The UrlBasedViewResolver instantiates the given viewClass for each view it has to resolve.

<bean id="viewResolver" class="org.springframework.web.servlet.view.UrlBasedViewResolver">
  <property name="viewClass" value="org.springframework.web.servlet.view.tiles.TilesView"/>
</bean>

The ResourceBundleViewResolver has to be provided with a property file containing viewnames and viewclasses the resolver can use:

<bean id="viewResolver" class="org.springframework.web.servlet.view.ResourceBundleViewResolver">
  <property name="basename" value="views"/>
</bean>

...
welcomeView.class=org.springframework.web.servlet.view.tiles.TilesView
welcomeView.url=welcome (this is the name of a Tiles definition)

vetsView.class=org.springframework.web.servlet.view.tiles.TilesView
vetsView.url=vetsView (again, this is the name of a Tiles definition)

findOwnersForm.class=org.springframework.web.servlet.view.JstlView
findOwnersForm.url=/WEB-INF/jsp/findOwners.jsp
...

As you can see, when using the ResourceBundleViewResolver, you can easily mix different view technologies.

This file is completely optional, but if specified, contains the values that are passed to the Velocity runtime in order to configure velocity itself. Only required for advanced configurations, if you need this file, specify its location on the VelocityConfigurer bean definition above.

<bean id="velocityConfig" class="org.springframework.web.servlet.view.velocity.VelocityConfigurer">
  <property name="configLocation value="/WEB-INF/velocity.properties"/>
</bean>

Alternatively, you can specify velocity properties directly in the bean definition for the Velocity config bean by replacing the "configLocation" property with the following inline properties.

<bean id="velocityConfig" class="org.springframework.web.servlet.view.velocity.VelocityConfigurer">
  <property name="velocityProperties">
    <props>
      <prop key="resource.loader">file</prop>
      <prop key="file.resource.loader.class">
        org.apache.velocity.runtime.resource.loader.FileResourceLoader
      </prop>
      <prop key="file.resource.loader.path">${webapp.root}/WEB-INF/velocity</prop>
      <prop key="file.resource.loader.cache">false</prop>
    </props>
  </property>
</bean>

Refer to the API documentation for Spring configuration of Velocity, or the Velocity documentation for examples and definitions of the 'velocity.properties' file itself.

FreeMarker 'Settings' and 'SharedVariables' can be passed directly to the FreeMarker Configuration object managed by Spring by setting the appropriate bean properties on the FreeMarkerConfigurer bean. The freemarkerSettings property requires a java.util.Properties object and the freemarkerVariables property requires a java.util.Map.

<bean id="freemarkerConfig" class="org.springframework.web.servlet.view.freemarker.FreeMarkerConfigurer">
  <property name="templateLoaderPath" value="/WEB-INF/freemarker/"/>
  <property name="freemarkerVariables">
    <map>
      <entry key="xml_escape" value-ref="fmXmlEscape"/>
    </map>
  </property>
</bean>

<bean id="fmXmlEscape" class="freemarker.template.utility.XmlEscape"/>

See the FreeMarker documentation for details of settings and variables as they apply to the Configuration object.

A standard set of macros are maintained within the spring.jar file for both languages, so they are always available to a suitably configured application. However they can only be used if your view sets the bean property exposeSpringMacroHelpers to 'true' on your VelocityView / FreeMarkerView beans. By way of a shortcut, you can also configure this property on VelocityViewResolver or FreeMarkerViewResolver too if you happen to be using it, in which case all of your views will inherit the value from it. Note that this property is not required for any aspect of HTML form handling except where you wish to take advantage of the Spring macros. Below is an example of a view.properties file showing correct configuration of such a view for either language;

personFormV.class=org.springframework.web.servlet.view.velocity.VelocityView
personFormV.url=personForm.vm
personFormV.exposeSpringMacroHelpers=true

personFormF.class=org.springframework.web.servlet.view.freemarker.FreeMarkerView
personFormF.url=personForm.ftl
personFormF.exposeSpringMacroHelpers=true

