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Spring IOC控制反转、DI注入以及配置

news 2025/9/11 16:58:43

1.使用xml的方式进行配置IOC容器，首先引入依赖

在Resource资源下配置，applicationContext.xml ,刷新mevan后可以直接选择配置spring.xml文件

<!--    spring核心用来管理bean    --><dependency><groupId>org.springframework</groupId><artifactId>spring-context</artifactId></dependency><dependency><groupId>junit</groupId><artifactId>junit</artifactId><scope>test</scope></dependency>

applicationContext.xml

配置bean:

id：实现标识给bean起名字

class属性标识给这个bean对象定义类型

name:属性是可以给当前bean起别名(使用“ ”，“，”，“；”分隔开来)

singleton:单例(默认)

prototype:非单例

<?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="bookDAO" class="org.itheima.dao.impl.BookDAOImpl"/><bean id="bookService" class="org.itheima.service.impl.BookServiceImpl"/>
</beans>

现在配置DAO层：

public interface BookDAO {public void book();
}

public class BookDAOImpl implements BookDAO {@Overridepublic void book() {System.out.println("BookDAO……");}
}

Service层:

public interface BookService {public void write();
}

public class BookServiceImpl implements BookService {private BookDAO bookDAO = new BookDAOImpl();@Overridepublic void write() {System.out.println("BookService……");}
}

测试文件1：

public class BookDAOTest {@Testpublic void book() {ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");BookDAO bookDAO = (BookDAO) ctx.getBean("bookDAO");bookDAO.book();}
}

打印结果：

测试文件2：

public class BookServiceTest {@Testpublic void write() {ClassPathXmlApplicationContext txc = new ClassPathXmlApplicationContext("applicationContext.xml");BookService bookService = (BookService) txc.getBean("bookService");bookService.write();}
}

打印结果：

依赖 new ClassPathXmlApplicationContext("applicationContext.xml")的方式不太合适，同样是创建对象的形式，那不如直接new一个实体DAO，因此此方法需要改进！！

2.使用dao与Service的关系

与以上不同的是BookServiceImpl与测试类不同：

public class BookServiceImpl implements BookService {
private BookDAO bookDAO = new BookDAOImpl();@Overridepublic void write() {bookDAO.book();System.out.println("BookService……");}
}

测试类：

public class BookServiceImplTest {@Testpublic void testWrite() {ClassPathXmlApplicationContext cax = new ClassPathXmlApplicationContext("applicationContext.xml");BookService bookService = (BookService) cax.getBean("bookService");bookService.write();}
}

测试结果：

3.使用DI注入 bean实例，并且使用service 调用dao层方法

首先配置Service的依赖关系properties

properties:配置当前bean的属性

name属性标识配置哪一个具体的属性

ref属性表示参照哪个bean对象

<?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="bookDAO" class="org.itheima.dao.impl.BookDAOImpl"/><bean id="bookService" class="org.itheima.service.impl.BookServiceImpl"><property name="bookDAO" ref="bookDAO"/></bean>
</beans>

dao层:

public interface BookDAO {public void book();
}

public class BookDAOImpl implements BookDAO {@Overridepublic void book() {System.out.println("BookDAO……");}
}

service层：

public interface BookService {public void write();
}

通过容器将bookDAO对象传入进去

public class BookServiceImpl implements BookService {private BookDAO bookDAO;@Overridepublic void write() {bookDAO.book();System.out.println("BookService……");}public void setBookDAO(BookDAO bookDAO) {this.bookDAO = bookDAO;}
}

测试类：

public class BookServiceImplTest {
private BookService bookService;@Testpublic void write() {ClassPathXmlApplicationContext cax = new ClassPathXmlApplicationContext("applicationContext.xml");BookService bookService = (BookService) cax.getBean("bookService");bookService.write();}
}

测试结果：