Case Study: strategies to do data binding and value building in the application tier

Introduction

One of the major tasks for the application tier in a wab application is the serialize and deserialize data between browsers (a plain-text format, the html document) and the target data beans in the appilcation tier (an object-oriented format), the translation between paremeters in HttpRequests and data beans that you use to invoke API in next tier. When doing the translation, people have been struggling amoung performance, maintainability and flexibility. The goal of this study is to find the suitable way to satisfy most of the struggling issues

In this article, I will first show you several approaches people have been doing and then bring up my solution. Since the situation is similar in vareity of web application frameworks such as Struts, JSF, Spring MVC and so on, I will use Spring MVC as my environment.

I will assume that we have a relatively "complicate" case where a single page contains content from two different data beans at the business tier, in our case, Bamboo and Source. (We will see the live page below in details) You will see a "Bamboo Administration" page when clicking at links "See the page with live code here" below. In the page, there are two subframes, list and edit. In the lower subframe, the edit area, you can modify the info about each selected (from the upper subframe) bamboo and select its whole sale source. What we are talking about for this study is the Save action. When users click at Save button, we submit content from two business data beans, Bamboo and Source.

Note: there are some other issues you may want to take a look on the pageShow details

The Problem:

• The old "ActionForm" style

In this approach, the old way Struts people did in their actions, a "ActionForm" (BambooAdminEditForm0Bean), is used to contain two flatted objects (other web frameworks also have similar "data storages" such as component tree in JSF, "pages" in Tapestry, that you can not use directly to invoke APIs at next tier). Then in the handler (BambooAdminEditForm0Controller), I "menually" do the value building. That is, I call the getters in BambooAdminEditForm0Bean and call the setters of Bamboo or Source to fill up these two objects so that I can use them to invoke APIs at next tier. See the problem diagramShow details



Show details


The advantage is


1. BambooAdminEditForm0Bean isolates the business info from presentation layer so that business objects Bamboo and Source never appear in the presentation layer, bamboo_admin_edit0.jsp.


The disadvantages are:


1. the "ActionForm" (BambooAdminEditForm0Bean) construction waste the process time since I can not use it to invoke next tier API directly and there is no need to have this "data storage" addition to the HttpRequest. That is, I lower down the performance for nothing.

2. the hard-coded areas like value building section in the controller (BambooAdminEditForm0Controller), configuration file (springapp-servlet.xml) and the view (bamboo_admin_edit0.jsp) will be a big task with a frequently-changed business tier (or even business requirements) during development and maintenance.

See the page with live code for "ActionForm" style here


Source CodesShow details


• The source files involves in thhis approach

The view

• bamboo_admin_edit0.jsp
• source0.jsp
• getSource0.jsp

The Business Data

• Bamboo.java
• Source.java

The Business Tier APIs

• BambooManager.java

The DAO

• BambooManagerDao.java
• BambooManagerDaoJdbc.java

The Controller

• BambooAdminEditForm0Controller.java

The Command

• BambooAdminEditForm0Bean.java

The Configuration

• springapp-servlet.xml



• Other related source files



Show details




• The Direct-Binding style

In this approach, I bind the business objects (Bamboo and Source) directly onto the edit page (JSP view). So there is no value building section in the hander (BambooAdminEditFormController). See the problem diagramShow details



Show details


The advantage is


1. the hard-coded value building section in the controller (BambooAdminEditFormBean) is eliminated.


The disadvantages are:


1. the isolation between presentation layer and business layer is gone. This means that I need to change my presentation layer (the edit jsp page) when the business beans are changed. You can see Bamboo and Source appear in the presentation layer (bamboo_admin_edit0.jsp).

2. I still have the "ActionForm" (BambooAdminEditFormBean) and there is still hard-coded sction (the names of business beans) in my config file (springapp-servlet.xml) and the "ActionForm" (BambooAdminEditFormBean). This means that I still need to make modification in my application tier chasing the modification in business tier

See the page with live code for Direct-Binding style here


Source CodesShow details


• The source files involves in thhis approach

The view

• bamboo_admin_edit.jsp
• source.jsp
• getSource.jsp

The Business Data

• Bamboo.java
• Source.java

The Business Tier APIs

• BambooManager.java

The DAO

• BambooManagerDao.java
• BambooManagerDaoJdbc.java

The Controller

• BambooAdminEditFormController.java

The Command

• BambooAdminEditFormBean.java

The Configuration

• springapp-servlet.xml



• Other related source files



Show details

The Solution:

See the details about my solution here