Find below an example of a complete (albeit trivial) Spring Web MVC configuration file that exposes the Velocity macros to every (Velocity) view.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN" "http://www.springframework.org/dtd/spring-beans-2.0.dtd">

<beans>

    <bean name="helloController" class="info.wilhelms.springwebapp.SampleController">
        <property name="commandName" value="command"/>
        <property name="commandClass" value="info.wilhelms.springwebapp.Message"/>
        <property name="formView" value="foo"/>
        <property name="successView" value="banjo"/>
        <property name="bindOnNewForm" value="true"/>
        <property name="sessionForm" value="true"/>
    </bean>

    <bean id="velocityConfig"
          class="org.springframework.web.servlet.view.velocity.VelocityConfigurer">
        <property name="resourceLoaderPath" value="/WEB-INF/velocity/"/>
    </bean>

    <bean id="viewResolver" class="org.springframework.web.servlet.view.velocity.VelocityViewResolver">
        <property name="cache" value="false"/>
        <property name="prefix" value=""/>
        <property name="suffix" value=".vm"/>
        <property name="exposeSpringMacroHelpers" value="true"/>
    </bean>

    <bean class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
        <property name="mappings">
            <value>
                **/hello.htm=helloController
            </value>
        </property>
    </bean>

</beans>

Some of the macros defined in the Spring libraries are considered internal (private) but no such scoping exists in the macro definitions making all macros visible to calling code and user templates. The following sections concentrate only on the macros you need to be directly calling from within your templates. If you wish to view the macro code directly, the files are called spring.vm / spring.ftl and are in the packages org.springframework.web.servlet.view.velocity or org.springframework.web.servlet.view.freemarker respectively.

In your html forms (vm / ftl templates) that act as the 'formView' for a Spring form controller, you can use code similar to the following to bind to field values and display error messages for each input field in similar fashion to the JSP equivalent. Note that the name of the command object is "command" by default, but can be overridden in your MVC configuration by setting the 'commandName' bean property on your form controller. Example code is shown below for the personFormV and personFormF views configured earlier;

<!-- velocity macros are automatically available -->
<html>
...
<form action="" method="POST">
  Name: 
  #springBind( "command.name" )
  <input type="text" 
    name="${status.expression}" 
    value="$!status.value" /><br>
  #foreach($error in $status.errorMessages) <b>$error</b> <br> #end
  <br>
  ... 
  <input type="submit" value="submit"/>
</form>
...
</html>

<!-- freemarker macros have to be imported into a namespace.  We strongly
recommend sticking to 'spring' -->
<#import "spring.ftl" as spring />
<html>
...
<form action="" method="POST">
  Name: 
  <@spring.bind "command.name" /> 
  <input type="text" 
    name="${spring.status.expression}" 
    value="${spring.status.value?default("")}" /><br>
  <#list spring.status.errorMessages as error> <b>${error}</b> <br> </#list>
  <br>
  ... 
  <input type="submit" value="submit"/>
</form>
...
</html>

#springBind / <@spring.bind> requires a 'path' argument which consists of the name of your command object (it will be 'command' unless you changed it in your FormController properties) followed by a period and the name of the field on the command object you wish to bind to. Nested fields can be used too such as "command.address.street". The bind macro assumes the default HTML escaping behavior specified by the ServletContext parameter defaultHtmlEscape in web.xml

The optional form of the macro called #springBindEscaped / <@spring.bindEscaped> takes a second argument and explicitly specifies whether HTML escaping should be used in the status error messages or values. Set to true or false as required. Additional form handling macros simplify the use of HTML escaping and these macros should be used wherever possible. They are explained in the next section.

Additional convenience macros for both languages simplify both binding and form generation (including validation error display). It is never necessary to use these macros to generate form input fields, and they can be mixed and matched with simple HTML or calls direct to the spring bind macros highlighted previously.

