我正在嘗試部署一個非常簡單的 Spring Boot 應用程序，其中導航到 localhost:8080/greetings 會顯示“來自 Spring Boot 的問候語！”。但是，該 URL 似乎不起作用。導航到鏈接提示我出現空指針異常。我對這個問題做了一些初步研究，但以下修復沒有奏效：將類從默認包中移出并移入定義的包中使用@ComponentScan將我的控制器類移動到我的應用程序類的子包控制器類：package controllers;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController;@RestControllerpublic class HelloController {    @RequestMapping("/greetings")    public String index() {        return "Greetings from Spring Boot!";    }}應用類：package controllers;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplicationpublic class Application {    public static void main(String[] args) {        SpringApplication.run(Application.class, args);    }}pom.xml<?xml version="1.0" encoding="UTF-8"?><project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>org.springframework</groupId><artifactId>gs-spring-boot</artifactId><version>0.1.0</version><parent>    <groupId>org.springframework.boot</groupId>    <artifactId>spring-boot-starter-parent</artifactId>    <version>2.1.4.RELEASE</version></parent>   <properties>    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>    <java.version>1.8</java.version></properties><dependencies>    <dependency>        <groupId>org.springframework.boot</groupId>        <artifactId>spring-boot-starter-web</artifactId>    </dependency>    <dependency>        <groupId>org.springframework.boot</groupId>        <artifactId>spring-boot-starter-test</artifactId>        <scope>test</scope>    </dependency></dependencies></project>