一) Spring 介绍、IOC控制反转思想与DI依赖注入

2022-11-08 16:47:05

一。spring介绍
1.IOC反转控制思想（Inversion of Control）与DI依赖注入（Dependency Injection）
2.AOP面向切面的编程思想与动态代理
3.作用：项目的粘合剂，总管，使项目的维护性和扩展性更好

二。spring作为bean的管理容器使用步骤
1.pom.xml加入spring的依赖

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>spring</groupId>

    <artifactId>spring</artifactId>

    <version>0.0.1-SNAPSHOT</version>

    <build>

        <sourceDirectory>src</sourceDirectory>

        <plugins>

            <plugin>

                <artifactId>maven-compiler-plugin</artifactId>

                <version>3.5.1</version>

                <configuration>

                    <source>1.8</source>

                    <target>1.8</target>

                </configuration>

            </plugin>

        </plugins>

    </build>

    <dependencies>

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-core</artifactId>

            <version>4.3.13.RELEASE</version>

        </dependency>

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-context</artifactId>

            <version>4.3.13.RELEASE</version>

        </dependency>

    </dependencies>

</project>

2.在src目录下创建beans.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" xmlns:context="http://www.springframework.org/schema/context"

    xmlns:aop="http://www.springframework.org/schema/aop"

    xsi:schemaLocation="http://www.springframework.org/schema/beans

         http://www.springframework.org/schema/beans/spring-beans.xsd

         http://www.springframework.org/schema/context

         http://www.springframework.org/schema/context/spring-context.xsd

         http://www.springframework.org/schema/aop

         http://www.springframework.org/schema/aop/spring-aop.xsd">

     <bean id="bt" class="com.bean.BeanTest"></bean> 

     <bean id="stuDAO" class="com.dao.StudentDAO"></bean>

     <bean id="stuMysqlDAO" class="com.dao.StudentMysqlDAO"></bean> 

     <bean id="stuSer" class="com.service.StudentService">

         <property name="stuDAO">

             <ref bean="stuMysqlDAO" />

         </property>

     </bean> 

     <bean id="stuControl" class="com.control.StudentControl">

         <property name="stuSer">

             <ref bean="stuSer" />

         </property>

     </bean> 

</beans>

3.将java对象加入到配置文件中注册
　　<bean id="hello" class="com.bean.Hello"></bean>
4.在代码中获取容器，拿到bean对象，运行
　　// 初始化spring的容器
　　BeanFactory bf = new ClassPathXmlApplicationContext("beans.xml");
　　// 从容器中拿到javabean
　　Hello h = (Hello) bf.getBean("hello");

三。ioc反转控制。依赖注入
1.set方法的注入
2.构造方法的注入

四。注解的方式完成注入
1.补充schema
2.打开注解开关
　　
　　<context:annotation-config></context:annotation-config>
　　
　　<context:component-scan base-package="com"></context:component-scan>
3.给类加注解
　　@comptent:表示注册为组件
　　@Repository:表示注册为DAO组件
　　@Service:表示注册为业务组件
　　@Controller:注册为控制器组件
4.注入的注解
　　@Autowired：写在属性上，表示自动按照类型注入
　　注意：
　　　　a。属性的类型必须是接口
　　　　b。如果一个接口有多个实现类，通过@Qualifier("db2")指定实现类
附:spring注解可参考此链接 https://www.cnblogs.com/wlxslsb/p/10718402.html

实例：使用注解的形式来写一个Spring项目

　1.dao层

IStudentDAO.java

package com.dao;

public interface IStudentDAO {

    public void saveStu();

}

StudentDAO.java

package com.dao;

import org.springframework.stereotype.Component;

import org.springframework.stereotype.Repository;

//@Component("oracle")

@Repository("oracle")

public class StudentDAO implements IStudentDAO{

    @Override

    public void saveStu() {

        System.out.println("使用oracle数据库");

        System.out.println("正在保存学员对象");

    }

}

StudentMysqlDAO.java

package com.dao;

import org.springframework.stereotype.Component;

@Component("mysql")

public class StudentMysqlDAO implements IStudentDAO{

    @Override

    public void saveStu() {

        System.out.println("正在使用mysql数据库");

        System.out.println("保存学员对象");

    }

}

　 2.Service层

IStudentService.java

package com.service;

public interface IStudentService {

    public void addStudent();

}

StudentService.java

package com.service;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.beans.factory.annotation.Qualifier;

import org.springframework.stereotype.Component;

import org.springframework.stereotype.Service;

import com.dao.IStudentDAO;

import com.dao.StudentDAO;

//@Component

@Service

public class StudentService implements IStudentService{

//    IStudentDAO stuDAO = new StudentDAO();

    @Autowired

    @Qualifier("mysql")//当借口有多个实现类时，必须指明注入哪个实现类

    IStudentDAO stuDAO;

    public void setStuDAO(IStudentDAO stuDAO) {

        this.stuDAO = stuDAO;

    }

    @Override

    public void addStudent() {

        System.out.println("拿到数据");

        System.out.println("调用dao保存数据");

        stuDAO.saveStu();

    }

}

3.Control层

StudentControl.java

package com.control;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Component;

import org.springframework.stereotype.Controller;

import com.service.IStudentService;

//@Component("sc")

@Controller

public class StudentControl {

    @Autowired

    IStudentService stuSer;

    public void setStuSer(IStudentService stuSer) {

        this.stuSer = stuSer;

    }

    public String execute(){

        System.out.println("接收页面参数");

        System.out.println("调用业务层");

        stuSer.addStudent();

        return "success";

    }

}

4.配置文件

　　beans.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:context="http://www.springframework.org/schema/context"

    xmlns:aop="http://www.springframework.org/schema/aop"

    xsi:schemaLocation="http://www.springframework.org/schema/beans

         http://www.springframework.org/schema/beans/spring-beans.xsd

         http://www.springframework.org/schema/context

         http://www.springframework.org/schema/context/spring-context.xsd

         http://www.springframework.org/schema/aop

         http://www.springframework.org/schema/aop/spring-aop.xsd">

    <!--     打开spring的注解功能 -->

    <context:annotation-config></context:annotation-config>

    <!-- 告诉spring到哪些包下去扫描bean对象 -->

    <context:component-scan base-package="com"></context:component-scan>

</beans>

5.测试代码

RunTest.java

package com.bean;

import org.springframework.beans.factory.BeanFactory;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.control.StudentControl;

import com.service.IStudentService;

public class RunTest {

    public static void main(String[] args) {

        //根据beans.xml去构造出bean工厂，就是spring的容器

        BeanFactory bf = new ClassPathXmlApplicationContext("beans.xml");

        StudentControl sc = (StudentControl) bf.getBean("sc");

        sc.execute();

    }

}

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