chore: Adds README for running the samples (#509)

samples/README.md

@@ -0,0 +1,46 @@
+# Getting Started with Cloud Spanner and the Google Cloud Client libraries
+
+<a href="https://console.cloud.google.com/cloudshell/open?git_repo=https://github.com/GoogleCloudPlatform/java-docs-samples&page=editor&open_in_editor=spanner/cloud-client/README.md">
+<img alt="Open in Cloud Shell" src ="http://gstatic.com/cloudssh/images/open-btn.png"></a>
+
+[Cloud Spanner][Spanner] is a horizontally-scalable database-as-a-service
+with transactions and SQL support.
+These sample Java applications demonstrate how to access the Spanner API using
+the [Google Cloud Client Library for Java][java-spanner].
+
+[Spanner]: https://cloud.google.com/spanner/
+[java-spanner]: https://github.com/googleapis/java-spanner
+
+## Quickstart
+
+Every command here should be run from the root directory of your project (`java-spanner`).
+
+Install [Maven](http://maven.apache.org/).
+
+Build your project with:
+
+    mvn clean package -DskipTests -DskipUTs -Penable-samples
+
+You can then run a given `ClassName` via:
+
+    mvn exec:java -Dexec.mainClass=com.example.spanner.ClassName \
+        -DpropertyName=propertyValue \
+        -Dexec.args="any arguments to the app"
+
+### Running a simple query (using the quickstart sample)
+
+    mvn exec:java -Dexec.mainClass=com.example.spanner.QuickstartSample -Dexec.args="my-instance my-database"
+
+## Tutorial
+
+### Running the tutorial
+    mvn exec:java -Dexec.mainClass=com.example.spanner.SpannerSample -Dexec.args="<command> my-instance my-database"
+
+## Tracing sample
+`TracingSample.java` demonstrates how to export traces generated by client library to StackDriver and to /tracez page.
+
+### Running the tracing sample
+    mvn exec:java -Dexec.mainClass=com.example.spanner.TracingSample -Dexec.args="my-instance my-database"
+
+## Test
+    mvn verify -Dspanner.test.instance=<instance id> -Dspanner.sample.database=<new database id>  -Dspanner.quickstart.database=<existing database id>