How to convert ArrayList to Pageable object springboot

Question

I was trying to return list as page object to my client side angular Application. But it return all the list not a page.

this is my server side controller method which return the list

    @GetMapping("/users/departmentAdminPageUsers")
    @Timed
    public ResponseEntity<List<DepartmentAdminPageUserDTO>> getDepartmentAdminPageUsers(@ApiParam Pageable pageable, @ApiParam String searchKey, @ApiParam String depId)
        throws URISyntaxException {
        List<DepartmentAdminPageUserDTO> userList=userService.getAllDepartmentAdminPageUsers(depId,searchKey);
        final Page<DepartmentAdminPageUserDTO> page = new PageImpl<>(userList, pageable,userList.size());
        HttpHeaders headers = PaginationUtil.generatePaginationHttpHeaders(page, "/users/departmentAdminPageUsers");
        return new ResponseEntity<>(page.getContent(), headers, HttpStatus.OK);

    }   

this is my client side angular method which send request

getAllUsersByDepId(req?: any):Observable<Response>{
        let params: URLSearchParams = new URLSearchParams();
        if (req) {
            params.set('page', req.page);
            params.set('size', req.size);
            params.set('searchKey', req.searchKey);
            params.set('depId', req.depId);  
        }
        let options = {
            search: params
        };
        return this.http.get(this.resourceUrl+ '/departmentAdminPageUsers', options);

    }

I need to return page instead the whole list.

Answer 1

you are returning the whole list as the page content, try:

List<DepartmentAdminPageUserDTO> userSubList = userList.subList((pageable.getPage()-1)*pageable.getSize(), (pageable.getPage()*pageable.getSize())-1);
final Page<DepartmentAdminPageUserDTO> page = new PageImpl<>(userSubList, pageable,userList.size());

Answer 2

protected Page<T> listToPage(Pageable pageable, List<T> entities) {
    int lowerBound = pageable.getPageNumber() * pageable.getPageSize();
    int upperBound = Math.min(lowerBound + pageable.getPageSize() - 1, entities.size());

    List<T> subList = entities.subList(lowerBound, upperBound);

    return new PageImpl<T>(subList, pageable, subList.size());
};