Chapter 15. iText PDF generation - JBoss Seam 1.1.6 正式版英文参考手册

iText support is provided by jboss-seam-pdf.jar. This JAR contains the iText JSF controls, which are used to construct views that can render to PDF, and the DocumentStore component, which serves the rendered documents to the user. To include PDF support in your application, included jboss-seam-pdf.jar in your WEB-INF/lib directory along with the iText JAR file. There is no further configuration needed to use Seam's iText support.

The Seam iText module requires the use of Facelets as the view technology. Future versions of the library may also support the use of JSP. Additionally, it requires the use of the seam-ui package.

The examples/itext project contains an example of the PDF support in action. It demonstrates proper deployment packaging, and it contains a number examples that demonstrate the key PDF generation features current supported.

Documents are generated by facelets documents using tags in the http://jboss.com/products/seam/pdf namespace. Documents should always have the document tag at the root of the document. The document tag prepares Seam to generate a document into the DocumentStore and renders an HTML redirect to that stored content. The following is a a small PDF document consisting only a single line of text:

<p:document xmlns:p="http://jboss.com/products/seam/pdf">                                                      
   The document goes here.                                                                                             
</p:document>
        

Useful documents will need to contain more than just text; however, the standard UI components are geared towards HTML generation and are not useful for generating PDF content. Instead, Seam provides a special UI components for generating suitable PDF content. Tags like <p:image> and <p:paragraph> are the basic foundations of simple documents. Tags like <p:font> provide style information to all the content surrounging them.

<p:document xmlns:p="http://jboss.com/products/seam/pdf"> 
    <p:image alignment="right" wrap="true" resource="/logo.jpg" />
    <p:font size="24">
        <p:paragraph spacingAfter="50">My First Document</p:paragraph>
    </p:font>

    <p:paragraph alignment="justify">
        This is a simple document.  It isn't very fancy.
    </p:paragraph>
</p:document>
        

<p:paragraph>
    The item costs <p:text value="#{product.price}">
        <f:convertNumber type="currency" currencySymbol="$"/>
    </p:text>
</p:paragraph>
            

<p:image resource="/jboss.jpg" />

<p:image imageData="#{images.chart}" />

If the generated document follows a book/article structure, the p:chapter and p:section tags can be used to provide the necessary structure. Sections can only be used inside of chapters, but they may be nested arbitrarily deep. Most PDF viewers provide easy navigation between chapters and sections in a document.

<p:document xmlns:p="http://jboss.com/products/seam/pdf"
            title="Hello">

   <p:chapter number="1">
      <p:title><p:paragraph>Hello</p:paragraph></p:title>
      <p:paragraph>Hello #{user.name}!</p:paragraph>
   </p:chapter>

   <p:chapter number="2">
      <p:title><p:paragraph>Goodbye</p:paragraph></p:title>
      <p:paragraph>Goodbye #{user.name}.</p:paragraph>
   </p:chapter>

</p:document>    
        

List structures can be displayed using the p:list and p:listItem tags. Lists may contain arbitrarily-nested sublists. List items may not be used outside of a list. he following document uses the ui:repeat tag to to display a list of values retrieved from a Seam component.

<p:document xmlns:p="http://jboss.com/products/seam/pdf"
            xmlns:ui="http://java.sun.com/jsf/facelets"
            title="Hello">
   <p:list style="numbered">
      <ui:repeat value="#{documents}" var="doc">
         <p:listItem>#{doc.name}</p:listItem>
      </ui:repeat>
   </p:list>
</p:document>                
        

Table structures can be created using the p:table and p:cell tags. Unlike many table structures, there is no explicit row declaration. If a table has 3 columns, then every 3 cells will automatically form a row. Header and footer rows can be declared, and the headers and footers will be repeated in the event a table structure spans multiple pages.

<p:document xmlns:p="http://jboss.com/products/seam/pdf"   
            xmlns:ui="http://java.sun.com/jsf/facelets"
            title="Hello">   
   <p:table columns="3" headerRows="1">
      <p:cell>name</p:cell>
      <p:cell>owner</p:cell>
      <p:cell>size</p:cell>
      <ui:repeat value="#{documents}" var="doc">
         <p:cell>#{doc.name}</p:cell>
         <p:cell>#{doc.user.name}</p:cell>
         <p:cell>#{doc.size}</p:cell>
      </ui:repeat>
   </p:table>
</p:document>            
        

This section documents some of the constants shared by attributes on multiple tags.

Document generation works out of the box with no additional configuration needed. However, there are a few points of configuration that are needed for more serious applications.

The default implementation serves PDF documents from a generic URL, /seam-doc.seam. Many browsers (and users) would prefer to see URLs that contain the actual PDF name like /myDocument.pdf. This capability requires some configuration. To serve PDF files, all *.pdf resources should be mapped to the Seam Servlet Filter, as shown here:

<filter>
    <filter-name>Seam Servlet Filter</filter-name>
    <filter-class>org.jboss.seam.servlet.SeamServletFilter</filter-class>
</filter>

<filter-mapping>
    <filter-name>Seam Servlet Filter</filter-name>
    <url-pattern>*.pdf</url-pattern>
</filter-mapping>

The useExtensions option on the document store component completes the functionality by instructing the document store to generate URLs with the correct filename extension for the document type being generated.

        
<components xmlns="http://jboss.com/products/seam/components"
            xmlns:pdf="http://jboss.com/products/seam/pdf">
    <pdf:documentStore useExtensions="true" />
</components>

Generated documents are stored in conversation scope and will expire when the conversation ends. At that point, references to the document will be invalid. To You can specify a default view to be shown when a document does not exist using the errorPage property of the documentStore.

        
<pdf:documentStore useExtensions="true" errorPage="/pdfMissing.seam" />

For further information on iText, see: