feat: Allow override of the message property for a violation exception

src/docs/asciidoc/index.adoc

@@ -472,8 +472,58 @@ The response JSON:
 
 ==== General override of error messages
 
-By using `error.handling.messages` property, it is possible to globally set an error message for a certain exception.
-This is most useful for the validation messages.
+By using `error.handling.messages` property, it is possible to globally set an error message for a certain exception or a certain validation annotation.
+
+===== Exception
+
+Suppose you have this defined:
+
+[source,properties]
+----
+error.handling.messages.com.company.application.user.UserNotFoundException=The user was not found
+----
+
+The response JSON:
+
+[source,json]
+----
+{
+  "code": "USER_NOT_FOUND",
+  "message": "The user was not found" //<.>
+}
+----
+
+<.> The output uses the configured override.
+
+This can also be used for exception types that are not part of your own application.
+
+For example:
+
+[source,properties]
+----
+error.handling.messages.jakarta.validation.ConstraintViolationException=There was a validation failure.
+----
+
+Will output the following JSON:
+
+[source,json]
+----
+{
+  "code": "VALIDATION_FAILED",
+  "message": "There was a validation failure.",
+  "fieldErrors": [
+    {
+      "code": "INVALID_SIZE",
+      "property": "name",
+      "message": "size must be between 10 and 2147483647",
+      "rejectedValue": "",
+      "path": "name"
+    }
+  ]
+}
+----
+
+===== Validation annotation
 
 Suppose you have this defined:
 

src/main/java/io/github/wimdeblauwe/errorhandlingspringbootstarter/handler/ConstraintViolationApiExceptionHandler.java

@@ -4,14 +4,13 @@
 import io.github.wimdeblauwe.errorhandlingspringbootstarter.mapper.ErrorCodeMapper;
 import io.github.wimdeblauwe.errorhandlingspringbootstarter.mapper.ErrorMessageMapper;
 import io.github.wimdeblauwe.errorhandlingspringbootstarter.mapper.HttpStatusMapper;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-import org.springframework.http.HttpStatus;
-
 import jakarta.validation.ConstraintViolation;
 import jakarta.validation.ConstraintViolationException;
 import jakarta.validation.ElementKind;
 import jakarta.validation.Path;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.http.HttpStatus;
 
 import java.util.Comparator;
 import java.util.Optional;
@@ -136,6 +135,7 @@ private String getMessage(ConstraintViolation<?> constraintViolation) {
     }
 
     private String getMessage(ConstraintViolationException exception) {
-        return "Validation failed. Error count: " + exception.getConstraintViolations().size();
+        return errorMessageMapper.getErrorMessageIfConfiguredInProperties(exception)
+                                 .orElseGet(() -> "Validation failed. Error count: " + exception.getConstraintViolations().size());
     }
 }

src/main/java/io/github/wimdeblauwe/errorhandlingspringbootstarter/mapper/ErrorMessageMapper.java

@@ -2,6 +2,8 @@
 
 import io.github.wimdeblauwe.errorhandlingspringbootstarter.ErrorHandlingProperties;
 
+import java.util.Optional;
+
 import static org.springframework.util.StringUtils.hasText;
 
 /**
@@ -22,6 +24,10 @@ public String getErrorMessage(Throwable exception) {
         return exception.getMessage();
     }
 
+    public Optional<String> getErrorMessageIfConfiguredInProperties(Throwable exception) {
+        return Optional.ofNullable(getErrorMessageFromProperties(exception.getClass()));
+    }
+
     public String getErrorMessage(String fieldSpecificCode, String code, String defaultMessage) {
         if (properties.getMessages().containsKey(fieldSpecificCode)) {
             return properties.getMessages().get(fieldSpecificCode);

src/test/java/io/github/wimdeblauwe/errorhandlingspringbootstarter/handler/ConstraintViolationApiExceptionHandlerTest.java

@@ -110,6 +110,20 @@ void testErrorCodeOverride(@Autowired ErrorHandlingProperties properties) throws
         ;
     }
 
+    @Test
+    @WithMockUser
+    void testErrorMessageOverride(@Autowired ErrorHandlingProperties properties) throws Exception {
+        properties.getMessages().put("jakarta.validation.ConstraintViolationException", "There was a validation failure.");
+        mockMvc.perform(post("/test/validation")
+                                .contentType(MediaType.APPLICATION_JSON)
+                                .content("{\"value2\": \"\"}")
+                                .with(csrf()))
+               .andExpect(status().isBadRequest())
+               .andExpect(jsonPath("code").value("VALIDATION_FAILED"))
+               .andExpect(jsonPath("message").value("There was a validation failure."))
+        ;
+    }
+
     @Test
     @WithMockUser
     void testFieldErrorCodeOverride(@Autowired ErrorHandlingProperties properties) throws Exception {