Implement Bootstrap Pagination With Spring Data And Thymeleaf

Twitter Bootstrap has a very nice pagination UI, and here I will show you how to implement it with Spring Data Web pagination function and Thymeleaf conditional evaluation features.

Standard Pagination in Bootstrap

Simple pagination inspired by Rdio, great for apps and search results. The large block is hard to miss, easily scalable, and provides large click areas.

The original source code to display pagination from Bootstrap document is very simple:

<div >  <ul>    <li><a href='#'>Prev</a></li>    <li><a href='#'>1</a></li>    <li><a href='#'>2</a></li>    <li><a href='#'>3</a></li>    <li><a href='#'>4</a></li>    <li><a href='#'>5</a></li>    <li><a href='#'>Next</a></li>  </ul></div>

You can see this is just a mock up code, and to make it display page number dynamically with correct hyperlink URL, I need to do many changes to my existing code. So let’s start from bottom up, change domain layer first, then application service layer, presentation layer. Finally the configuration to glue them together.

Domain Layer Changes

The only change in domain layer is at BlogPostRepository. Before it has a method to retrieve a list of published BlogPost sorted by publishedTime:

public interface BlogPostRepository extends MongoRepository<BlogPost, String>{...    List<BlogPost> findByPublishedIsTrueOrderByPublishedTimeDesc();...}

Now we need to get paginated result list. With Spring Data Page, we will return Page<BlogPost> instead of List<BlogPost>, and pass Pageable parameter:

public interface BlogPostRepository extends MongoRepository<BlogPost, String>{...    Page<BlogPost> findByPublishedIsTrueOrderByPublishedTimeDesc(Pageable pageable);...}

Application Service Layer Changes:

The applicaiton service layer change is also very simple, just using new function from BlogPostRepository:

BlogService interface

public interface BlogService {...    Page<BlogPost> getAllPublishedPosts(Pageable pageable);...}

BlogServiceImpl class

public class BlogServiceImpl implements BlogService {...   private final BlogPostRepository blogPostRepository;...    @Override    public Page<BlogPost> getAllPublishedPosts(Pageable pageable) {        Page<BlogPost> blogList = blogPostRepository.findByPublishedIsTrueOrderByPublishedTimeDesc(pageable);        return blogList;    }...}

Presentation Layer Changes:

Spring Data Page interface has many nice functions to get current page number, get total pages, etc. But it’s still lack of ways to let me only display partial page range of total pagination. So I created an adapter class to wrap Sprng Data Page interface with additional features.

public class PageWrapper<T> {    public static final int MAX_PAGE_ITEM_DISPLAY = 5;    private Page<T> page;    private List<PageItem> items;    private int currentNumber;    private String url;    public String getUrl() {        return url;    }    public void setUrl(String url) {        this.url = url;    }    public PageWrapper(Page<T> page, String url){        this.page = page;        this.url = url;        items = new ArrayList<PageItem>();        currentNumber = page.getNumber() + 1; //start from 1 to match page.page        int start, size;        if (page.getTotalPages() <= MAX_PAGE_ITEM_DISPLAY){            start = 1;            size = page.getTotalPages();        } else {            if (currentNumber <= MAX_PAGE_ITEM_DISPLAY - MAX_PAGE_ITEM_DISPLAY/2){                start = 1;                size = MAX_PAGE_ITEM_DISPLAY;            } else if (currentNumber >= page.getTotalPages() - MAX_PAGE_ITEM_DISPLAY/2){                start = page.getTotalPages() - MAX_PAGE_ITEM_DISPLAY + 1;                size = MAX_PAGE_ITEM_DISPLAY;            } else {                start = currentNumber - MAX_PAGE_ITEM_DISPLAY/2;                size = MAX_PAGE_ITEM_DISPLAY;            }        }        for (int i = 0; i<size; i++){            items.add(new PageItem(start+i, (start+i)==currentNumber));        }    }    public List<PageItem> getItems(){        return items;    }    public int getNumber(){        return currentNumber;    }    public List<T> getContent(){        return page.getContent();    }    public int getSize(){        return page.getSize();    }    public int getTotalPages(){        return page.getTotalPages();    }    public boolean isFirstPage(){        return page.isFirstPage();    }    public boolean isLastPage(){        return page.isLastPage();    }    public boolean isHasPreviousPage(){        return page.hasPreviousPage();    }    public boolean isHasNextPage(){        return page.hasNextPage();    }    public class PageItem {        private int number;        private boolean current;        public PageItem(int number, boolean current){            this.number = number;            this.current = current;        }        public int getNumber(){            return this.number;        }        public boolean isCurrent(){            return this.current;        }    }}

