Pagination with PagedResourcesAssembler

Our goal is a REST api response (paginated data with pagination information, next/previous links etc), like:

    {
         ....
         ....// your DTO object list //
         ....,
        "attr": "XXXXXXX",
        "amount": -6010,
        "transactionCode": 107,
        "transactionId": "T3ce4ea05fabf2dd8a664011e9f79de120da18da0.1",
        "typeOfTransaction": "",
        "dateOfTransaction": "2020-03-20T00:00:00.000Z"
      },
      {
        "attr": "ZZZZz",
        "amount": -18200,
        "transactionCode": 105,
        "transactionId": "T1645f70098774fd23e42867f914348bdbdd047a3.1"
        "typeOfTransaction": "",
        "dateOfTransaction": "2020-03-17T00:00:00.000Z"
      }
    ]
  },
  "_links": {
    "first": {
      "href": "http://localhost:8080/api/store/account/transactions?accId=A&page=0&size=5"
    },
    "self": {
      "href": "http://localhost:8080/api/store/account/transactions?accId=A"
    },
    "next": {
      "href": "http://localhost:8080/api/store/account/transactions?accId=A&page=1&size=5"
    },
    "last": {
      "href": "http://localhost:8080/api/store/account/transactions?accnId=A&page=13&size=5"
    }
  },
  "page": {
    "size": 5,
    "totalElements": 68,
    "totalPages": 14,
    "number": 0
  }
}

1. Pom.xml

        <dependency>
            <groupId>org.springframework.hateoas</groupId>
            <artifactId>spring-hateoas</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-hateoas</artifactId>
        </dependency>




2. Controller/Resource method


    @GetMapping("/your/path")
    public ResponseEntity<PagedResources<yourDTO>> getPagedDTOs(

           @RequestParam(name = "page", defaultValue = "0") int page,
           @RequestParam(name = "size", defaultValue = "5") int size,
           UriComponentsBuilder uriBuilder, HttpServletResponse response,
           PagedResourcesAssembler assembler) {

        Pageable pageable = PageRequest.of(page, size);
        Page<yourDTO> retrievedData = yourService.getTransactions(pageable);
        PagedResources<yourDTO> pr = assembler.toResource(retrievedData , linkTo(YourResource.class).slash("/your" +
            "/path").withSelfRel());
        HttpHeaders responseHeaders = new HttpHeaders();
        responseHeaders.add("Link", createLinkHeader(pr));
        return new ResponseEntity<>(assembler.toResource(retrievedData, linkTo(YourResource.class).slash("/your" +
            "/path").withSelfRel()), responseHeaders, HttpStatus.OK);
    }




3. Controller/Resource helper methods



  private String createLinkHeader(PagedResources<yourDTO> pr){
        List<String> linksList = new ArrayList<>();
        List<Link> links = pr.getLinks();
        for(Link link : links) {
            linksList.add(buildLinkHeader(link.getHref(), link.getRel()));
        }
        return String.join(",", linksList);
  }

  public static String buildLinkHeader(final String uri, final String rel) {
        return "<" + uri + ">; rel=\"" + rel + "\"";
  }




4. Service layer method



   Page<yourDTO> getTransactions(Pageable pageable);



5. Service Impl method



   @Override
    public Page<yourDTO> getTransactions(Pageable pageable) {
        List<yourDTO> allTransactions = getAllTransactions();
        return getPage(pageable, allTransactions);
   }



6. Helper method



    private <T> Page<T> getPage(Pageable pageable, List<T> list) {
        int start = (int) pageable.getOffset();
        int end = ((start + pageable.getPageSize()) > list.size() ? list.size()
            : (start + pageable.getPageSize()));
        return new PageImpl<>(list.subList(start, end), pageable, list.size());
    }