xds: add support for setting bootstrap file with java system property

examples/example-xds/README.md

@@ -6,7 +6,7 @@ being configured with the XDS management protocol. Out-of-the-box they behave th
 as their hello-world version.
 
 __XDS support is incomplete and experimental, with limited compatibility. It
-will be very hard to produce a working enviornment just by this example. Please
+will be very hard to produce a working environment just by this example. Please
 refer to documentation specific for your XDS management server and
 environment.__
 
@@ -24,8 +24,8 @@ This creates the scripts `build/install/example-xds/bin/hello-world-client-xds`
 ### Run the example without using XDS Credentials
 
 To use XDS, you should first deploy the XDS management server in your deployment environment
-and know its name. You need to set the `GRPC_XDS_BOOTSTRAP` environment variable to point to the
-gRPC XDS bootstrap file (see
+and know its name. You need to set the `GRPC_XDS_BOOTSTRAP` environment variable (preferred) or if that is not set then
+the `io.grpc.xds.bootstrap` java system property to point to the gRPC XDS bootstrap file (see
 [gRFC A27](https://github.com/grpc/proposal/blob/master/A27-xds-global-load-balancing.md#xdsclient-and-bootstrap-file) for the
 bootstrap format). This is needed by both `build/install/example-xds/bin/hello-world-client-xds`
 and `build/install/example-xds/bin/hello-world-server-xds`.
@@ -61,7 +61,7 @@ $ export GRPC_XDS_BOOTSTRAP=/path/to/bootstrap.json
 $ ./build/install/example-xds/bin/hello-world-server-xds 8000 my-test-xds-server --secure
 ```
 
-2. Similarly, add `--secure` on the comamnd line when you run the xDS client:
+2. Similarly, add `--secure` on the command line when you run the xDS client:
 ```
 $ export GRPC_XDS_BOOTSTRAP=/path/to/bootstrap.json
 $ ./build/install/example-xds/bin/hello-world-client-xds xds:///yourServersName:8000 my-test-xds-client --secure

xds/src/main/java/io/grpc/xds/Bootstrapper.java

@@ -47,21 +47,28 @@ public abstract class Bootstrapper {
 
   private static final String LOG_PREFIX = "xds-bootstrap";
   private static final String BOOTSTRAP_PATH_SYS_ENV_VAR = "GRPC_XDS_BOOTSTRAP";
+  private static final String BOOTSTRAP_PATH_SYS_PROPERTY_VAR = "io.grpc.xds.bootstrap";
   @VisibleForTesting
   static final String CLIENT_FEATURE_DISABLE_OVERPROVISIONING =
       "envoy.lb.does_not_support_overprovisioning";
 
   private static final Bootstrapper DEFAULT_INSTANCE = new Bootstrapper() {
     @Override
     public BootstrapInfo readBootstrap() throws XdsInitializationException {
-      String filePath = System.getenv(BOOTSTRAP_PATH_SYS_ENV_VAR);
+      String filePathSource = BOOTSTRAP_PATH_SYS_ENV_VAR;
+      String filePath = System.getenv(filePathSource);
+      if (filePath == null) {
+        filePathSource = BOOTSTRAP_PATH_SYS_PROPERTY_VAR;
+        filePath = System.getProperty(filePathSource);
+      }
       if (filePath == null) {
         throw new XdsInitializationException(
-            "Environment variable " + BOOTSTRAP_PATH_SYS_ENV_VAR + " not defined.");
+            "Environment variable " + BOOTSTRAP_PATH_SYS_ENV_VAR
+            + " or Java System Property " + BOOTSTRAP_PATH_SYS_PROPERTY_VAR + " not defined.");
       }
       XdsLogger
           .withPrefix(LOG_PREFIX)
-          .log(XdsLogLevel.INFO, BOOTSTRAP_PATH_SYS_ENV_VAR + "={0}", filePath);
+          .log(XdsLogLevel.INFO, filePathSource + "={0}", filePath);
       String fileContent;
       try {
         fileContent = new String(Files.readAllBytes(Paths.get(filePath)), StandardCharsets.UTF_8);

xds/src/test/java/io/grpc/xds/XdsClientWrapperForServerSdsTestMisc.java

@@ -201,7 +201,9 @@ public void startXdsClient_expectException() {
     } catch (IOException expected) {
       assertThat(expected)
               .hasMessageThat()
-              .contains("Environment variable GRPC_XDS_BOOTSTRAP not defined");
+              .contains(
+                      "Environment variable GRPC_XDS_BOOTSTRAP"
+                      + " or Java System Property io.grpc.xds.bootstrap not defined.");
     }
     ArgumentCaptor<Status> argCaptor = ArgumentCaptor.forClass(null);
     verify(mockServerWatcher).onError(argCaptor.capture());
@@ -210,7 +212,9 @@ public void startXdsClient_expectException() {
     assertThat(captured.getCause()).isInstanceOf(XdsInitializationException.class);
     assertThat(captured.getCause())
         .hasMessageThat()
-        .contains("Environment variable GRPC_XDS_BOOTSTRAP not defined");
+        .contains(
+                "Environment variable GRPC_XDS_BOOTSTRAP"
+                + " or Java System Property io.grpc.xds.bootstrap not defined.");
   }
 
   private DownstreamTlsContext sendListenerUpdate(

xds/src/test/java/io/grpc/xds/XdsServerBuilderTest.java

@@ -236,7 +236,9 @@ public void xdsServerWithoutMockXdsClient_startError()
     } catch (IOException expected) {
       assertThat(expected)
               .hasMessageThat()
-              .contains("Environment variable GRPC_XDS_BOOTSTRAP not defined");
+              .contains(
+                      "Environment variable GRPC_XDS_BOOTSTRAP"
+                      + " or Java System Property io.grpc.xds.bootstrap not defined.");
     }
     ArgumentCaptor<Status> argCaptor = ArgumentCaptor.forClass(null);
     verify(mockErrorNotifier).onError(argCaptor.capture());
@@ -245,7 +247,9 @@ public void xdsServerWithoutMockXdsClient_startError()
     assertThat(captured.getCause()).isInstanceOf(XdsInitializationException.class);
     assertThat(captured.getCause())
             .hasMessageThat()
-            .contains("Environment variable GRPC_XDS_BOOTSTRAP not defined");
+            .contains(
+                    "Environment variable GRPC_XDS_BOOTSTRAP"
+                    + " or Java System Property io.grpc.xds.bootstrap not defined.");
   }
 
   @Test