Chapter 22. Spring.NET Web Framework

• Dependency Injection for all ASP.NET artifacts. This includes pages and user controls but also modules, providers and HTTP handlers. Your pages, controls, etc., do not have any Spring dependencies in order to be configured via dependency injection.

• Bi-directional data binding. This allows you to declaratively define the data that will be marshaled out of your html/user controls and into a data model that in turn is generally submitted to the application layer. After the data model is updated in the application layer, those changes are automatically reflected in the html/user controls on post back. This removes large amounts of tedious, error prone boilerplate code.

• Web object scopes. Object definitions can be defined at the application, session or request scope. This makes it easy to inject, say a session scoped shopping cart, into your page without having to do any lower level programming.

• Data Model Management. While ASP.NET managed the view state of your form, it does not offer facilities to manage the data model that you build up to submit to the application layer. Spring provides a mechanism similar to view state to help manage your data model.

• UI agnostic validation framework. Declaratively define complex validation rules, for example that take into account complex relationships in your data model. Error controls are provided to easily render validation failure. This allows you to centralize your validation logic and also reuse it on the server side, for example using parameter validation advice described in the aspect library chapter

• Externalized page navigation through 'result mapping'. Instead of hard coding urls and data to direct where a page should go next, result mappings are externally defined and configured that associate logical names and a URL (+ data). This also allows for the encryption of values that are sent via Response.Redirect.

• Improved localization and master page support - Advanced localization features (including image localization) as well as declarative configuration of what mater page to apply to different parts of your web application are easy to perform.

Unsurprisingly, Spring.Web builds on top of the Spring.NET IoC container, and makes heavy use (internally) of the easy pluggability and standardized configuration afforded by the IoC container. This also means that all of the controllers (ASP.NET Pages) that make up a typical Spring.Web enabled application will be configured using the same standard Spring.NET XML configuration syntax. Spring.Web uses a custom PageHandlerFactory implementation to load and configure a Spring.NET IoC container, which is in turn used to locate an appropriate Page to handle a HTTP request. The WebSupportModule configures miscellaneous Spring infrastructure classes for use in a web environment, for example setting the storage strategy of LogicalThreadContext to be HybridContextStorage.

The instantiation and configuration of the Spring.NET IoC container by the Spring.Web infrastructure is wholly transparent to application developers, who will typically never have to explicitly instantiate and configure an IoC container manually (by for example using the new operator in C#). In order to effect the transparent bootstrapping of the IoC container, the Spring.Web infrastructure requires the insertion of the following configuration snippet into each and every Spring.Web-enabled web application's root Web.config file (the verb and path properties can of course be changed from the values that are shown below):

<system.web>
    <httpHandlers>
        <add verb="*" path="*.aspx" type="Spring.Web.Support.PageHandlerFactory, Spring.Web"/>
    </httpHandlers>
    <httpModules>
        <add name="Spring" type="Spring.Context.Support.WebSupportModule, Spring.Web"/>
    </httpModules>
    ...
</system.web>

Please note that this snippet of standard ASP.NET configuration is only required to be present in the root directory of each Spring.Web web application (i.e. in the web.config file present in the top level virtual directory of an ASP.NET web application).

The above XML configuration snippet will direct the ASP.NET infrastructure to use Spring.NET's page factory, which will in turn create instances of the appropriate .aspx Page, (possibly) inject dependencies into said Page (as required), and then forward the handling of the request to said Page.

After the Spring.Web page factory is configured, you will also need to define a root application context by adding a Spring.NET configuration section to that same web.config file. The final configuration file should look a little like this (your exact configuration will no doubt vary in particulars)...

<?xml version="1.0" encoding="utf-8"?>
<configuration>

    <configSections>
        <sectionGroup name="spring">
          <section name="context" type="Spring.Context.Support.WebContextHandler, Spring.Web"/>
        </sectionGroup>
    </configSections>

    <spring>
        <context>
            <resource uri="~/Config/CommonObjects.xml"/>
            <resource uri="~/Config/CommonPages.xml"/>

            <!-- TEST CONFIGURATION -->
            <!--
            <resource uri="~/Config/Test/Services.xml"/>
            <resource uri="~/Config/Test/Dao.xml"/>
            -->

            <!-- PRODUCTION CONFIGURATION -->

            <resource uri="~/Config/Production/Services.xml"/>
            <resource uri="~/Config/Production/Dao.xml"/>

        </context>
    </spring>

    <system.web>
        <httpHandlers>
            <add verb="*" path="*.aspx" type="Spring.Web.Support.PageHandlerFactory, Spring.Web"/>
        </httpHandlers>
        <httpModules>
            <add name="Spring" type="Spring.Context.Support.WebSupportModule, Spring.Web"/>
        </httpModules>
    </system.web>

</configuration>

There are a few important points that need to be noted with regard to the above configuration:

<system.webServer>
  <validation validateIntegratedModeConfiguration="false"/>
  <modules>
    <add name="Spring" type="Spring.Context.Support.WebSupportModule, Spring.Web"/>
  </modules>
  <handlers>
    <add name="SpringPageHandler" verb="*" path="*.aspx" type="Spring.Web.Support.PageHandlerFactory, Spring.Web"/>
    <add name="SpringContextMonitor" verb="*" path="ContextMonitor.ashx" type="Spring.Web.Support.ContextMonitor, Spring.Web"/>
  </handlers>
</system.webServer>

ASP.NET provides a hierarchical configuration mechanism by allowing application developers to override configuration settings specified at a higher level in the web application directory hierarchy with configuration settings specified at the lower level.

For example, a web application's root Web.config file overrides settings from the (lower level) machine.config file. In the same fashion, settings specified within the web.config file within a subdirectory of a web application will override settings from the root Web.config and so on. Lower level Web.config files can also add settings of their own that were not previously defined anywhere.

Spring.Web leverages this ASP.NET feature to provide support for a context hierarchy. Your lower level Web.config files can be used to add new object definitions or to override existing ones per virtual directory.

What this means to application developers is that one can easily componentize an application by creating a virtual directory per component and creating a custom context for each component that contains the necessary configuration info for that particular context. The configuration for a lower level component will generally contain only those definitions for the pages that the component consists of and (possibly) overrides for some of the definitions from the root context (for example, menus).

Because each such lower level component will usually contain only a few object definitions, application developers are encouraged to embed those object definitions directly into the Web.config for the lower level context instead of relying on an external resource containing object definitions. This is easily accomplished by creating a component Web.config similar to the following one:

<?xml version="1.0" encoding="utf-8"?>
<configuration>

  <configSections>
    <sectionGroup name="spring">
       <section name="objects" type="Spring.Context.Support.DefaultSectionHandler, Spring.Core"/>
    </sectionGroup>
  </configSections>

  <spring>
    <context type="Spring.Context.Support.WebApplicationContext, Spring.Web">
        <resource uri="config://spring/objects"/>
    </context>

    <objects xmlns="http://www.springframework.net">
        <object type="MyPage.aspx" parent="basePage">
              <property name="MyRootService" ref="myServiceDefinedInRootContext"/>
              <property name="MyLocalService" ref="myServiceDefinedLocally"/>
              <property name="Results">
                 <!-- ... -->
              </property>
        </object>
        <object id="myServiceDefinedLocally" type="MyCompany.MyProject.Services.MyServiceImpl, MyAssembly"/>
    </objects>
  </spring>
</configuration>

The <context/> element seen above (contained within the <spring/> element) simply tells the Spring.NET infrastructure code to load (its) object definitions from the spring/objects section of the configuration file.

You can (and should) avoid the need to specify <configSections/> element by moving the configuration handler definition for the <objects> element to a higher level (root) Web.config file, or even to the level of the machine.config file if Spring.NET is to be used for multiple applications on the same server.

A very important point to be aware of is that this component-level context can reference definitions from its parent context(s). Basically, if a referenced object definition is not found in the current context, Spring.NET will search all the ancestor contexts in the context hierarchy until it finds said object definition (or ultimately fails and throws an exception).

1. The first definition is an abstract definition for the base page that many other pages in the application will inherit from. In this case, the definition simply specifies which page is to be referenced as the master page, but it will typically also configure localization-related dependencies and root folders for images, scripts and CSS stylesheets.

2. The second definition defines a login page that neither inherits from the base page nor references the master page. What it does show is how to inject a service object dependency into a page instance (the authenticationService is defined elsewhere).

3. The final definition defines a default application page. In this case it simply inherits from the base page in order to inherit the master page dependency, but apart from that it doesn't need any additional dependency injection configuration.

Spring.Web also allows application developers to inject dependencies into controls (both user controls and standard controls) that are contained within a page. This can be accomplished globally for all controls of a particular Type by using the location of the .ascx as the object type identifier. This is similar to injecting into .aspx pages shown above.

<object type="~/controls/MyControl.ascx" abstract="true">
   <!-- inject dependencies here... -->
</object>

In either case, be sure to mark the object definition as abstract (by adding abstract="true" to the attribute list of the <object/> element).

You can perform dependency injection on custom HTTP modules through the use of the class Spring.Context.Support.HttpApplicationConfigurer. You register your custom HTTP module as you would normally, for example a module of the type HtmlCommentAppenderModule, taken from the Web Quickstart, appends additional comments into the http response. It is registered as shown below

<httpModules>
  <add name="HtmlCommentAppender" type="HtmlCommentAppenderModule"/>
</httpModules>

To configure this module, naming conventions are used to identify the module name with configuration instructions in the Spring configuration file. The ModuleTemplates property of HttpApplicationConfigurer is a dictionary that takes as a key the name of the HTTP module, HtmlCommentAppender, and as a value the configuration instructions as you would normally use for configuring an object with Spring. An example is shown below. HttpApplicationConfigurer' ModuleTemplates property.

<object name="HttpApplicationConfigurer" type="Spring.Context.Support.HttpApplicationConfigurer, Spring.Web">
  <property name="ModuleTemplates">
     <dictionary>
       <entry key="HtmlCommentAppender"> <!-- this name must match the module name -->
         <object>
           <!-- select "view source" in your browser on any page to see the appended html comment -->
           <property name="AppendText" value="My configured comment!" />
         </object>
       </entry>
     </dictionary>
  </property>
</object>

You can see this example in action in the Web Quickstart.

You can perform dependency injection on IHttpHandlers and IHttpHandlerFactory. This effectively allows for a fully Spring-managed <httpHandlers> configuration section. To configure an IHttpHandler or IHttpHandlerFactory you should register Spring's MappingHandlerFactory with a specific path or wildcard string (i.e. *.aspx) using the standard configuration of an <httpHandler> in web.config. This is shown below

<system.web>
  <httpHandlers>
    <!-- 
      the lines below map *any* request ending with *.ashx or *.whatever
      to the global(!) MappingHandlerFactory. Further "specialication" 
      of which handler to map to is done within MappingHandlerFactory's configuration -
      use MappingHandlerFactoryConfigurer for this (see below)
    -->
    <add verb="*" path="*.ashx" type="Spring.Web.Support.MappingHandlerFactory, Spring.Web" validate="true"/>
    <add verb="*" path="*.whatever" type="Spring.Web.Support.MappingHandlerFactory, Spring.Web" validate="false"/>
  </httpHandlers>
</system.web>

The specialization of which specific handler is mapped to the path is done by configuration of Spring's MappingHandlerFactoryConfigurer class. The MappingHandlerFactoryConfigurer is configured by specifying a dictionary of key value paris, the key value is a regular expression that will match the request URL and the value is an instance of an IHttpHandler or IHttpHandlerFactory configured via dependency injection.

the configuration of MappingHandlerFactoryConfigurer is shown below

<objects xmlns="http://www.springframework.net">

    <!-- configures the global GenericHandlerFactory instance -->
    <object name="mappingHandlerFactoryConfigurer" type="Spring.Web.Support.MappingHandlerFactoryConfigurer, Spring.Web">
        <property name="HandlerMap">
            <dictionary>
                <!-- map any request ending with *.whatever to NoOpHandler -->
                <entry key="\.whatever$" value="myCustomHandler" />
                <entry key="\.ashx$" value="standardHandlerFactory" />
            </dictionary>
        </property>
    </object>

    <object name="standardHandlerFactory" type="Spring.Web.Support.DefaultHandlerFactory, Spring.Web" />

    <!-- defines a standard singleton that will handle *.whatever requests -->
    <object name="myCustomHandler" type="MyCustomHttpHandler, App_Code">
        <property name="MessageText" value="This text is injected via Spring" />
    </object>
    
    <!-- 
        used for configuring ~/DemoHandler.ashx custom handler
        note, that this is an abstract definition because 'type' is not specified 
    -->
    <object name="DemoHandler.ashx">
        <property name="OutputText">
            <value>This text is injected via Spring</value>
        </property>
    </object>
</objects>

Spring's DefaultHandlerFactory will use the .NET class System.Web.UI.SimpleHandlerFactory to create handler instaces and will configure each instances used an object definition whose name matches the request url's filename. The abstract object definition of DemoHandler.ashx is an example of this approach. You may also configure standard classes that implment the IHttpHandler interface as demonstrated in the example above for the class MyCustomHttpHandler.

Please refer to the Web Quickstart application too see this in action.

Custom providers can be configured with Spring. The approach to configuration is a family of adapters that correspond 1-to-1 with the standard ASP.NET providers that are registered using the standard ASP.NET mechanism. The adapters inherit from their correspondingly named provider class in the BCL.

Here is an example of how to register the adapter for membership providers.

        <membership defaultProvider="mySqlMembershipProvider">
            <providers>
                <clear/>
                <add connectionStringName="" name="mySqlMembershipProvider" type="Spring.Web.Providers.MembershipProviderAdapter, Spring.Web"/>
            </providers>
        </membership>

The name of the provider must match the name of the object in the spring configuration that will serve as the actual provider implementation. For convenience there are configurable versions of the providers found in ASP.NET so that you can use the full functionality of spring to configure these standard provider implementations, for example using property place holders, etc. These are

Here is an example configuration taken from the Web Quickstart that simply sets the description property and connection string.

    <object id="mySqlMembershipProvider" type="Spring.Web.Providers.ConfigurableSqlMembershipProvider">
        <property name="connectionStringName" value="MyLocalSQLServer" />
        <property name="parameters">
            <name-values>
                <add key="description" value="membershipprovider description" />
            </name-values>
        </property>
    </object>

Your own custom providers of course will contain additional configuration specific to your implementation.

There might be situations where it is necessary to customize Spring.Web's dependency injection processing. In particular when using GridViews, which create a large number of child controls, dependency injection can slow down your page. To overcome this problem, you may tell Spring to handle the dependency injection process yourself by implementing the interface ISupportsWebDependencyInjection as shown below:

[C#]
class MyControl : Control, ISupportsWebDependencyInjection
{
  private IApplicationContext _defaultApplicationContext;

  public IApplicationContext DefaultApplicationContext
  {
    get { return _defaultApplicationContext; }
    set { _defaultApplicationContext = value; }
  }

  override protected AddedControl( Control control, int index )
  {
    // handle DI for children ourselves -
    // defaults to a call to InjectDependenciesRecursive
    WebUtils.InjectDependenciesRecursive( _defaultApplicationContext, control );
    base.AddedControl( control, index );
  }
}

There is a Spring server control, Panel, that provides an easier way to turn of dependency injection for parts of your page. Example use is shown below

<spring:Panel runat="server"
   suppressDependencyInjection="true"  
   renderContainerTag="false">

   .. put your heavy controls here - they won't be touched by DI

</spring:Panel>

By wrapping the performance sensitive parts of your page within this panel, you can easily turn off DI using the attribute suppressDependencyInjection. By default <spring:Panel/> won't render a container tag (<div>, <span>, etc.). You can modify this behavior by setting the attribute "renderContainerTag" accordingly.

The Spring.Web.UI.Page class exposes a property called MasterPageFile, which can be used to specify the master page.

The recommended way to do this is by leveraging the Spring.NET IoC container and creating definitions similar to the following:

<?xml version="1.0" encoding="utf-8" ?>
<objects xmlns="http://www.springframework.net">

  <object name="basePage" abstract="true">
      <property name="MasterPageFile" value="~/MasterLayout.ascx"/>
  </object>

  <object type="Child.aspx" parent="basePage">
      <!-- inject other objects that page needs -->
  </object>

</objects>

This approach allows application developers to change the master page being used for a number of pages within a web application. Of course, the master page can still be overridden on a per context or per page basis by creating a new abstract page definition within a child context, or by specifying the MasterPageFile property directly.

1. When the page is initially loaded (IsPostback == false), the InitializeModel() method is called which initializes the trip object by creating a new instance and setting its properties to desired values. Right before the page is rendered, the SaveModel() method will be invoked and whatever the value it returns will be stored within the HTTP Session. Finally, on each postback, the LoadModel() method will be called and the value returned by the previous call to SaveModel will be passed to it as an argument.

   In this particular case the implementation is very simple because our whole model is just the trip object. As such, SaveModel() simply returns the trip object and LoadModel() casts the savedModel() argument to Trip and assigns it to the trip field within the page. In the more complex scenarios, you will typically return a dictionary containing your model objects from the SaveModel() method, and read the values from that dictionary within the LoadModel().

2. InitializeDataBindings method defines the binding rules for all five input controls on our form. It does so by invoking AddBinding method on the BindingManager exposed by the page. AddBinding method is heavily overloaded and it allows you to specify a binding direction and a formatter to use in addition to the source and target binding expressions that are used above. We'll discuss these optional parameters shortly, but for now let's focus on the source and target expressions.

   The Data Binding framework uses Spring.NET Expression Language to define binding expressions. In most cases, like in the example above, both source and target expression will evaluate to a property or a field within one of the controls or a data model. This is always the case when you are setting a bi-directional binding, as both binding expressions need to be "settable". What is important to remember about InitializeDataBindings method is that it is executed only once per page type. Basically, all of the binding expressions are parsed the first time the page is instantiated, and are the cached and used by all instances of that same page type that are created at a later time. This is done for performance reasons, as data binding expression parsing on every postback is unnecessary and would add a significant overhead to the overall page processing time.

3. If you look at the SearchForFlights event handler, you will notice that it has no dependencies on the view elements. It simply uses the injected bookingAgent service and a trip object that in order to obtain a list of suggested flights. Furthermore, if you make any modifications to the trip object within your event handler, bound controls will be updated accordingly just before the page is rendered.

   This accomplishes one of the major goals we set out to achieve, allowing developers to remove view element references from the page event handlers and decouple controller-type methods from the view.

Spring.NET Data Binding framework revolves around two main interfaces: IBinding and IBindingContainer. The IBinding interface is definitely the more important one of the two, as it has to be implemented by all binding types. This interface defines several methods, with some of them being overloaded for convenience:

public interface IBinding
{
    void BindSourceToTarget(object source, object target, ValidationErrors validationErrors);

    void BindSourceToTarget(object source, object target, ValidationErrors validationErrors, 
                            IDictionary variables);

    void BindTargetToSource(object source, object target, ValidationErrors validationErrors);

    void BindTargetToSource(object source, object target, ValidationErrors validationErrors, 
                            IDictionary variables);

    void SetErrorMessage(string messageId, params string[] errorProviders);
}

As their names imply, BindSourceToTarget method is used to extract and copy bound values from the source object to the target object, while BindTargetToSource does the opposite. Both method names and parameter types are very generic for a good reason -- data binding framework can indeed be used to bind any two objects. Using it to bind web forms to model objects is just one of its possible uses, although a very common one and tightly integrated into the Spring.NET Web Framework.

The validationErrors parameter requires further explanation. While the data binding framework is not in any way coupled to the data validation framework, they are in some ways related. For example, while the data validation framework is best suited to validate the populated model according to the business rules, the data binding framework is in a better position to validate data types during the binding process. However, regardless of where specific validation is performed, all error messages should be presented to the user in a consistent manner. In order to accomplish this, Spring.NET Web Framework passes the same ValidationErrors instance to binding methods and to any validators that might be executed within your event handlers. This ensures that all error messages are stored together and are displayed consistently to the end user, using Spring.NET validation error controls.

The last method in the IBinding interface, SetErrorMessage, enables this by allowing you to specify the resource id of the error message to be displayed in the case of binding error, as well as the list of error providers that messages should be displayed in. We will see an example of the SetErrorMessage usage shortly.

The IBindingContainer interface extends the IBinding interface and adds the following members:

public interface IBindingContainer : IBinding
{
  bool HasBindings { get; }

  IBinding AddBinding(IBinding binding);
  IBinding AddBinding(string sourceExpression, string targetExpression);
  IBinding AddBinding(string sourceExpression, string targetExpression, BindingDirection direction);
  IBinding AddBinding(string sourceExpression, string targetExpression, IFormatter formatter);
  IBinding AddBinding(string sourceExpression, string targetExpression, BindingDirection direction, 
                      IFormatter formatter);
}

As you can see, this interface has a number of overloaded AddBinding methods. The first one, AddBinding(IBinding binding) is the most generic one, as it can be used to add any binding type to the container. The other four are convenience methods that provide a simple way to add the most commonly used binding type, SimpleExpressionBinding. The SimpleExpressionBinding is what we used in the example at the beginning of this section to bind our web form to a Trip instance. It uses Spring.NET Expression Language to extract and to set values within source and target objects. We discussed sourceExpression and targetExpression arguments earlier, so let's focus on the remaining ones.

namespace SpringAir.Domain
{
    [Serializable]
    public class TripPoint
    {
        // fields
        private Airport airport;
        private DateTime date;

        // constructors
        public TripPoint()
        {}

        public TripPoint(Airport airport, DateTime date)
        {
            this.airport = airport;
            this.date = date;
        }

        // properties
        public Airport Airport
        {
            get { return this.airport; }
            set { this.airport = value; }
        }

        public DateTime Date
        {
            get { return this.date; }
            set { this.date = value; }
        }
    }

    [Serializable]
    public class Airport
    {
        // fields
        private string code;
        private string name;

       // properties
        public string Code
        {
            get { return this.code; }
            set { this.code = value; }
        }

        public string Name
        {
            get { return this.name; }
            set { this.name = value; }
        }
    }
}

protected override void InitializeDataBindings()
    {
        BindingManager.AddBinding("leavingFromAirportCode.SelectedValue", "Trip.StartingFrom.Airport.Code", BindingDirection.TargetToSource);
        BindingManager.AddBinding("goingToAirportCode.SelectedValue", "Trip.ReturningFrom.Airport.Code", BindingDirection.TargetToSource);
        ...
    }

protected override void InitializeDataBindings()
    {
        BindingManager.AddBinding("@(airportDao).GetAirport(leavingFromAirportCode.SelectedValue)", "Trip.StartingFrom.Airport", BindingDirection.SourceToTarget);
        BindingManager.AddBinding("leavingFromAirportCode.SelectedValue", "Trip.StartingFrom.Airport.Code", BindingDirection.TargetToSource);

        BindingManager.AddBinding("@(airportDao).GetAirport(goingToAirportCode.SelectedValue)", "Trip.ReturningFrom.Airport", BindingDirection.SourceToTarget);
        BindingManager.AddBinding("goingToAirportCode.SelectedValue", "Trip.ReturningFrom.Airport.Code", BindingDirection.TargetToSource);
        ...
    }

public interface IFormatter
{
    string Format(object value);
    object Parse(string value);
}

[Default.aspx.cs]

protected override void InitializeDataBindings()
{
  // collect txtId.Text binding errors in "id.errors" collection
  BindingManager.AddBinding("txtId.Text", "Employee.Id").SetErrorMessage("ID has to be an integer", "id.errors");
  ...

[Default.aspx]
...
<asp:TextBox ID="txtId" runat="server" />
<!-- output validation errors from "id.errors" collection -->
<spring:ValidationError Provider="id.errors" runat="server" />
...

22.7.1.6. HttpRequestListBindingContainer

HttpRequestListBindingContainer extracts posted raw values from the request and populates the specified IList by creating objects of the type specified and populating each of these objects according to the requestBindings collection.

Please checkout the WebQuickStart sample's demo of HttpRequestListBindingContainer. Below

protected override void InitializeDataBindings()
{
  // HttpRequestListBindingContainer unbinds specified values from Request -> Productlist
  HttpRequestListBindingContainer requestBindings =
      new HttpRequestListBindingContainer("sku,name,quantity,price", "Products", typeof(ProductInfo));
  requestBindings.AddBinding("sku", "Sku");
  requestBindings.AddBinding("name", "Name");
  requestBindings.AddBinding("quantity", "Quantity", quantityFormatter);
  requestBindings.AddBinding("price", "Price", priceFormatter);

  BindingManager.AddBinding(requestBindings);
}

	Note
	Due to the fact, that browsers don't send the values of unchecked checkboxes, you can't use HttpRequestListBindingContainer with <input type="checkbox" > html controls.

To simplify use of Spring's Data Binding feature on web pages and controls, Spring.Web provides a special DataBindingPanel container control. A DataBindingPanel does not render any html code itself, but allows for specifying additional, data binding related attributes to its child controls:

<%@ Page Language="C#" CodeFile="Default.aspx.cs" Inherits="DataBinding_EasyEmployeeInfo_Default" %>
<%@ Register TagPrefix="spring" Namespace="Spring.Web.UI.Controls" Assembly="Spring.Web" %>
<html>
<body>
<spring:DataBindingPanel ID="ctlDataBindingPanel" runat="server">
    <table cellpadding="3" cellspacing="3" border="0">
        <tr>
            <td>Employee ID:</td>
            <td>
                <asp:TextBox ID="txtId" runat="server" BindingTarget="Employee.Id" />
            </td>
        </tr>
        <tr>
            <td>First Name:</td>
            <td><asp:TextBox ID="txtFirstName" runat="server" BindingTarget="Employee.FirstName" /></td>
        </tr>
    </table>
</spring.DataBindingPanel>
</body>
</html>

Using DataBindingPanel the binding information can be specified directly on the control declaration. The following attributes are recognized by a DataBindingPanel:

	Note
	The Visual Studio Web Form Editor will of course complain about binding attributes because it doesn't know them. You can safely ignore those warnings.

As was already mentioned in the introduction to this chapter, model management needs an application developer to override InitializeModel(), SaveModel() and LoadModel() for storing model information between requests in the user's session. On web farms this of course storing information in a user's session is not a good strategy. Thus it is possible to choose another persistence strategy by setting a Spring.Web.UI.Page's resp. Spring.Web.UI.UserControl's ModelPersistenceMedium property:

<object id="modelPersister" type="Sample.DatabaseModelPersistenceMedium, MyCode"/>

<object type="UserRegistration.aspx">
    <property name="ModelPersistenceMedium" ref="modelPersister"/>
</object>

To implement any arbitrary persistence strategy, one simply needs to implement the IModelPersistenceMedium interface:

public interface IModelPersistenceMedium
{
  // Load the model for the specified control context.
  object LoadFromMedium( Control context );

  // Save the specified model object.
  void SaveToMedium( Control context, object modelToSave );
}

The central idea behind 'push' localization is that an application developer should be able to specify localization resources in the resource file for the page and have those resources automatically applied to the user controls on the page by the framework. For example, an application developer could define a page such as UserRegistration.aspx...

