Fix MongoDBIO ignore SSL KeyStore not initialized (#29403)

Co-authored-by: Yi Hu <yathu@google.com>

sdks/java/io/mongodb/src/main/java/org/apache/beam/sdk/io/mongodb/SSLUtils.java

@@ -68,12 +68,12 @@ static SSLContext ignoreSSLCertificate() {
       InputStream inputStream = classLoader.getResourceAsStream("resources/.keystore");
       if (inputStream != null) {
         LOG.info("Found keystore in classpath 'resources/.keystore'. Loading...");
-        ks.load(inputStream, "changeit".toCharArray());
       } else {
         LOG.info(
             "Unable to find keystore under 'resources/.keystore' in the classpath. "
                 + "Continuing with an empty keystore.");
       }
+      ks.load(inputStream, "changeit".toCharArray());
       KeyManagerFactory kmf =
           KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm());
       kmf.init(ks, "changeit".toCharArray());

sdks/java/io/mongodb/src/test/java/org/apache/beam/sdk/io/mongodb/SSLUtilsTest.java

@@ -0,0 +1,32 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.beam.sdk.io.mongodb;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Test on the MongoDbIO SSLUtils. */
+@RunWith(JUnit4.class)
+public class SSLUtilsTest {
+  @Test
+  public void testIgnoreSSLCertificate() {
+    // smoke test
+    SSLUtils.ignoreSSLCertificate();
+  }
+}