fix: Add GraalVM configuration for the JDK's DNS Resolver.

This fixes the GraalVM distribution so that it can resolve DNS Names.

Author: hessjcg

core/src/main/java/com/google/cloud/sql/core/JndiDnsResolver.java

@@ -18,7 +18,9 @@
 
 import java.util.Collection;
 import java.util.Collections;
+import java.util.Hashtable;
 import java.util.stream.Collectors;
+import javax.naming.Context;
 import javax.naming.NameNotFoundException;
 import javax.naming.NamingException;
 import javax.naming.directory.Attribute;
@@ -51,13 +53,18 @@ class JndiDnsResolver implements DnsResolver {
    * @throws javax.naming.NameNotFoundException when the domain name did not resolve.
    */
   @Override
+  @SuppressWarnings("JdkObsolete")
   public Collection<String> resolveTxt(String domainName)
       throws javax.naming.NameNotFoundException {
     try {
       // Notice: This is old Java 1.2 style code. It uses the ancient JNDI DNS Provider api.
       // See https://docs.oracle.com/javase/7/docs/technotes/guides/jndi/jndi-dns.html
+
+      Hashtable contextProps = new Hashtable<>();
+      contextProps.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.dns.DnsContextFactory");
+      contextProps.put(Context.OBJECT_FACTORIES, "com.sun.jndi.url.dns.dnsURLContextFactory");
       Attribute attr =
-          new InitialDirContext()
+          new InitialDirContext(contextProps)
               .getAttributes(jndiPrefix + domainName, new String[] {"TXT"})
               .get("TXT");
       // attr.getAll() returns a Vector containing strings, one for each record returned by dns.

core/src/main/java/com/google/cloud/sql/nativeimage/CloudSqlFeature.java

@@ -45,6 +45,8 @@ final class CloudSqlFeature implements Feature {
   private static final String POSTGRES_SOCKET_CLASS = "com.google.cloud.sql.postgres.SocketFactory";
 
   private static final String MYSQL_SOCKET_CLASS = "com.google.cloud.sql.mysql.SocketFactory";
+  private static final String JNDI_DNS_FACTORY = "com.sun.jndi.dns.DnsContextFactory";
+  private static final String JNDI_DNS_OBJECT_FACTORY = "com.sun.jndi.url.dns.dnsURLContextFactory";
 
   @Override
   public void beforeAnalysis(BeforeAnalysisAccess access) {
@@ -55,6 +57,10 @@ public void beforeAnalysis(BeforeAnalysisAccess access) {
     // The Core Cloud SQL Socket
     NativeImageUtils.registerClassForReflection(access, CLOUD_SQL_SOCKET_CLASS);
 
+    // The JNDI DNS factory for looking up DNS names.
+    NativeImageUtils.registerClassForReflection(access, JNDI_DNS_FACTORY);
+    NativeImageUtils.registerClassForReflection(access, JNDI_DNS_OBJECT_FACTORY);
+
     // Register Hikari configs if used with Cloud SQL.
     if (access.findClassByName("com.zaxxer.hikari.HikariConfig") != null) {
       NativeImageUtils.registerClassForReflection(access, "com.zaxxer.hikari.HikariConfig");

core/src/main/resources/META-INF/native-image/com.google.cloud.sql/cloud-sql-jdbc-socket-factory-parent/proxy-config.json

@@ -18,5 +18,17 @@
       "jnr.enxio.channels.Native$LibC",
       "jnr.ffi.provider.LoadedLibrary"
     ]
+  },
+  {
+    "name": "com.sun.jndi.dns.DnsContextFactory",
+    "interfaces": [
+      "javax.naming.spi.InitialContextFactory"
+    ]
+  },
+  {
+    "name": "com.sun.jndi.url.dns.dnsURLContextFactory",
+    "interfaces": [
+      "javax.naming.spi.ObjectFactory"
+    ]
   }
 ]

core/src/main/resources/META-INF/native-image/com.google.cloud.sql/cloud-sql-jdbc-socket-factory-parent/resource-config.json

@@ -2,6 +2,7 @@
   "resources":[
     {"pattern":"\\Qcom.google.cloud.sql/project.properties\\E"},
     {"pattern":"\\QMETA-INF/services/java.sql.Driver\\E"},
+    {"pattern":"\\QMETA-INF/services/java.sql.Driver\\E"},
     {"pattern":"\\Qcom/mysql/cj/util/TimeZoneMapping.properties\\E"},
     {"pattern":"jni/.*\\.so"},
     {"pattern":"jni/.*\\.dll"}

core/src/test/java/com/google/cloud/sql/core/JndiDnsResolverTest.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Licensed 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 com.google.cloud.sql.core;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import java.util.Collection;
+import org.junit.Test;
+
+public class JndiDnsResolverTest {
+  @Test
+  public void testResolveName() throws Exception {
+    JndiDnsResolver r = new JndiDnsResolver();
+    Collection<String> got = r.resolveTxt("valid-san-test.csqlconnectortest.com");
+    assertThat(got)
+        .containsExactly("cloud-sql-connector-testing:us-central1:postgres-customer-cas-test");
+  }
+}