Spring Boot - HelloWorld

Question

我想用 SpringBoot 创建一个简单的 hello world 应用程序，其中 localhost:8080/welcome.html 将向我们显示 Hello World。

我认为我做得很好，但我看不到 HelloWorld，只是 Whitelabel 错误页面。

这是我的仓库的链接。如果有人可以检查出什么问题，我会很高兴！ https://github.com/BElluu/ElenXHello

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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.springbelluu</groupId>
    <artifactId>springboot-helloworld</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>springboot-helloworld</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.0.BUILD-SNAPSHOT</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>10</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>

        <dependency>
            <groupId>org.apache.tomcat.embed</groupId>
            <artifactId>tomcat-embed-jasper</artifactId>
        </dependency>

        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
        </dependency>

    </dependencies>

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

    <repositories>
        <repository>
            <id>spring-snapshots</id>
            <name>Spring Snapshots</name>
            <url>https://repo.spring.io/snapshot</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </repository>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
    </repositories>

    <pluginRepositories>
        <pluginRepository>
            <id>spring-snapshots</id>
            <name>Spring Snapshots</name>
            <url>https://repo.spring.io/snapshot</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </pluginRepository>
        <pluginRepository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </pluginRepository>
    </pluginRepositories>


</project>

SpringbootHelloworldApplication.java

package com.springbelluu.springboothelloworld;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SpringbootHelloworldApplication {

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

TestController.java

package com.javainuse.controllers;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

@Controller
public class TestController {

    @RequestMapping("/welcome.html")
    public ModelAndView firstPage() {
        return new ModelAndView("welcome");
    }

}

application.properties

spring.mvc.view.prefix:/WEB-INF/jsp/
spring.mvc.view.suffix:.jsp

Answer 1

对于初学者，如果您想使用 Spring Boot 入门，我强烈建议 不 使用 JSP。使用 JSP 时有很多 some limitations，其中之一是它不适用于 jar 包装。其次，它是一项过时的技术，除了在较新的 JEE 版本中保持功能之外，不再受到太多关注/更新。最好使用Thymeleaf之类的东西。

接下来，您将使用 Spring Boot 版本的快照版本，该版本已经位于 2.1.3.RELEASE（在撰写本文时）。

话虽如此，请将您的pom.xml 更改为以下内容（修复版本，删除 JSP 内容并替换为 Thymeleaf）。

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.springbelluu</groupId>
    <artifactId>springboot-helloworld</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>springboot-helloworld</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.3.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <java.version>10</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-thymeleaf</artifactId>
        </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>

注意：因为您现在使用的是最终版本，所以您不再需要 pom.xml 中的所有存储库！。

现在删除您的 JSP 并在 src/main/resources/templates/ 中创建一个 welcome.html。 （您实际上可以完全删除您的 webapp 目录。

<html>
<body>
<h1>Welcome! Spring Boot for ElenX</h1>
</body>
</html>

您现在拥有的设置比 JSP 更现代且更易于使用。

在您的 application.properties 中删除 spring.mvc.view 属性，因为 Spring Boot 将自动使用正确的设置配置 Thymeleaf。

Answer 2

@BElluu ...您的主应用程序和 Controller 类位于不同的包中，因此 componentscan 无法正常工作...只需检查包级别

package com.springbelluu.springboothelloworld;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SpringbootHelloworldApplication {

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


package com.javainuse.controllers;  
 // use this package package com.springbelluu.springboothelloworld;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

@Controller
public class TestController {

    @RequestMapping("/welcome.html")
    public ModelAndView firstPage() {
        return new ModelAndView("welcome");
    }

}

Answer 3

通过 Spring Framework 转到以下链接以创建全新的 Springboot 项目：

https://start.spring.io/

或

1.创建一个简单的网络应用程序

现在您可以为简单的 Web 应用程序创建一个 Web 控制器。

src/main/java/hello/HelloController.java

打包你好；

导入 org.springframework.web.bind.annotation.RestController； 导入 org.springframework.web.bind.annotation.RequestMapping;

@RestController 公共类 HelloController {

@RequestMapping("/")
public String index() {
    return "Greetings from Spring Boot!";
}

}

1. 创建应用程序类

   Here you create an Application class with the components:
   
   src/main/java/hello/Application.java
   
    package hello;
   
    import java.util.Arrays;
    import org.springframework.boot.CommandLineRunner;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.annotation.Bean;
   
    @SpringBootApplication
    public class Application {
   
    public static void main(String[] args) {
       SpringApplication.run(Application.class, args);
     }
   
     @Bean
     public CommandLineRunner commandLineRunner(ApplicationContext ctx) {
        return args -> {
       System.out.println("Let's inspect the beans provided by Spring Boot:");
   
       String[] beanNames = ctx.getBeanDefinitionNames();
       Arrays.sort(beanNames);
           for (String beanName : beanNames) {
               System.out.println(beanName);
            }
         };
       }
     }
   

Answer 4

   Here is SpringBoot Main class file Noting Changed Here.  
    -----------------------------------------

    package com.Encee.SpringBoot_HelloWorld;

    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;

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

     }

    Here is controller package class 
    -----------------------------------------
    package com.Encee.SpringBoot_HelloWorld.controller;

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

    @RestController

    public class Controller {
        @RequestMapping("/hello.html")
       public String hello() {
            return "Hello World";
        }
    }

    -----------------------------------------        
    Now Main file run as Java Application will get your output.
     SCREEN SHOT

Answer 5

您的问题已解决，您可以在我的提交中查看更改。

https://github.com/farooqrahu/ElenXHello/commits/master