Spring で画面表示がされない。

前提・実現したいこと

Spring Bootで初めて開発を行っており、動作確認のために"Hello World"を表示させたいがエラーが表示される。

発生している問題・エラーメッセージ

:: Spring Boot :: (v2.2.7.RELEASE)

2020-05-16 11:57:08.582 ERROR 8084 --- [ restartedMain] o.a.c.c.C.[Tomcat].[localhost].[/] : Exception sending context initialized event to listener instance of class [com.vaadin.flow.spring.VaadinServletContextInitializer$DevModeServletContextListener]

java.lang.RuntimeException: Unable to initialize Vaadin DevModeHandler
at com.vaadin.flow.spring.VaadinServletContextInitializer$DevModeServletContextListener.contextInitialized(VaadinServletContextInitializer.java:349) ~[vaadin-spring-12.1.4.jar:na]
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4688) [tomcat-embed-core-9.0.34.jar:9.0.34]
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5151) [tomcat-embed-core-9.0.34.jar:9.0.34]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) [tomcat-embed-core-9.0.34.jar:9.0.34]
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1384) [tomcat-embed-core-9.0.34.jar:9.0.34]
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1374) [tomcat-embed-core-9.0.34.jar:9.0.34]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_202]
at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75) [tomcat-embed-core-9.0.34.jar:9.0.34]
at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:134) [na:1.8.0_202]
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:909) [tomcat-embed-core-9.0.34.jar:9.0.34]
at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:841) [tomcat-embed-core-9.0.34.jar:9.0.34]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) [tomcat-embed-core-9.0.34.jar:9.0.34]
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1384) [tomcat-embed-core-9.0.34.jar:9.0.34]
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1374) [tomcat-embed-core-9.0.34.jar:9.0.34]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_202]
at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75) [tomcat-embed-core-9.0.34.jar:9.0.34]
at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:134) [na:1.8.0_202]
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:909) [tomcat-embed-core-9.0.34.jar:9.0.34]
at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:262) [tomcat-embed-core-9.0.34.jar:9.0.34]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) [tomcat-embed-core-9.0.34.jar:9.0.34]
at org.apache.catalina.core.StandardService.startInternal(StandardService.java:421) [tomcat-embed-core-9.0.34.jar:9.0.34]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) [tomcat-embed-core-9.0.34.jar:9.0.34]
at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:930) [tomcat-embed-core-9.0.34.jar:9.0.34]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) [tomcat-embed-core-9.0.34.jar:9.0.34]
at org.apache.catalina.startup.Tomcat.start(Tomcat.java:468) [tomcat-embed-core-9.0.34.jar:9.0.34]
at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.initialize(TomcatWebServer.java:106) [spring-boot-
Caused by: javax.servlet.ServletException: com.vaadin.flow.server.ExecutionFailedException:

該当のソースコード

以下がControllerクラスです。

Java
1package com.example.demo.trySpring;
2
3import org.springframework.stereotype.Controller;
4import org.springframework.web.bind.annotation.GetMapping;
5
6@Controller
7public class HelloController {
8
9	@GetMapping("/hello")
10	public String getHello() {
11		return "hello";
12	}
13}
14

以下がHTMLです。

HTML
1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
2<html xmlns:th="http://www.thymeleaf.org">
3<head>
4<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"></meta>
5<title>Hello World</title>
6</head>
7<body>
8<h1>Hello World</h1>
9</body>
10</html>
11