The following table of available macros show the VTL and FTL definitions and the parameter list that each takes.

* In FTL (FreeMarker), these two macros are not actually required as you can use the normal formInput macro, specifying 'hidden' or 'password' as the value for the fieldType parameter.

The parameters to any of the above macros have consistent meanings:

Examples of the macros are outlined below some in FTL and some in VTL. Where usage differences exist between the two languages, they are explained in the notes.

<!-- the Name field example from above using form macros in VTL -->
...
    Name:
    #springFormInput("command.name" "")<br>
    #springShowErrors("<br>" "")<br>

<@spring.formInput "command.name"/>
<@spring.showErrors "<br>"/>

Name:
  <input type="text" name="name" value=""     
>
<br>
  <b>required</b>
<br>
<br>

...
  Town:
  <@spring.formRadioButtons "command.address.town", cityMap, "" /><br><br>

Town:
<input type="radio" name="address.town" value="London"
   
>
London
<input type="radio" name="address.town" value="Paris"
  checked="checked" 
>
Paris
<input type="radio" name="address.town" value="New York"
   
>
New York

protected Map referenceData(HttpServletRequest request) throws Exception {
  Map cityMap = new LinkedHashMap();
  cityMap.put("LDN", "London");
  cityMap.put("PRS", "Paris");
  cityMap.put("NYC", "New York");
  
  Map m = new HashMap();
  m.put("cityMap", cityMap);
  return m;
}

Town:
<input type="radio" name="address.town" value="LDN"
   
>
London
<input type="radio" name="address.town" value="PRS"
  checked="checked" 
>
Paris
<input type="radio" name="address.town" value="NYC"
   
>
New York

Default usage of the form macros above will result in HTML tags that are HTML 4.01 compliant and that use the default value for HTML escaping defined in your web.xml as used by Spring's bind support. In order to make the tags XHTML compliant or to override the default HTML escaping value, you can specify two variables in your template (or in your model where they will be visible to your templates). The advantage of specifying them in the templates is that they can be changed to different values later in the template processing to provide different behavior for different fields in your form.

To switch to XHTML compliance for your tags, specify a value of 'true' for a model/context variable named xhtmlCompliant:

## for Velocity..
#set($springXhtmlCompliant = true)

<#-- for FreeMarker -->
<#assign xhtmlCompliant = true in spring>

Any tags generated by the Spring macros will now be XHTML compliant after processing this directive.

In similar fashion, HTML escaping can be specified per field:

<#-- until this point, default HTML escaping is used -->

<#assign htmlEscape = true in spring>
<#-- next field will use HTML escaping -->
<@spring.formInput "command.name" />

<#assign htmlEscape = false in spring>
<#-- all future fields will be bound with HTML escaping off -->

Configuration is standard for a simple Spring application. The dispatcher servlet config file contains a reference to a ViewResolver, URL mappings and a single controller bean...

<bean id="homeController"class="xslt.HomeController"/>

... that encapsulates our word generation logic.

The controller logic is encapsulated in a subclass of AbstractController, with the handler method being defined like so...

protected ModelAndView handleRequestInternal(
    HttpServletRequest request,
    HttpServletResponse response) throws Exception {
        
    Map map = new HashMap();
    List wordList = new ArrayList();
        
    wordList.add("hello");
    wordList.add("world");
       
    map.put("wordList", wordList);
      
    return new ModelAndView("home", map);
}

So far we've done nothing that's XSLT specific. The model data has been created in the same way as you would for any other Spring MVC application. Depending on the configuration of the application now, that list of words could be rendered by JSP/JSTL by having them added as request attributes, or they could be handled by Velocity by adding the object to the VelocityContext. In order to have XSLT render them, they of course have to be converted into an XML document somehow. There are software packages available that will automatically 'domify' an object graph, but within Spring, you have complete flexibility to create the DOM from your model in any way you choose. This prevents the transformation of XML playing too great a part in the structure of your model data which is a danger when using tools to manage the domification process.

