Handling tons of data – LazyDataModel
by Oleg Varaksin, Mert Çalışkan
PrimeFaces Cookbook - Second Edition
- PrimeFaces Cookbook Second Edition
- Table of Contents
- PrimeFaces Cookbook Second Edition
- Credits
- Foreword
- Foreword
- About the Authors
- About the Reviewers
- www.PacktPub.com
- Preface
- 1. Getting Started with PrimeFaces
- 2. Theming Concepts
- 3. Enhanced Inputs and Selects
- Introduction
- Formatted input with inputMask
- Auto suggestion with autoComplete
- Usable features of inputTextArea
- Discovering selectBooleanCheckbox and selectManyCheckbox
- Choosing a single item with selectOneMenu
- Basic and advanced calendar scenarios
- Spinner – different ways to provide input
- Slider – different ways to provide input
- Rich text editing with the editor
- Advanced editing with an in-place editor
- Enhanced password input
- Star-based rating input
- 4. Grouping Content with Panels
- Introduction
- Grouping content with a standard panel
- PanelGrid with colspan and rowspan support
- Vertical stacked panels with accordion
- Displaying overflowed content with scrollPanel
- Working with a tabbed panel
- Grouping of buttons and more with toolbar
- The multipurpose output panel
- Simulating the portal environment with dashboard
- Creating complex layouts
- Responsive layout with Grid CSS
- 5. Data Iteration Components
- Introduction
- Selecting rows in dataTable
- Sorting and filtering data in dataTable
- In-cell editing with dataTable
- Resizing, reordering, and toggling columns in dataTable
- Making dataTable responsive
- Using subTable for grouping
- Handling tons of data – LazyDataModel
- Listing data with dataList
- Listing data with pickList
- Listing data with orderList
- Visualizing data with tree
- Visualizing data with treeTable
- Exporting data in various formats
- Managing events with schedule by leveraging lazy loading
- Visualizing data with dataScroller
- 6. Endless Menu Variations
- Introduction
- Statically and dynamically positioned menus
- Creating programmatic menus
- The context menu with nested items
- Integrating the context menu
- Breadcrumb – providing contextual information about page hierarchy
- SlideMenu – menu in the iPod style
- TieredMenu – submenus in nested overlays
- MegaMenu – the multicolumn menu
- PanelMenu – hybrid of accordion and tree
- MenuButton – multiple items in a popup
- Accessing commands via menubar
- Displaying checkboxes in selectCheckboxMenu
- 7. Working with Files, Images, and Multimedia
- Introduction
- Basic, automatic, drag and drop, and multiple file uploading
- Downloading files
- Cropping images
- Creating dynamic image streaming programmatically
- Displaying a collection of images with galleria
- Displaying a collection of images with imageSwitch
- Displaying a collection of images with contentFlow
- Embedding the multimedia content in JSF pages
- Capturing images with photoCam
- 8. Drag Me, Drop Me
- 9. Creating Charts and Maps
- Introduction
- Creating line, area, bar, and pie charts
- Creating combined charts
- Updating live data in charts with polling
- Interacting with charts via AJAX
- Basic mapping with GMaps
- Adding, selecting, and dragging markers in maps
- Creating rectangles, circles, polylines, and polygons in maps
- Enabling InfoWindow and streetView on maps
- 10. Client-side Validation
- 11. Miscellaneous Advanced Use Cases
- Introduction
- Programmatic updating and scrolling with RequestContext
- Two ways of triggering the JavaScript execution
- Adding AJAX callback parameters – validation within a dialog
- Opening external pages in dynamically generated dialogs
- Polling – sending periodical AJAX requests
- Blocking page pieces during long-running AJAX calls
- Controlling form submission using defaultCommand
- Clever focus management in forms
- Layout pitfalls of menus and dialogs
- Targetable messages with severity levels
- Conditional coloring in dataTable
- Sticking a component when scrolling
- Reducing page load time using content caching
- Possibilities for exception handling in PrimeFaces
- Index
The dataTable component provides support for displaying tons of data by enabling lazy loading. In order to handle large datasets, a data model needs to be implemented based on org.primefaces.model.LazyDataModel to support pagination, sorting, filtering, and live scrolling.
First, the lazy attribute should be set to true for lazy loading to be enabled for the table, and the abstract load method should be implemented in org.primefaces.model.LazyDataModel. We must also implement the getRowData and getRowKey methods when selection is enabled in the table. The lazy data model should be constructed with the list of Car instances and be bound to the table:
List<Car> cars = new ArrayList<Car>(millions_of_cars); LazyDataModel<Car>lazyModel = new LazyCarDataModel(cars);
The table calls the load method implementation with the following parameters when paging, sorting, or filtering actions occur:
first: This is the index of the first data to displaypageSize: This is the number of data items to load on the pagesortField: This is the name of the sort field (for example,"name"forsortBy="#{car.name}")sortOrder: This is theorg.primefaces.model.SortOrderenumeration; the value could be eitherASCENDING,DESCENDING, orUNSORTEDfilter: This filters the map with a field name as the key (for example,"name"forfilterBy="#{car.name}") and the value
The total row count should also be set to the lazy data model in order to get the pagination work done properly by invoking the setRowCount method of the data model.
The field attribute is provided by <p:column>; this is where the name of the field is passed to the load method in the sortField or filter method arguments according to the action taken. If field is not provided, the name of the field will be extracted from the values of the filterBy or sortBy attributes.
This recipe is available in the demo web application on GitHub (https://github.com/ova2/primefaces-cookbook/tree/second-edition). Clone the project if you have not done it yet, explore the project structure, and build and deploy the WAR file on application servers compatible with Servlet 3.x, such as JBoss WildFly and Apache TomEE.
The showcase for the recipe is available at http://localhost:8080/pf-cookbook/views/chapter5/dataTableLazyDataModel.jsf.
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