fix: add javadoc comments for configurable properties

src/main/java/com/google/api/generator/spring/composer/SpringPropertiesClassComposer.java

@@ -138,16 +138,19 @@ private static List<Statement> createMemberVariables(
             true,
             defaultCredentialScopes,
             nestedPropertyAnnotations);
+    statements.add(SpringPropertiesCommentComposer.createCredentialsPropertyComment());
     statements.add(credentialsStatement);
     //   private String quotaProjectId;
     ExprStatement quotaProjectIdVarStatement =
         ComposerUtils.createMemberVarStatement(
             "quotaProjectId", TypeNode.STRING, false, null, null);
+    statements.add(SpringPropertiesCommentComposer.createQuotaProjectIdPropertyComment());
     statements.add(quotaProjectIdVarStatement);
     //   private Integer executorThreadCount;
     ExprStatement executorThreadCountVarStatement =
         ComposerUtils.createMemberVarStatement(
             "executorThreadCount", TypeNode.INT_OBJECT, false, null, null);
+    statements.add(SpringPropertiesCommentComposer.createExecutorThreadCountPropertyComment());
     statements.add(executorThreadCountVarStatement);
     if (hasRestOption) {
       ExprStatement useRestVarStatement =
@@ -158,6 +161,7 @@ private static List<Statement> createMemberVariables(
               ValueExpr.withValue(
                   PrimitiveValue.builder().setType(TypeNode.BOOLEAN).setValue("false").build()),
               null);
+      statements.add(SpringPropertiesCommentComposer.createUseRestPropertyComment());
       statements.add(useRestVarStatement);
     }
     //   private Retry retrySettings;

src/main/java/com/google/api/generator/spring/composer/comment/SpringPropertiesCommentComposer.java

@@ -23,6 +23,13 @@
 public class SpringPropertiesCommentComposer {
   private static final String CLASS_HEADER_GENERAL_DESCRIPTION =
       "Provides default property values for %s client bean";
+  private static final String CREDENTIALS_DESCRIPTION =
+      "OAuth2 credentials to authenticate and authorize calls to Google Cloud Client Libraries.";
+  private static final String QUOTA_PROJECT_ID_DESCRIPTION = "Quota project to use for billing.";
+  private static final String EXECUTOR_THREAD_COUNT_DESCRIPTION =
+      "Number of threads used for executors.";
+  private static final String USE_REST_DESCRIPTION =
+      "Allow override of default transport channel provider to use REST instead of gRPC.";
 
   public static List<CommentStatement> createClassHeaderComments(
       String configuredClassName, String serviceName) {
@@ -34,4 +41,24 @@ public static List<CommentStatement> createClassHeaderComments(
         CommentComposer.AUTO_GENERATED_CLASS_COMMENT,
         CommentStatement.withComment(javaDocCommentBuilder.build()));
   }
+
+  public static CommentStatement createCredentialsPropertyComment() {
+    return toSimpleJavaDocComment(CREDENTIALS_DESCRIPTION);
+  }
+
+  public static CommentStatement createQuotaProjectIdPropertyComment() {
+    return toSimpleJavaDocComment(QUOTA_PROJECT_ID_DESCRIPTION);
+  }
+
+  public static CommentStatement createExecutorThreadCountPropertyComment() {
+    return toSimpleJavaDocComment(EXECUTOR_THREAD_COUNT_DESCRIPTION);
+  }
+
+  public static CommentStatement createUseRestPropertyComment() {
+    return toSimpleJavaDocComment(USE_REST_DESCRIPTION);
+  }
+
+  private static CommentStatement toSimpleJavaDocComment(String comment) {
+    return CommentStatement.withComment(JavaDocComment.withComment(comment));
+  }
 }

src/test/java/com/google/api/generator/spring/composer/goldens/EchoSpringPropertiesFull.golden

@@ -30,12 +30,15 @@ import org.springframework.boot.context.properties.NestedConfigurationProperty;
 @BetaApi("Autogenerated Spring autoconfiguration is not yet stable")
 @ConfigurationProperties("com.google.showcase.v1beta1.spring.auto.echo")
 public class EchoSpringProperties implements CredentialsSupplier {
+  /** OAuth2 credentials to authenticate and authorize calls to Google Cloud Client Libraries. */
   @NestedConfigurationProperty
   private final Credentials credentials =
       new Credentials("https://www.googleapis.com/auth/cloud-platform");
-
+  /** Quota project to use for billing. */
   private String quotaProjectId;
+  /** Number of threads used for executors. */
   private Integer executorThreadCount;
+
   @NestedConfigurationProperty private Retry retrySettings;
   @NestedConfigurationProperty private Retry echoRetrySettings;
   @NestedConfigurationProperty private Retry expandRetrySettings;

src/test/java/com/google/api/generator/spring/composer/goldens/EchoSpringPropertiesGrpc.golden

@@ -10,12 +10,15 @@ import org.springframework.boot.context.properties.NestedConfigurationProperty;
 /** Provides default property values for Echo client bean */
 @ConfigurationProperties("com.google.showcase.v1beta1.spring.auto.echo")
 public class EchoSpringProperties implements CredentialsSupplier {
+  /** OAuth2 credentials to authenticate and authorize calls to Google Cloud Client Libraries. */
   @NestedConfigurationProperty
   private final Credentials credentials =
       new Credentials("https://www.googleapis.com/auth/cloud-platform");
-
+  /** Quota project to use for billing. */
   private String quotaProjectId;
+  /** Number of threads used for executors. */
   private Integer executorThreadCount;
+
   @NestedConfigurationProperty private Retry retrySettings;
   @NestedConfigurationProperty private Retry echoRetrySettings;
   @NestedConfigurationProperty private Retry expandRetrySettings;

src/test/java/com/google/api/generator/spring/composer/goldens/EchoSpringPropertiesGrpcRest.golden

@@ -10,13 +10,17 @@ import org.springframework.boot.context.properties.NestedConfigurationProperty;
 /** Provides default property values for Echo client bean */
 @ConfigurationProperties("com.google.showcase.v1beta1.spring.auto.echo")
 public class EchoSpringProperties implements CredentialsSupplier {
+  /** OAuth2 credentials to authenticate and authorize calls to Google Cloud Client Libraries. */
   @NestedConfigurationProperty
   private final Credentials credentials =
       new Credentials("https://www.googleapis.com/auth/cloud-platform");
-
+  /** Quota project to use for billing. */
   private String quotaProjectId;
+  /** Number of threads used for executors. */
   private Integer executorThreadCount;
+  /** Allow override of default transport channel provider to use REST instead of gRPC. */
   private boolean useRest = false;
+
   @NestedConfigurationProperty private Retry retrySettings;
   @NestedConfigurationProperty private Retry echoRetrySettings;
   @NestedConfigurationProperty private Retry expandRetrySettings;