In order to create a DOM document from our list of words or any other model data, we must subclass the (provided) org.springframework.web.servlet.view.xslt.AbstractXsltView class. In doing so, we must also typically implement the abstract method createXsltSource(..) method. The first parameter passed to this method is our model map. Here's the complete listing of the HomePage class in our trivial word application:

package xslt;

// imports omitted for brevity

public class HomePage extends AbstractXsltView {

    protected Source createXsltSource(Map model, String rootName, HttpServletRequest
        request, HttpServletResponse response) throws Exception {

        Document document = DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();
        Element root = document.createElement(rootName);

        List words = (List) model.get("wordList");
        for (Iterator it = words.iterator(); it.hasNext();) {
            String nextWord = (String) it.next();
            Element wordNode = document.createElement("word");
            Text textNode = document.createTextNode(nextWord);
            wordNode.appendChild(textNode);
            root.appendChild(wordNode);
        }
        return new DOMSource(root);
    }

}

A series of parameter name/value pairs can optionally be defined by your subclass which will be added to the transformation object. The parameter names must match those defined in your XSLT template declared with <xsl:param name="myParam">defaultValue</xsl:param>. To specify the parameters, override the getParameters() method of the AbstractXsltView class and return a Map of the name/value pairs. If your parameters need to derive information from the current request, you can (from Spring version 1.1) override the getParameters(HttpServletRequest request) method instead.

Unlike JSTL and Velocity, XSLT has relatively poor support for locale based currency and date formatting. In recognition of the fact, Spring provides a helper class that you can use from within your createXsltSource(..) method(s) to get such support. See the Javadocs for the org.springframework.web.servlet.view.xslt.FormatHelper class.

The views.properties file (or equivalent xml definition if you're using an XML based view resolver as we did in the Velocity examples above) looks like this for the one-view application that is 'My First Words':

home.class=xslt.HomePage
home.stylesheetLocation=/WEB-INF/xsl/home.xslt
home.root=words

Here, you can see how the view is tied in with the HomePage class just written which handles the model domification in the first property '.class'. The 'stylesheetLocation' property points to the XSLT file which will handle the XML transformation into HTML for us and the final property '.root' is the name that will be used as the root of the XML document. This gets passed to the HomePage class above in the second parameter to the createXsltSource(..) method(s).

Finally, we have the XSLT code used for transforming the above document. As shown in the above 'views.properties' file, the stylesheet is called 'home.xslt' and it lives in the war file in the 'WEB-INF/xsl' directory.

<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

    <xsl:output method="html" omit-xml-declaration="yes"/>

    <xsl:template match="/">
        <html>
            <head><title>Hello!</title></head>
            <body>
                <h1>My First Words</h1>
                <xsl:apply-templates/>
            </body>
        </html>
    </xsl:template>

    <xsl:template match="word">
        <xsl:value-of select="."/><br/>
    </xsl:template>

</xsl:stylesheet>

Firstly, let's amend the views.properties file (or xml equivalent) and add a simple view definition for both document types. The entire file now looks like this with the XSLT view shown from earlier..

home.class=xslt.HomePage
home.stylesheetLocation=/WEB-INF/xsl/home.xslt
home.root=words

xl.class=excel.HomePage

pdf.class=pdf.HomePage

If you want to start with a template spreadsheet to add your model data to, specify the location as the 'url' property in the view definition

The controller code we'll use remains exactly the same from the XSLT example earlier other than to change the name of the view to use. Of course, you could be clever and have this selected based on a URL parameter or some other logic - proof that Spring really is very good at decoupling the views from the controllers!

