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 {

    @Test

    public 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

    //@Resource

    private 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 {

    @Autowired

    private 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 {

    @Test

    public 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>

巴特西

spring 注解简单使用

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