Add test case for #1668

querydsl-core/src/test/java/com/querydsl/core/CycleClassInitDependencyTest.java

@@ -0,0 +1,61 @@
+package com.querydsl.core;
+
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.util.Collection;
+
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.reflections.util.ClasspathHelper;
+
+public class CycleClassInitDependencyTest {
+
+    private static ClassLoader loader;
+
+    @BeforeClass
+    public static void overrideClassLoader() {
+        loader = Thread.currentThread().getContextClassLoader();
+        Collection<URL> urls = ClasspathHelper.forClassLoader();
+        ClassLoader cl = URLClassLoader.newInstance(urls.toArray(new URL[urls.size()]), null/*no delegation*/);
+        Thread.currentThread().setContextClassLoader(cl);
+    }
+
+    @AfterClass
+    public static void resetClassLoader() {
+        Thread.currentThread().setContextClassLoader(loader);
+    }
+
+    @Test(timeout = 2000)
+    public void test() throws InterruptedException {
+
+        // each thread wants to load one part of the dependency circle
+        Thread t1 = new Thread(new LoadClassRunnable("com.querydsl.core.types.dsl.NumberExpression"));
+        Thread t2 = new Thread(new LoadClassRunnable("com.querydsl.core.types.dsl.Expressions"));
+        t1.start();
+        t2.start();
+
+        t1.join();
+
+    }
+
+    private static class LoadClassRunnable implements Runnable {
+
+        private final String classToLoad;
+
+        public LoadClassRunnable(String classToLoad) {
+            this.classToLoad = classToLoad;
+        }
+
+        @Override
+        public void run() {
+            try {
+                Class.forName(classToLoad, true, Thread.currentThread().getContextClassLoader());
+            } catch (ClassNotFoundException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+    }
+
+}