Ioc控制反转

Ioc（Inversion of control）控制反转

• 使用对象时，由主动new产生对象转化为外部提供对象，此过程对象控制权由对象转移到外部，此思想称为控制反转。

spring技术对Ioc思想进行了实现

• spring提供了一个容器称为Ioc容器，用来充当Ioc思想的“外部”
• Ioc容器负责对象的创建，初始化等一系列工作，被创建或者被管理的对象在Ioc容器中统称为Bean

DI（Dependency Injection）依赖注入

• 在容器中建立Bean与Bean之间的依赖关系的整个过程，被称为依赖注入

Ioc入门案例

pom.xml

<?xml version="1.0" encoding="UTF-8"?>

<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>com.itheima</groupId>
  <artifactId>spring_01_quickstart</artifactId>
  <version>1.0-SNAPSHOT</version>

  <dependencies>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>5.2.10.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
</project>

---

applicationContext.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:util="http://www.springframework.org/schema/util"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/util https://www.springframework.org/schema/util/spring-util.xsd">
    <!--1.导入spring的坐标spring-context，对应版本是5.2.10.RELEASE-->

    <!--2.配置bean-->
    <!--bean标签标示配置bean
    id属性标示给bean起名字
    class属性表示给bean定义类型-->
    <bean id="bookDao" class="dang.dao.impl.BookDaoImpl"/>
    <bean id="bookService" class="dang.service.BookServiceImpl"/>

</beans>

---

BookDAoImpl

package dang.dao.impl;

public class BookDaoImpl implements BookDao {
    public void save() {
        System.out.println("Book dao save...");
    }
}

---

BookServiceImpl

package dang.service;
import dang.dao.impl.BookDao;
import dang.dao.impl.BookDaoImpl;

public class BookServiceImpl implements BookService {
    private BookDao bookDao=new BookDaoImpl();

    public void save() {
        System.out.println("book service save ...");
        bookDao.save();
    }

    //6.提供对应的set方法
    public void setBookDao(BookDao bookDao) {
        this.bookDao = bookDao;
    }
}

---

app.java

package dang;

import dang.service.BookService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class app {
    public static void main(String[] args) {
//3.获取Ioc容器
        ApplicationContext ctx=new ClassPathXmlApplicationContext("applicationContext.xml");

        //        4.获取bean（根据bean配置id获取）
//        BookDao bookDao=(BookDao)ctx.getBean("bookDao");
//        bookDao.save();


        BookService bookService = (BookService) ctx.getBean("bookService");
        bookService.save();
    }
}

DI依赖注入

applicationContext.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:util="http://www.springframework.org/schema/util"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/util https://www.springframework.org/schema/util/spring-util.xsd">
    <!--1.导入spring的坐标spring-context，对应版本是5.2.10.RELEASE-->

    <!--2.配置bean-->
    <!--bean标签标示配置bean
    id属性标示给bean起名字
    class属性表示给bean定义类型-->
    <bean id="bookDao" class="dang.dao.impl.BookDaoImpl"/>
    <bean id="bookService" class="dang.service.BookServiceImpl">
        <!--7.配置server与dao的关系-->
        <!--property标签表示配置当前bean的属性
        name属性表示配置哪一个具体的属性
        ref属性表示参照哪一个bean-->
        <property name="bookDao" ref="bookDao"/>
    </bean>




</beans>

---

bookService

package dang.service;
import dang.dao.impl.BookDao;

public class BookServiceImpl implements BookService {
    //5.删除业务层中使用new的方式创建的dao对象
    private BookDao bookDao;

    public void save() {
        System.out.println("book service save ...");
        bookDao.save();
    }

    //6.提供对应的set方法
    public void setBookDao(BookDao bookDao) {
        this.bookDao = bookDao;
    }
}