Update the paging calculation, to correctly handle requests from the Scroller plugin (darrachequesne#24)

Fix darrachequesne#23

Author: darrachequesne

src/main/java/org/springframework/data/jpa/datatables/qrepository/QDataTablesRepositoryImpl.java

@@ -73,6 +73,10 @@ public <R> DataTablesOutput<R> findAll(DataTablesInput input, Predicate addition
  Predicate preFilteringPredicate, Converter<T, R> converter) {
  DataTablesOutput<R> output = new DataTablesOutput<R>();
  output.setDraw(input.getDraw());
+ if (input.getLength() == 0) {
+ return output;
+ }
+
  try {
  long recordsTotal = preFilteringPredicate == null ? count() : count(preFilteringPredicate);
  if (recordsTotal == 0) {

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

@@ -58,6 +58,9 @@ public <R> DataTablesOutput<R> findAll(DataTablesInput input,
  Converter<T, R> converter) {
  DataTablesOutput<R> output = new DataTablesOutput<R>();
  output.setDraw(input.getDraw());
+ if (input.getLength() == 0) {
+ return output;
+ }
 
  try {
  long recordsTotal =

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

@@ -3,7 +3,6 @@
 import java.util.ArrayList;
 import java.util.List;
 
-import org.springframework.data.domain.PageRequest;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.domain.Sort.Direction;
@@ -42,7 +41,7 @@ public static Pageable getPageable(DataTablesInput input) {
  input.setStart(0);
  input.setLength(Integer.MAX_VALUE);
  }
- return new PageRequest(input.getStart() / input.getLength(), input.getLength(), sort);
+ return new DataTablesPageRequest(input.getStart(), input.getLength(), sort);
  }
 
  public static boolean isBoolean(String filterValue) {
@@ -55,4 +54,57 @@ public static String getLikeFilterValue(String filterValue) {
  + "%";
  }
 
+ private static class DataTablesPageRequest implements Pageable {
+
+ private final int offset;
+ private final int pageSize;
+ private final Sort sort;
+
+ public DataTablesPageRequest(int offset, int pageSize, Sort sort) {
+ this.offset = offset;
+ this.pageSize = pageSize;
+ this.sort = sort;
+ }
+
+ @Override
+ public int getOffset() {
+ return offset;
+ }
+
+ @Override
+ public int getPageSize() {
+ return pageSize;
+ }
+
+ @Override
+ public Sort getSort() {
+ return sort;
+ }
+
+ @Override
+ public Pageable next() {
+ throw new UnsupportedOperationException();
+ }
+
+ @Override
+ public Pageable previousOrFirst() {
+ throw new UnsupportedOperationException();
+ }
+
+ @Override
+ public Pageable first() {
+ throw new UnsupportedOperationException();
+ }
+
+ @Override
+ public boolean hasPrevious() {
+ throw new UnsupportedOperationException();
+ }
+
+ @Override
+ public int getPageNumber() {
+ throw new UnsupportedOperationException();
+ }
+ }
+
 }

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

@@ -241,8 +241,8 @@ public void testWithZeroLength() {
  input.setLength(0);
  DataTablesOutput<User> output = userRepository.findAll(input);
  assertNotNull(output);
- assertNotNull(output.getError());
- assertEquals(output.getError(), "java.lang.ArithmeticException: / by zero");
+ assertEquals(0, output.getData().size());
+ assertEquals(0, output.getRecordsFiltered());
  }
 
  @Test
@@ -278,6 +278,27 @@ public UserDto convert(User user) {
  assertEquals("BLOCKED", user.getStatus());
  }
 
+ @Test
+ public void testWithFancyPaging() {
+ DataTablesInput input = getBasicInput();
+
+ input.setLength(5);
+ input.setStart(7);
+ DataTablesOutput<User> output = userRepository.findAll(input);
+ assertNotNull(output);
+ assertNull(output.getError());
+ assertEquals(5, output.getData().size());
+ assertEquals(8, (int) output.getData().get(0).getId());
+ assertEquals(8 + 5 - 1, (int) output.getData().get(4).getId());
+
+ input.setLength(7);
+ input.setStart(22);
+ output = userRepository.findAll(input);
+ assertNotNull(output);
+ assertEquals(2, output.getData().size());
+ assertEquals(23, (int) output.getData().get(0).getId());
+ }
+
  /**
  * 
  * @return basic input parameters