Exactly as we did for the XSLT example, we'll subclass suitable abstract classes in order to implement custom behavior in generating our output documents. For Excel, this involves writing a subclass of org.springframework.web.servlet.view.document.AbstractExcelView (for Excel files generated by POI) or org.springframework.web.servlet.view.document.AbstractJExcelView (for JExcelApi-generated Excel files). and implementing the buildExcelDocument

Here's the complete listing for our POI Excel view which displays the word list from the model map in consecutive rows of the first column of a new spreadsheet..

package excel;

// imports omitted for brevity

public class HomePage extends AbstractExcelView {

    protected void buildExcelDocument(
        Map model,
        HSSFWorkbook wb,
        HttpServletRequest req,
        HttpServletResponse resp)
        throws Exception {
    
        HSSFSheet sheet;
        HSSFRow sheetRow;
        HSSFCell cell;

        // Go to the first sheet
        // getSheetAt: only if wb is created from an existing document
        //sheet = wb.getSheetAt( 0 );
        sheet = wb.createSheet("Spring");
        sheet.setDefaultColumnWidth((short)12);

        // write a text at A1
        cell = getCell( sheet, 0, 0 );
        setText(cell,"Spring-Excel test");

        List words = (List ) model.get("wordList");
        for (int i=0; i < words.size(); i++) {
            cell = getCell( sheet, 2+i, 0 );
            setText(cell, (String) words.get(i));

        }
    }
}

And this a view generating the same Excel file, now using JExcelApi:

package excel;
			
// imports omitted for brevity

public class HomePage extends AbstractExcelView {

    protected void buildExcelDocument(Map model,
        WritableWorkbook wb,
        HttpServletRequest request,
        HttpServletResponse response)
    throws Exception {
			
        WritableSheet sheet = wb.createSheet("Spring");

        sheet.addCell(new Label(0, 0, "Spring-Excel test");
		
        List words  = (List)model.get("wordList");
        for (int i = -; i < words.size(); i++) {
            sheet.addCell(new Label(2+i, 0, (String)words.get(i));
        }
    }
}

Note the differences between the APIs. We've found that the JExcelApi is somewhat more intuitive and furthermore, JExcelApi has a bit better image-handling capabilities. There have been memory problems with large Excel file when using JExcelApi however.

If you now amend the controller such that it returns xl as the name of the view (return new ModelAndView("xl", map);) and run your application again, you should find that the Excel spreadsheet is created and downloaded automatically when you request the same page as before.

The PDF version of the word list is even simpler. This time, the class extends org.springframework.web.servlet.view.document.AbstractPdfView and implements the buildPdfDocument() method as follows..

package pdf;

// imports omitted for brevity

public class PDFPage extends AbstractPdfView {

    protected void buildPdfDocument(
        Map model,
        Document doc,
        PdfWriter writer,
        HttpServletRequest req,
        HttpServletResponse resp)
        throws Exception {
        
        List words = (List) model.get("wordList");
        
        for (int i=0; i<words.size(); i++)
            doc.add( new Paragraph((String) words.get(i)));
    
    }
}

Once again, amend the controller to return the pdf view with a return new ModelAndView("pdf", map); and reload the URL in your application. This time a PDF document should appear listing each of the words in the model map.

Typically, you will use the ResourceBundleViewResolver to map view names to view classes and files in a properties file.

<bean id="viewResolver" class="org.springframework.web.servlet.view.ResourceBundleViewResolver">
    <property name="basename" value="views"/>
</bean>

Here we've configured an instance of the ResourceBundleViewResolver class that will look for view mappings in the resource bundle with base name views. (The content of this file is described in the next section.)

The Spring Framework contains five different View implementations for JasperReports, four of which correspond to one of the four output formats supported by JasperReports, and one that allows for the format to be determined at runtime:

Mapping one of these classes to a view name and a report file is a matter of adding the appropriate entries into the resource bundle configured in the previous section as shown here:

simpleReport.class=org.springframework.web.servlet.view.jasperreports.JasperReportsPdfView
simpleReport.url=/WEB-INF/reports/DataSourceReport.jasper

Here you can see that the view with name simpleReport is mapped to the JasperReportsPdfView class, causing the output of this report to be rendered in PDF format. The url property of the view is set to the location of the underlying report file.

