spring 注解简单使用

一、通用注解

1、项目结构：

2、新建Person类，注解@Component未指明id，则后期使用spring获取实例对象时使用默认id="person"方式获取或使用类方式获取

package hjp.spring.annotation.commen;import org.springframework.stereotype.Component;//@Component
@Component("personId")
public class Person {
private String name;
private Integer age;
public String getName() {return name;
}
public void setName(String name) {this.name = name;
}
public Integer getAge() {return age;
}
public void setAge(Integer age) {this.age = age;
}
@Override
public String toString() {return "Person [name=" + name + ", age=" + age + "]";
}
}

Person

3、新建beans.xml文件，相比之前配置多了

xmlns:context="http://www.springframework.org/schema/context"
和
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
不再使用bean节点配置，而是使用context:component-scan节点，属性base-package指明要扫描注解的包

<?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 http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"><!-- <bean id="personId" class="hjp.spring.annotation.commen.Person"></bean> --><context:component-scan base-package="hjp.spring.annotation.commen"></context:component-scan>
</beans>

4、新建测试类

package hjp.spring.annotation.commen;import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.stereotype.Component;public class TestApp {@Testpublic void demo1() {ApplicationContext applicationContext = new ClassPathXmlApplicationContext("hjp/spring/annotation/commen/beans.xml");//注解未指定id时,默认id为person//Person person = applicationContext.getBean("person", Person.class);        //注解指定id，即@Component("personId")时        //Person person = applicationContext.getBean("personId",Person.class);//不管是否指定id，使用类方式获取实例都可以Person person = applicationContext.getBean(Person.class);System.out.println(person);}
}

测试类

二、衍生三层开发注解

@Controller 修饰Web层；@Service 修饰service层；@Repository 修饰dao层

依赖注入：方式1、普通数据 @Value

　　　　方式2、引用数据 @Autowired，默认按照类型进行注入；如果想要按照名称进行注入，还需要使用注解@Qualifier("名称")

1、项目结构

2、新建UserDao类

package hjp.spring.annotation.web;import org.springframework.stereotype.Repository;//@Repository
@Repository("userDaoId")
public class UserDao {public void save() {System.out.println("add user");}
}

UserDao

3、新建UserService类

package hjp.spring.annotation.web;import javax.annotation.Resource;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;@Service
public class UserService {@Autowired//@Qualifier("userDaoId") //指向UserDao类注解@Repository("userDaoId")指定的Id//属性注入也可以使用注解@Resource//@Resourceprivate UserDao userDao;public void setUserDao(UserDao userDao) {this.userDao = userDao;}public void addUser() {userDao.save();}
}

UserService

4、新建UserAction类

package hjp.spring.annotation.web;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Controller;@Controller("userActionId")
//@Scope("prototype")//多例
public class UserAction {@Autowiredprivate UserService userService;public void setUserService(UserService userService) {this.userService = userService;}public void execute() {userService.addUser();}
}

UserAction

5、新建测试类

package hjp.spring.annotation.web;import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;public class TestApp {@Testpublic void demo1() {ApplicationContext applicationContext = new ClassPathXmlApplicationContext("hjp/spring/annotation/web/beans.xml");UserAction userAction = applicationContext.getBean("userActionId", UserAction.class);System.out.println(userAction);//用于测试单例和多例
        userAction.execute();userAction=applicationContext.getBean("userActionId", UserAction.class);System.out.println(userAction);//用于测试单例和多例
    }
}

测试类

6、新建beans.xml配置文件，内容和通用注解一样，只是修改下扫描包的地址

<?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 http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"><!-- <bean id="personId" class="hjp.spring.annotation.commen.Person"></bean> --><!-- 让spring对含有注解的类进行扫描 --><context:component-scan base-package="hjp.spring.annotation.web"></context:component-scan>
</beans>

beans.xml

三、其他注解：如@PostConstruct修饰初始化；@PreDestroy修饰销毁

四、项目中对XML和注解的使用情况

1、纯XML，整合第三方（jar包）

2、纯注解，限制条件必须有源码，简化代码开发

3、xml+注解，xml配置bean，代码中使用注入注解

如果混合使用不需要扫描，只需要加入<context:annotation-config></context:annotation-config>配置

测试Demo可以将UserDao类的@Repository、UserService类的@Service、UserAction类的@Controller去掉，只保留注入注解，

然后修改beans.xml文件为

<?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 http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"><!-- 只使用注入的注解 --><bean id="userDaoId" class="hjp.spring.annotation.web.UserDao"></bean><bean id="userServiceId" class="hjp.spring.annotation.web.UserService"></bean><bean id="userActionId" class="hjp.spring.annotation.web.UserAction"></bean><context:annotation-config></context:annotation-config>
</beans>