JSP in Spring Boot application yields 404 Error no matter what I do

I'll start off by saying I've looked at and tried the solutions in every question regarding this that I can find. The biggest problem is that most of these solutions are very old, and Spring Boot has changed a lot in the last several years. To be clear, I've tried this, this, this, this, and more. I've also read numerous tutorials. Nothing works.

I have a brand new Spring Boot application and I'm trying to get JSP rendering working with it. These are my dependencies:

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
        <version>[2.3.4.RELEASE,3)</version>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
        <version>[2.3.4.RELEASE,3)</version>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-validation</artifactId>
        <version>[2.3.4.RELEASE,3)</version>
    </dependency>

    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jstl</artifactId>
        <version>1.2</version>
    </dependency>

    <dependency>
        <groupId>commons-io</groupId>
        <artifactId>commons-io</artifactId>
        <version>[2.8.0,3)</version>
    </dependency>

    <dependency>
        <groupId>de.mkammerer</groupId>
        <artifactId>argon2-jvm</artifactId>
        <version>[2.7,3)</version>
    </dependency>

    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>[8.0.21,9)</version>
        <scope>runtime</scope>
    </dependency>

    <dependency>
        <groupId>org.glassfish.jaxb</groupId>
        <artifactId>jaxb-runtime</artifactId>
        <version>[2.3.2,)</version>
        <scope>runtime</scope>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-tomcat</artifactId>
        <version>[2.3.4.RELEASE,3)</version>
        <scope>runtime</scope>
    </dependency>

    <dependency>
        <groupId>org.apache.tomcat.embed</groupId>
        <artifactId>tomcat-embed-jasper</artifactId>
        <version>[9.0.38,)</version>
        <scope>runtime</scope>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <version>[2.3.4.RELEASE,3)</version>
        <scope>test</scope>
        <exclusions>
            <exclusion>
                <groupId>org.junit.vintage</groupId>
                <artifactId>junit-vintage-engine</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
</dependencies>

My project is laid out as follows:

- source
  - production
    - java
      - [my source code packages]
    - resources
      - WEB-APP
        - jsp
          - initialization
            - begin.jsp
      - [my resource packages]
  - test
    - java
    - resources

"WEB-APP/jsp" is just the latest iteration I've tried. I've tried "WEB-INF/jsp", "META-INF/jsp", "webapp/jsp", no parent (just "jsp"), etc., all with the same results.

I know the parent directories are a bit non-standard, but it's configured correctly in Maven and I've confirmed it's not the source of my problems:

<build>
    <sourceDirectory>source/production/java</sourceDirectory>
    <resources>
        <resource>
            <directory>source/production/resources</directory>
        </resource>
    </resources>
    ...
</build>

My Application class is as follows:

@SpringBootApplication(scanBasePackages="com.my.project")
@EnableWebMvc
@EnableJpaRepositories("com.my.project.repository")
@EntityScan("com.my.project.model")
public class Application
{
    private static final Logger LOGGER = LogManager.getLogger(Application.class);

    public Application()
    {
    }

    @Bean
    public ViewResolver viewResolver()
    {
        LOGGER.info("Constructing InternalResourceViewResolver[JstlView]");
        InternalResourceViewResolver resolver = new InternalResourceViewResolver();
        resolver.setPrefix("/WEB-APP/jsp/");
        resolver.setSuffix(".jsp");
        resolver.setViewClass(JstlView.class);
        resolver.setRedirectContextRelative(true);
        resolver.setRedirectHttp10Compatible(false);
        return resolver;
    }

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

And my Controller:

@Controller
public class InitializationController
{
    private static final Logger LOGGER = LogManager.getLogger(InitializationController.class);

    @GetMapping("/initialize_application")
    public String beginInitialization(ModelMap model)
    {
        LOGGER.info("Beginning initialization");
        ...
        LOGGER.info("Returning view");
        return "initialization/begin";
    }
    ...
}

On startup I see the "Constructing InternalResourceViewResolver" log entry (my view resolver bean is created). When I go to /initialize_application, I get the following error:

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

Sun Oct 18 21:45:26 CDT 2020
There was an unexpected error (type=Not Found, status=404).

Looking in the log again, I see "Beginning initialization" and "Returning view," so I know that the 404 is for my JSP and not my controller. My controller is working.

Other things I've tried:

• Initially I did not have @EnableWebMvc on my application. Without it, the log was empty except my log statements. When I added @EnableWebMvc, this is now logged with the 404: No mapping for GET /WEB-APP/jsp/initialization/begin.jsp (or whatever other directory I've tried other than "WEB-APP").
• I've tried running this directly on the pure command line with mvn spring-boot:run
• I've tried running this in IntelliJ IDEA with a Maven run configuration and command spring-boot:run (same result)
• I've tried both <packaging>jar</packaging> and <packaging>war</packaging>, but neither make a difference, because neither a JAR nor a WAR are ever made. Maven runs the application directly out of the target/classes directory instead of creating an artifact.
• When I've tried WEB-INF or META-INF instead of WEB-APP or webapp or something else, I've seen a logged warning: Path with "WEB-INF" or "META-INF": [WEB-INF/jsp/initialization/begin.jsp]

I have also confirmed that my JSPs are present in target/classes/WEB-APP/jsp (or whatever other directory I've tried other than "WEB-APP"), so they do exist.

