diff --git hbase-client/src/main/java/org/apache/hadoop/hbase/client/Result.java hbase-client/src/main/java/org/apache/hadoop/hbase/client/Result.java index 2cc38bf..12922b5 100644 --- hbase-client/src/main/java/org/apache/hadoop/hbase/client/Result.java +++ hbase-client/src/main/java/org/apache/hadoop/hbase/client/Result.java @@ -102,7 +102,7 @@ public class Result implements CellScannable, CellScanner { private static ThreadLocal localBuffer = new ThreadLocal(); private static final int PAD_WIDTH = 128; - public static final Result EMPTY_RESULT = new Result(); + public static final Result EMPTY_RESULT = new Result(true); private final static int INITIAL_CELLSCANNER_INDEX = -1; @@ -112,6 +112,8 @@ public class Result implements CellScannable, CellScanner { private int cellScannerIndex = INITIAL_CELLSCANNER_INDEX; private ClientProtos.RegionLoadStats stats; + private final boolean readonly; + /** * Creates an empty Result w/ no KeyValue payload; returns null if you call {@link #rawCells()}. * Use this to represent no results if {@code null} won't do or in old 'mapred' as opposed @@ -119,7 +121,16 @@ public class Result implements CellScannable, CellScanner { * {@link #copyFrom(Result)} call. */ public Result() { - super(); + this(false); + } + + /** + * Allows to construct special purpose immutable Result objects, + * such as EMPTY_RESULT. + * @param readonly whether this Result instance is readonly + */ + private Result(boolean readonly) { + this.readonly = readonly; } /** @@ -172,6 +183,7 @@ public class Result implements CellScannable, CellScanner { this.exists = exists; this.stale = stale; this.partial = partial; + this.readonly = false; } /** @@ -834,9 +846,12 @@ public class Result implements CellScannable, CellScanner { /** * Copy another Result into this one. Needed for the old Mapred framework + * @throws UnsupportedOperationException if invoked on instance of EMPTY_RESULT + * (which is supposed to be immutable). * @param other */ public void copyFrom(Result other) { + checkReadonly(); this.row = null; this.familyMap = null; this.cells = other.cells; @@ -891,8 +906,11 @@ public class Result implements CellScannable, CellScanner { /** * Add load information about the region to the information about the result * @param loadStats statistics about the current region from which this was returned + * @throws UnsupportedOperationException if invoked on instance of EMPTY_RESULT + * (which is supposed to be immutable). */ public void addResults(ClientProtos.RegionLoadStats loadStats) { + checkReadonly(); this.stats = loadStats; } @@ -903,4 +921,10 @@ public class Result implements CellScannable, CellScanner { public ClientProtos.RegionLoadStats getStats() { return stats; } + + private void checkReadonly() { + if (this.readonly == true) { + throw new UnsupportedOperationException("Attempting to modify readonly EMPTY_RESULT!"); + } + } } \ No newline at end of file diff --git hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestResult.java hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestResult.java index fd4b01a..9715904 100644 --- hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestResult.java +++ hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestResult.java @@ -34,6 +34,7 @@ import org.apache.hadoop.hbase.Cell; import org.apache.hadoop.hbase.CellScanner; import org.apache.hadoop.hbase.CellUtil; import org.apache.hadoop.hbase.KeyValue; +import org.apache.hadoop.hbase.protobuf.generated.ClientProtos; import org.apache.hadoop.hbase.testclassification.ClientTests; import org.apache.hadoop.hbase.testclassification.SmallTests; import org.apache.hadoop.hbase.util.Bytes; @@ -229,6 +230,26 @@ public class TestResult extends TestCase { } } + /** + * Verifies that one can't modify instance of EMPTY_RESULT. + */ + public void testEmptyResultIsReadonly() { + Result emptyResult = Result.EMPTY_RESULT; + Result otherResult = new Result(); + + try { + emptyResult.copyFrom(otherResult); + fail("UnsupportedOperationException should have been thrown!"); + } catch (UnsupportedOperationException ex) { + LOG.debug("As expected: " + ex.getMessage()); + } + try { + emptyResult.addResults(ClientProtos.RegionLoadStats.getDefaultInstance()); + fail("UnsupportedOperationException should have been thrown!"); + } catch (UnsupportedOperationException ex) { + LOG.debug("As expected: " + ex.getMessage()); + } + } /** * Microbenchmark that compares {@link Result#getValue} and {@link Result#loadValue} performance.