velocitymenudisplayer.java

Struts Menu这是为基于JSP和Struts的应用程序提供的Web菜单框架。菜单可以在一个XML文件中定义

/*
 * VelocityMenuDisplayer.java
 *
 * Created on December 7, 2002, 12:35 AM
 */
package net.sf.navigator.displayer;

import java.io.IOException;
import java.io.StringWriter;
import java.util.*;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;

import net.sf.navigator.menu.MenuComponent;

import org.apache.commons.lang.StringUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts.util.RequestUtils;
import org.apache.struts.util.ResponseUtils;
import org.apache.velocity.Template;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.Velocity;
import org.apache.velocity.app.tools.VelocityFormatter;
import org.apache.velocity.runtime.RuntimeConstants;
import org.apache.velocity.tools.view.servlet.ServletLogger;
import org.apache.velocity.tools.view.servlet.WebappLoader;


/**
 * @author  <a href="mailto:[e-mail]">Matt Raible</a>
 * @version 1.0
 */
public class VelocityMenuDisplayer extends MessageResourcesMenuDisplayer {
    //~ Instance fields ========================================================

    private Log log = LogFactory.getLog(VelocityMenuDisplayer.class);
    private PageContext pageContext = null;

	/**
	 * Key used to access the ServletContext in
	 * the Velocity application attributes.
	 */
	public static final String SERVLET_CONTEXT_KEY = ServletContext.class.getName();

    //~ Methods ================================================================

    public void init(PageContext pageContext, MenuDisplayerMapping mapping) {
        super.init(pageContext, mapping);
        this.pageContext = pageContext;

		// MR: Copied from VelocityViewServlet to initialize WebappLoader
		Velocity.setApplicationAttribute(SERVLET_CONTEXT_KEY, pageContext.getServletContext());

		// default to servletlogger, which logs to the servlet engines log
		Velocity.setProperty(RuntimeConstants.RUNTIME_LOG_LOGSYSTEM_CLASS,
							 ServletLogger.class.getName());

		// by default, load resources with webapp resource loader
		Velocity.setProperty(RuntimeConstants.RESOURCE_LOADER, "webapp");
		Velocity.setProperty("webapp.resource.loader.class", WebappLoader.class.getName());

		// now all is ready - init Velocity
        try {
            // look to see if the user has overridden velocity.properties by
            // placing velocity.properties in WEB-INF/classes
            ResourceBundle rb = null;

            try {
                rb = ResourceBundle.getBundle("velocity");
            } catch (MissingResourceException mre) {
                // use default
                rb = ResourceBundle.getBundle("net.sf.navigator.displayer.velocity");
            }

            Properties props = new Properties();

            for (Enumeration keys = rb.getKeys(); keys.hasMoreElements();) {
                String key = (String) keys.nextElement();
                props.put(key, rb.getString(key));
            }

            // only initialized the first time it's called, from:
            //	http://jakarta.apache.org/velocity/developer-guide.html
            //	it's ignored for subsequent calls
            Velocity.init(props);
        } catch (Exception e) {
            log.error("Error initializing Velocity: " + e.getMessage());
            e.printStackTrace();
        }
    }

    public void display(MenuComponent menu) throws JspException, IOException {
        if (isAllowed(menu)) {
            displayComponents(menu);
        }
    }

    protected void displayComponents(MenuComponent menu)
    throws JspException, IOException {
        HttpServletRequest request =
            (HttpServletRequest) pageContext.getRequest();
        Template t = null;
        boolean debug =
            Boolean.valueOf(request.getParameter("debug")).booleanValue();

        if (debug) {
            // Print this element to our output writer
            ResponseUtils.write(pageContext, " [ " + getConfig() + " ] ");
        } else {
            try {
                String template = getConfig();

                if (template == null) {
                    throw new JspException("You must specify a template using the 'config' attribute.");
                } else {
                    log.debug("using template: " + template);
                }

                t = Velocity.getTemplate(template);
            } catch (Exception e) {
                String msg = "Error initializing Velocity: " + e.toString();
                log.error(msg, e);
                throw new JspException(msg, e);
            }

            StringWriter sw = new StringWriter();
            VelocityContext context = new VelocityContext();

            context.put("formatter", new VelocityFormatter(context));
            context.put("now", Calendar.getInstance().getTime());
            context.put("ctxPath", request.getContextPath());
            // add a helper class for string manipulation
            context.put("stringUtils", new StringUtils());

            // add a Map for use by the Explandable List Menu
            context.put("map", new HashMap());

            // see if a name and property were passed in
            if (!StringUtils.isEmpty(name)) {
                Object val1 =
                    RequestUtils.lookup(pageContext, name, null, null);

                if (val1 != null) {
                    context.put(name, val1);
                }
            }

            // request-scope attributes
            Enumeration enum = request.getAttributeNames();

            while (enum.hasMoreElements()) {
                String name = (String) enum.nextElement();
                Object value = request.getAttribute(name);
                context.put(name, value);
            }

            context.put("request", request);
            context.put("session", request.getSession());

            context.put("menu", menu);
            context.put("displayer", this);

            try {
                t.merge(context, sw);
            } catch (Exception e) {
                e.printStackTrace();
                throw new JspException(e);
            }

            String result = sw.getBuffer().toString();

            // Print this element to our output writer
            ResponseUtils.write(pageContext, result);
        }
    }

    public void end(PageContext context) {
        this.pageContext = null;
    }
}