I'm at a loss how to proceed. I'm beginning to think I need to ditch Spring Boot and stick with a traditional boilerplate Spring Web MVC application with a Servlet config and a Tomcat installation, but I was really excited about the "just runs" aspect of Spring Boot. Any help would be appreciated.

UPDATE 1

After reading this Spring documentation about JSP limitations, I now know that I have to use <packaging>war</packaging>, and I'm using that now, but it hasn't made a difference. I'm starting to suspect that the underlying problem here is that maven spring-boot:run doesn't create a WAR and run it, it just builds everything to target/classes and runs it from there.

Also, after finding this old, official Spring boot samples application, I've changed my project structure a little:

- source
  - production
    - java
      - [my source code packages]
    - resources
      - [my resource packages]
    - webapp
      - META-INF
      - WEB-INF
      - jsp
        - initialization
          - begin.jsp
  - test
    - java
    - resources

Updated my view resolver configuration:

resolver.setPrefix("/jsp/");
resolver.setSuffix(".jsp");

And added this to my POM:

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-war-plugin</artifactId>
            <version>3.3.1</version>
            <configuration>
                <warSourceDirectory>source/production/webapp</warSourceDirectory>
            </configuration>
        </plugin>

If I run mvn package, my WAR gets created correctly (classes and JSPs all where they should be), but neither mvn spring-boot:run nor mvn package spring-boot:run work—I still get 404 errors resolving my JSPs.

The old Spring Boot sample application linked to above puts the JSPs in WEB-INF/jsp, but I can't do that, because that results in the warning Path with "WEB-INF" or "META-INF": [WEB-INF/jsp/initialization/begin.jsp] (and still 404). What's frustrating is that this sample application doesn't exist anymore, nor does any new variation of it. I can't find any updated version that works with the newest version of Spring Boot. The sample application was deleted in 2.2.x.

Can you try by changing the scope of tomcat-embed-jasper to provided as this dependency is needed to compile JSPs.

    <dependency>
        <groupId>org.apache.tomcat.embed</groupId>
        <artifactId>tomcat-embed-jasper</artifactId>
        <version>[9.0.38,)</version>
        <scope>provided</scope>
    </dependency>

Edit:

I looked for various spring-boot + jsp projects over internet. I noticed that they have they also have spring-boot-starter-tomcat with provided scope. Can you try this.

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-tomcat</artifactId>
        <version>[2.3.4.RELEASE,3)</version>
        <scope>provided</scope>
    </dependency>

References :

https://mkyong.com/spring-boot/spring-boot-hello-world-example-jsp/

https://dzone.com/articles/spring-boot-2-with-jsp-view

Edit-2 :

So this time i created a new springboot project. Did bare minimum setup to get jsp rendered. So basically i followed this tutorial and my project was running fine.

Then I replaced the pom.xml with yours and the i got the same error you mentioned in the question.

Then while doing trial and error i removed the <version>[9.0.38,)</version> from <artifactId>tomcat-embed-jasper</artifactId> and it started working for me.

        <!--I have removed version here and it started working for me-->
        <dependency>
            <groupId>org.apache.tomcat.embed</groupId>
            <artifactId>tomcat-embed-jasper</artifactId>
<!--            <version>[9.0.38,)</version>-->
            <scope>provided</scope>
        </dependency>

Although i have different directory structure. But as you mentioned that is not the cause of issue.

I have uploaded the project to github. Feel free to pull it run it locally.

Github

Assuming the following location for your web content (which should be outside the classpath AFAIK) source/production/webapp. Spring Boot will ignore this due to a hardcoded path in DocumentRoot for detection of directories when running from the command-line or IDE (it will work when building a war and running that).

As a workaround you can add a TomcatContextCustomizer as a bean to detect the path and set it as the correct base.

package com.my.project;

@SpringBootApplication
public class Application extends SpringBootServletInitializer 
{
    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) 
    {
        return application.sources(DemoApplication.class);
    }

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

    @Bean
    public TomcatContextCustomizer docBaseCustomizer() 
    {
        return new TomcatContextCustomizer() 
        {
            public void customize(Context context) 
            {
                File root = new File("source/production/webapp");
                if (root.exists() && root.isDirectory()) 
                {
                    context.setDocBase(root.getAbsolutePath());
                }        
            }
        }
    } 
}

Now add the following to your application.properties

spring.mvc.view.prefix=/jsp/
spring.mvc.view.suffix=.jsp

NOTE: The removal of the other annotations can only be done if your @SpringBootApplication annotated class is in the com.my.project package. It will then automatically detect the other classes (like entities and repositories).