深入学习Spring IOC和AOP 实例代码

这次主要是通过Spring官网的文档学习,使用的代码也是官网提供的代码,并且把代码放到本地运行和学习,博客记录一下学习心得.

官网文档地址:
https://docs.spring.io/spring-framework/docs/current/reference/html/core.html#beans-basics

IOC

IOC控制反转, 当一个了类需要注入其他类的对象的时候, 对象不需要自己手动创建引用类的对象, 执行需要从Spring IOC 容器获取,把创建对象的控制权交给容器.
BeanFactory 接口提供了对象信息的配置, 开发者可以通过这个接口获取对象, ApplicationContext是BeanFactory的子类, 提供了更多的功能,所以一般情况,我们都使用ApplicationContext.

Configuration Metadata

我们可以在XML中定义对象的信息, spring 3.0开始可以采用java注解的方式实现Spring IOC的元数据定义. 目前最受欢迎的方式是采用java 注解的方式.

XML方式配置元数据演示

源码地址:
https://gitee.com/bseaworkspace/study_java_web/tree/master/springDemo

代码结构

代码的使用

执行com.xsz.AppConfig的main方法,如果控制台中看到如下信息,表示我们从IOC容器中成功获取到了对象.

代码解释

ApplicationContext有不同的实现类, 如果我们把类信息配置在xml,那么可以实现ClassPathXmlApplicationContext 对象来获取IOC容器.

package com.xsz;import com.xsz.services.PetStoreService;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;import java.util.List;
@SpringBootApplication
public class AppConfig {public static void main(String[] args) {// create and configure beansApplicationContext context = new ClassPathXmlApplicationContext("services.xml", "daos.xml");// retrieve configured instancePetStoreService service = context.getBean("petStore", PetStoreService.class);// use configured instanceList<String> userList = service.getUsernameList();System.out.println(userList);SpringApplication.run(AppConfig.class, args);}}

src\main\resources\daos.xml
一个 "<bean"就是配置一个类,把这个类的创建控制交给spring ioc 容器.

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttps://www.springframework.org/schema/beans/spring-beans.xsd"><bean id="accountDao"class="com.xsz.dao.JpaAccountDao"><!-- additional collaborators and configuration for this bean go here --></bean><bean id="itemDao" class="com.xsz.dao.JpaItemDao"><!-- additional collaborators and configuration for this bean go here --></bean><!-- more bean definitions for data access objects go here --></beans>

这个类有两个属性的数据类型是其他的类, 可以在配置文件中设置, 这里一定要注意,这两个属性要有get,set方法.

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttps://www.springframework.org/schema/beans/spring-beans.xsd"><!-- services --><bean id="petStore" class="com.xsz.services.PetStoreServiceImpl"><property name="accountDao" ref="accountDao"/><property name="itemDao" ref="itemDao"/><!-- additional collaborators and configuration for this bean go here --></bean><!-- more bean definitions for services go here --></beans>

PetStoreServiceImpl 类中,添加了get,set方法.

package com.xsz.services;import com.xsz.dao.JpaAccountDao;
import com.xsz.dao.JpaItemDao;import java.util.Arrays;
import java.util.List;public class PetStoreServiceImpl implements PetStoreService {public JpaAccountDao accountDao;public JpaItemDao itemDao;@Overridepublic List<String> getUsernameList() {return Arrays.asList("张三","李四","周瑜");}public JpaAccountDao getAccountDao() {return accountDao;}public void setAccountDao(JpaAccountDao accountDao) {this.accountDao = accountDao;}public JpaItemDao getItemDao() {return itemDao;}public void setItemDao(JpaItemDao itemDao) {this.itemDao = itemDao;}
}