From 39132718fbf7cd43d1dbee5fd5365638ddd9fd90 Mon Sep 17 00:00:00 2001
From: Brett Okken <brett.okken.os@gmail.com>
Date: Thu, 4 May 2023 12:52:29 -0500
Subject: [PATCH] retry looking up a class if trying to define it fails

---
 .../dynamic/loading/ClassInjector.java          | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/byte-buddy-dep/src/main/java/net/bytebuddy/dynamic/loading/ClassInjector.java b/byte-buddy-dep/src/main/java/net/bytebuddy/dynamic/loading/ClassInjector.java
index 5880b2dde6f..c51ad13508a 100644
--- a/byte-buddy-dep/src/main/java/net/bytebuddy/dynamic/loading/ClassInjector.java
+++ b/byte-buddy-dep/src/main/java/net/bytebuddy/dynamic/loading/ClassInjector.java
@@ -1818,9 +1818,24 @@ public Map<String, Class<?>> injectRaw(Map<? extends String, byte[]> types) {
                     : classLoader) {
                 for (Map.Entry<? extends String, byte[]> entry : types.entrySet()) {
                     try {
+                        // first try to load the class from the given class loader
                         result.put(entry.getKey(), Class.forName(entry.getKey(), false, classLoader));
                     } catch (ClassNotFoundException ignored) {
-                        result.put(entry.getKey(), dispatcher.defineClass(classLoader, entry.getKey(), entry.getValue(), protectionDomain));
+                        try {
+                            // if the class does not exist, try to define it
+                            result.put(entry.getKey(), dispatcher.defineClass(classLoader, entry.getKey(), entry.getValue(), protectionDomain));
+                        } catch (Exception defFailure) {
+                            // when the bootstrap loader is in use (i.e. the classloader is null), synchronizing on the BOOTSTRAP_LOADER_LOCK
+                            // is sufficient to prevent this instance of ClassInjector from concurrently trying to define a class.
+                            // however, in an environment where many ClassInjectors exist (either because shaded into multiple projects or
+                            // it is present in multiple classloaders)
+                            try {
+                                result.put(entry.getKey(), Class.forName(entry.getKey(), false, classLoader));
+                            } catch (ClassNotFoundException ignored2) {
+                                //throw the failure from actually trying to define the class
+                                throw defFailure;
+                            }
+                        }
                     }
                 }
             }