Spring IoC之DI实现注解配置形式

Spring IoC之DI实现注解配置形式

文章目录

• • Spring Annotaiton Config Bean
  • • 如何注解的方式IoC
    • • 扫描注解：XML配置形式
      • 注解的方式将注入bean
      • • Component、Service、Repository、Controller
        • 四个注解的区别
      • 注解的方式注入属性
      • • Value注解
        • Spring Autowired 自动注入注解
        • • Qualifier注解
          • 给方法注入对象类型参数
        • jdk Resource自动注入注解
      • 扫描注解：Java配置形式
    • 其他方式
    • 持续更新
    • 更新
  • 结语

Spring Annotaiton Config Bean

Spring.io:annotaition
Spring IoC之DI实现XML配置形式]

如何注解的方式IoC 扫描注解：XML配置形式

import org.springframework.stereotype.Component;
@Component
public class User {
    private String uid;
    private String uname;
    public void setUid(String uid) {
        this.uid = uid;
    }
    public void setUname(String uname) {
        this.uname = uname;
    }
    @Override
    public String toString() {
        return "User{" +
                "uid='" + uid + ''' +
                ", uname='" + uname + ''' +
                '}';
    }
}

测试方法

public class Test01 {
    private ApplicationContext ac = new ClassPathXmlApplicationContext("applicationcontext.xml");
        @Test
        public void test00(){
            System.out.println(ac.getBean("user", User.class));
        }	
}

注解的方式将注入bean Component、Service、Repository、Controller

这四个注解的含义相同，被标注的类会被spring注入进spring容器中

//以Component为例
@Component
public class User{
    @Override
    public String toString() {
        return "this is User";
    }
}

测试代码

System.out.println(ac.getBean("user", User.class));

四个注解的区别

• Controller一般用于控制层类上
• service 一般用于业务处理层类上
• Repository一般用于数据持久层类上
• Component一般用于不是以上三种情况

注解的方式注入属性 Value注解

@Component
public class User {
    @Value("101")
    private String uid;
    @Value("小明")
    private String uname;
    @Override
    public String toString() {
        return "User{" +
                "uid='" + uid + ''' +
                ", uname='" + uname + ''' +
                ", book=" + book +
                '}';
    }
}

测试代码

System.out.println(ac.getBean("user", User.class));

Spring Autowired 自动注入注解

@Component
public class User {
    @Value("103")
    private String uid;
    @Value("小美")
    private String uname;
    @Autowired
    private Book book;
    @Override
    public String toString() {
        return "User{" +
                "uid='" + uid + ''' +
                ", uname='" + uname + ''' +
                ", book=" + book +
                '}';
    }
}

//Book接口
public interface Book {}

//Book接口的实现类
import org.springframework.stereotype.Component;
@Component
public class JavaBook implements Book{
    @Override
    public String toString() {
        return "JavaBook{}";
    }
}

测试代码

System.out.println(ac.getBean("user", User.class));

//多加一个Book的实现类
@Component
public class SpringBook implements Book{
    @Override
    public String toString() {
        return "SpringBook{}";
    }
}

**注意：**如果多了一个实现类，并且也注入时，会报Book存在多个bean，spring不知道使用哪一个注入属性,此时需要Qualifier 注解

Qualifier注解

指定需要注入的对象，此时需要对Component类型的对象，添加value属性(指明生成bean的id)

注入类

@Component(value = "spring")
public class SpringBook implements Book{
    @Override
    public String toString() {
        return "SpringBook{}";
    }
}

被注入类User

@Autowired
//添加注解
@Qualifier("spring")
private Book book;

给方法注入对象类型参数

修改User类

@Component
public class User {
    @Value("103")
    private String uid;
    @Value("小美")
    private String uname;
    private Book book;
    @Autowired
    @Qualifier("javaBook")
    public void setBook(Book book) {
        this.book = book;
    }
    @Override
    public String toString() {
        return "User{" +
                "uid='" + uid + ''' +
                ", uname='" + uname + ''' +
                ", javaBook=" + book +
                '}';
    }
}

JavaBook类

@Component()
public class JavaBook implements Book{
    @Value("101")
    private int bid;
    @Value("java")
    private String bname;
    @Override
    public String toString() {
        return "JavaBook{" +
                "bid=" + bid +
                ", bname='" + bname + ''' +
                '}';
    }
}

测试类

 @Test
    public void test05(){
        AnnotationConfigApplicationContext acac = new AnnotationConfigApplicationContext(SpringConfig.class);
        System.out.println(acac.getBean("user",User.class));
    }

jdk Resource自动注入注解

import javax.annotation.Resource;
@Component
public class User {
    @Value("103")
    private String uid;
    @Value("小美")
    private String uname;
    @Resource()
    private Book book;
    @Override
    public String toString() {
        return "User{" +
                "uid='" + uid + ''' +
                ", uname='" + uname + ''' +
                ", book=" + book +
                '}';
    }
}

测试代码

System.out.println(ac.getBean("user", User.class));

扫描注解：Java配置形式

@ComponentScan(value = "com.test.springdome02")
public class SpringConfig {
}

@Component
public class User {
    @Value("102")
    private String uid;
    @Value("小明")
    private String uname;
    @Autowired
    private Book book;
    @Override
    public String toString() {
        return "User{" +
                "uid='" + uid + ''' +
                ", uname='" + uname + ''' +
                ", book=" + book +
                '}';
    }
}

@Test
    public void test02(){
        AnnotationConfigApplicationContext acac = new AnnotationConfigApplicationContext(SpringConfig.class);
        System.out.println(acac.getBean("user", User.class));
    }

其他方式

• Spring XML配置

• Spring 注解配置

持续更新 更新

• 2022/1/3

结语

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