简单的 Spring 引导项目给出 404 错误

Question

I am learning Spring Boot but I am not able to execute the basic "Hello World" program. I have built the basic project using https://start.spring.io/ and updated the code as per below code snippets:

Spring Boot Main Class:

package com.rohit.springboot.practice.selfspringboot;

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


@SpringBootApplication
@ComponentScan(basePackages = "com.rohit.springboot.practice.selfspringboot")
public class SelfSpringBootApplication {

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

}

Controller Class:

package com.rohit.springboot.practice.selfspringboot;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class ThisWorldSpringContainer {
    
    
    @RequestMapping(method = RequestMethod.GET, value = "/hello-world")
    public String getWelcome() {
        
        return "Hello World";
    }

}

POM.xml file:

<?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>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.6.6</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.rohit.springboot.practice</groupId>
    <artifactId>self-spring-boot</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>self-spring-boot</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

Error:

Message: The requested resource [/hello-world] is not available

I know this question has been asked by multiple people but i have gone through those answers and tried those given answers but didn't work.

Technologies used are Java 8, Tomcat 9, Spring Boot 2.6.6 etc.

Kindly help.

Answer 1

Since you don't have the Tomcat dependency, I'm implying that you want your application to run in a standalone Tomcat instance. Also, given your comment, I believe you're working on either Eclipse or Spring Tools Suite (Which is the same, really).

With that, it seems your problem is the lack of a packaging method. Tomcat needs the code its going to run in a package. This package is a zip-like file with .war extension. Maven, the program that handles the dependencies of your project according to the pom.xml file, can package it in either war of jar format. Since you are running it in an external Tomcat, you want the war extension. So please, add the following line to your pom.xml file. It has to be in the same level as <name> :

<packaging>war</packaging>

Then, update your project (Alt + F5, check your project and hit OK) then try running your project again. You should see an stylish "SPRING" output in your console.

Now, since you are running this externally, you need to specify the name of the project, so you should call your endpoint with

http://localhost:8080/<your_project_name_here>/hello-world

Answer 2

I advise you to check this new change in Spring Boot 2.6:

PathPattern Based Path Matching Strategy for Spring MVC

In this release, the default strategy for matching request paths against registered Spring MVC handler mappings has changed from AntPathMatcher to PathPatternParser .

If you need to switch the default strategy back to AntPathMatcher , you can set the property spring.mvc.pathmatch.matching-strategy to ant-path-matcher as in the line below to add in the file application.properties :

spring.mvc.pathmatch.matching-strategy=ant-path-matcher

I encountered the same issue of HTTP 404 error when upgrading to Spring Boot 2.6 and adding this property solved my problem and should solve yours.

Answer 3

I have modified your code as below:

@RequestMapping
@RestController
public class ThisWorldSpringContainer {
    
    @GetMapping(value = "/hello-world")
    public String getWelcome() {
        
        return "Hello World";
    }

}

I thinking you are missing

@Requestmapping

in classlevel