关于springweb-mvc衍生注解

目录

衍生注解

容器配置

User类

Userdao类

spring容器配置

创建测试类

将User类修改

修改spring容器配置

@Component使用

衍生注解

在web开发中,会根据webmvc的三层加购分层,这时候每层都有相同一个不同的注解名字,但功能都相同。

Service层:@Service用于标注业务层组件

controller层:@Controller用于标注控制层组件

dao层:@Repository用于标注数据访问组件

组件归类层,名字可以随便定义,例如User层,@Component可以进行标注

注解:使用了注解之后,在容器中不需要注入bean,但要指定查找的的项目。

容器配置 <?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"> <!--指定注入时需要查找的项目--> <context:component-scan base-package="com.yc.ch"/> </beans>

创建一个dao层和一个组件归类层,文件样式如下

User类 import com.yc.dao.Userdao; import org.springframework.beans.factory.annotation.Value; import org.springframework.stereotype.Component; //该注释表示注册到容器中,直接由spring容器托管, @Component public class User { //表示设置name的参数值为为Tom //等价于 <property name="name" value="Tom"/> @Value("Tom") private String name; private Userdao userdao; public String getName() { return name; } public void setName(String name) { this.name = name; } public Userdao getUserdao() { return userdao; } public void setUserdao(Userdao userdao) { this.userdao = userdao; } @Override public String toString() { return "User{" + "name='" + name + '\'' + ", userdao=" + userdao + '}'; } } Userdao类 import org.springframework.beans.factory.annotation.Value; import org.springframework.stereotype.Repository; //该注释表示注册到容器中,直接由spring容器托管, @Repository public class Userdao { //表示设置name的参数值为为游泳 //等价于 <property name="name" value="游泳"/> @Value("游泳") private String name; public String getName() { return name; } public void setName(String name) { this.name = name; } @Override public String toString() { return "Userdao{" + "name='" + name + '\'' + '}'; } } spring容器配置 <?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"> <!--表示查找到com.yc下的所有层--> <context:component-scan base-package="com.yc"/> </beans> 创建测试类 ApplicationContext context=new ClassPathXmlApplicationContext("beans.xml"); User u=context.getBean("user",User.class); System.out.println(u);

输出

User{name=‘Tom’, userdao=null}

最终输出的只有User类,但是Userdao层次却直接显示空,问题是没有把Userdao的bean引入到User的bean中,所以在测试User类时显示空。解决:使用使用注解 @Autowired方式匹配到Userdao中

将User类修改 import com.yc.dao.Userdao; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Value; import org.springframework.stereotype.Component; @Component public class User { @Value("Tom") private String name; @Autowired private Userdao userdao; public String getName() { return name; } public void setName(String name) { this.name = name; } public Userdao getUserdao() { return userdao; } public void setUserdao(Userdao userdao) { this.userdao = userdao; } @Override public String toString() { return "User{" + "name='" + name + '\'' + ", userdao=" + userdao + '}'; } } 修改spring容器配置 <?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"> <context:component-scan base-package="com.yc"/> <context:annotation-config/> </beans>

创建测试类,输出

User{name=‘Tom’, userdao=Userdao{name=‘游泳’}}

@Component使用

@Component还可以加参数,里面值相当于注入bean中的id值,上面的案例默认为User类的小写user,如果设置为@Component(value = “user2”)或者@Component(“user2”),则将测试类改写为

ApplicationContext context=new ClassPathXmlApplicationContext("beans.xml"); User u=context.getBean("user2",User.class); System.out.println(u);

以上为个人经验,希望能给大家一个参考,也希望大家多多支持易知道(ezd.cc)。 

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