Spring使用注解开发

首先我们要先配置好对应的ApplicationContext.xml,填写好组件扫描，然后就无需在xml中声明bean也能正常运行了。

<?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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        https://www.springframework.org/schema/context/spring-context.xsd">

    <!--启用包扫描-->
    <context:component-scan base-package="com.spring"/>
    <!--启用注解-->
    <context:annotation-config/>

</beans>

1. @Component

在对应的实体类上声明@Component注解即可将类注册为一个组件，从而被Spring扫描到。

@Component
public class User {
    private String name;

    public User() {
        super();
    }

    public User(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                '}';
    }
}

2. @Value

@Value()注解可以为属性注入值

	@Value("jack")
    private String name;

3. @Repository

@Repository跟@Component作用相同，但Repository一般是加在mapper层上的注解

@Repository
public interface UserMapper {

}

4. @Service

@Service跟@Repository作用相同，都是加在mapper层上的注解

@Service
public interface UserMapper {

}

5. @Controller

@Controller跟@Service,@Repository,@Component作用相同，但却是加在controller层上的注解

@Controller
public class UserController {
}

6. @Scope

@Scope指定在类上声明作用域

@Component
@Scope("singletion")
public class User {

    @Value("jack")
    private String name;

    public User() {
        super();
    }

    public User(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                '}';
    }
}