<%@ Register TagPrefix="spring" Namespace="Spring.Web.UI.Controls" Assembly="Spring.Web" %>
<%@ Page language="c#" Codebehind="UserRegistration.aspx.cs"
    AutoEventWireup="false" Inherits="ArtFair.Web.UI.Forms.UserRegistration" %>
<html>
    <body>
        <spring:Content id="mainContent" contentPlaceholderId="main" runat="server">
            <div align="right">
                <asp:LinkButton ID="english" Runat="server" CommandArgument="en-US">English</asp:LinkButton>&nbsp;
                <asp:LinkButton ID="serbian" Runat="server" CommandArgument="sr-SP-Latn">Srpski</asp:LinkButton>
            </div>
            <table>
                <tr>
                    <td><asp:Label id="emailLabel" Runat="server"/></td>
                    <td><asp:TextBox id="email" Runat="server" Width="150px"/></td>
                </tr>
                <tr>
                    <td><asp:Label id="passwordLabel" Runat="server"/></td>
                    <td><asp:TextBox id="password" Runat="server" Width="150px"/></td>
                </tr>
                <tr>
                    <td><asp:Label id="passwordConfirmationLabel" Runat="server"/></td>
                    <td><asp:TextBox id="passwordConfirmation" Runat="server" Width="150px"/></td>
                </tr>
                <tr>
                    <td><asp:Label id="nameLabel" Runat="server"/></td>
                    <td><asp:TextBox id="name" Runat="server" Width="150px"/></td>
                </tr>
...

                <tr>
                    <td colspan="2">
                        <asp:Button id="saveButton" Runat="server"/>&nbsp;
                        <asp:Button id="cancelButton" Runat="server"/>
                    </td>
                </tr>
            </table>
        </spring:Content>
    </body>
</html>

A close inspection of the above .aspx code reveals that none of the Label or Button controls have had a value assigned to the Text property. The values of the Text property for these controls are stored in the local resource file (of the page) using the following convention to identify the resource (string).

$this.controlId.propertyName

The corresponding local resource file, UserRegistration.aspx.resx, is shown below.

<root>
  <data name="$this.emailLabel.Text">
    <value>Email:</value>
  </data>
  <data name="$this.passwordLabel.Text">
    <value>Password:</value>
  </data>
  <data name="$this.passwordConfirmationLabel.Text">
    <value>Confirm password:</value>
  </data>
  <data name="$this.nameLabel.Text">
    <value>Full name:</value>
  </data>

...

  <data name="$this.countryLabel.Text">
    <value>Country:</value>
  </data>
  <data name="$this.saveButton.Text">
    <value>$messageSource.save</value>
  </data>
  <data name="$this.cancelButton.Text">
    <value>$messageSource.cancel</value>
  </data>
</root>

VS2003

To view the .resx file for a page, you may need to enable "Project/Show All Files" in Visual Studio. When "Show All Files" is enabled, the .resx file appears like a "child" of the code-behind page. When Visual Studio creates the .resx file, it will include a xds:schema element and several reshead elements. Your data elements will follow the reshead elements. When working with the .resx files, you may want to choose "Open With" from the context menu and select the "Source Code" text editor.

	VS2005
	To create a resource file in VS2005, open your control or page in design mode and select "Tools/Generate local resource" from the menu

Finally a localizer must be configured for the page to enable automatic localization:

<object id="localizer" type="Spring.Globalization.Localizers.ResourceSetLocalizer, Spring.Core"/>

<object type="UserRegistration.aspx">
    <property name="Localizer" ref="localizer"/>
</object>

For more information on configuring localizers see Section 22.8.3, “Working with Localizers”

The last two resource definitions from the previous section require some additional explanation:

<data name="$this.saveButton.Text">
    <value>$messageSource.save</value>
  </data>
  <data name="$this.cancelButton.Text">
    <value>$messageSource.cancel</value>
  </data>

In some cases it makes sense to apply a resource that is defined globally as opposed to locally. In this example, it makes better sense to define values for the Save and Cancel buttons globally as they will probably be used throughout the application.

The above example demonstrates how one can achieve that by defining a resource redirection expression as the value of a local resource by prefixing a global resource name with the following string.

$messageSource.

Taking the case of the above example, this will tell the localizer to use the save and cancel portions of the resource key as lookup keys to retrieve the actual values from a global message source. The important thing to remember is that one need only define a resource redirect once, typically in the invariant resource file – any lookup for a resource redirect will simply fall back to the invariant culture, and result in a global message source lookup using the correct culture.

Global resources are (on a per-context basis) defined as a plain vanilla object definition using the reserved name of 'messageSource', which one can add to one's Spring.NET configuration file as shown below.

<object id="messageSource" type="Spring.Context.Support.ResourceSetMessageSource, Spring.Core">
    <property name="ResourceManagers">
        <list>
            <value>MyApp.Web.Resources.Strings, MyApp.Web</value>
        </list>
    </property>
</object>

	NET 2.0
	To use resources from your App_GlobalResources folder, specify App_GlobalResources as assembly name (see the SpringAir example application for more): <value>Resources.Strings, App_GlobalResources</value>

The global resources are cached within the Spring.NET IApplicationContext and are accessible through the Spring.NET IMessageSource interface.

The Spring.Web Page and UserControl classes have a reference to their owning IApplicationContext and it's associated IMessageSource. As such, they will automatically redirect resource lookups to a global message source if a local resource cannot be found.

Currently, the ResourceSetMessageSource is the only message source implementation that ships with Spring.NET.

In order to apply resources automatically, a localizer needs to be injected into all pages requiring this feature (typically accomplished using a base page definition that other pages will inherit from). The injected localizer will inspect the resource file when the page is first requested, cache the resources that start with the '$this' marker string value, and apply the values to the controls that populate the page prior to the page being rendered.

A localizer is simply an object that implements the Spring.Globalization.ILocalizer interface. Spring.Globalization.AbstractLocalizer is provided as a convenient base class for localization: this class has one abstract method, LoadResources. This method must load and return a list of all the resources that must be automatically applied from the resource store.

Spring.NET ships with one concrete implementation of a localizer, Spring.Globalization.Localizers.ResourceSetLocalizer, that retrieves a list of resources to apply from the local resource file. Future releases of Spring.NET may provide other localizers that read resources from an XML file or even a flat text file that contains resource name-value pairs which will allow application developers to store resources within the files in a web application instead of as embedded resources in an assembly. Of course, if an application developer would rather store such resources in a database, he or she can write their own ILocalizer implementation that will load a list of resources to apply from a database.

