Merge pull request apache#14 from hejiang2000/flume-1.8-hejiang-header-join-interceptor

修改 joinKeys 默认值为 key，简化代码。

Author: hejiang2000

flume-ng-core/src/main/java/org/apache/flume/interceptor/HeaderJoinInterceptor.java

@@ -76,8 +76,7 @@ public class HeaderJoinInterceptor implements Interceptor {
   private HeaderJoinInterceptor(String joinKeys, String joinKeyDefaultValues,
           String joinDelimiter, boolean preserveExisting,
           String key) {
-    this.joinKeys = (joinKeys == null || joinKeys.isEmpty())
-      ? new String[]{ key } : joinKeys.split(" ");
+    this.joinKeys = joinKeys.split(" ");
     this.joinKeyDefaultValues = joinKeyDefaultValues.split(" ");
     this.joinDelimiter = joinDelimiter;
     this.preserveExisting = preserveExisting;
@@ -162,7 +161,7 @@ public Interceptor build() {
 
   public static class Constants {
     public static final String JOIN_KEYS = "joinKeys";
-    public static final String JOIN_KEYS_DEFAULT = null;
+    public static final String JOIN_KEYS_DEFAULT = "key";
 
     public static final String JOIN_KEY_DEFAULT_VALUES = "joinKeyDefaultValues";
     public static final String JOIN_KEY_DEFAULT_VALUES_DEFAULT = "NA";

flume-ng-core/src/test/java/org/apache/flume/interceptor/TestHeaderJoinInterceptor.java

@@ -107,8 +107,6 @@ public void testReplace() throws ClassNotFoundException,
   @Test
   public void testPreserve() throws ClassNotFoundException,
       InstantiationException, IllegalAccessException {
-    Interceptor.Builder builder = InterceptorBuilderFactory.newInstance(
-        InterceptorType.STATIC.toString());
     Context ctx = new Context();
     ctx.put(Constants.PRESERVE, "true");
     ctx.put(Constants.JOIN_KEY_DEFAULT_VALUES, "replacement+value");