ZK Essentials/Chapter 6: Implementing CRUD

Target Application

In this chapter, we are going to build an application with 4 basic operations, CRUD (Create, Read, Update, and Delete). The application's user interface looks like the images below:

Select an Item:

Select a Todo Item

It is a personal todo list management system and it has following features:

1. Create a todo item.

   Type item name in upper-left textbox and click File:Tutorial-chi6-plus.png or press "Enter" key to create a new todo item.

2. Finish a todo item.

   Click the checkbox in front of a todo item to mark it as finished and the item name will be decorated with line-through.

3. Modify a todo item.

   Click an existing item and the detail editor appears. Then you can edit the item's details.

4. Delete a todo item.

   Click File:Tutorial-chi6-cross.png to delete an existing todo item.

MVC Approach

If you have read previous chapters, constructing user interface for the example application should not be a big problem. Let's look at the layout first and ignore the details.

Layout in chapter6/todolist-mvc.zul

<?link rel="stylesheet" type="text/css" href="/style.css"?>
<window apply="org.zkoss.tutorial.chapter6.mvc.TodoListController" 
	border="normal" hflex="1" vflex="1" contentStyle="overflow:auto">
	<caption src="/imgs/todo.png" sclass="fn-caption" label="Todo List (MVC)"/>
	<borderlayout>
		<center autoscroll="true" border="none">
			<vlayout hflex="1" vflex="1">
				<!-- todo creation function-->	
				<!-- todo list -->
			</vlayout>
		</center>
		<east id="selectedTodoBlock" visible="false" width="300px" border="none" collapsible="false" splittable="true" minsize="300" autoscroll="true">
			<vlayout >
				<!-- detail editor -->
			</vlayout>
		</east>
	</borderlayout>
</window>

• Line 5: We construct the user interface with Border Layout to separate layout into 2 areas.
• Line 6: The center area contains a todo creation function and a todo list.
• Line 12: The east area is a todo item editor which is invisible if no item selected.

Read

As we talked in previous chapters, we can use Template to define how to display a data model list with implicit variable each.

Display a To-do List

...
	<listbox id="todoListbox" vflex="1">
		<listhead>
			<listheader width="30px" />
			<listheader/>
			<listheader hflex="min"/>
		</listhead>
		<template name="model">
			<listitem sclass="${each.complete?'complete-todo':''}" value="${each}">
				<listcell>
					<checkbox forward="onCheck=todoListbox.onTodoCheck" checked="${each.complete}"/>
				</listcell>
				<listcell>
					<label value="${each.subject}"/>
				</listcell>
				<listcell>
					<button forward="onClick=todoListbox.onTodoDelete" image="/imgs/cross.png" width="36px"/>
				</listcell>
			</listitem>
		</template>
	</listbox>
...

• Line 8: The default value for required attribute name is "model".
• Line 9: We can implement simple presentation logic with EL expression. Here we apply different styles according to a flag each.complete. We also set a whole object in value attribute, and later we can get the object in the composer.
• Line 11: The each.complete is a boolean variable so that we can assign it to checked. By doing this, the Checkbox will be checked if the to-do item's compelete variable is true.
• Line 11, 17: The forward attribute is used to forward events to another component and we will talk about it in later sections.

In the composer, we should provide a data model for the Listbox.

public class TodoListController extends SelectorComposer<Component>{


	//wire components
	...
	@Wire
	Listbox todoListbox;
	
	...
	
	//services
	TodoListService todoListService = new TodoListServiceChapter6Impl();
	
	//data for the view
	ListModelList<Todo> todoListModel;
	ListModelList<Priority> priorityListModel;
	Todo selectedTodo;
	
	
	@Override
	public void doAfterCompose(Component comp) throws Exception{
		super.doAfterCompose(comp);
		
		//get data from service and wrap it to list-model for the view
		List<Todo> todoList = todoListService.getTodoList();
		todoListModel = new ListModelList<Todo>(todoList);
		todoListbox.setModel(todoListModel);
		
		...
	}
...
}

• Line 25 ~ 27: We initialize the data model in doAfterCompose(). Get data from the service class todoListService and create a ListModelList object. Then set it as the data model of todoListbox.