-method="getUserDao" factory-bean="userFactory"/>

---

四. FactoryBean

UserDaoFactoryBean

package dang.factory;

import dang.dao.UserDao;
import dang.dao.impl.UserDaoImpl;
import org.springframework.beans.factory.FactoryBean;

//FactoryBean创建对象
public class UserDaoFactoryBean implements FactoryBean<UserDao> {
    //代替原始实例工厂中创建对象的方法
    public UserDao getObject() throws Exception {
        return new UserDaoImpl();
    }

    public Class<?> getObjectType() {
        return UserDao.class;
    }

}

<details>
<summary>配置</summary>

</details>

配置

<bean id="userDao" class="dang.factory.UserDaoFactoryBean"/>