[FIXED] Neither BindingResult nor plain target object for bean name 'watchlist' available as request attribute

Issue

I've been trying to submit an html form to spring boot but can't get it working.

I have this in my pom.xml

<!-- Enable JSP with Spring Boot  -->
<dependency>
    <groupId>org.apache.tomcat.embed</groupId>
    <artifactId>tomcat-embed-jasper</artifactId>
    <scope>provided</scope>
</dependency>       

I have this in my application.properties file:

spring.mvc.view.prefix=/WEB-INF/views/
spring.mvc.view.suffix=.jsp

I have created a jsp page in <project-name>/src/main/webapp/WEB-INF/views/index.jsp

At the very top of that page, I put

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>  

I also have a similar html file called index.html located in

<project-name>/src/main/resources/static/index.html

But the code doesn't seem to be recognizing the taglib because I see this in the web page:

Notice how the taglib is not recognized and just prints it at the top of the page?

So I delete the index.html page to force it to find the index.jsp file instead. In that case I see the following error in the web page:

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

Sun Oct 18 11:11:20 MDT 2020 There was an unexpected error (type=Internal Server Error, status=500). Neither BindingResult nor plain target object for bean name 'watchlist' available as request attribute

Here is the part of the jsp file that sends the form:

<dialog id="favDialog">
   <form:form method="POST" action="/api/v1/AddSymbolToWatchlist" modelAttribute="watchlist">
      <form:label path="symbol">Enter Symbol:</form:label>
      <form:input path="symbol"/><br><br>
      <form:button>Add</form:button>
   </form:form>
</dialog>

My spring boot controller looks like this:

@RequestMapping(value = "/AddSymbolToWatchlist", method = RequestMethod.POST)
public String addSymbolToWatchlist(@Valid @ModelAttribute("watchlist") Watchlist watchlist,
        BindingResult result, ModelMap modelMap) {
    if (result.hasErrors()) {
        return "error";
    }
    System.out.println("symbol="+watchlist.getSymbol());

    return watchlistService.addSymbolToWatchlist(watchlist);
}

The error seems to imply that I have already clicked the button that posts the request, but I haven't.

What am I doing wrong?

EDIT Per gtiwari333 response I changed the controller to look like this:

    @RequestMapping(value = "/AddSymbolToWatchlist", method = RequestMethod.POST)
    public String addSymbolToWatchlist(@ModelAttribute("watchlist") Watchlist watchlist, Model m){
        String symbol = watchlist.getSymbol();
        System.out.println("symbol=" +symbol);
        Watchlist wlist = new Watchlist();
        wlist.setSymbol(symbol);
        m.addAttribute("msg", symbol +" was submitted.");
        m.addAttribute("watchlist", wlist);

        return "index";
    }

class Watchlist {
     String symbol;
     
     public String getSymbol() {
         return symbol;
     }
     public void setSymbol(String sym) {
         this.symbol = sym;
     }
}

And the popup form in index.jsp looks like this:

<dialog id="favDialog">
   <h2>Message: ${msg}</h2>
   <form:form method="POST" action="/api/v1/AddSymbolToWatchlist" modelAttribute="watchlist">
      <form:label path="symbol">Enter Symbol:</form:label>
      <form:input path="symbol"/><br><br>
      <form:button>Add</form:button>
   </form:form>
</dialog>

Solution

If you use modelAttribute="watchlist" on your jsp, you must return the Model with attribute watchlist as following

 @GetMapping("/")
 String index(Model m) {
   // you should have this so that modelAttribute="watchlist" on jsp renders
   m.addAttribute("watchlist", new Watchlist()); 

   return "myjspform";
 }

Here's working code:

package soquestion64416269;

import lombok.Data;
import lombok.RequiredArgsConstructor;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.*;

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

@Controller
@RequiredArgsConstructor
class Ctrl {

    @GetMapping("/")
    String index(Model m) {
        m.addAttribute("msg", "Enter symbol and click Add");
        m.addAttribute("watchlist", new Watchlist());

        return "myjspform";
    }

    @PostMapping(value = "/AddSymbolToWatchlist")
    public String addSymbolToWatchlist(@ModelAttribute("watchlist") Watchlist watchlist, Model m) {
        m.addAttribute("msg", watchlist.getSymbol() + " was submitted. Now enter new symbol and click Add");
        m.addAttribute("watchlist", new Watchlist());

        return "myjspform";
    }
}

@Data
class Watchlist {
    String symbol;
}

myjspform.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1" %>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<!DOCTYPE html>
<html lang="en">
<body>

<h2>Message: ${msg}</h2>

<form:form method="POST" action="/AddSymbolToWatchlist" modelAttribute="watchlist">
    <form:label path="symbol">Enter Symbol:</form:label>
    <form:input path="symbol"/><br><br>
    <form:button>Add</form:button>
</form:form>

</body>
</html>

Answered By - gtiwari333
Answer Checked By - Clifford M. (JavaFixing Volunteer)