SSM框架-获取容器的方式

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();

    }
}
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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();
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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();
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2. 第二个参数指定类型

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

Process finished with exit code 0
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• 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");
    }
}
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• 结果

ApplicationContext初始化会提前加载

constructor

Process finished with exit code 0
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如果要延迟，可以在appliacation.xnl中延迟加载

    <bean id = "bookDao" class="com.itheima.dao.impl.BookDaoImpl" lazy-init="true">
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