How can I show custom error messages using Thymeleaf? - spring

Question

I'm trying to do CRUD operations with Spring. I'm using HTML and Thymeleaf on the frontend. I return the results of certain actions I have made and error messages, if any, using a custom class that I write. I don't have any problems so far. However, if an error occurs during these operations and I return this error through the class I wrote, I do not know how to display it on HTML using Thymeleaf.
I'm returning an object of this class type;
#Getter
#Setter
public class WarehouseAPIResponseHolder<T> {
private T responseData;
private HttpStatus httpStatus;
private WarehouseAPIResponseError error;
public WarehouseAPIResponseHolder(HttpStatus httpStatus) {
this.httpStatus = httpStatus;
}
public WarehouseAPIResponseHolder(T responseData, HttpStatus httpStatus) {
this.responseData = responseData;
this.httpStatus = httpStatus;
}
public WarehouseAPIResponseHolder(HttpStatus httpStatus,
WarehouseAPIResponseError error) {
this.httpStatus = httpStatus;
this.error = error;
}
}
My error class;
#Getter
#Builder
public class WarehouseAPIResponseError {
private String code;
private String message;
}
Example of an error;
if (CollectionUtils.isEmpty(warehouseEntities)) {
return new WarehouseAPIResponseHolder<>(HttpStatus.NOT_FOUND, WarehouseAPIResponseError
.builder()
.code("DATA_NOT_FOUND")
.message("No records found in the database.")
.build());
}
The method in my controller class;
#GetMapping
public String getAllWarehouses(Model model) {
model.addAttribute("listOfWarehouses",warehouseCRUDService.list().getResponseData());
return "warehouses";
}
My HTML code;
<div class="container my-2">
<h1 align="center">Warehouse List</h1>
<table>
<thead>
<tr>
<th>ID</th>
<th>Code</th>
<th>Name</th>
<th>Status</th>
</tr>
</thead>
<tbody>
<tr th:each="warehouse : ${listOfWarehouses}">
<td th:text="${warehouse.id}"></td>
<td th:text="${warehouse.code}"></td>
<td th:text="${warehouse.name}"></td>
<td th:text="${warehouse.status}"></td>
</tr>
</tbody>
</table>
</div>
I am successfully listing, but if there is an error message I don't know how to display it. I did not use Spring validation methods. Is there any way I can do this in a simple way?

Answer 1

You can set the error on backend using model.addAttribute("errorMessage", error)
and then show it in an element if error exists. For example:
<span th:if="${errorMessage != null}" th:text=${errorMessage}/>