As mentioned previously, one would typically configure the localizer to be used within an abstract base definition for those pages that require localization as shown below.

<object id="localizer" type="Spring.Globalization.Localizers.ResourceSetLocalizer, Spring.Core"/>

<object name="basePage" abstract="true">
    <description>
        Pages that reference this definition as their parent
        (see examples below) will automatically inherit following properties.
    </description>
    <property name="Localizer" ref="localizer"/>
</object>

Of course, nothing prevents an application developer from defining a different localizer for each page in the application; in any case, one can always override the localizer defined in a base (page) definition. Alternatively, if one does want any resources to be applied automatically one can completely omit the localizer definition.

One last thing to note is that Spring.NET UserControl instances will (by default) inherit the localizer and other localization settings from the page that they are contained within, but one can similarly also override that behavior using explicit dependency injection.

While automatic localization as described above works great for many form-like pages, it doesn't work nearly as well for the controls defined within any iterative controls because the IDs for such iterative controls are not fixed. It also doesn't work well in those cases where one needs to display the same resource multiple times within the same page. For example, think of the header columns for outgoing and return flights tables within the SpringAir application (see Chapter 37, SpringAir - Reference Application).

In these situations, one should use a pull-style mechanism for localization, which boils down to a simple GetMessage call as shown below.

<asp:Repeater id="outboundFlightList" Runat="server">
  <HeaderTemplate>
    <table border="0" width="90%" cellpadding="0" cellspacing="0" align="center" class="suggestedTable">
      <thead>
        <tr class="suggestedTableCaption">
          <th colspan="6">
            <%= GetMessage("outboundFlights") %>
          </th>
        </tr>
        <tr class="suggestedTableColnames">
          <th><%= GetMessage("flightNumber") %></th>
          <th><%= GetMessage("departureDate") %></th>
          <th><%= GetMessage("departureAirport") %></th>
          <th><%= GetMessage("destinationAirport") %></th>
          <th><%= GetMessage("aircraft") %></th>
          <th><%= GetMessage("seatPlan") %></th>
        </tr>
      </thead>
      <tbody>
  </HeaderTemplate>

The GetMessage method is available within both the Spring.Web.UI.Page and Spring.Web.UI.UserControl classes, and it will automatically fall back to a global message source lookup if a local resource is not found.

Spring.Web provides an easy (and consistent) way to localize images within a web application. Unlike text resources, which can be stored within embedded resource files, XML files, or even a database, images in a typical web application are usually stored as files on the file system. Using a combination of directory naming conventions and a custom ASP.NET control, Spring.Web allows application developers to localize images within the page as easily as text resources.

The Spring.Web Page class exposes the ImagesRoot property, which is used to define the root directory where images are stored. The default value is 'Images', which means that the localizer expects to find an 'Images' directory within the application root, but one can set it to any value in the definition of the page.

In order to localize images, one needs to create a directory for each localized culture under the ImagesRoot directory as shown below.

/MyApp
   /Images
      /en
      /en-US
      /fr
      /fr-CA
      /sr-SP-Cyrl
      /sr-SP-Latn
      ...

Once an appropriate folder hierarchy is in place all one need do is put the localized images in the appropriate directories and make sure that different translations of the same image are named the same. In order to place a localized image on a page, one needs to use the <spring:LocalizedImage> as shown below.

<%@ Page language="c#" Codebehind="StandardTemplate.aspx.cs"
                AutoEventWireup="false" Inherits="SpringAir.Web.StandardTemplate" %>
<%@ Register TagPrefix="spring" Namespace="Spring.Web.UI.Controls" Assembly="Spring.Web" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<html>
  <body>
    <spring:LocalizedImage id="logoImage" imageName="spring-air-logo.jpg" borderWidth="0" runat="server" />
  </body>
</html>

This control will find the most specific directory that contains an image with the specified name using standard localization fallback rules and the user's culture. For example, if the user's culture is 'en-US', the localizer will look for the spring-air-logo.jpg file in Images/en-US, then in Images/en and finally, if the image file has still not been found, in the root Images directory (which for all practical purposes serves as an invariant culture folder).

In addition to global and local resource management, Spring.Web also adds support for user culture management by exposing the current CultureInfo through the UserCulture property on the Page and UserControl classes.

The UserCulture property will simply delegate culture resolution to an implementation of Spring.Globalization.ICultureResolver interface. One can specify exactly which culture resolver to use by configuring the CultureResolver property of the Page class in the relevant object definition as shown below.

<object name="BasePage" abstract="true">
    <property name="CultureResolver">
        <object type="Spring.Globalization.Resolvers.CookieCultureResolver, Spring.Web"/>
    </property>
</object>

Several useful implementations of ICultureResolver ship as part of Spring.Web, so it is unlikely that application developers will have to implement their own culture resolver. However, if one does have such a requirement, the resulting implementation should be fairly straightforward as there are only two methods that one need implement. The following sections discuss each available implementation of the ICultureResolver interface.

22.8.6.4. CookieCultureResolver

This resolver will look for culture information in a cookie, and return it if it finds one. If not, it will fall back to the behavior of the DefaultWebCultureResolver.

Warning

CookieCultureResolver will not work if your application uses localhost as the server URL, which is a typical setting in a development environment. In order to work around this limitation you should use SessionCultureResolver during development and switch to CookieCultureResolver before you deploy the application in a production. This is easily accomplished in Spring.Web (simply change the config file) but is something that you should be aware of.

In order to be able to change the culture application developers will need to use one of the culture resolvers that support culture changes, such as SessionCultureResolver or CookieCultureResolver. One could also write a custom ICultureResolver that will persist culture information in a database, as part of a user's profile.

