Spring IOC控制反转、DI注入以及配置

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 {
    @Override
    public void book() {
        System.out.println("BookDAO……");
    }
}

Service层:

public interface BookService {
    public void write();
}

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

测试文件1：

public class BookDAOTest {
    @Test
    public 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 {
    @Test
    public 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();
    @Override
    public void write() {
        bookDAO.book();
        System.out.println("BookService……");
    }
}

测试类：

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

测试结果：

4.动态工厂bean的实例化：

DAO层：

public interface BookDAO {
    public void book();
}

实例化工厂：

public class FactoryImpl implements FactoryBean<BookDAO> {
    @Override
    public BookDAO getObject() throws Exception {
        System.out.println("工厂正在创造DAO对象......");
        return new BookDAOImpl();
    }

    @Override
    public Class<?> getObjectType() {
        return BookDAO.class;
    }

    @Override
    public boolean isSingleton() {
        return true;
    }
}

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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="bookService" name="service" class="org.itheima.service.impl.BookServiceImpl">
        <property name="bookDAO" ref="bookDAO"/>
    </bean>
    <bean id="bookDAO" class="org.itheima.factory.FactoryImpl"/>
</beans>

测试文件：

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

运行结果：