Java Vaadin树中的项目太多
我正在使用Vaadin构建一个web应用程序,其中一个特性需要一个树来显示元素,问题是这个树最多加载40K个项目,甚至更多 在几千项的水平上,Vaadin树是可以接受的,但现在不行,它正在减缓web浏览器中的一切 我想到的是在web服务器和web客户端之间对负载进行分页,并显示一些在用户滚动树时更新的项目,问题是我不知道从哪里开始,即使这是否适用 这是一个好方法吗?有更好的吗?Java Vaadin树中的项目太多,java,vaadin,Java,Vaadin,我正在使用Vaadin构建一个web应用程序,其中一个特性需要一个树来显示元素,问题是这个树最多加载40K个项目,甚至更多 在几千项的水平上,Vaadin树是可以接受的,但现在不行,它正在减缓web浏览器中的一切 我想到的是在web服务器和web客户端之间对负载进行分页,并显示一些在用户滚动树时更新的项目,问题是我不知道从哪里开始,即使这是否适用 这是一个好方法吗?有更好的吗? 为表放弃树不是一个解决方案,客户不希望。据我所知,树组件不支持内置的延迟加载(这对我们所有人来说都是最方便的) 一种办
为表放弃树不是一个解决方案,客户不希望。据我所知,树组件不支持内置的延迟加载(这对我们所有人来说都是最方便的) 一种办法是:
- 实现您自己的容器作为数据源
- 使用展开树节点后,从容器中惰性加载树元素
您可以找到可折叠容器的示例实现
我希望它能有所帮助。在这种情况下,我建议您使用
TreeTable
而不是Tree
。它将行从服务器延迟加载到客户端,这样不会减慢浏览器的速度。您可以通过在展开树的节点时动态添加子节点来延迟加载树的内容。我多次使用的方法的基本思想是
final Tree tree = new Tree();
//get the top level collection of entities
Collection<MyEntity> myEntitiesCategories = findEntities(MyEntity.class);//findEntities is one of your method that retrieves entities from a datasource
for (MyEntity myEntity : myEntitiesCategories) {
tree.addItem(myEntity);
}
tree.addListener(new Tree.ExpandListener() {
@Override
public void nodeExpand(ExpandEvent event) {
MyEntity myEntityCategory = (MyEntity) event.getItemId();
Collection<MyEntity> myEntities = myEntityCategory.getChildrenMyEntities();
for (MyEntity myEntity : myEntities) {
tree.addItem(myEntity);
tree.setParent(myEntity, myEntityCategory);
tree.setChildrenAllowed(myEntity, false);//the boolean value could also be true, it depends on whether it can have children or not
}
}
});
final Tree=new Tree();
//获取顶级实体集合
集合MyEntityCategories=findentials(MyEntity.class)//findEntities是从数据源检索实体的方法之一
对于(MyEntity MyEntity:myEntitiesCategories){
树。addItem(myEntity);
}
addListener(new tree.ExpandListener()){
@凌驾
public void nodeExpand(ExpandEvent事件){
MyEntity myEntityCategory=(MyEntity)事件。getItemId();
集合myEntities=myEntityCategory.getChildrenMyEntities();
for(MyEntity MyEntity:myEntities){
树。addItem(myEntity);
setParent(myEntity,myEntityCategory);
tree.setChildrenAllowed(myEntity,false);//布尔值也可以为true,这取决于它是否可以有子级
}
}
});
即使在Vaadin文档中,它说树的延迟加载是,我还是设法实现了以下延迟加载分层接口。
将所有元素存储在本地结构中非常重要(在我的示例中是HashMap
层次结构中),不要多次读取元素,这不起作用。我想是因为Vaadin没有使用equals()
和hashCode()
我希望这个例子能帮助其他人,因为我在互联网上找不到真实的例子
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import com.softmodeler.common.CommonPlugin;
import com.softmodeler.model.OutputNode;
import com.softmodeler.service.IViewService;
import com.vaadin.data.Container.Hierarchical;
import com.vaadin.data.Item;
import com.vaadin.data.Property;
import com.vaadin.data.util.BeanItem;
/**
* @author Flavio Donzé
* @version 1.0
*/
public class OutputNodeHierachical implements Hierarchical {
private static final long serialVersionUID = 8289589835030184018L;
/** the view service */
private IViewService service = CommonPlugin.getService(IViewService.class);
/** collection of all root nodes */
private List<OutputNode> rootNodes = null;
/** parent=>children mapping */
private Map<OutputNode, List<OutputNode>> hierarchy = new HashMap<>();
/**
* constructor
*
* @param rootNodes collection of all root nodes
*/
public OutputNodeHierachical(List<OutputNode> rootNodes) {
this.rootNodes = Collections.unmodifiableList(rootNodes);
addToHierarchy(rootNodes);
}
@Override
public Collection<?> getChildren(Object itemId) {
try {
List<OutputNode> children = hierarchy.get(itemId);
if (children == null) {
OutputNode node = (OutputNode) itemId;