JasperReports has two distinct types of report file: the design file, which has a .jrxml extension, and the compiled report file, which has a .jasper extension. Typically, you use the JasperReports Ant task to compile your .jrxml design file into a .jasper file before deploying it into your application. With the Spring Framework you can map either of these files to your report file and the framework will take care of compiling the .jrxml file on the fly for you. You should note that after a .jrxml file is compiled by the Spring Framework, the compiled report is cached for the lifetime of the application. To make changes to the file you will need to restart your application.

The JasperReportsMultiFormatView allows for report format to be specified at runtime. The actual rendering of the report is delegated to one of the other JasperReports view classes - the JasperReportsMultiFormatView class simply adds a wrapper layer that allows for the exact implementation to be specified at runtime.

The JasperReportsMultiFormatView class introduces two concepts: the format key and the discriminator key. The JasperReportsMultiFormatView class uses the mapping key to lookup the actual view implementation class and uses the format key to lookup up the mapping key. From a coding perspective you add an entry to your model with the formay key as the key and the mapping key as the value, for example:

public ModelAndView handleSimpleReportMulti(HttpServletRequest request,
HttpServletResponse response) throws Exception {

  String uri = request.getRequestURI();
  String format = uri.substring(uri.lastIndexOf(".") + 1);

  Map model = getModel();
  model.put("format", format);

  return new ModelAndView("simpleReportMulti", model);
}

In this example, the mapping key is determined from the extension of the request URI and is added to the model under the default format key: format. If you wish to use a different format key then you can configure this using the formatKey property of the JasperReportsMultiFormatView class.

By default the following mapping key mappings are configured in JasperReportsMultiFormatView:

So in the example above a request to URI /foo/myReport.pdf would be mapped to the JasperReportsPdfView class. You can override the mapping key to view class mappings using the formatMappings property of JasperReportsMultiFormatView.

To control which sub-report files are included in a master report using Spring, your report file must be configured to accept sub-reports from an external source. To do this you declare a parameter in your report file like so:

<parameter name="ProductsSubReport" class="net.sf.jasperreports.engine.JasperReport"/>

Then, you define your sub-report to use this sub-report parameter:

<subreport>
    <reportElement isPrintRepeatedValues="false" x="5" y="25" width="325"
        height="20" isRemoveLineWhenBlank="true" backcolor="#ffcc99"/>
    <subreportParameter name="City">
        <subreportParameterExpression><![CDATA[$F{city}]]></subreportParameterExpression>
    </subreportParameter>
    <dataSourceExpression><![CDATA[$P{SubReportData}]]></dataSourceExpression>
    <subreportExpression class="net.sf.jasperreports.engine.JasperReport">
                  <![CDATA[$P{ProductsSubReport}]]></subreportExpression>
</subreport>

This defines a master report file that expects the sub-report to be passed in as an instance of net.sf.jasperreports.engine.JasperReports under the parameter ProductsSubReport. When configuring your Jasper view class, you can instruct Spring to load a report file and pass into the JasperReports engine as a sub-report using the subReportUrls property:

<property name="subReportUrls">
    <map>
        <entry key="ProductsSubReport" value="/WEB-INF/reports/subReportChild.jrxml"/>
    </map>
</property>

Here, the key of the Map corresponds to the name of the sub-report parameter in th report design file, and the entry is the URL of the report file. Spring will load this report file, compiling it if necessary, and will pass into the JasperReports engine under the given key.

This step is entirely optional when using Spring configure your sub-reports. If you wish, you can still configure the data source for your sub-reports using static queries. However, if you want Spring to convert data returned in your ModelAndView into instances of JRDataSource then you need to specify which of the parameters in your ModelAndView Spring should convert. To do this configure the list of parameter names using the subReportDataKeys property of the your chosen view class:

<property name="subReportDataKeys"
    value="SubReportData"/>

Here, the key you supply MUST correspond to both the key used in your ModelAndView and the key used in your report design file.