编写第一个spring程序

1.创建一个maven工程，在DAO层创建接口和对应的实现类

package com.zhu.dao;

public interface UserDao {

    void getUser();
}

package com.zhu.dao;

public class UserDaoImpl implements UserDao{

    @Override
    public void getUser() {
        System.out.println("默认获取用户的数据");
    }
}

package com.zhu.dao;

public class UserDaoImpl2 implements  UserDao{
    @Override
    public void getUser() {
        System.out.println("默认获取用户的数据2");
    }
}

package com.zhu.dao;

public class UserDaoImpl3 implements  UserDao{
    @Override
    public void getUser() {
        System.out.println("默认获取用户的数据3");
    }
}

package com.zhu.dao;

public class UserDaoImpl4 implements  UserDao{
    @Override
    public void getUser() {
        System.out.println("默认获取用户的数据4");
    }
}

2.在pom.xml文件中导入依赖包

   <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>5.2.0.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

3.在Service层创建接口和实现类

package com.zhu.service;

public interface UserService {
    void getUser();
}

package com.zhu.service;

import com.zhu.dao.UserDao;
import com.zhu.dao.UserDaoImpl;
import com.zhu.dao.UserDaoImpl2;
import com.zhu.dao.UserDaoImpl3;

public class UserServiceImpl implements UserService{

    private UserDao userDao;

    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }
    @Override
    public void getUser() {
userDao.getUser();
    }
}

4.创建bean配置文件，并且将实现类配置在bean文件中

<?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-3.0.xsd">

    <bean id="UserDaoImpl1" class="com.zhu.dao.UserDaoImpl"></bean>
    <bean id="UserDaoImpl2" class="com.zhu.dao.UserDaoImpl2"></bean>
    <bean id="UserDaoImpl3" class="com.zhu.dao.UserDaoImpl3"></bean>
    <bean id="UserDaoImpl4" class="com.zhu.dao.UserDaoImpl4"></bean>

    <bean id="UserServiceImpl" class="com.zhu.service.UserServiceImpl">
        <property name="userDao" ref="UserDaoImpl1"></property>
    </bean>
</beans>

5.创建一个测试类执行程序

import com.zhu.dao.UserDao;
import com.zhu.dao.UserDaoImpl;
import com.zhu.dao.UserDaoImpl2;
import com.zhu.dao.UserDaoImpl4;
import com.zhu.service.UserService;
import com.zhu.service.UserServiceImpl;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {

    public static void main(String[] args){

//        UserServiceImpl userService =new UserServiceImpl();
//        userService.setUserDao(new UserDaoImpl());
//        userService.getUser();

        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
        UserServiceImpl userService = (UserServiceImpl) context.getBean("UserServiceImpl");
        userService.getUser();
    }
}

本文地址：https://blog.csdn.net/weixin_45723003/article/details/111937188