How to use

toOptional

method

in

org.springframework.data.domain.Pageable

/**
 * Constructor of {@code PageImpl}.
 *
 * @param content the content of this page, must not be {@literal null}.
 * @param pageable the paging information, must not be {@literal null}.
 * @param total the total amount of items available. The total might be adapted considering the length of the content
 *          given, if it is going to be the content of the last page. This is in place to mitigate inconsistencies.
 */
public PageImpl(List<T> content, Pageable pageable, long total) {
  super(content, pageable);
  this.total = pageable.toOptional().filter(it -> !content.isEmpty())//
      .filter(it -> it.getOffset() + it.getPageSize() > total)//
      .map(it -> it.getOffset() + content.size())//
      .orElse(total);
}

@Override
public Pageable resolveArgument(MethodParameter methodParameter, @Nullable ModelAndViewContainer mavContainer,
    NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) {
  assertPageableUniqueness(methodParameter);
  Optional<Pageable> defaultOrFallback = getDefaultFromAnnotationOrFallback(methodParameter).toOptional();
  String pageString = webRequest.getParameter(getParameterNameToUse(pageParameterName, methodParameter));
  String pageSizeString = webRequest.getParameter(getParameterNameToUse(sizeParameterName, methodParameter));
  Optional<Integer> page = parseAndApplyBoundaries(pageString, Integer.MAX_VALUE, true);
  Optional<Integer> pageSize = parseAndApplyBoundaries(pageSizeString, maxPageSize, false);
  if (!(page.isPresent() && pageSize.isPresent()) && !defaultOrFallback.isPresent()) {
    return Pageable.unpaged();
  }
  int p = page
      .orElseGet(() -> defaultOrFallback.map(Pageable::getPageNumber).orElseThrow(IllegalStateException::new));
  int ps = pageSize
      .orElseGet(() -> defaultOrFallback.map(Pageable::getPageSize).orElseThrow(IllegalStateException::new));
  // Limit lower bound
  ps = ps < 1 ? defaultOrFallback.map(Pageable::getPageSize).orElseThrow(IllegalStateException::new) : ps;
  // Limit upper bound
  ps = ps > maxPageSize ? maxPageSize : ps;
  Sort sort = sortResolver.resolveArgument(methodParameter, mavContainer, webRequest, binderFactory);
  return PageRequest.of(p, ps,
      sort.isSorted() ? sort : defaultOrFallback.map(Pageable::getSort).orElseGet(Sort::unsorted));
}

@SuppressWarnings({ "rawtypes", "unchecked" })
protected KeyValueQuery<?> prepareQuery(KeyValueQuery<?> instance, Object[] parameters) {
  ParametersParameterAccessor accessor = new ParametersParameterAccessor(getQueryMethod().getParameters(),
      parameters);
  Object criteria = instance.getCriteria();
  if (criteria instanceof SpelCriteria || criteria instanceof SpelExpression) {
    SpelExpression spelExpression = getSpelExpression(criteria);
    EvaluationContext context = this.evaluationContextProvider.getEvaluationContext(getQueryMethod().getParameters(),
        parameters);
    criteria = new SpelCriteria(spelExpression, context);
  }
  KeyValueQuery<?> query = new KeyValueQuery(criteria);
  Pageable pageable = accessor.getPageable();
  Sort sort = accessor.getSort();
  query.setOffset(pageable.toOptional().map(Pageable::getOffset).orElse(-1L));
  if (pageable.isPaged()) {
    query.setRows(pageable.getPageSize());
  } else if (instance.getRows() >= 0) {
    query.setRows(instance.getRows());
  }
  query.setSort(sort.isUnsorted() ? instance.getSort() : sort);
  return query;
}

@SuppressWarnings({ "rawtypes", "unchecked" })
protected KeyValueQuery<?> prepareQuery(KeyValueQuery<?> instance, Object[] parameters) {
  ParametersParameterAccessor accessor = new ParametersParameterAccessor(getQueryMethod().getParameters(),
      parameters);
  Object criteria = instance.getCriteria();
  if (criteria instanceof SpelCriteria || criteria instanceof SpelExpression) {
    SpelExpression spelExpression = getSpelExpression(criteria);
    EvaluationContext context = this.evaluationContextProvider.getEvaluationContext(getQueryMethod().getParameters(),
        parameters);
    criteria = new SpelCriteria(spelExpression, context);
  }
  KeyValueQuery<?> query = new KeyValueQuery(criteria);
  Pageable pageable = accessor.getPageable();
  Sort sort = accessor.getSort();
  query.setOffset(pageable.toOptional().map(Pageable::getOffset).orElse(-1L));
  if (pageable.isPaged()) {
    query.setRows(pageable.getPageSize());
  } else if (instance.getRows() >= 0) {
    query.setRows(instance.getRows());
  }
  query.setSort(sort.isUnsorted() ? instance.getSort() : sort);
  return query;
}

@SuppressWarnings({ "rawtypes", "unchecked" })
protected KeyValueQuery<?> prepareQuery(KeyValueQuery<?> instance, Object[] parameters) {
  ParametersParameterAccessor accessor = new ParametersParameterAccessor(getQueryMethod().getParameters(),
      parameters);
  Object criteria = instance.getCriteria();
  if (criteria instanceof SpelCriteria || criteria instanceof SpelExpression) {
    SpelExpression spelExpression = getSpelExpression(criteria);
    EvaluationContext context = this.evaluationContextProvider.getEvaluationContext(getQueryMethod().getParameters(),
        parameters);
    criteria = new SpelCriteria(spelExpression, context);
  }
  KeyValueQuery<?> query = new KeyValueQuery(criteria);
  Pageable pageable = accessor.getPageable();
  Sort sort = accessor.getSort();
  query.setOffset(pageable.toOptional().map(Pageable::getOffset).orElse(-1L));
  if (pageable.isPaged()) {
    query.setRows(pageable.getPageSize());
  } else if (instance.getRows() >= 0) {
    query.setRows(instance.getRows());
  }
  query.setSort(sort.isUnsorted() ? instance.getSort() : sort);
  return query;
}