1、简介

        在容器中的Bean要实例化为对象有三种方式

        1、构造方法

        2、静态工厂

        3、实例工厂

        4、实现工厂接口

2、构造方法

        构造方法实例化Bean即是直接通过构造方法创建对象

<bean id="bookDao" class="com.wn.spring.dao.impl.BookDaoImpl"/>

        当不存在无参构造是会抛出异常

3、静态工厂

        静态工厂类实现

public class BookDaoFactory {public static BookDao getBookDao(){return new BookDaoImpl();}}

        配置静态工厂Bean

<bean id="bookDaoFactory" class="com.wn.spring.factory.BookDaoFactory" factory-method="getBookDao"/>

4、实例工厂

        实例工厂类实现

public class BookServiceFactory {public BookService getBookService(){return new BookServiceImpl();}}

        实例工程Bean配置

<bean id="bookServiceFactory" class="com.wn.spring.factory.BookServiceFactory"/>
<bean factory-bean="bookServiceFactory" factory-method="getBookService"/>

5、继承工厂接口

        继承工厂接口实现

public class BookDaoFactoryBean implements FactoryBean<BookDao> {@Overridepublic BookDao getObject() throws Exception {return new BookDaoImpl();}@Overridepublic Class<?> getObjectType() {return null;}
}

        继承工厂的Bean的配置

<bean id="bookDao" class="com.wn.spring.factory.BookDaoFactoryBean"/>