From dda421519080b85fd5b41a48352e4716177d316c Mon Sep 17 00:00:00 2001
From: Lukas Eder <lukas.eder@gmail.com>
Date: Sun, 21 Mar 2021 19:31:25 +0100
Subject: [PATCH] [jOOQ/jOOQ#11684] Cannot use
 ConcurrentHashMap.computeIfAbsent()

Because that would prevent calling it recursively due to an implementation flaw in the JDK method.
---
 jOOQ/src/main/java/org/jooq/impl/Tools.java | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/jOOQ/src/main/java/org/jooq/impl/Tools.java b/jOOQ/src/main/java/org/jooq/impl/Tools.java
index 76c50f9040..b3453534d5 100644
--- a/jOOQ/src/main/java/org/jooq/impl/Tools.java
+++ b/jOOQ/src/main/java/org/jooq/impl/Tools.java
@@ -3354,8 +3354,20 @@ final class Tools {
             if (cacheOrNull == NULL)
                 return operation.get();
 
-            // The cache is guaranteed to be thread safe by the CacheProvider contract
-            Object result = ((Map<Object, Object>) cacheOrNull).computeIfAbsent(key.get(), k -> defaultIfNull(operation.get(), NULL));
+            // The cache is guaranteed to be thread safe by the CacheProvider
+            // contract. However since we cannot use ConcurrentHashMap.computeIfAbsent()
+            // recursively, we have to revert to double checked locking nonetheless.
+            Map<Object, Object> cache = (Map<Object, Object>) cacheOrNull;
+            Object result = cache.get(key);
+            if (result == null) {
+                synchronized (cache) {
+                    result = cache.get(key);
+
+                    if (result == null)
+                        cache.put(key, (result = operation.get()) == null ? NULL : result);
+                }
+            }
+
             return (V) (result == NULL ? null : result);
         }