• 注解代替了xml的繁琐配置

spring 原始注解

1.1 @Component注解

<!--spring 使用注解创建对象 component-scan 组件扫描器 用来扫描包下面的注解 -->
<context:component-scan base-package="com.lovely"/>

• 利用ClassPathXmlApplicationContext可创建对象

package com.lovely.test;
@Component("app")
public Class App {// coding...
}

public static void main(String[] args) {ClassPathXmlApplicationContext application =new ClassPathXmlApplicationContext("classpath:applicationContext.xml");App app = (App) application.getBean("app");// sout(app);
}

1.2 @Controller,@Service,@Repository同上

1.3 注解方式依赖注入

    // 利用注解进行 属性注入// 1. @Autowired // 根据类型/* 2. @Autowired // 根据类型 进行依赖注入@Qualifier("userDao") // 与autowired根据名称进行依赖注入*/@Resource // 3. 按照名称注入private UserDao userDao;/*public void setUserDao(UserDao userDao) {// bean 的 依赖注入 配置xml property 通过setthis.userDao = userDao;}*/// 4. 对普通值注入 组件扫描器 扫描spring容器中得key 拿value@Value("${jdbc.driver}")private String driver;@Value("a simple string...")private String str;

spring 新注解

1. 用来解析配置类，利用配置类替代xml

• 具体使用

package com.lovely.config;import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;/*** @author echo lovely* @date 2020/7/22 16:59* 用于替代applicationContext.xml的配置核心类*/@Configuration // 标志该类是spring的核心配置类 替换xml
@ComponentScan("com.lovely") // 扫描com.lovely包下的spring注解 替换<context:component-scan base-package="com.lovely"/>
@Import(DataSourceConfiguration.class) // 引入 DataSourceConfiguration 配置类
public class SpringConfiguration {}

• 以数据源解析为例子

/*** @author echo lovely* @date 2020/7/22 17:03* 数据源配置类*/
// 加载配置文件 相当于 property-placeholder
@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.userPassword}")private String password;@Bean("druidDataSource") // spring 会将当前方法的返回值以指定名称(druidDataSource) 储存到spring容器中public DataSource getDataSource() {DruidDataSource dataSource = new DruidDataSource();dataSource.setDriverClassName(driver);dataSource.setUrl(url);dataSource.setUsername(username);dataSource.setPassword(password);System.out.println(dataSource);return dataSource;}}

• 测试demo

package com.lovely.web;import com.lovely.config.SpringConfiguration;
import com.lovely.service.UserService;
// import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
// import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.stereotype.Controller;/*** @author echo lovely* @date 2020/7/21 16:15*/// 在web层上实例化bean
@Controller("userController")
public class UserController {public static void main(String[] args) {/*ClassPathXmlApplicationContext app =new ClassPathXmlApplicationContext("classpath:applicationContext.xml");*/AnnotationConfigApplicationContext app = new AnnotationConfigApplicationContext(SpringConfiguration.class);UserService user = (UserService) app.getBean("userService");user.service();/*Object obj = app.getBean("druidDataSource");System.out.println(obj);*/app.close();}}