获取 Spring-boot 应用程序的白标签错误答案

【问题标题】：Getting whitelabel error for Spring-boot application获取 Spring-boot 应用程序的白标签错误
【发布时间】：2020-06-22 16:27:18
【问题描述】：

我是 Spring Boot 开发新手，请帮我解决以下错误

目录结构（仅包括重要文件的结构）

src
   -main
       -java
           -com.example.handlingformsubmission
               -Greeting.java
               -GreetingController.java
               -HandlingFormSubmissionApplication.java
       -resources
           -templates
               -greeting.html
               -result.html
           -application.properties
   -test
       -java
           -com.example.handlingformsubmission
               -HandlingFormSubmissionApplicationTest.java
   -build.gradle

在浏览器上运行时遇到这个错误

Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.

Wed Mar 11 19:08:44 IST 2020
There was an unexpected error (type=Not Found, status=404).
No message available

当我终止或停止应用程序时

Execution failed for task ':HandlingFormSubmissionApplication.main()'.
> Process 'command '/usr/lib/jvm/java-11-amazon-corretto/bin/java'' finished with non-zero exit value 143

目前我使用的是springboot 2.2.2版

这是我的代码

build.gradle

plugins {
    id 'org.springframework.boot' version '2.2.2.RELEASE'
    id 'io.spring.dependency-management' version '1.0.8.RELEASE'
    id 'java'
    id 'war'
}

group = 'com.example'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '1.8'

repositories {
    mavenCentral()
}

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-thymeleaf'
    implementation 'org.springframework.boot:spring-boot-starter-web'
    testImplementation('org.springframework.boot:spring-boot-starter-test') {
        exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
    }
}

test {
    useJUnitPlatform()
}

HandlingFormSubmissionApplication.java

package com.example.handlingformsubmission;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;

@ComponentScan(basePackages = {"com.example.handlingformsubmission.greeting"})
@SpringBootApplication
public class HandlingFormSubmissionApplication {

    public static void main(String[] args) {
        SpringApplication.run(HandlingFormSubmissionApplication.class, args);
    }

}

GreetingController.java


package com.example.handlingformsubmission.greeting;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PostMapping;

@Controller
public class GreetingController {

    @GetMapping("/greeting")
    public String greetingForm(Model model) {
        model.addAttribute("greeting", new Greeting());
        return "greeting";
    }

    @PostMapping("/greeting")
    public String greetingSubmit(@ModelAttribute Greeting greeting, Model model) {
        model.addAttribute("greeting", greeting);
        return "result";
    }

}

application.properties

server.port=8000

greeting.html

<!DOCTYPE HTML>
<html xmlns:th="https://www.thymeleaf.org">
<head> 
    <title>Getting Started: Handling Form Submission</title>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
</head>
<body>
    <h1>Form</h1>
    <form action="#" th:action="@{/greeting}" th:object="${greeting}" method="post">
        <p>Id: <input type="text" th:field="*{id}" /></p>
        <p>Message: <input type="text" th:field="*{content}" /></p>
        <p><input type="submit" value="Submit" /> <input type="reset" value="Reset" /></p>
    </form>
</body>
</html>

结果.html

<!DOCTYPE HTML>
<html xmlns:th="https://www.thymeleaf.org">
<head> 
    <title>Getting Started: Handling Form Submission</title>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
</head>
<body>
    <h1>Result</h1>
    <p th:text="'id: ' + ${greeting.id}" />
    <p th:text="'content: ' + ${greeting.content}" />
    <a href="/greeting">Submit another message</a>
</body>
</html>

【问题讨论】：

日志说什么？很高兴看到异常
@Thomas__ 我无法找出错误。我是这门课程的初学者
请阅读你为什么should not post screenshots of code or errors。
除非绝对必要，否则请不要将信息共享为图像。请参阅：meta.stackoverflow.com/questions/303812/…、idownvotedbecau.se/imageofcode、idownvotedbecau.se/imageofanexception。
@nobar 我已经添加了目录结构。

标签： spring-boot gradle thymeleaf

【解决方案1】：

问题中没有指定，但我猜你想执行GET http://localhost:8000/greeting

我不会修复你的表单，但是404可以通过修复你的@ComponentScan来解决，例如...

// wrong: '.greeting' excludes the 'GreetingController'
@ComponentScan(basePackages = {"com.example.handlingformsubmission.greeting"})

// fixed: specifies a valid path that includes the controller
@ComponentScan(basePackages = {"com.example.handlingformsubmission"})

解决此问题后，您将能够继续前进并解决下一个问题：

出现意外错误（类型=内部服务器错误，状态=500）。模板解析时出错（模板： "类路径资源 [templates/greeting.html]")

您也可以通过完全删除 @ComponentScan 来解决此问题 - 此初始场景不需要它。

【讨论】：