#4 - suggested docs changes and streaming impl

readme.md

@@ -17,10 +17,14 @@ _The name of this project refers to the `BareLocalFileSystem` and `NakedLocalFil
 
 2. Then specify that you want to use the Bare Local File System implementation `com.globalmentor.apache.hadoop.fs.BareLocalFileSystem` for the `file` scheme. (`BareLocalFileSystem` internally uses `NakedLocalFileSystem`.)  The following example does this for Spark in Java:
 ```java
-SparkSession spark = SparkSession.builder().appName("Foo Bar").master("local").getOrCreate();
-spark.sparkContext().hadoopConfiguration().setClass("fs.file.impl", BareLocalFileSystem.class, FileSystem.class);
+SparkSession spark = SparkSession.builder().appName("Foo Bar").master("local").
+        config("spark.hadoop.fs.file.impl", BareLocalFileSystem.class.getName()).
+        config("spark.hadoop.fs.AbstractFileSystem.file.impl", BareStreamingLocalFileSystem.class.getName()).
+        getOrCreate();
 ```
 
+The config should be set before getOrCreate as Spark processes such as local meta-stores are already evaluating the Hadoop FS _before_ any hadoop config setClass call.  The AbstractFileSystem property is required to enable streaming checkpoint operations.
+
 _Note that you may still get warnings that "HADOOP_HOME and hadoop.home.dir are unset" and "Did not find winutils.exe". This is because the Winutils kludge permeates the Hadoop code and is hard-coded at a low-level, executed statically upon class loading, even for code completely unrelated to file access. See [HADOOP-13223: winutils.exe is a bug nexus and should be killed with an axe.](https://issues.apache.org/jira/browse/HADOOP-13223)_
 
 ## Limitations

src/main/java/org/apache/hadoop/fs/local/BareStreamingLocalFileSystem.java

@@ -0,0 +1,20 @@
+package org.apache.hadoop.fs.local;
+
+import com.globalmentor.apache.hadoop.fs.BareLocalFileSystem;
+import org.apache.hadoop.fs.DelegateToFileSystem;
+
+import java.io.IOException;
+import java.net.URISyntaxException;
+
+/**
+ * Required to handle streaming and checkpointing
+ *
+ * fs.AbstractFileSystem.file.impl
+ * spark.hadoop.fs.AbstractFileSystem.file.impl
+ *
+ */
+public class BareStreamingLocalFileSystem extends DelegateToFileSystem {
+    public BareStreamingLocalFileSystem(java.net.URI uri, org.apache.hadoop.conf.Configuration conf) throws IOException, URISyntaxException {
+        super(uri, new BareLocalFileSystem(), conf, "file", false);
+    }
+}