Displaytag allows you to display a collection of Objects as a table including direct support for paging and sorting
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Displaytag allows you to display a collection of Objects as a table including direct support for paging and sorting, It would do a request to a controller for every action such as a sorting or selecting a next page.
In this example we want to display episodes in a table using DWR:
1- we create a domain object called Episode:
public class Episode {
long id;
String show;
String name;
String episode;
String airDate;
....
}
2- we create a repository:
public class EpisodeRepository extends HibernateDaoSupport {
public List<Episode> getAllEpisodes(int firstResult, int maxResults, String orderBy,
boolean ascending) {
Criteria criteria = getSession().createCriteria(Episode.class)
.setFirstResult(firstResult)
.setMaxResults(maxResults)
.addOrder(ascending ? Order.asc(orderBy) : Order.desc(orderBy));
return criteria.list();
}
public int getNumberOfEpisodes() {
Criteria criteria = getSession().createCriteria(Episode.class);
criteria.setProjection(Projections.count("id"));
return (Integer)criteria.uniqueResult();
}
}
And a Jsp containing the Displaytag for presenting the collection of Episodes.
<display:table id="ep" name="eps" sort="external" requestURI="replaceURI" pagesize="30" partialList="true" size="${nrOfEps}">
<display:setProperty name="basic.empty.showtable" value="true" />
<display:column title="Show" property="show" sortable="true" sortName="show" />
<display:column title="Name" property="name" sortable="true" sortName="name" />
<display:column class="Episode" property="episode" sortable="true" sortName="episode" />
<display:column title="Airdate" property="airDate" sortable="true" sortName="airDate" />
</display:table>
Now you will create an abstract generic class to use it to enable any service you like, you can allow the following methods to add abstract class:
public abstract class AbstractExposedDisplayTagService<T> implements InitializingBean {
public void afterPropertiesSet() throws Exception {
....
}
public String findAllObjects(String criteria) {
WebContext wctx = WebContextFactory.get();
HttpServletRequest request = wctx.getHttpServletRequest();
// split results and set values;
int maxResults = Integer.parseInt(getCriterionValue(criteria, "maxResults", DEFAULT_MAXIMUM_RESULTS));
int page = Integer.parseInt(getCriterionValue(criteria, displayTagPage, "1"));
boolean ascending = Integer.parseInt(getCriterionValue(criteria, displayTagSortOrder, "1")) == 1 ? true : false;
String orderBy = getCriterionValue(criteria, displayTagOrderBy, "id");
int firstResult = (page - 1) * maxResults;
int numberOfObjects = getNumberOfObjects();
// set the episodes on the request so dwr can reload the jsp part.
request.setAttribute(getObjectsName(), getObjects(firstResult, maxResults, orderBy, ascending));
request.setAttribute(getNumberOfObjectsName(), numberOfObjects);
try {
String html = wctx.forwardToString(viewFragment);
html = DisplayTagReplacementUtil.updatePagingHtml(html, page, maxResults, numberOfObjects, displayTagPage);
html = DisplayTagReplacementUtil.updateSortOrderHtml(html, ascending, displayTagSortOrder);
html = DisplayTagReplacementUtil.updateHtmlLinks(html);
return html;
} catch (ServletException e) {
return "";
} catch (IOException e) {
return "";
}
}
}
Here is the implementation.
public class EpisodeService extends AbstractExposedDisplayTagService<Episode> {
private EpisodeRepository episodeRepository;
@Override
public int getNumberOfObjects() {
return episodeRepository.getNumberOfEpisodes();
}
@Override
public String getNumberOfObjectsName() {
return "numberOfEpisodes";
}
@Override
public List<Episode> getObjects(int firstResult, int maxResults, String orderBy, boolean ascending) {
return episodeRepository.getAllEpisodes(firstResult, maxResults, orderBy, ascending);
}
@Override
public String getObjectsName() {
return "episodes";
}
public void setEpisodeRepository(EpisodeRepository episodeRepository) {
this.episodeRepository = episodeRepository;
}
}
3- Adding javascript to call the exposed service methods, You must to add this code in the head of the jsp , Here is the code:
<script type='text/javascript' src='<c:url value="/dwr/interface/EpisodeService.js"/>'></script>
<script type='text/javascript' src='<c:url value="/dwr/engine.js"/>'></script>
<script type='text/javascript' src='<c:url value="/dwr/util.js"/>'></script>
<link rel="stylesheet" type="text/css" href='<c:url value="/css/displaytag.css"/>' />
and the javascript:
<script type="text/javascript">
function update(criteria) {
EpisodeService.findAllObjects(criteria, function(data) {
dwr.util.setValue("displayTable", data, { escapeHtml:false });
});
}
update("");
</script>
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