Spring注解之@Configuration和@Bean功能简介说明

spring中生成bean的方式

	1.在Spring的.xml配置文件中配置Bean
	2.使用Spring注解@Controller,@Service,@Component
	3.使用@Configuration和@Bean注解
注意事项:
    1.@Configuration注解类似于spring .xml配置中beans标签
    2.@Bean可理解为用spring.xml配置文件里面的bean标签
    3.使用Spring时,注意加上扫包配置
    和其他注解一样,只有被扫到改注解才会生效
    4.在SpringBoot项目中,SpringBoot默认扫描Main入口文件,所在包下的所有类

@Configuration
public class BeansConfig {

    @Value("com.mysql.jdbc.Driver")
    private String className;

    @Value("jdbc://xxxx.ooo.xx")
    private String url;

    @Value("${userName}")
    private String username;

    @Value("${password}")
    private String password;

    @Bean(name = "mysqlDataSource")
    //name:BeanId
    //如果不指定name属性则BeanId默认类名首字符小写
    public DataSource createDataSourceBean() {
        BasicDataSource dataSource = new BasicDataSource();
        dataSource.setDriverClassName(driverClassName);
        dataSource.setUrl(driverUrl);
        dataSource.setUsername(driverUsername);
        dataSource.setPassword(driverPassword);
        return dataSource;
    }

    @Bean
    //存在依赖关系的Bean
    public PlatformTransactionManager transactionManager() {
        return new DataSourceTransactionManager(createDataSourceBean());
    }

    @Bean
    public User peopleBean(){
        return new User(888,"nnnn","广东深圳");
    }
}