Using Template

As a demonstration, you can return a String that contains HTML like <html><body>Hello, world!</body></html>. But in real world, the complex web pages are rendered by kinds of template engines. WebWind supports two build-in template engines: JSP and Velocity.

Rendering web pages by template in WebWind is simple:

Put all data into a Map<String, Object> as model;
Create a TemplateRenderer and return.

See example bellow:

public class IndexPage {

    @Mapping("/")
    public Renderer index() {
        Map<String, Object> model = new HashMap<String, Object>();
        model.put("name", "Michael");
        model.put("date", new Date());
        return new TemplateRenderer("/index.jsp", model);
    }
}

If you configure nothing about template, the default template engine JSP is used. For example, the index.jsp for code above should be like:

<html>
<body>
  Hello, <%=request.getAttribute("name") %>!
  It is <%=request.getAttribute("date") %>!
</body>
</html>

To use Velocity template, prepare a Velocity template file index.htm like:

<html>
<body>
  Hello, ${name}! It is ${date.toString()}!
</body>
</html>

See Configurations to get more about configuration of Velocity.

Need More Template Engine Support

If you want to use any other template engine rather than Jsp or Velocity, you need additional work to do.

WebWind allows you to add any template engine (such as FreeMarker, etc) by writing your own TemplateFactory class. For example:

package sample;

import org.expressme.wind.template.ContainerFactory;

public class MyTemplateFactory implements TemplateFactory {

    public Template loadTemplate(String path) throws Exception {
        return new MyTemplate(path);
    }

    public void init(Config config) {
        // TODO: init your template engine here...
    }
}

You need implement two methods above. It is easy for experienced developers. See JspTemplateFactory.java and VelocityTemplateFactory.java as examples.

And also MyTemplate class must be inherited from Template:

package sample;

import java.io.PrintWriter;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.expressme.wind.template.Template;

public class MyTemplate implements Template {

    private String path;

    public MyTemplate(String path) {
        this.path = path;
    }

    public void render(HttpServletRequest request, HttpServletResponse response, Map<String, Object> model) throws Exception {
        String content = build_content_by_template(model);
        PrintWriter pw = response.getWriter();
        pw.write(content);
        pw.flush();
    }
}

Specify your own template engine in web.xml with FULL CLASS NAME:

<init-param>
    <param-name>template</param-name>
    <param-value>sample.MyTemplateFactory</param-value>
</init-param>

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