With this PageWrapper, we can wrap Page<BlogPost> returned from BlogService and put it into SpringMVC UI model. See the controller code for the blog page:

@Controllerpublic class BlogController...    @RequestMapping(value = '/blog', method = RequestMethod.GET)    public String blog(Model uiModel, Pageable pageable) {        PageWrapper<BlogPost> page = new PageWrapper<BlogPost>        	(blogService.getAllPublishedPosts(pageable), '/blog');        uiModel.addAttribute('page', page);        return 'blog';    }...}

The Pageable is passed in from PageableArgumentResolver, which I will explain later. Another trick is I also pass the view URL to PageWrapper, and it can be used to construct Thymeleaf hyperlinks in pagination bar.

Since my PageWrapper is very generic, I created an html fragment for pagination bar, so I can use it for anywhere in my application pages when pagination needed. This fragment html uses Thymeleaf th:if to dynamically switch between static text or hyperlink based on if the link is disabled or not. And it uses th:href to construct URL with correct page number and page size.

<!-- Pagination Bar --><div th:fragment='paginationbar'>  <div >    <ul>      <li th:disabled' : '''>        <span th:if='${page.firstPage}'>← First</span>        <a th:if='${not page.firstPage}' th:href='@{${page.url}(page.page=1,page.size=${page.size})}'>← First</a>      </li>      <li th:' : 'disabled''>        <span th:if='${not page.hasPreviousPage}'>«</span>        <a th:if='${page.hasPreviousPage}' th:href='@{${page.url}(page.page=${page.number-1},page.size=${page.size})}' title='Go to previous page'>«</a>      </li>      <li th:each='item : ${page.items}' th:active' : '''>        <span th:if='${item.current}' th:text='${item.number}'>1</span>        <a th:if='${not item.current}' th:href='@{${page.url}(page.page=${item.number},page.size=${page.size})}'><span th:text='${item.number}'>1</span></a>      </li>      <li th:' : 'disabled''>        <span th:if='${not page.hasNextPage}'>»</span>        <a th:if='${page.hasNextPage}' th:href='@{${page.url}(page.page=${page.number+1},page.size=${page.size})}' title='Go to next page'>»</a>      </li>      <li th:disabled' : '''>        <span th:if='${page.lastPage}'>Last →</span>        <a th:if='${not page.lastPage}' th:href='@{${page.url}(page.page=${page.totalPages},page.size=${page.size})}'>Last →</a>      </li>    </ul>  </div></div>

Spring Configuration Change

The last step is to put them all together. Fortunately I did some research before I updated my code. There is a very good blog post Pagination with Spring MVC, Spring Data and Java Config by Doug Haber. In his blog, Doug mentioned several gotchas, especially the Pageable parameter needs some configuration magic:

In order for Spring to know how to convert the parameter to a Pageable object you need to configure a HandlerMethodArgumentResolver. Spring Data provides a PageableArgumentResolver but it uses the old ArgumentResolver interface instead of the new (Spring 3.1) HandlerMethodArgumentResolver interface. The XML config can handle this discrepancy for us, but since we’re using Java Config we have to do it a little more manually. Luckily this can be easily resolved if you know the right magic incantation…
Doug Haber

With Doug’s help, I added this argument resolver to my WebConfig class:

@Configuration@EnableWebMvc@ComponentScan(basePackages = 'com.jiwhiz.blog.web')public class WebConfig extends WebMvcConfigurerAdapter {...    @Override    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {        PageableArgumentResolver resolver = new PageableArgumentResolver();        resolver.setFallbackPagable(new PageRequest(1, 5));        argumentResolvers.add(new ServletWebArgumentResolverAdapter(resolver));    }...}

After all those changes, my Blog list will have pagination bar at the top and bottom of the page, and it always have at most 5 page numbers, with current number at the middle and disabled. The pagination bar also has First and Previous links at the beginning, Next and Last links at the end. I also used it in my admin pages, for user list and comment list, and it works very well.
 

Reference: Implement Bootstrap Pagination With Spring Data And Thymeleaf from our JCG partner Yuan Ji at the Jiwhiz blog.

Source : feedproxy[dot]google[dot]com