Forward to JSP within Spring Controller after form submission - spring

Question

Using Spring #Controller, #RequestMapping and #ModelAttribute, I'd like to achieve a basic form submission flow in which the user is forwarded to a new JSP with attributes set. Spring provides different ways to achieve this, but I have received various errors.
Example 1
Based on tutorial: https://www.baeldung.com/spring-mvc-form-tutorial
form.html
<form action="/submitForm" method="POST">
<input type="text"id="field1" name="field1">
<!-- other input fields -->
<button type="submit">Submit</button>
</form>
success.jsp
<p>Thanks for signing up ${userName}!!</p>
MyController.java
#Controller
public class MyController{
#RequestMapping(
value = "/submitForm",
method = RequestMethod.POST,
consumes = MediaType.APPLICATION_FORM_URLENCODED_VALUE)
public String post(#ModelAttribute SignupRequest request, ModelMap model){
// At this point, the SignupRequest is populated correctly
model.addAttribute("userName", request.getUserName());
return "success";
}
}
Results
Using return "success" - the result is HTTP 404 Not Found
Using return "success.jsp", the result is HTTP 405 Request method
'POST' not supported
Using return "redirect:/success.jsp", the client is redirected,
but attributes are not set, and ${userName} is visible.
Example 2
Based on the accepted answer here: Redirect after POST method in spring MVC
MyController.java
#Controller
public class MyController{
#RequestMapping(
value = "/submitForm",
method = RequestMethod.POST,
consumes = MediaType.APPLICATION_FORM_URLENCODED_VALUE)
public ModelAndView post(#ModelAttribute SignupRequest request){
// At this point, the SignupRequest is populated correctly
ModelAndView mAV = new ModelAndView("redirect:/success.jsp");
mAV.addObject("userName", request.getUserName());
return mAV;
}
}
Result
the client is redirected, but attributes are not set, and ${userName} is visible.
What is the correct way to do this?
Thanks!
EDIT
Additional details
Using SpringBoot with embedded Tomcat. JSP file located in src>main>resources>public. The raw JSP is being served. I believe the project is not treating JSP as it should. Adding POM deps.
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<exclusions>
<exclusion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jetty</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
</dependency>
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>18.0</version>
</dependency>
<dependency>
<groupId>commons-codec</groupId>
<artifactId>commons-codec</artifactId>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-email</artifactId>
<version>1.4</version>
</dependency>
<dependency>
<groupId>com.sun.xml.bind</groupId>
<artifactId>jaxb-impl</artifactId>
<version>2.2.11</version>
</dependency>
<dependency>
<groupId>javax.xml.bind</groupId>
<artifactId>jaxb-api</artifactId>
</dependency>
<dependency>
<groupId>com.sun.xml.bind</groupId>
<artifactId>jaxb-core</artifactId>
<version>2.2.11</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aspects</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
<dependency>
<groupId>commons-dbcp</groupId>
<artifactId>commons-dbcp</artifactId>
<version>1.4</version>
</dependency>
<dependency>
<groupId>org.javassist</groupId>
<artifactId>javassist</artifactId>
<version>3.23.1-GA</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-annotations</artifactId>
</dependency>
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>2.5</version>
</dependency>
</dependencies>

Answer 1

#Controller
public class MyController{
#RequestMapping(
value = "/submitForm",
method = RequestMethod.POST,
consumes = MediaType.APPLICATION_FORM_URLENCODED_VALUE)
public RedirectView post(#ModelAttribute SignupRequest request, RedirectAttributes ra){
// At this point, the SignupRequest is populated correctly
RedirectView rw = new RedirectView();
rw.setUrl("success.jsp");
ra.addFlashAttribute("userName", request.getUserName());
return rw;
}
}