hbase-maven-plugin writes seperate core-site.xml file.

Previously, the hbase-maven-plugin, after startup, would write an hbase-site.xml file containing
all configuration used to start the HDFS, MapReduce, and HBase clusters to the test-classes
folder of the build directory of the project. There's a disadvantage to this, in that client test
code must add HBase resources to a Configuratin object in order to get HDFS and MapReduce
configuration, even if they don't intend to use HBase.

This commit changes the hbase-maven-plugin so that it writes both an hbase-site.xml and
a core-site.xml file.  core-site.xml contains MapReduce/HDFS configuration, and hbase-site.xml
contains HBase-specific configuration. This has been tested by using the plugin in a sample
project and verifying that creating a new configuration adds the configuration found in
core-site.xml.

.gitignore

@@ -7,6 +7,8 @@
 /.settings/
 /prj.el
 /.jde/
+.idea
+*.iml
 
 # Build artifacts.
 /target/

src/main/java/com/wibidata/maven/plugins/hbase/StartMojo.java

@@ -77,6 +77,15 @@ public class StartMojo extends AbstractMojo {
    */
   private File mHBaseSiteFile;
 
+  /**
+   * The file that will store the configuration required to connect to the started mini HDFS and
+   * MapReduce clusters. This file will be generated by the goal.
+   *
+   * @parameter property="coreSiteFile" expression="${core.site.file}" default-value="${project.build.testOutputDirectory}/core-site.xml"
+   * @required
+   */
+  private File mCoreSiteFile;
+
   /**
    * If true, this goal should write an index file that provides the paths to the HBase
    * configuration files written by this goal.
@@ -148,6 +157,15 @@ public void setHbaseSiteFile(File hbaseSiteFile) {
     mHBaseSiteFile = hbaseSiteFile;
   }
 
+  /**
+   * Sets the file that we should write the MapReduce/HDFS cluster configuration to.
+   *
+   * @param coreSiteFile The file we should write to.
+   */
+  public void setCoreSiteFile(File coreSiteFile) {
+    mCoreSiteFile = coreSiteFile;
+  }
+
   /**
    * Sets whether this goal should write a configuration index file.
    *
@@ -225,6 +243,8 @@ public void execute() throws MojoExecutionException {
 
     // Write the HBase configuration file.
     writeHBaseSiteFile(conf);
+    // Write the MapReduce/HDFS configuration file.
+    writeCoreSiteFile(conf);
     // Write the configuration index.
     if (mWriteConfIndex) {
       writeConfigurationIndex();
@@ -297,27 +317,91 @@ private String getClassPath() throws MojoExecutionException {
   }
 
   /**
-   * Writes the contents of the specified configuration to the HBase site file.
+   * Writes the HBase-specific contents of the specified configuration to the HBase site file.
    *
    * @param conf The configuration to write.
    * @throws MojoExecutionException If there is an error writing the file.
    */
   private void writeHBaseSiteFile(Configuration conf) throws MojoExecutionException {
-    // Create the parent directory for the hbase conf file if it does not already exist.
-    createFileParentDir(mHBaseSiteFile);
+    writeSiteFile(getHBaseOnlyConfiguration(conf), mHBaseSiteFile);
+  }
+
+  /**
+   * Writes the MapReduce/HDFS-specific contents of the specified configuration to the core
+   * site file.
+   *
+   * @param conf The configuration to write.
+   * @throws MojoExecutionException If there is an error writing the file.
+   */
+  private void writeCoreSiteFile(Configuration conf) throws MojoExecutionException {
+    writeSiteFile(getMapReduceOnlyConfiguration(conf), mCoreSiteFile);
+  }
+
+  /**
+   * Writes the specified configuration to the specified file.
+   *
+   * @param conf The configuration to write.
+   * @param siteFile The file to write the configuration to.
+   * @throws MojoExecutionException If there is an error writing the file.
+   */
+  private void writeSiteFile(Configuration conf, File siteFile) throws MojoExecutionException {
+    // Create the parent directory for the site file if it does not already exist.
+    createFileParentDir(siteFile);
 
     // Write the file.
     FileOutputStream fileOutputStream = null;
     try {
-      fileOutputStream = new FileOutputStream(mHBaseSiteFile);
+      fileOutputStream = new FileOutputStream(siteFile);
       conf.writeXml(fileOutputStream);
     } catch (IOException e) {
       throw new MojoExecutionException(
-          "Unable to write to hbase conf file: " + mHBaseSiteFile.getPath(), e);
+          "Unable to write to site file: " + siteFile.getPath(), e);
     } finally {
       closeFileOutputStream(fileOutputStream);
     }
-    getLog().info("Wrote " + mHBaseSiteFile.getPath() + ".");
+    getLog().info("Wrote " + siteFile.getPath() + ".");
+  }
+
+  /**
+   * Gets a new configuration created from the specified configuration, including only HBase
+   * configuration variables.
+   *
+   * @param conf The configuration to filter.
+   * @return A new configuration containing copies of the appropriate configuration variables.
+   */
+  private Configuration getHBaseOnlyConfiguration(Configuration conf) {
+    return getFilteredConfiguration(conf, true);
+  }
+
+  /**
+   * Gets a new configuration created from the specified configuration, including only
+   * MapReduce/HDFS configuration variables.
+   *
+   * @param conf The configuration to filter.
+   * @return A new configuration containing copies of the appropriate configuration variables.
+   */
+  private Configuration getMapReduceOnlyConfiguration(Configuration conf) {
+    return getFilteredConfiguration(conf, false);
+  }
+
+  /**
+   * Gets a new configuration created from the specified configuration,
+   * including only MapReduce/HDFS configuration variables or HBase only configuration variables.
+   *
+   * @param conf The configuration to filter.
+   * @param hBaseOnly <code>true</code> if only HBase configuration variables should be included,
+   *     <code>false</code> if only MapReduce/HDFS configuration variables should be included.
+   * @return A new configuration with copies of the appropriate configuration variables.
+   */
+  private Configuration getFilteredConfiguration(Configuration conf, boolean hBaseOnly) {
+    Configuration filteredConf = new Configuration(false);
+    for (Map.Entry<String, String> entry: conf) {
+      boolean startsWithHBase = entry.getKey().startsWith("hbase");
+      if ((startsWithHBase && hBaseOnly) || (!startsWithHBase && !hBaseOnly)) {
+        filteredConf.set(entry.getKey(), entry.getValue());
+      }
+    }
+    return filteredConf;
   }
 
   /**