修复DigestUtils在多线程下的问题

hsweb-core/src/test/java/org/hswebframework/web/utils/DigestUtilsTest.java

@@ -0,0 +1,28 @@
+package org.hswebframework.web.utils;
+
+import lombok.SneakyThrows;
+import org.junit.Test;
+
+import java.util.HashSet;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+
+import static org.junit.Assert.*;
+
+public class DigestUtilsTest {
+
+
+    @Test
+    @SneakyThrows
+    public void test() {
+        Set<String> check = ConcurrentHashMap.newKeySet();
+
+        for (int i = 0; i < 1000; i++) {
+            new Thread(() -> check.add(DigestUtils.md5Hex("test")))
+                    .start();
+        }
+        Thread.sleep(1000);
+        System.out.println(check);
+        assertEquals(1, check.size());
+    }
+}