[FLINK-2090] [core] Truncate 'toString()' of CollectionInputFormat wh…

…en the collection is huge

This closes apache#2323

flink-java/src/main/java/org/apache/flink/api/java/io/CollectionInputFormat.java

@@ -41,6 +41,7 @@
 public class CollectionInputFormat<T> extends GenericInputFormat<T> implements NonParallelInput {
 
  private static final long serialVersionUID = 1L;
+ private static final int MAX_TO_STRING_LEN = 100;
 
  private TypeSerializer<T> serializer;
 
@@ -117,7 +118,23 @@ private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundE
 
  @Override
  public String toString() {
- return this.dataSet.toString();
+ StringBuilder sb = new StringBuilder();
+ sb.append('[');
+
+ int num = 0;
+ for (T e : dataSet) {
+ sb.append(e);
+ if (num != dataSet.size() - 1) {
+ sb.append(", ");
+ if (sb.length() > MAX_TO_STRING_LEN) {
+ sb.append("...");
+ break;
+ }
+ }
+ num++;
+ }
+ sb.append(']');
+ return sb.toString();
  }
 
  // --------------------------------------------------------------------------------------------

flink-java/src/test/java/org/apache/flink/api/java/io/CollectionInputFormatTest.java

@@ -76,6 +76,13 @@ public boolean equals(Object obj) {
  public int hashCode() {
  return id;
  }
+
+ @Override
+ public String toString() {
+ return "ElementType{" +
+ "id=" + id +
+ '}';
+ }
  }
 
  @Test
@@ -253,7 +260,37 @@ public void testDeserializationFailure() {
  fail(e.getMessage());
  }
  }
-
+
+ @Test
+ public void testToStringOnSmallCollection() {
+ ArrayList<ElementType> smallList = new ArrayList<>();
+ smallList.add(new ElementType(1));
+ smallList.add(new ElementType(2));
+ CollectionInputFormat<ElementType> inputFormat = new CollectionInputFormat<>(
+ smallList,
+ new TestSerializer(true, false)
+ );
+
+ assertEquals("[ElementType{id=1}, ElementType{id=2}]", inputFormat.toString());
+ }
+
+ @Test
+ public void testToStringOnBigCollection() {
+ ArrayList<ElementType> list = new ArrayList<>();
+ for (int i = 0; i < 10; i++) {
+ list.add(new ElementType(i));
+ }
+ CollectionInputFormat<ElementType> inputFormat = new CollectionInputFormat<>(
+ list,
+ new TestSerializer(true, false)
+ );
+
+ assertEquals(
+ "[ElementType{id=0}, ElementType{id=1}, ElementType{id=2}, " +
+ "ElementType{id=3}, ElementType{id=4}, ElementType{id=5}, ...]",
+ inputFormat.toString());
+ }
+
  private static class TestException extends IOException{
  private static final long serialVersionUID = 1L;
  }