SpringBoot报错：Unable to start web server； nested exception is org.springframework.context.Application_unable to start web server; nested exception is or

报错前配置

• Controller类：

@Controller
public class HelloController {
    @ResponseBody
    @RequestMapping("/hello")
    public String hello(){
        return "hello SpringBoot!";
    }
}
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• 主程序：

@SpringBootApplication
public class HelloApplication {
    public static void main(String[] args) throws Exception {
        SpringApplication.run(HelloController.class, args);
    }
}
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运行报错：

ApplicationContextException:无法开始ServletWebServerApplicationContext由于缺少ServletWebServerFactory bean
原因是因为我这里的启动类是Controller类，而Controller类并没有做任何配置标注。
解决方法：在启动类之前添加一个：@EnableAutoConfiguration注解来解决问题。

• 修改Controller如下：

@EnableAutoConfiguration
@Controller
public class HelloController {
    @ResponseBody
    @RequestMapping("/hello")
    public String hello(){
        return "hello SpringBoot!";
    }
}
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如果你的springboot出现下面错误：

ERROR StatusLogger Log4j2 could not find a logging implementation. Please add log4j-core to the classpath. Using SimpleLogger to log to the console…
ERROR SpringApplication Application run failed

解决方法是添加依赖：

<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-core</artifactId>
    <version>2.10.0</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-api -->
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-api</artifactId>
    <version>2.10.0</version>
</dependency>
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另外，附上springboot、maven、jdk版本对应: