spring思路梳理2--基于黑马程序员--Spring中的bean

1.Bean的实例化:以构造器方式为例

通过默认的无参构造方法

package com.itheima.instance.constructor
public class Bean1{
}

注：xml文件的引用的约束均省略

<beans>
<bean id="bean1" class="con,itheima.instance,contructor.Bean1"/>
</beans>

测试类InstanceTest1

package com.itheima.instance.contructor
import org,springframe.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class InstanceTset1(String[] args){

	//定义配置文件路径
	String xmlPath = "com/itheima/instance/ClassPathXmlApplicationCOntext";
	//ApplicationContext在加载配置文件时，对Bean进行初始化
	ApplicationContext applicationContext =
	    new ClassPathXmlApplicationContext(xmlPath);
	Bean1 bean = (Bean1) applicationContext.getBean("bean1");
	System.out.println("bean");
}

对其中几个名字的解释：Bean1为类名，bean1为spring容器中对应的bean的名字，可用getBean()引用，bean则为实例化的对象

2.Bean的作用域

主要介绍，singleton(单例,默认)和prototype(原型)

通过<Bean>元素的scope属性指定

<bean id="scope" class="com.itheima.scope.Scope" scope="singleton"/>

3.Bean的装配:以基于注解为例

package com.itheima.annotation;
public interface UserDao{
	public void save();
}

package com.itheima.annotation;

package com.itheima.annotation;
import org.springframework.sterotype.Repository;
@Repository("userDao")
public class UserDaoImpl implements UserDao{
	public void save(){
		System.out.println("userdao...save");
	}
}

package com.itheima.annotation;
import javax.annotation.Resource;
import org.springframework.sterotype.Controller;
@Repository("userDao")
public class UserController{
	@Resource(name="userService")
	private UserService userService;
	public void save(){
		this.userService.save();
		System.out.println("userController....save....");
	}
	
}

<beans>
<!-- 使用Context命名空间，通知Spring扫描指定包下所有Bean类，进行注解解析 -->
<context:component-scan base-package="com.itheima.annotation"/>
</Beans>

package com.itheima.annotation;
import org.springframework.context.ApplicationContext;
import 
    org.springframework.context.support.ClassPathXmlApplicationContext;
public classs AnnotationAssembleTest{
	public void main(String[] args){
		String xmlPath = "com/itheima/annotation/bean6.xml";
		ApplicationContext applicationContext =
		     new ClassPathXmlApplicationContext(xmlPath);
	    //获取UserController实例
		UserController userController =
		(UserController) applicationContext.getBean("userController");
		//调用userController的save()方法
		userController.save();
	}
} 

输出结果

userDao...save

userService...save..

userController...save..

程序注释:@Repository,@Service,@Controller分别在数据访问层(DAO层)，业务层(Service层)，控制层（Controller）标识了Spring中的Bean，@Resource则是对Bean进行装配