From fda719d0ca243cd3cbacf8eb928ae6e238fbb6af Mon Sep 17 00:00:00 2001
From: Jimmy Praet <jimmy.praet@ksz-bcss.fgov.be>
Date: Mon, 9 Feb 2026 11:56:54 +0100
Subject: [PATCH] Fix concurrency issue in
 InputValidationIssues.BELGIF_ISSUE_TYPE_HREFS cache

---
 .../problem/api/InputValidationIssues.java    |  4 +--
 .../api/InputValidationIssuesTest.java        | 30 +++++++++++++++++++
 src/main/asciidoc/release-notes.adoc          |  6 ++++
 3 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/belgif-rest-problem/src/main/java/io/github/belgif/rest/problem/api/InputValidationIssues.java b/belgif-rest-problem/src/main/java/io/github/belgif/rest/problem/api/InputValidationIssues.java
index 23e74171..b3d6a3c5 100644
--- a/belgif-rest-problem/src/main/java/io/github/belgif/rest/problem/api/InputValidationIssues.java
+++ b/belgif-rest-problem/src/main/java/io/github/belgif/rest/problem/api/InputValidationIssues.java
@@ -3,9 +3,9 @@
 import java.net.URI;
 import java.time.temporal.Temporal;
 import java.util.Arrays;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.stream.Collectors;
 
 import io.github.belgif.rest.problem.config.ProblemConfig;
@@ -61,7 +61,7 @@ public class InputValidationIssues {
 
     public static final String DETAIL_JSON_SYNTAX_ERROR = "JSON syntax error";
 
-    private static final Map<URI, URI> BELGIF_ISSUE_TYPE_HREFS = new HashMap<>();
+    private static final Map<URI, URI> BELGIF_ISSUE_TYPE_HREFS = new ConcurrentHashMap<>();
 
     private InputValidationIssues() {
     }
diff --git a/belgif-rest-problem/src/test/java/io/github/belgif/rest/problem/api/InputValidationIssuesTest.java b/belgif-rest-problem/src/test/java/io/github/belgif/rest/problem/api/InputValidationIssuesTest.java
index edda833a..bb42165a 100644
--- a/belgif-rest-problem/src/test/java/io/github/belgif/rest/problem/api/InputValidationIssuesTest.java
+++ b/belgif-rest-problem/src/test/java/io/github/belgif/rest/problem/api/InputValidationIssuesTest.java
@@ -2,13 +2,19 @@
 
 import static org.assertj.core.api.Assertions.*;
 
+import java.lang.reflect.Field;
 import java.net.URI;
 import java.time.LocalDate;
 import java.time.OffsetDateTime;
 import java.time.OffsetTime;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
 import java.util.stream.Stream;
 
 import org.junit.jupiter.api.AfterEach;
@@ -765,6 +771,30 @@ void equalExpected(boolean extIssueTypes, boolean extInputsArray) {
                 .allMatch(this::isEmpty);
     }
 
+    @Test
+    @SuppressWarnings("unchecked")
+    void getHrefConcurrently() throws Exception {
+        Field field = InputValidationIssues.class.getDeclaredField("BELGIF_ISSUE_TYPE_HREFS");
+        field.setAccessible(true);
+        ((Map<URI, URI>) field.get(null)).clear();
+        int threads = 16;
+        ExecutorService executorService = Executors.newFixedThreadPool(threads);
+        List<Future<Void>> results = new ArrayList<>(threads);
+        for (int i = 0; i < threads; i++) {
+            results.add(executorService.submit(() -> {
+                assertThat(InputValidationIssues.schemaViolation(InEnum.BODY, "name", "value", "detail").getHref())
+                        .hasToString("https://www.belgif.be/specification/rest/api-guide/issues/schemaViolation.html");
+                assertThat(InputValidationIssues.invalidInput(InEnum.BODY, "name", "value", "detail").getHref())
+                        .hasToString("https://www.belgif.be/specification/rest/api-guide/issues/invalidInput.html");
+                return null;
+            }));
+        }
+        executorService.shutdown();
+        for (Future<Void> future : results) {
+            future.get();
+        }
+    }
+
     public boolean isEmpty(Object value) {
         return value == null || Integer.valueOf(0).equals(value) || Collections.emptyList().equals(value)
                 || Collections.emptyMap().equals(value);
diff --git a/src/main/asciidoc/release-notes.adoc b/src/main/asciidoc/release-notes.adoc
index a98575d1..f533ab63 100644
--- a/src/main/asciidoc/release-notes.adoc
+++ b/src/main/asciidoc/release-notes.adoc
@@ -12,6 +12,12 @@
 
 // tag::recent-versions[]
 
+== Version 0.21
+
+*belgif-rest-problem:*
+
+* Fix concurrency issue in InputValidationIssues.BELGIF_ISSUE_TYPE_HREFS cache
+
 == Version 0.20
 
 *belgif-rest-problem:*