Spring框架之入坑

最新推荐文章于 2022-07-30 20:27:19 发布

原创最新推荐文章于 2022-07-30 20:27:19 发布 · 207 阅读

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Spring介绍

The Spring Framework provides a comprehensive programming and configuration model for modern Java-based enterprise applications - on any kind of deployment platform.
A key element of Spring is infrastructural support at the application level: Spring focuses on the “plumbing” of enterprise applications so that teams can focus on application-level business logic, without unnecessary ties to specific deployment environments.
前面这么大一坨浓缩下来就是，spring提供基础设施支持，不用与特定的部署环境绑定。
spring核心技术主要是IOC、AOP

IOC

inverse of control 即控制反转，就是将你设计好的类交给系统控制，不由你自己在内部控制。
DI（依赖注入）是实现IOC的一种方式在这里插入图片描述
上图可以帮助我们理解，左图是自己控制类的调度，右图是spring容器控制调度，你需要什么他就给你什么，如果没有就抛异常。两则最直观的区别就是，前者自己控制对象，后者由spring容器控制对象，这就是控制反转。

代码举例

public class LoginController {
    //这个属性没有被实例化
    private LoginService loginService;
    public String login(String username, String password){
       String result= loginService.login(username,password);
        return result;
    }

    public void setLoginService(LoginService loginService) {
        this.loginService = loginService;
    }
}

public interface LoginService {
        public String login(String username,String password);
}

public class LoginServiceImpl implements LoginService {

    private UserDAO userDAO;
    @Override
    public String login(String username, String password) {

        User user=userDAO.findByuser(username,password);

        return user!=null?"成功":"失败";
    }

    public void setUserDAO(UserDAO userDAO) {
        this.userDAO = userDAO;
    }
}

public interface UserDAO {

     public User findByuser(String username,String password);
}

public class UserDAOImpl implements UserDAO {


    @Override
    public User findByuser(String username, String password) {
        System.out.println(username+password);
        return new User(username,password);
    }
}

在idea中maven创建的项目的resources下的xml配置文件

<?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/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
<bean id="UserDAO" class="com.ldl.etc.DAO.Impl.UserDAOImpl"></bean>
<bean id="LoginService" class="com.ldl.etc.service.impl.LoginServiceImpl">
    <property name="userDAO" ref="UserDAO"></property>
</bean>
<bean id="LoginController" class="com.ldl.etc.controller.LoginController">
    <property name="LoginService" ref="LoginService"></property>
</bean>

</beans>