在Datatable JSF中显示Set集合中的对象不起作用

As to why a

Set

in
general isn’t supported, this is because this data structure is never intented
to hold a collection of objects which is ordered by an index. The

List

does that and this data structure is the most sensible data structure to
represent the value of an

UIData

component. The

DataModel

interface, which represents the wrapped value of the

UIData

components and holds the row indexes and remembers the current row for
iteration on render and form submit processing on postback, supports from the
Java collection classes only the

List

interface in flavor of

ListDataModel

.

After a long decision process (especially pushed by Hibernate/JPA community
who generally uses

Set

for
n-m relationships), the JSF spec team has for the upcoming JSF 2.2 finally
decided to let the

DataModel

interface support the

Collection

interface instead of alone the

List

,
with help of the new

CollectionDataModel

implementation. This supports sets
as well. See also JSF spec issue
479. You should
only keep in mind to use

linkedHashSet

instead of

HashSet

,
certainly if your intention is to have an editable data table. A

linkedHashSet

maintains the ordering of the elements.