SpringBoot Web, JPA, JSP with JSTL - type conversion error - spring-boot

Question

I am trying to use Spring Boot Web with a JSP and JSTL combination. All is well, except the Update method for the JPA queries.
When I submit the form for the edit page, I always get a Type Conversion error for my #Entity which has an #Id column of datatype Long. The control does not even come to the Controller Method with the URL pattern /update, even when I make it hidden in the form:hidden tag.
I am clueless, how to go past this issue?
FYI, I am pasting the relevant sections of the code.
Entity - Quote.java
#Entity
#Data
public class Quote { //implements Auditable {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "id", nullable = false)
private Long id;
#Column(name = "quote")
#NonNull
private String quote;
...
//other attributes omitted for brevity
}
Controller Method - QuoteController.java
#RequestMapping(value = "/update",method = RequestMethod.POST)
public String updateQuote(#ModelAttribute("quote") Quote quote, Model model,
BindingResult bindingResult) {
LOGGER.info("/update POST request received, quote :: " + quote);
if (bindingResult.hasErrors()) {
LOGGER.error("/update POST request has errors :: " + bindingResult.getAllErrors());
model.addAttribute("error", bindingResult.getAllErrors());
return "qms/edit";
}
quoteService.updateQuote(quote);
return "qms/list";
}
JSP - edit.jsp
<%# include file="header.jsp"%>
<h3>Edit a Quote</h3>
<c:choose>
<c:when test="${error}">
<div>
<span class='error'>No matching quotes. Try again!</span>
</div>
<div>
<b>Errors : </b> : ${error}
</div>
</c:when>
<c:otherwise>
<c:url var="update_quote_url" value="/qms/update"/>
<form:form action="${update_quote_url}" method="post" modelAttribute="quote">
<form:errors path="*" cssClass="errorBox"/>
<table class='table table-striped'>
<form:hidden path="id"/>
<tr>
<td>
<form:label path="id">Id: </form:label>
</td>
<td>
<form:label path="id">${quote.id}</form:label>
</td>
</tr>
<tr>
<td>
<form:label path="quote">Quote: </form:label>
</td>
<td>
<form:input type="text" path="quote" size="50"
placeholder="Beginning is half done!"
value="${quote.quote}"/>
</td>
</tr>
<tr>
<td>
<form:label path="category">Category: </form:label>
</td>
<td>
<form:input type="text" path="category" size="50"
placeholder="Motivation" value="${quote.category}"/>
</td>
</tr>
<tr>
<td>
<form:label path="author">Author Name: </form:label>
</td>
<td>
<form:input type="text" path="author" size="50"
placeholder="Raghavan Muthu" value="${quote.author}"/>
</td>
</tr>
<tr>
` <td colspan="2" class='colspan2'>
<input type="submit" value="Update"/>
</td>`
</tr>
</table>
</form:form>
</c:otherwise>
</c:choose>
<%# include file="footer.jsp"%>
Error
Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.
Mon Sep 20 14:21:03 IST 2021
There was an unexpected error (type=Bad Request, status=400).
Failed to convert value of type 'java.lang.String' to required type 'com.raghsonline.springbootweb.qms.model.Quote'; nested exception is org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type [java.lang.Long] for value 'When you learn a little, you feel you know a lot. But when you learn a lot, you realize that you know very little.'; nested exception is java.lang.NumberFormatException: For input string: "Whenyoulearnalittle,youfeelyouknowalot.Butwhenyoulearnalot,yourealizethatyouknowverylittle."
org.springframework.beans.TypeMismatchException: Failed to convert value of type 'java.lang.String' to required type 'com.raghsonline.springbootweb.qms.model.Quote'; nested exception is org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type [java.lang.Long] for value 'When you learn a little, you feel you know a lot. But when you learn a lot, you realize that you know very little.'; nested exception is java.lang.NumberFormatException: For input string: "Whenyoulearnalittle,youfeelyouknowalot.Butwhenyoulearnalot,yourealizethatyouknowverylittle."
at org.springframework.beans.TypeConverterSupport.convertIfNecessary(TypeConverterSupport.java:79)
at org.springframework.beans.TypeConverterSupport.convertIfNecessary(TypeConverterSupport.java:53)
at org.springframework.validation.DataBinder.convertIfNecessary(DataBinder.java:696)
Question
Why it always considers the #Id Column?
Usage of DTO - a different issue
I have used a DTO which has all the attributes of the main Entity except the #Id column, in the Controller method. However, it has a different issue. It inserts a new record in DB because it does not have the ID attribute.
#RequestMapping(value = "/update",method = RequestMethod.POST)
public String updateQuote(#ModelAttribute("quote") QuoteDTO quoteDTO, Model model,
BindingResult bindingResult) {
LOGGER.info("/update POST request received, quote :: " + quoteDTO);
if (bindingResult.hasErrors()) {
LOGGER.error("/update POST request has errors :: " + bindingResult.getAllErrors());
model.addAttribute("error", bindingResult.getAllErrors());
return "qms/edit";
}
//Convert from the DTO to Model
Quote quote = getModelFromDTO(quoteDTO);
quoteService.updateQuote(quote);
return "qms/list";
}
Any help will be highly appreciated.
Thanks.

Answer 1

A few things solved this issue.
Added the type field for the ID column in the element, where it resolved the type mismatch issue. Thanks to Mohammed Khan for the hint. I kinda ignored it earlier.
Also there was a clash with the actual quote ('quote') of the Model object and also the reference variable of the ModelAttribute ('quote'). I updated the model object to 'quoteObj`, which also helped the issue to be resolved.
Still the /id in the #PathVariable was not working well.. I have updated the #PathVariable in the URL, where instead of having it as /qms/update/{id} , now it is just /qms/update because I get the Model Attribute in the Request Body.
Additionally I enabled the Web Development tool (Network mode/Tab) on the browser to inspect the REQ and RESP elements for each URL being hit. It helped me ensure that the right values are actually passed from the UI to Controller.
My final method now looks like this.
#RequestMapping(value = "/update",method = RequestMethod.POST)
public String updateQuote(#ModelAttribute("quoteObj") Quote quoteObj) {
LOGGER.info("/update POST request received, quote :: " + quoteObj);
quoteService.updateQuote(quoteObj);
return "qms/list";
}
And the form element looks like this.
<tr>
<td>
<form:label path="id">Id: </form:label>
</td>
<td>
<%-- ${quote.id} --%>
<form:input path="id" type="number" value="${quote.id}"/>
</td>
</tr>