以下がpom.xmlです。

xml
1<?xml version="1.0" encoding="UTF-8"?>
2<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
3	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
4	<modelVersion>4.0.0</modelVersion>
5	<parent>
6		<groupId>org.springframework.boot</groupId>
7		<artifactId>spring-boot-starter-parent</artifactId>
8		<version>2.2.7.RELEASE</version>
9		<relativePath/> <!-- lookup parent from repository -->
10	</parent>
11	<groupId>com.example</groupId>
12	<artifactId>SpringSample</artifactId>
13	<version>0.0.1-SNAPSHOT</version>
14	<name>SpringSample</name>
15	<description>Demo project for Spring Boot</description>
16
17	<properties>
18		<java.version>1.8</java.version>
19		<vaadin.version>14.1.28</vaadin.version>
20	</properties>
21
22	<dependencies>
23		<dependency>
24			<groupId>org.springframework.boot</groupId>
25			<artifactId>spring-boot-starter-data-jdbc</artifactId>
26		</dependency>
27		<dependency>
28			<groupId>org.springframework.boot</groupId>
29			<artifactId>spring-boot-starter-jdbc</artifactId>
30		</dependency>
31		<dependency>
32			<groupId>org.springframework.boot</groupId>
33			<artifactId>spring-boot-starter-jersey</artifactId>
34		</dependency>
35		<dependency>
36			<groupId>org.springframework.boot</groupId>
37			<artifactId>spring-boot-starter-thymeleaf</artifactId>
38		</dependency>
39		<dependency>
40			<groupId>org.springframework.boot</groupId>
41			<artifactId>spring-boot-starter-web</artifactId>
42		</dependency>
43		<dependency>
44			<groupId>org.springframework.boot</groupId>
45			<artifactId>spring-boot-starter-web-services</artifactId>
46		</dependency>
47		<dependency>
48			<groupId>org.springframework.boot</groupId>
49			<artifactId>spring-boot-starter-webflux</artifactId>
50		</dependency>
51		<dependency>
52			<groupId>org.springframework.boot</groupId>
53			<artifactId>spring-boot-starter-websocket</artifactId>
54		</dependency>
55		<dependency>
56			<groupId>com.vaadin</groupId>
57			<artifactId>vaadin-spring-boot-starter</artifactId>
58		</dependency>
59
60		<dependency>
61			<groupId>org.springframework.boot</groupId>
62			<artifactId>spring-boot-devtools</artifactId>
63			<scope>runtime</scope>
64			<optional>true</optional>
65		</dependency>
66		<dependency>
67			<groupId>com.h2database</groupId>
68			<artifactId>h2</artifactId>
69			<scope>runtime</scope>
70		</dependency>
71		<dependency>
72			<groupId>org.projectlombok</groupId>
73			<artifactId>lombok</artifactId>
74			<optional>true</optional>
75		</dependency>
76		<dependency>
77			<groupId>org.springframework.boot</groupId>
78			<artifactId>spring-boot-starter-test</artifactId>
79			<scope>test</scope>
80			<exclusions>
81				<exclusion>
82					<groupId>org.junit.vintage</groupId>
83					<artifactId>junit-vintage-engine</artifactId>
84				</exclusion>
85			</exclusions>
86		</dependency>
87		<dependency>
88			<groupId>io.projectreactor</groupId>
89			<artifactId>reactor-test</artifactId>
90			<scope>test</scope>
91		</dependency>
92	</dependencies>
93
94	<dependencyManagement>
95		<dependencies>
96			<dependency>
97				<groupId>com.vaadin</groupId>
98				<artifactId>vaadin-bom</artifactId>
99				<version>${vaadin.version}</version>
100				<type>pom</type>
101				<scope>import</scope>
102			</dependency>
103		</dependencies>
104	</dependencyManagement>
105
106	<build>
107		<plugins>
108			<plugin>
109				<groupId>org.springframework.boot</groupId>
110				<artifactId>spring-boot-maven-plugin</artifactId>
111			</plugin>
112		</plugins>
113	</build>
114
115</project>
116

補足情報（FW/ツールのバージョンなど）

ここにより詳細な情報を記載してください。

rubytomato

2020/05/16 05:37

pom.xmlにたくさんの依存ライブラリを追加されているようですが、なにか理由があるのでしょうか？というのも、とりあえずHello Worldを表示するだけであればこんなにたくさんのライブラリは使いません。最初は依存ライブラリが少ない状態で始めた方が、問題が起きたときに原因が切り分けやすいと思います。