Spring的核心api和两种实例化方式

一.spring的核心api

Spring有如下的核心api

BeanFactory ：这是一个工厂，用于生成任意bean。采取延迟加载，第一次getBean时才会初始化Bean

ApplicationContext：是BeanFactory的子接口，功能更强大。（国际化处理、事件传递、Bean自动装配、各种不同应用层的Context实现）。当配置文件被加载，就进行对象实例化。

ClassPathXmlApplicationContext 用于加载classpath（类路径、src）下的xml,加载xml运行时位置 --> /WEB-INF/classes/...xml

FileSystemXmlApplicationContext 用于加载指定盘符下的xml,加载xml运行时位置 --> /WEB-INF/...xml,通过java web ServletContext.getRealPath() 获得具体盘符

二.spring的两种实例化方式

1.使用ApplicationContext方式进行加载

2.使用BeanFactory方式进行加载

第一步 建立Spring工程，并向其中导入必须的jar包

第二步 建立BookDao接口，BookDaoImpl实现类，BookService接口，BookServiceImpl实现类

package com.zk.myspring;

public interface BookDao {
	public void addBook();
}

package com.zk.myspring;

public class BookDaoImpl implements BookDao{

	@Override
	public void addBook() {
		// TODO Auto-generated method stub
		System.out.println("addBook");
	}

}

package com.zk.myspring;

public interface BookService {
	public abstract void addBook();
}

package com.zk.myspring;

public class BookServiceImpl implements BookService{

	//方式一：接口等于实现类
	//private BookDao bookDao=new BookDaoImpl();
	//方式二：接口+set方法
	private BookDao bookdao;
	
	//BookService依赖注入 BookDao
	public void setBookdao(BookDao bookdao) {//依赖注入
		this.bookdao = bookdao;
	}

	@Override
	public void addBook() {
		// TODO Auto-generated method stub
		//this.bookdao.addBook();
		System.out.println("add book");
	}
}

第三步 创建一个ApplicationContext.xml文件，并在文件中配置BookDao和BookService的bean

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:util="http://www.springframework.org/schema/util"
       xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd">
<!-- 创建Dao -->
<!-- 模拟spring执行过程
创建Service实例:BookService bookservice=new BookServiceImpl();  IOC <bean>
创建Dao实例:BookDao bookDao=new BookDaoImpl();   IOC
将dao设置给service:bookservice.setBookDao(bookDao);    DI  <property>

<property> 用于属性注入
name:bean的属性名，通过setter方法获得
ref:另一个bean的id值的引用
 -->
<!--创建Dao  -->
<bean id="bookDaoId" class="com.zk.myspring.BookDaoImpl" ></bean>
<!-- 创建service 依赖注入bookdaoId-->
<bean id="bookServiceId" class="com.zk.myspring.BookServiceImpl">
<property name="bookdao" ref="bookDaoId"></property>
</bean>
</beans>

　　

最后一步 使用两种方式实例化bean,我们可以使用ApplicationContext和BeanFactory分别实例化Bean

package com.zk.myspring;

import org.junit.Test;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.core.io.ClassPathResource;

public class TestBook {
	public static void main(String[]args)
	{
		//从spring容器中获得
		String path="ApplicationContext.xml";
		ApplicationContext ac=new ClassPathXmlApplicationContext(path);
		BookService bs=(BookService) ac.getBean("bookServiceId");
		bs.addBook();
	}
	@Test
	public void test1(){
		//使用BeanFactory实例化
		String path="ApplicationContext.xml";
		BeanFactory bf=new XmlBeanFactory(new ClassPathResource(path));
		BookService bs=(BookService) bf.getBean("bookServiceId");
		bs.addBook();
	}
}

分别运行两个实例

ApplicationContext运行结果

BeanFactory运行结果

成功

三.自定义工厂

新建一个Spring_003 工程，并加入MyBeanFactory.java、TestBeanFactory.java、UserService.java、UserServiceImpl.java

MyBeanFactory表示自定义工厂

package com.zk.BeanFactory;

public class MyBeanFactory {
	public static UserService createService(){
		return new UserServiceImpl();
	}
}

UserService.java

package com.zk.BeanFactory;

public interface UserService {
	public void addUser();
}

UserServiceImpl.java

package com.zk.BeanFactory;

public class UserServiceImpl implements UserService{

	@Override
	public void addUser() {
		// TODO Auto-generated method stub
		System.out.println("UserService");
	}

}

配置ApplicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:util="http://www.springframework.org/schema/util"
       xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
<bean id="userservice" class="com.zk.BeanFactory.UserServiceImpl"></bean>
<!--  <bean id="user" class="com.zk.BeanFactory.User"></bean>-->
</beans>

最后写一个TestBeanFactory.java文件

package com.zk.BeanFactory;

import org.junit.Test;


public class TestBeanFactory {
	@Test
	public void Demo(){
		UserService userservice=MyBeanFactory.createService();
		userservice.addUser();
	}
}

执行结果

success