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| <a name="Embedded Usage"><strong>Embedded Usage</strong></a> |
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| <blockquote> |
| <p> |
| This is an example of using Velocity within an application. |
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| <td bgcolor="#023264" width="1" height="1"><img src="/images/void.gif" width="1" height="1" vspace="0" hspace="0" border="0"/></td> |
| <td bgcolor="#023264" height="1"><img src="/images/void.gif" width="1" height="1" vspace="0" hspace="0" border="0"/></td> |
| <td bgcolor="#023264" width="1" height="1"><img src="/images/void.gif" width="1" height="1" vspace="0" hspace="0" border="0"/></td> |
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| <td bgcolor="#023264" width="1"><img src="/images/void.gif" width="1" height="1" vspace="0" hspace="0" border="0"/></td> |
| <td bgcolor="#ffffff"><pre> |
| OutputStreamWriter writer = new OutputStreamWriter(output, encoding); |
| Template template = RunTime.getTemplate(filename); |
| template.merge( context, writer ); |
| </pre></td> |
| <td bgcolor="#023264" width="1"><img src="/images/void.gif" width="1" height="1" vspace="0" hspace="0" border="0"/></td> |
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| <tr> |
| <td bgcolor="#023264" width="1" height="1"><img src="/images/void.gif" width="1" height="1" vspace="0" hspace="0" border="0"/></td> |
| <td bgcolor="#023264" height="1"><img src="/images/void.gif" width="1" height="1" vspace="0" hspace="0" border="0"/></td> |
| <td bgcolor="#023264" width="1" height="1"><img src="/images/void.gif" width="1" height="1" vspace="0" hspace="0" border="0"/></td> |
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| <p> |
| In other words, the above is translated into: |
| </p> |
| <ol type="1" start="1"> |
| <li>Create a Writer.</li> |
| <li>Ask the Velocity RunTime to retrieve the Template.</li> |
| <li>Merge the Context with the Template.</li> |
| </ol> |
| <p> |
| Velocity templates can contain *any* type of data. It can be XML, SQL, |
| HTML, plain text, internationalized text, anything. The parser is very |
| robust in terms of only parsing out what it cares about and ignoring the |
| rest. As demonstrated above, it is possible to embed Velocity's template |
| engine into any other Java code. The advantage of this is that it |
| provides users with a single template system for all sorts of uses. |
| </p> |
| <p> |
| For example, in the <a href="http://java.sun.com/j2ee/blueprints/sample_application/index.html">PetStore |
| example</a> on the J2EE website, there is a JavaBean which sends an |
| email confirmation when an order is complete. The unfortunate part about |
| this example is that in order to change the contents of the email, one |
| needs to edit Java code. Of course this example could have been done |
| differently to use a JSP based template as the base format. However, the |
| implementation of this is more difficult than simply creating a <a href="http://www.working-dogs.com/turbine/cvsweb/index.cgi/turbine/src/java/org/apache/turbine/util/velocity/">Java |
| object</a> which resides in the Context that can take as arguments the |
| template to render. |
| </p> |
| <p> |
| Another example of this is the <a href="http://jakarta.apache.org/velocity/texen.html">Texen</a> and <a href="http://jakarta.apache.org/velocity/anakia.html">Anakia</a> tools |
| that come with Velocity. The advantage again is the ability to use |
| Velocity as an embedded tool to produce other useful applications that |
| are not bound strictly to a web application. While it is most likely |
| possible to do this with the JSP engine, it is significantly more |
| difficult to do so. |
| </p> |
| <p> |
| You make the decision. |
| </p> |
| <p> |
| <strong>[ <a href="ymtd-taglibs.html">Taglibs</a> <- Previous | |
| Next -> <a href="./ymtd-implementation.html">Implementation</a> ] |
| </strong></p> |
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