children = service.getChildren(node.getNodeId(), false);
hierarchy.put(node, children);
// add children to hierarchy, their children will be added on click
addToHierarchy(children);
}
return children;
} catch (Exception e) {
VaadinUtil.handleException(e);
}
return null;
}
/**
* add each element to the hierarchy without their children hierarchy(child=>null)
*
* @param children elements to add
*/
private void addToHierarchy(List<OutputNode> children) {
for (OutputNode child : children) {
hierarchy.put(child, null);
}
}
@Override
public boolean areChildrenAllowed(Object itemId) {
return !((OutputNode) itemId).getChilds().isEmpty();
}
@Override
public boolean hasChildren(Object itemId) {
return !((OutputNode) itemId).getChilds().isEmpty();
}
@Override
public Object getParent(Object itemId) {
String parentId = ((OutputNode) itemId).getParentId();
for (OutputNode node : hierarchy.keySet()) {
if (node.getNodeId().equals(parentId)) {
return node;
}
}
return null;
}
@Override
public Collection<?> rootItemIds() {
return rootNodes;
}
@Override
public boolean isRoot(Object itemId) {
return rootNodes.contains(itemId);
}
@Override
public Item getItem(Object itemId) {
return new BeanItem<OutputNode>((OutputNode) itemId);
}
@Override
public boolean containsId(Object itemId) {
return hierarchy.containsKey(itemId);
}
@Override
public Collection<?> getItemIds() {
return hierarchy.keySet();
}
@Override
public int size() {
return hierarchy.size();
}
@Override
public boolean setParent(Object itemId, Object newParentId) throws UnsupportedOperationException {
throw new UnsupportedOperationException();
}
@Override
public boolean setChildrenAllowed(Object itemId, boolean areChildrenAllowed) throws UnsupportedOperationException {
throw new UnsupportedOperationException();
}
@Override
public Item addItem(Object itemId) throws UnsupportedOperationException {
throw new UnsupportedOperationException();
}
@Override
public Object addItem() throws UnsupportedOperationException {
throw new UnsupportedOperationException();
}
@Override
public boolean removeItem(Object itemId) throws UnsupportedOperationException {
throw new UnsupportedOperationException();
}
@Override
public boolean removeAllItems() throws UnsupportedOperationException {
throw new UnsupportedOperationException();
}
@Override
public Class<?> getType(Object propertyId) {
throw new UnsupportedOperationException();
}
@Override
public Collection<?> getContainerPropertyIds() {
throw new UnsupportedOperationException();
}
@Override
public Property<?> getContainerProperty(Object itemId, Object propertyId) {
throw new UnsupportedOperationException();
}
@Override
public boolean addContainerProperty(Object propertyId, Class<?> type, Object defaultValue) throws UnsupportedOperationException {
throw new UnsupportedOperationException();
}
@Override
public boolean removeContainerProperty(Object propertyId) throws UnsupportedOperationException {
throw new UnsupportedOperationException();
}
}
OutputNodeHierachical dataSource = new OutputNodeHierachical(rootNodes);
Tree mainTree = new Tree();
mainTree.setSizeFull();
mainTree.setContainerDataSource(dataSource);
mainTree.addItemClickListener(new ItemClickListener() {
private static final long serialVersionUID = -413371711541672605L;
@Override
public void itemClick(ItemClickEvent event) {
OutputNode node = (OutputNode) event.getItemId();
openObject(node.getObjectId());
}
});