Question 302185 in Html Question posted in
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Html – How to use abstract class from Thymeleaf template to Spring boot controller?

I have this structure model for my application :

public class Garage
List<Vehicule> vehicules;

...

public abstract class Vehicule
List<Wheel> wheels

...

public class Car extends Vehicule
public class Bike extends Vehicule

... 

public class Wheel
boolean damaged

And I have a form which contains a checkbox input to let him know if a wheel is damaged :

<form id="garage"
      action="#"
      th:action="@{/save}"
      th:object="${garage}"
      method="post">
            <div th:each="vehicule, i : ${garage.getVehicules()}">
               <ul>
                  <li th:each="wheel, j : ${garage.getWheels()}">
                     <input type="checkbox" th:field="*{{vehicules[__${i.index}__].wheels}}" th:value="${wheel}" />
                    <label th:for="${#ids.next('wheels')}" th:text="${wheel.value}">Label</label>
                  </li>
               </ul>
            </div>
<input type="submit" value="Submit" /> <input type="reset" value="Reset" />
</form>

What I get is this error because of abstract keyword on my vehicule class :

java.lang.InstantiationException: null
at java.base/jdk.internal.reflect.InstantiationExceptionConstructorAccessorImpl.newInstance(InstantiationExceptionConstructorAccessorImpl.java:48) ~[na:na] at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:502) ~[na:na] at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:486) ~[na:na] at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:197)

Last thing, this is not my real code but it’s to provide you the most similar context for the question.

Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    Ok, as Alfred said I use DTO now.

    But I found the solution for my original question with a Converter configuration class and a hidden input in the template :

    <input type="hidden" th:field="*{vehicules[__${i.index}__]}" />

    public class VehiculeConverter implements Converter<String, Vehicule> {
    @Override
    public Vehicule convert(String source) {
        // return Car or Bike
    }
}

    @Configuration
public class FormattersConfig implements WebMvcConfigurer {
    @Override
    public void addFormatters(FormatterRegistry registry) {
        registry.addConverter(new VehiculeConverter());
    }
}

    What I understand is in the template the hidden field calls the converter because the controller needs to create Vehicule object from a String. It works even with abstract keyword.


  2. 0

    It means obviously, you handled abstraction inappropriately. You can always use/create Data Transfer Objects as the middleman to handle your data to and from thymeleaf forms.

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