目标：使用Spring Initializr 方式创建SpringBoot工程，实现入门案例的需求。
准备工程 新建模块，选择spring initializr，然后下一步 填写项目相关信息 勾选需要的依赖启动器 完成，查看工程的目录结构如下测试工程 创建HelloController
工程的src目录下创建com.itheima.controller.HelloController
@RestController public class HelloController { /*** * 请求 /hello 输出hello springboot! * @return */ @RequestMapping(value = "hello2") public String hello(){ return "hello springboot2!"; } } 启动引导类访问: http://localhost:8080/hello2
启动报错：
Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled. 2019-10-31 20:32:33.885 ERROR 17980 --- [ restartedMain] o.s.b.d.LoggingFailureAnalysisReporter : *************************** APPLICATION FAILED TO START *************************** Description: Failed to configure a DataSource: 'url' attribute is not specified and no embedded datasource could be configured. Reason: Failed to determine a suitable driver class Action: Consider the following: If you want an embedded database (H2, HSQL or Derby), please put it on the classpath. If you have database settings to be loaded from a particular profile you may need to activate it (no profiles are currently active). Process finished with exit code 0原因是：
引入的jdbc 没有配置数据源：解决方法很简单： 要么暂时先把它注释起来，要么配置文件里配置好数据库信息。
