Added support for negative length

Author: darrachequesne

src/main/java/org/springframework/data/jpa/datatables/mapping/DataTablesInput.java

@@ -39,7 +39,7 @@ public class DataTablesInput {
  * negates any benefits of server-side processing!)
  */
 @NotNull
-@Min(0)
+@Min(-1)
 private Integer length;
 
 /**

src/main/java/org/springframework/data/jpa/datatables/repository/DataTablesRepositoryImpl.java

@@ -85,6 +85,10 @@ private Pageable getPageable(DataTablesInput input) {
 }
 Sort sort = orders.isEmpty() ? null : new Sort(orders);
 
+if (input.getLength() == -1) {
+input.setStart(0);
+input.setLength(Integer.MAX_VALUE);
+}
 return new PageRequest(input.getStart() / input.getLength(),
 input.getLength(), sort);
 }

src/test/java/org/springframework/data/jpa/datatables/repository/UserRepositoryTest.java

@@ -266,6 +266,30 @@ public void testWithAdditionalSpecification() {
 
 }
 
+@Test
+public void testWithZeroLength() {
+DataTablesInput input = getBasicInput();
+
+input.setLength(0);
+DataTablesOutput<User> output = userRepository.findAll(input);
+assertNotNull(output);
+assertNotNull(output.getError());
+assertEquals(output.getError(),
+"java.lang.ArithmeticException: / by zero");
+}
+
+@Test
+public void testWithNegativeLength() {
+DataTablesInput input = getBasicInput();
+
+input.setLength(-1);
+DataTablesOutput<User> output = userRepository.findAll(input);
+assertNotNull(output);
+assertNull(output.getError());
+assertEquals(24, (long) output.getRecordsFiltered());
+assertEquals(24, (long) output.getRecordsTotal());
+}
+
 /**
  * 
  * @return basic input parameters