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 + "]"; } }
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); } }
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"); } }
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(); } }
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(); } }
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 } }
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>
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>
