feat: fix ConcurrentModificationException bug that breaks Enforcer wh…

…en calling Enforce() (#390)

examples/haslink_synchronized_model.conf

@@ -0,0 +1,14 @@
+[request_definition]
+r = sub, obj
+
+[policy_definition]
+p = sub, obj, eft
+
+[role_definition]
+g = _, _
+
+[policy_effect]
+e = !some(where (p.eft == deny))
+
+[matchers]
+m = r.sub == p.sub && g(r.obj, p.obj)

src/main/java/org/casbin/jcasbin/rbac/DefaultRoleManager.java

@@ -176,7 +176,7 @@ public void deleteLink(String name1, String name2, String... domain) {
      * hasLink determines whether role: name1 inherits role: name2. domain is a prefix to the roles.
      */
     @Override
-    public boolean hasLink(String name1, String name2, String... domain) {
+    public synchronized boolean hasLink(String name1, String name2, String... domain) {
         if (name1.equals(name2) || (this.matchingFunc != null && this.matchingFunc.test(name1, name2))) {
             return true;
         }

src/test/java/org/casbin/jcasbin/main/EnforcerUnitTest.java

@@ -19,17 +19,21 @@
 import org.casbin.jcasbin.model.Model;
 import org.casbin.jcasbin.persist.Adapter;
 import org.casbin.jcasbin.persist.file_adapter.FileAdapter;
+import org.casbin.jcasbin.util.BuiltInFunctions;
 import org.casbin.jcasbin.util.EnforceContext;
 import org.casbin.jcasbin.util.Util;
 import org.junit.Assert;
 import org.junit.Test;
 
+import java.io.File;
 import java.io.FileInputStream;
 import java.io.IOException;
+import java.nio.file.Files;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.CountDownLatch;
 
 import static java.util.Arrays.asList;
 import static org.casbin.jcasbin.main.CoreEnforcer.newModel;
@@ -632,6 +636,64 @@ public void testMultiplePolicyDefinitions() {
         testEnforceWithContext(e, enforceContext, new AbacAPIUnitTest.TestEvalRule("alice", 30), "/data1", "read", true);
     }
 
+    @Test
+    public void testHasLinkSynchronized(){
+        File testingDir = null;
+        try {
+            testingDir = Files.createTempDirectory("testingDir").toFile();
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+
+        File f = null;
+        try {
+            f = File.createTempFile("policies", null, testingDir);
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+
+        FileAdapter a = new FileAdapter(f.getAbsolutePath());
+
+        Enforcer e = new Enforcer("examples/haslink_synchronized_model.conf", a);
+
+        e.enableAutoSave(true);
+        e.addNamedMatchingFunc("g", "keyMatch4", BuiltInFunctions::keyMatch4);
+
+        // 添加 gs 角色的关系
+        String[][] gs = new String[1001][3];
+        gs[0] = new String[]{"[email protected]", "temp", "alice"};
+        for (int i = 0; i < 1000; i++) {
+            gs[i+1] = new String[]{i + "@alice.co", "temp", "alice"};
+        }
+        e.addGroupingPolicies(gs);
+
+        String[][] policy = {{"alice", "/data", "allow"}};
+        e.addPolicies(policy);
+        e.savePolicy();
+
+        int n = 100;
+        CountDownLatch countDownLatch = new CountDownLatch(n);
+
+        for (int i = 0; i < n; i++) {
+            int finalI = i;
+            new Thread(() -> {
+                boolean res = e.enforce("alice", "data");
+                if (!res){
+                    System.out.println("result failure: " + finalI);
+                }
+                countDownLatch.countDown();
+            }).start();
+        }
+
+        try {
+            countDownLatch.await();
+        } catch (InterruptedException ex) {
+            ex.printStackTrace();
+        }
+
+        System.out.println("Done!");
+    }
+
     public static class TestSub{
         private String name;