feat: populate location info if we already called GetWriteStream

google-cloud-bigquerystorage/src/main/java/com/google/cloud/bigquery/storage/v1/JsonStreamWriter.java

@@ -246,6 +246,15 @@ public Descriptor getDescriptor() {
     return this.descriptor;
   }
 
+  /**
+   * Gets the location of the destination
+   *
+   * @return Descriptor
+   */
+  public String getLocation() {
+    return this.streamWriter.getLocation();
+  }
+
   /**
    * Returns the wait of a request in Client side before sending to the Server. Request could wait
    * in Client because it reached the client side inflight request limit (adjustable when
@@ -407,6 +416,7 @@ private Builder(String streamOrTableName, TableSchema tableSchema, BigQueryWrite
         TableSchema writeStreamTableSchema = writeStream.getTableSchema();
 
         this.tableSchema = writeStreamTableSchema;
+        this.location = writeStream.getLocation();
       } else {
         this.tableSchema = tableSchema;
       }
@@ -526,6 +536,10 @@ public Builder setEnableConnectionPool(boolean enableConnectionPool) {
      * @return Builder
      */
     public Builder setLocation(String location) {
+      if (this.location != null && !this.location.equals(location)) {
+        throw new IllegalArgumentException(
+            "Specified location " + location + " does not match the system value " + this.location);
+      }
       this.location = location;
       return this;
     }

google-cloud-bigquerystorage/src/main/java/com/google/cloud/bigquery/storage/v1/StreamWriter.java

@@ -51,6 +51,11 @@ public class StreamWriter implements AutoCloseable {
   /** Every writer has a fixed proto schema. */
   private final ProtoSchema writerSchema;
 
+  /*
+   * Location of the destination.
+   */
+  private final String location;
+
   /*
    * A String that uniquely identifies this writer.
    */
@@ -162,6 +167,7 @@ private StreamWriter(Builder builder) throws IOException {
     BigQueryWriteClient client;
     this.streamName = builder.streamName;
     this.writerSchema = builder.writerSchema;
+    this.location = builder.location;
     boolean ownsBigQueryWriteClient;
     if (builder.client == null) {
       BigQueryWriteSettings stubSettings =
@@ -193,7 +199,7 @@ private StreamWriter(Builder builder) throws IOException {
                   client,
                   ownsBigQueryWriteClient));
     } else {
-      if (builder.location == "") {
+      if (builder.location == null || builder.location.isEmpty()) {
         throw new IllegalArgumentException("Location must be specified for multiplexing client!");
       }
       // Assume the connection in the same pool share the same client and trace id.
@@ -318,6 +324,11 @@ public ProtoSchema getProtoSchema() {
     return writerSchema;
   }
 
+  /** @return the location of the destination. */
+  public String getLocation() {
+    return location;
+  }
+
   /** Close the stream writer. Shut down all resources. */
   @Override
   public void close() {
@@ -379,7 +390,7 @@ public static final class Builder {
 
     private TableSchema updatedTableSchema = null;
 
-    private String location;
+    private String location = null;
 
     private boolean enableConnectionPool = false;
 

google-cloud-bigquerystorage/src/test/java/com/google/cloud/bigquery/storage/v1/JsonStreamWriterTest.java

@@ -393,15 +393,48 @@ public void testAppendOutOfRangeException() throws Exception {
   public void testCreateDefaultStream() throws Exception {
     TableSchema tableSchema =
         TableSchema.newBuilder().addFields(0, TEST_INT).addFields(1, TEST_STRING).build();
+    testBigQueryWrite.addResponse(
+        WriteStream.newBuilder()
+            .setName(TEST_STREAM)
+            .setLocation("aa")
+            .setTableSchema(tableSchema)
+            .build());
     try (JsonStreamWriter writer =
-        JsonStreamWriter.newBuilder(TEST_TABLE, tableSchema)
+        JsonStreamWriter.newBuilder(TEST_TABLE, client)
             .setChannelProvider(channelProvider)
             .setCredentialsProvider(NoCredentialsProvider.create())
             .build()) {
       assertEquals("projects/p/datasets/d/tables/t/_default", writer.getStreamName());
+      assertEquals("aa", writer.getLocation());
     }
   }
 
+  @Test
+  public void testCreateDefaultStreamWrongLocation() throws Exception {
+    TableSchema tableSchema =
+        TableSchema.newBuilder().addFields(0, TEST_INT).addFields(1, TEST_STRING).build();
+    testBigQueryWrite.addResponse(
+        WriteStream.newBuilder()
+            .setName(TEST_STREAM)
+            .setLocation("aa")
+            .setTableSchema(tableSchema)
+            .build());
+    IllegalArgumentException ex =
+        assertThrows(
+            IllegalArgumentException.class,
+            new ThrowingRunnable() {
+              @Override
+              public void run() throws Throwable {
+                JsonStreamWriter.newBuilder(TEST_TABLE, client)
+                    .setChannelProvider(channelProvider)
+                    .setCredentialsProvider(NoCredentialsProvider.create())
+                    .setLocation("bb")
+                    .build();
+              }
+            });
+    assertEquals("Specified location bb does not match the system value aa", ex.getMessage());
+  }
+
   @Test
   public void testSimpleSchemaUpdate() throws Exception {
     try (JsonStreamWriter writer =