[Java知识库]Spring注解开发

Spring原始注解

Spring原始注解主要是代替Bean的配置
使用注解进行开发时。需要在applicationContext.xml中配置组件扫描。作用是指定哪个包及其子包下的Bean需要进行扫描以便识别使用注解配置的类、字段和方法。

<!--配置组件扫描-->
    <context:component-scan base-package="com.ch"/>

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation=
               "http://www.springframework.org/schema/context  http://www.springframework.org/schema/context/spring-context.xsd
                http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">


  <!--  <bean id="userDao" class="com.ch.test.Dao.impl.UserDaoImpl"></bean>

    <bean id="userService" class="com.ch.test.service.impl.UserServiceImp">
        <property name="userDao" ref="userDao"></property>
    </bean>-->

    <!--配置组件扫描-->
    <context:component-scan base-package="com.ch"/>

    <context:property-placeholder location="jdbc.properties"/>

</beans>

//<bean id="userDao" class="com.ch.test.Dao.impl.UserDaoImpl"></bean>
//@Component("userDao")
@Repository("userDao")
public class UserDaoImpl implements UserDao {
    @Override
    public void save() {
        System.out.println("save running...");
    }
}

//<bean id="userService" class="com.ch.test.service.impl.UserServiceImp"></bean>
//@Component("userService")
@Service("userService")
//@Scope("prototype")
@Scope("singleton")
public class UserServiceImp implements UserService {

    @Value("${jdbc.url}")
    private String driver;

    //<property name="userDao" ref="userDao"></property>
   // @Autowired//自动注入,按照数据类型从Spring容器中进行匹配
   // @Qualifier("userDao")//要注入的id，按照id的名称从Spring容器中进行匹配，此处Qualifier要结合Autowired一起用
    @Resource(name = "userDao")//@Resource相当于@Qualifier+@Autowired
    private UserDao userDao;
//    public void setUserDao(UserDao userDao) {
//        this.userDao = userDao;
//    }

    @Override
    public void save() {
        System.out.println(driver);
        userDao.save();
    }

    @PostConstruct
    public void init(){
        System.out.println("Service对象的初始化方法");
    }

    @PreDestroy
    public void destroy(){
        System.out.println("Service对象的销毁方法");
    }
}

Spring新注解

使用原始注解不能完全替代xml配置文件，还需要使用注解替代配置如下：

• 非自定义的Bean配置；Bean
• 加载properties文件配置：context:property-placeholder
• 组件扫描配置：context:component-scan
• 引入其他文件：import

//标志该类是Spring的核心配置类
//<!--配置组件扫描-->
//<context:component-scan base-package="com.ch"/>
@ComponentScan("com.ch")
//<import resource=""/>
@Import({DataSourceConfiguration.class})//逗号后直接加另外要加载的类
public class SpringConfiguration {


}

//<context:property-placeholder location="jdbc.properties"/>
@PropertySource("classpath:jdbc.properties")
public class DataSourceConfiguration {

    @Value("${jdbc.driver")
    private String driver;

    @Value("${jdbc.url")
    private String url;

    @Value("${jdbc.username")
    private String username;

    @Value("${jdbc.password")
    private String password;

    @Bean("dataSource")//Spring会将当前方法的返回值以指定名称存储到Spring容器当中
    public DataSource getDataSource() throws Exception{
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setDriverClassName(driver);
        dataSource.setUrl(url);
        dataSource.setUsername(username);
        dataSource.setPassword(password);
        return dataSource;
    }
}

 public static void main(String[] args) {
        //ClassPathXmlApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
        ApplicationContext app = new AnnotationConfigApplicationContext(SpringConfiguration.class);
        UserService userService = app.getBean(UserService.class);
        userService.save();
    }