Once that requirement is satisfied, all that one need do is to set the UserCulture property to a new CultureInfo object before the page is rendered. In the following .aspx example, there are two link buttons that can be used to change the user's culture. In the code-behind, this is all one need do to set the new culture. A code snippet for the code-behind file (UserRegistration.aspx.cs) is shown below.

protected override void OnInit(EventArgs e)
{
    InitializeComponent();

    this.english.Command += new CommandEventHandler(this.SetLanguage);
    this.serbian.Command += new CommandEventHandler(this.SetLanguage);

    base.OnInit(e);
}

private void SetLanguage(object sender, CommandEventArgs e)
{
    this.UserCulture = new CultureInfo((string) e.CommandArgument);
}

• redirect

• transfer

• TransferNoPreserve

You may also register a custom interpreter that can parse the short-hand string representation that creates a Result object.. The string representation can be broken down into two parts shown below

<resultmode>:<textual result representation>

The interface IResultFactory is responsible for creating an IResult object from these two pieces, as shown below

public interface IResultFactory
{
    IResult CreateResult( string resultMode, string resultText );
}

A ResultFactoryRegistry is used to associate a given resultmode string with an IResultFactory implementation. Here is an example

class MySpecialResultLogic : IResult
{
  ...
}

class MySpecialResultLogicFactory : IResultFactory
{
   IResult Create( string mode, string expression ) { 
     /* ... convert 'expression' into MySpecialResultLogic */ 
   }
}

// register with global factory
ResultFactoryRegistry.RegisterResultFactory( "mySpecialMode", new MySpecialResultLogicFactory );

You would then use the custom 'continue' mode in your page as shown below

// configure your Results
<object type="mypage.aspx">
   <property name="Results">
      <dictionary>
         <entry key="continue" value="mySpecialMode:<some MySpecialResultLogic string representation>" />
      </dictionary>
   </property>
</object>

The result redirection is done as before, by calling myPage.SetResult("continue");

Spring.Web adds several methods to enhance client-side scripting to the base Spring.Web.UI.Page class: RegisterHeadScriptBlock and RegisterHeadScriptFile, each with a few overrides. You can call these methods from your custom pages and controls in order to register script blocks and script files that must be included in the <head> section of the final HTML page.

The only additional thing that is required to make this work is that you use the <spring:Head> server-side control to define your <head> section instead of using the standard HTML <head> element. This is shown below.

<%@ Page language="c#" Codebehind="StandardTemplate.aspx.cs"
                AutoEventWireup="false" Inherits="SpringAir.Web.StandardTemplate" %>
<%@ Register TagPrefix="spring" Namespace="Spring.Web.UI.Controls" Assembly="Spring.Web" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<html>
  <spring:Head runat="server" id="Head1">
    <title>
      <spring:ContentPlaceHolder id="title" runat="server">
        <%= GetMessage("default.title") %>
      </spring:ContentPlaceHolder>
    </title>
    <LINK href="<%= CssRoot %>/default.css" type="text/css" rel="stylesheet">
    <spring:ContentPlaceHolder id="head" runat="server"></spring:ContentPlaceHolder>
  </spring:Head>
  <body>
  ...
  </body>
</html>

The example above shows you how you would typically set-up a <head> section within a master page template in order to be able to change the title value and to add additional elements to the <head> section from the child pages using <spring:ContentPlaceholder> controls. However, only the <spring:Head> declaration is required in order for Spring.NET Register* scripts to work properly.

In a similar fashion, you can add references to CSS files, or even specific styles, directly to the <head> HTML section using Page.RegisterStyle and Page.RegisterStyleFile methods. The latter one simply allows you to include a reference to an external CSS file, while the former one allows you to define embedded style definitions by specifying the style name and definition as the parameters. The final list of style definitions registered this way will be rendered within the single embedded style section of the final HTML document.

In order to make the manual inclusion of client-side scripts, CSS files and images easier, the Spring.Web Page class exposes several properties that help you reference such artifacts using absolute paths. This affords web application developers a great deal of convenience functionality straight out of the box if they stick to common conventions such as a web application (directory) structure..

These properties are ScriptsRoot, CssRoot and ImagesRoot. They have default values of Scripts, CSS and Images, which will work just fine if you create and use these directories in your web application root. However, if you prefer to place them somewhere else, you can always override default values by injecting new values into your page definitions (you will typically inject these values only in the base page definition, as they are normally shared by all the pages in the application). An example of such configuration is shown below:

<object name="basePage" abstract="true">
    <description>
        Convenience base page definition for all the pages.

        Pages that reference this definition as their parent (see the examples below)
        will automatically inherit the following properties....

    </description>
    <property name="CssRoot" value="Web/CSS"/>
    <property name="ImagesRoot" value="Web/Images"/>
</object>

The location in the web page where validation errors are to be rendered can be specifies by using the ValidationSummary and ValidationError controls. There are two controls since they have different defaults for how errors are rendered. ValidationSummary is used to display potentially multiple errors identified by the validation framework. ValidationError is used to display field-level validation errors. Please refer to the section ASP.NET usage tips in the chapter on the Validation Framework more information.

Some standard controls are not easy to use with Spring's databinding support. Examples are check boxes and ratio button groups. In this case you should use the CheckBoxList and RadioButtonGroup controls. Databinding itself can be done using the DataBindingPanel instead of the using the BindingManager API within the code behind page.

A pop-up DHTML calendar control is provided. It is a slightly modified version of the Dynarch.com DHTML Calendar control written by Mihai Bazon.

You can suppress dependency injection for controls inside your ASP.NET by using the Panel control. See the section Customizing control dependency injection for more information.