spring的作用和配置

1.建立一个实体类，建立一个dao类

package com.sun.model;

public class User {
    private String username;
    private String password;
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    

}

package com.sun.dao;

import com.sun.model.User;

public class UserDAO {
    
    public void save(User u) {
        System.out.println("saved");
    }

}

2.将user存入数据库，一般的情况是数据库连接，然后session.save(user);但是有了service这一层，就将这句话给封装了，变成了service.save（u），我们不再接触数据库那一层了。

package com.sun.service;

import com.sun.dao.UserDAO;
import com.sun.model.User;

public class UserService {
    private UserDAO userdao;
    
    

    public UserDAO getUserdao() {
        return userdao;
    }



    public void setUserdao(UserDAO userdao) {
        this.userdao = userdao;
    }



    public void add(User u) {
        this.userdao.save(u);
        
    }

}

package com.sun.service;

import com.sun.dao.UserDAO;
import com.sun.model.User;

public class Test {

        public static void main(String[] args) {
            UserService service=new UserService();
            UserDAO userdao=new UserDAO();
            service.setUserdao(userdao);
            User u=new User();
            service.add(u);
        }

    


}

3.将service.add(u);与userdao.save(u);比较就知道service的大致作用了

4.需要的spring jar包

5.写一个程序测试(spring 的作用就是你现在还不用new 一个service了，它来帮你完成即控制反转的含义)

6.service代码

package com.sun.spring;

public interface UserService {
    public void addUser();

}

package com.sun.spring;

public class serviceimpl implements UserService {
    public void addUser() {
        System.out.println("hello");
        
    }

}

7.加入.xml文件，文件帮助内容在下面找

8.配置xml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 definitions here -->
        <bean id="userService" class="com.sun.spring.serviceimpl"> </bean>

</beans>

9.测试

package com.sun.spring;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {
    public static void main(String[] agrs) {
        String xmlPath="com/sun/spring/beans.xml";
        ApplicationContext appicationcantext=new ClassPathXmlApplicationContext(xmlPath);
        UserService userservice=(UserService) appicationcantext.getBean("userService");
        userservice.addUser();
    }

}

10.spring就是帮你管类文件的，所有你需要new的它都帮你用配置文件统一完成。