9 容器

9.1 获取容器

1. 记载类路径下的容器所在的配置文件,也就是之前用的

public class App2 {public static void main(String[] args) {ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");BookDao bookDao = (BookDao) ctx.getBean("bookDao");bookDao.save();}
}

2. 使用文件的绝对位置,少用

        //2. 使用文件的绝对位置，哪个盘符下进行加载ApplicationContext ctx2 = new FileSystemXmlApplicationContext("C:\\Users\\CZyue\\Desktop\\javaSE\\10-ssm\\spring_10_container\\spring_10_container\\src\\main\\resources\\applicationContext.xml");BookDao bookDao = (BookDao) ctx2.getBean("bookDao");bookDao.save();

3. 总结

9.2 获取bean

1. 通过强转类型

        //1.1获取bean，通过强转类型BookDao bookDao = (BookDao) ctx.getBean("bookDao");bookDao.save();

2. 第二个参数指定类型

        BookDao bookDao = ctx.getBean("bookDao", BookDao.class);bookDao.save();

3. 按照类型找

        //1.3 按照类型找,要求容器中只有一个就好,不然找不到BookDao bookDao = ctx.getBean(BookDao.class);bookDao.save();

4. 总结

9.3 容器类层次结构

1. ApplicationContext,ConfigurableApplicationContext接口

• ApplicationContext接口提供了基础功能，ConfigurableApplicationContext接口对ApplicationContext接口实现了功能的追加

• ClassPathXmlApplicationContext和FileSystemXmlApplicationContext是两个常用的实现类

• ApplicationContext接口的上层接口是BeanFactory

2. 容器类结构图

BeanFactory是顶层接口

ApplicationContext常用接口

ConfigurableApplicationContext关闭容器的

ClassPathXmlApplicationContext是常用实现类：

ApplicationContext ctx = new ClassPathXmlApplicationContext(“applicationContext.xml”);

9.4 BeanFactory

1. 代码

• AppForBeanFactory

BeanFactory来获取容器，通过ClassPathResource来造resources，然后把xml传进去

public class AppForBeanFactory {public static void main(String[] args) {Resource resources = new ClassPathResource("applicationContext.xml");BeanFactory bf = new XmlBeanFactory(resources);BookDao bookDao = bf.getBean(BookDao.class);bookDao.save();}
}

2. 和ApplicationContext获取容器的区别

加载bean的时机不同

• 接口实现类BookDaoImpl写一个构造器

public class BookDaoImpl implements BookDao{public BookDaoImpl(){System.out.println("constructor");
}public void save(){System.out.println("book dao save");}
}

• 用BeanFactory获取bean

public class AppForBeanFactory {public static void main(String[] args) {Resource resources = new ClassPathResource("applicationContext.xml");BeanFactory bf = new XmlBeanFactory(resources);}
}

• 结果

Process finished with exit code 0

• 用ApplicationContext获取bean

public class App2 {public static void main(String[] args) {//1.记载类路径下的配置文件ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");}
}

• 结果

ApplicationContext初始化会提前加载

constructorProcess finished with exit code 0

如果要延迟，可以在appliacation.xnl中延迟加载