DisplayTag Paging
Tip to keep track of which page you're at
In a filter or (in your controller), add something like this
public class DisplayTagUtil {
private DisplayTagUtil() {
//empty
}
private static Pattern extractPagePattern = Pattern.compile("(?sim)(d-\\d+-p=\\d+)");
public static String extractPageNameAndValue(String queryString) {
if (null == queryString) {
return null;
}
Matcher m = extractPagePattern.matcher(queryString);
StringBuilder ret = new StringBuilder();
int i=0;
for (;m.find();i++) {
if (i > 0) {
ret.append("&");
}
ret.append(m.group());
}
if (i==0) {
return null;
}
return ret.toString();
}
}
Now, in your jsp page (or velocity page or what have you), for each link back to a page with a displayTag add the session value for that page like so
slashdotpublic class DisplayTagPageTracking implements Filter {
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) req;
if ("GET".equals(request.getMethod()) && (null != request.getQueryString() && request.getQueryString().length()>0)) {
final String queryString = request.getQueryString();
final String pageQueryString = DisplayTagUtil.extractPageNameAndValue(queryString);
request.getSession().setAttribute("displaytag_pages",pageQueryString);
}
chain.doFilter(req, res);
}
}
The DisplayTagUtil function looks like this
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) req;
if ("GET".equals(request.getMethod()) && (null != request.getQueryString() && request.getQueryString().length()>0)) {
final String queryString = request.getQueryString();
final String pageQueryString = DisplayTagUtil.extractPageNameAndValue(queryString);
request.getSession().setAttribute("displaytag_pages",pageQueryString);
}
chain.doFilter(req, res);
}
}
public class DisplayTagUtil {
private DisplayTagUtil() {
//empty
}
private static Pattern extractPagePattern = Pattern.compile("(?sim)(d-\\d+-p=\\d+)");
public static String extractPageNameAndValue(String queryString) {
if (null == queryString) {
return null;
}
Matcher m = extractPagePattern.matcher(queryString);
StringBuilder ret = new StringBuilder();
int i=0;
for (;m.find();i++) {
if (i > 0) {
ret.append("&");
}
ret.append(m.group());
}
if (i==0) {
return null;
}
return ret.toString();
}
}
<a href="http://waelchatila.com/many_pages_page.do?${displaytag_pages}">Bla Bla</a>
That's it!
Links
DisplayTag
Posted by Wael Chatila on November 7, 2006 3:37:41 PM PST
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Re: DisplayTag Paging
If you want to get the current page for a particular table you can use the following:
int curPage = Integer.parseInt(request.getParameter(
(new ParamEncoder("theTableId").encodeParameterName(TableTagParameters.PARAMETER_PAGE))));
Of course, when you define the table you also need to give it the matching id.