New annotations in Spring

* New annotations in spring
* @Configuration
* Role: a configuration class when specifying the current class
* Details: When the configuration class is used as a parameter created by the AnnotationConfigApplicationContext object, the annotation can be omitted
* @ComponentScan
* Function: Used to specify the package that Spring will scan when creating the container through annotations
* Attributes:
* value: It has the same function as basePackages, both are used to specify the package to be scanned when creating the container
* Our use of this annotation is equivalent to configuring in xml:
*                  <context:component-scan base-package="com.itheima"></context:component-scan>
* @Bean
* Role: used to store the return value of the current method as a bean object in the spring's ioc container
* Attributes:
* name: used to specify the id of the bean, when not written, the default value is the name of the current method
* Details: When we use the annotation configuration method, if the method has parameters, the spring framework will go to the container to find out if there is a bean object that can be used
* The search method is the same as Autowired annotations.
* @Import
* Role: used to import other configuration classes
* Attributes:
* value: the bytecode used to specify other configuration classes
* When we use the Import annotation, the class with Import annotation is the parent configuration class, and the imported is the child configuration class
* @PropertySource
* Role: used to specify the configuration of the properties file
* Attributes:
* value: specify the path of the file name
* Keyword: classpath means under the class path

@Configuration
@ComponentScan("com.itheima")
@Import(JdbcConfig.class)
@PropertySource("classpath:jdbcConfig.properties")
public class SpringConfiguration {
    @Value("${jdbcDriver}")
    private String driver;
    @Value("${jdbcUrl}")
    private String url;
    @Value("${user}")
    private String username;
    @Value("${password}")
    private String password;
    /**
     * 用于创建一个QueryRunner对象
     * @param dataSource
     * @return
     */
    @Bean(name = "runner")
    @Scope("prototype") //表示是个多例的
    public QueryRunner createQueryRunner(DataSource dataSource)
    {
        return new QueryRunner(dataSource);
    }

    /**
     * 创建数据源对象
     * @return
     */
    @Bean(name = "dataSource")
    public DataSource createDataSource(){
        try{
            ComboPooledDataSource ds = new ComboPooledDataSource();
            ds.setDriverClass(driver);
            ds.setJdbcUrl(url);
            ds.setUser(username);
            ds.setPassword(password);
            return ds;
        } catch (Exception e){
            throw new RuntimeException(e);
        }
    }
}