xds: replace static initializers with hardcoded registration of 3 cert providers (#7606)

Author: sanjaypujare

xds/src/main/java/io/grpc/xds/internal/certprovider/CertificateProviderRegistry.java

@@ -38,6 +38,10 @@ public CertificateProviderRegistry() {
   public static synchronized CertificateProviderRegistry getInstance() {
     if (instance == null) {
       instance = new CertificateProviderRegistry();
+      // TODO(sanjaypujare): replace with Java's SPI mechanism and META-INF resource
+      instance.register(new FileWatcherCertificateProviderProvider());
+      instance.register(new DynamicReloadingCertificateProviderProvider());
+      instance.register(new MeshCaCertificateProviderProvider());
     }
     return instance;
   }

xds/src/main/java/io/grpc/xds/internal/certprovider/DynamicReloadingCertificateProviderProvider.java

@@ -43,19 +43,17 @@ final class DynamicReloadingCertificateProviderProvider implements CertificatePr
 
   static final String DYNAMIC_RELOADING_PROVIDER_NAME = "gke-cas-certs";
 
-  static {
-    CertificateProviderRegistry.getInstance()
-        .register(
-            new DynamicReloadingCertificateProviderProvider(
-                DynamicReloadingCertificateProvider.Factory.getInstance(),
-                ScheduledExecutorServiceFactory.DEFAULT_INSTANCE,
-                TimeProvider.SYSTEM_TIME_PROVIDER));
-  }
-
   final DynamicReloadingCertificateProvider.Factory dynamicReloadingCertificateProviderFactory;
   private final ScheduledExecutorServiceFactory scheduledExecutorServiceFactory;
   private final TimeProvider timeProvider;
 
+  DynamicReloadingCertificateProviderProvider() {
+    this(
+        DynamicReloadingCertificateProvider.Factory.getInstance(),
+        ScheduledExecutorServiceFactory.DEFAULT_INSTANCE,
+        TimeProvider.SYSTEM_TIME_PROVIDER);
+  }
+
   @VisibleForTesting
   DynamicReloadingCertificateProviderProvider(
       DynamicReloadingCertificateProvider.Factory dynamicReloadingCertificateProviderFactory,

xds/src/main/java/io/grpc/xds/internal/certprovider/FileWatcherCertificateProviderProvider.java

@@ -45,19 +45,17 @@ final class FileWatcherCertificateProviderProvider implements CertificateProvide
 
   static final String FILE_WATCHER_PROVIDER_NAME = "file_watcher";
 
-  static {
-    CertificateProviderRegistry.getInstance()
-        .register(
-            new FileWatcherCertificateProviderProvider(
-                FileWatcherCertificateProvider.Factory.getInstance(),
-                ScheduledExecutorServiceFactory.DEFAULT_INSTANCE,
-                TimeProvider.SYSTEM_TIME_PROVIDER));
-  }
-
   final FileWatcherCertificateProvider.Factory fileWatcherCertificateProviderFactory;
   private final ScheduledExecutorServiceFactory scheduledExecutorServiceFactory;
   private final TimeProvider timeProvider;
 
+  FileWatcherCertificateProviderProvider() {
+    this(
+        FileWatcherCertificateProvider.Factory.getInstance(),
+        ScheduledExecutorServiceFactory.DEFAULT_INSTANCE,
+        TimeProvider.SYSTEM_TIME_PROVIDER);
+  }
+
   @VisibleForTesting
   FileWatcherCertificateProviderProvider(
       FileWatcherCertificateProvider.Factory fileWatcherCertificateProviderFactory,

xds/src/main/java/io/grpc/xds/internal/certprovider/MeshCaCertificateProviderProvider.java

@@ -75,25 +75,23 @@ final class MeshCaCertificateProviderProvider implements CertificateProviderProv
   private static final String AUDIENCE_PREFIX = "identitynamespace:";
   static final String MESH_CA_NAME = "meshCA";
 
-  static {
-    CertificateProviderRegistry.getInstance()
-        .register(
-            new MeshCaCertificateProviderProvider(
-                StsCredentials.Factory.getInstance(),
-                MeshCaCertificateProvider.MeshCaChannelFactory.getInstance(),
-                new ExponentialBackoffPolicy.Provider(),
-                MeshCaCertificateProvider.Factory.getInstance(),
-                ScheduledExecutorServiceFactory.DEFAULT_INSTANCE,
-                TimeProvider.SYSTEM_TIME_PROVIDER));
-  }
-
   final StsCredentials.Factory stsCredentialsFactory;
   final MeshCaCertificateProvider.MeshCaChannelFactory meshCaChannelFactory;
   final BackoffPolicy.Provider backoffPolicyProvider;
   final MeshCaCertificateProvider.Factory meshCaCertificateProviderFactory;
   final ScheduledExecutorServiceFactory scheduledExecutorServiceFactory;
   final TimeProvider timeProvider;
 
+  MeshCaCertificateProviderProvider() {
+    this(
+        StsCredentials.Factory.getInstance(),
+        MeshCaCertificateProvider.MeshCaChannelFactory.getInstance(),
+        new ExponentialBackoffPolicy.Provider(),
+        MeshCaCertificateProvider.Factory.getInstance(),
+        ScheduledExecutorServiceFactory.DEFAULT_INSTANCE,
+        TimeProvider.SYSTEM_TIME_PROVIDER);
+  }
+
   @VisibleForTesting
   MeshCaCertificateProviderProvider(
       StsCredentials.Factory stsCredentialsFactory,