/**
* A utility method for generating a string to represent a single item's entry in the browse
*
* @param config
* @return
* @throws SQLException
*/
private String fullListingString(ItemListConfig config) throws SQLException {
// report on all the results contained herein
StringBuffer sb = new StringBuffer();
Iterator itr = results.iterator();
while (itr.hasNext()) {
BrowseItem bi = (BrowseItem) itr.next();
if (bi == null) {
sb.append("{{ NULL ITEM }}");
break;
}
sb.append("{{Item ID: " + Integer.toString(bi.getID()) + " :: ");
for (int j = 1; j <= config.numCols(); j++) {
String[] md = config.getMetadata(j);
if (md == null) {
sb.append("{{ NULL METADATA }}");
break;
}
Metadatum[] values = bi.getMetadata(md[0], md[1], md[2], Item.ANY);
StringBuffer value = new StringBuffer();
if (values != null) {
for (int i = 0; i < values.length; i++) {
if (i > 0) {
value.append(",");
}
value.append(values[i].value);
}
} else {
value.append("-");
}
String metadata = "[" + md[0] + "." + md[1] + "." + md[2] + ":" + value.toString() + "]";
sb.append(metadata);
}
sb.append("}}");
}
return sb.toString();
}
/**
* Get the database id of the item at the top of what will be the previous page of results. This
* is so that a "back" button can be generated by the User Interface when paging through results.
* The callback argument is there so that if the caller wishes the actual results from the
* previous page can also be returned (this is useful, for example, if you are on the very last
* page of results, and need some previous results to pad out the full number of results per
* page). If the callback is null, then no results are kept
*
* @param callback A List object for holding BrowseItem objects indexed numerically in the correct
* order
* @return the database id of the top of the previous page
* @throws SQLException
* @throws BrowseException
*/
private int getPreviousPageID(List callback) throws SQLException, BrowseException {
log.debug(LogManager.getHeader(context, "get_previous_page_id", ""));
// do we want to capture the results?
boolean capture = false;
if (callback != null) {
capture = true;
}
// the only thing we need to do is reverse the direction
// of the query, and set it to not use the "=" part of the
// comparator (i.e. < and > not <= and >=).
boolean isAscending = dao.isAscending();
dao.setAscending(!isAscending);
boolean useEquals = dao.useEqualsComparator();
dao.setEqualsComparator(false);
// store in local scope the things that we are going to change
// during this method
int resultLimit = dao.getLimit();
// if the database supports it (postgres does), we use limit
// and offset to minimise the work it has to do.
// the limit will be the size of a page, or double the size of the
// page if we are capturing the result set (because the first page's worth
// will be the results, so the previous link will need to come from the
// page *before* that)
int limit = scope.getResultsPerPage();
if (capture) {
limit *= 2;
}
dao.setLimit(limit);
// now we have a query which is exactly the opposite of the
// original query. So lets execute it:
List results = dao.doQuery();
// before we continue, put back the variables we messed with
dao.setAscending(isAscending);
dao.setEqualsComparator(useEquals);
dao.setLimit(resultLimit);
Iterator itr = results.iterator();
// work our way through the list, capturing if necessary, and finally
// having the last result, which will be the top of the previous page
int i = 0;
BrowseItem prev = null;
while (itr.hasNext()) {
BrowseItem browseItem = (BrowseItem) itr.next();
// we need to copy this, because of the scoping vs by-reference issue
prev = browseItem;
// if we need to capture the results in the call back, do it here.
// Note that since the results will come in backwards, we place
// each one at the start of the array so that it displaces the others
// in the right direction. By the end, they should be sorted correctly
// we use the index i to be sure that we only grab one page's worth
// of results (see note above about limit)
if (capture && i < scope.getResultsPerPage()) {
callback.add(0, browseItem);
i++;
}
}
if (prev != null) {
return prev.getID();
} else {
return -1;
}
}
