Hi Lance, getting back to the tree grid again. I want to say thanks for all
your help thus far. I believe I'm getting much closer. Would you mind
reviewing what I have thus far and comment? As you indicated the query
string in the getChildren method will need to be repaired and I'll need to
setup the join in the category table. I still have to fix the value encoder
as well.
Category entity.
public class Category implements Serializable {
@Id
private String categoryId;
private String label;
private String parentCategoryId;
getters/setters
Category Node
public class CategoryNode {
private Category category;
private boolean leaf;
private boolean children;
getters/setters
CategoryTreeModelAdapter
public class CategoryTreeModelAdapter implements
TreeModelAdapter<CategoryNode> {
private Session session;
public CategoryTreeModelAdapter(Session session) {
this.session = session;
}
public boolean isLeaf(CategoryNode node) {
return node.isLeaf();
// since this was determined in a single query,
//we have avoided the n + 1 selects problem
}
public boolean hasChildren(CategoryNode node) {
return node.hasChildren();
// since this was determined in a single query,
//we have avoided the n + 1 selects problem
}
public List<CategoryNode> getChildren(CategoryNode node) {
List<Category> categories =
session.createCriteria(Category.class).add(Restrictions.eq("parentCategoryId",
node.getCategory().getCategoryId())).list();
Map<String, CategoryNode> nodes = new HashMap();
for (Category category : categories) {
CategoryNode newNode = new CategoryNode();
newNode.setCategory(category);
nodes.put(category.getCategoryId(), newNode);
}
// for each of node's children, count the number of children (ie
node's grandchildren)
// my hibernate is a bit rusty so this might need to be tweaked
List<Object[]> results = session.createSQLQuery(
"select c1.categoryId, count(c2.*) from Category c1 "
+ "join Category c2 on c2.parentId = c1.categoryId "
+ "where c1.parentId = ? "
+ "group by c1.categoryId",
node.getCategory().getCategoryId()).list();
for (Object[] result : results) {
String childId = (String) result[0];
int grandChildCount = (Integer) result[1];
CategoryNode childNode = nodes.get(childId);
childNode.setLeaf(grandChildCount == 0);
childNode.setChildren(grandChildCount != 0);
}
return new ArrayList(nodes.values());
}
public String getLabel(CategoryNode node) {
return node.getCategory().getLabel();
}
}
Tree Page.
public class Tree {
private TreeModel<Category> treeModel;
@Inject
private Session session;
public TreeModel<Category> getStuffModel() {
if (treeModel == null) {
ValueEncoder<Category> treeEncoder = new
ValueEncoder<Category>() {
@Override
public String toClient(Category category) {
return category.getCategoryId();
}
@Override
public Category toValue(String uuid) {
return Category.ROOT.searchSubTree(uuid);
}
};
treeModel = new DefaultTreeModel<Category>(treeEncoder, new
CategoryTreeModelAdapter(session), Stuff.ROOT.children);
}
return treeModel;
}
}
Thanks Lance.
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