displaymenutag.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

package net.sf.navigator.taglib.el;

import java.net.MalformedURLException;

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

import net.sf.navigator.menu.MenuComponent;

import org.apache.struts.util.RequestUtils;


/**
 * This tag acts the same as net.sf.navigator.taglib.DisplayMenuTag, except
 * that it allows JSTL Expressions in it's name and target attributes.
 *
 * @author Matt Raible
 * @version $Revision: 1.2 $ $Date: 2004/03/31 19:30:38 $
 */
public class DisplayMenuTag extends net.sf.navigator.taglib.DisplayMenuTag {
    /** Holds value of property name. */
    private String _name;

    /** Holds value of property target. */
    private String _target;

    /** Setter for property name.
     * @param name New value of property name.
     */
    public void setName(String name) {
        this._name = name;
    }

    /** Setter for property target.
     * @param target New value of property target.
     */
    public void setTarget(String target) {
        this._target = target;
    }

    public DisplayMenuTag() {
        super();
        init();
    }

    private void init() {
        _name = null;
        _target = null;
    }

    public void release() {
        super.release();
        init();
    }

    public int doStartTag() throws JspException {
        evaluateExpressions();

        return super.doStartTag();
    }

    /**
     * Overrides the setPageLocation in parentTag to use JSTL to evaluate
     * the URL.  It's definitely ugly, so if you have a cleaner way, please
     * let me know!
     *
     * @param menu
     */
    protected void setPageLocation(MenuComponent menu)
    throws MalformedURLException, JspException {
        HttpServletRequest request =
            (HttpServletRequest) pageContext.getRequest();

        // if the location attribute is null,
        // then set it with a context relative page
        // attribute if it exists
        if (menu.getLocation() == null) {
            if (menu.getPage() != null) {
                // are we sure we'll get an HttpServletRequest?
                menu.setLocation(request.getContextPath() +
                                 getPage(menu.getPage()));
            } else if (menu.getForward() != null) {
                String fwd =
                    RequestUtils.computeURL(pageContext, menu.getForward(),
                                            null, null, null, null, null, false);
                menu.setLocation(fwd);
            } else if (menu.getAction() != null) {
                // generate Struts Action URL,
                // this will append Context Path (if any),
                // Servlet Mapping (path mapping or extension mapping)
                // Module Prefix (if any) & Session ID (if any)
                String action =
                    RequestUtils.computeURL(pageContext, null, null, null,
                                            menu.getAction(), null, null, false);
                menu.setLocation(action);
            }
        }

        String url = menu.getLocation();

        // Use JSTL to replace dynamic values in the URL
        ExpressionEvaluator eval = new ExpressionEvaluator(this, pageContext);

        String s;

        if ((s = eval.evalString("url", url)) != null) {
            menu.setUrl(s);
        }

        // do all contained menus
        MenuComponent[] subMenus = menu.getMenuComponents();

        if (subMenus.length > 0) {
            for (int i = 0; i < subMenus.length; i++) {
                setPageLocation(subMenus[i]);
            }
        }
    }

    private void evaluateExpressions() throws JspException {
        ExpressionEvaluator eval = new ExpressionEvaluator(this, pageContext);
        String s;

        if ((s = eval.evalString("name", _name)) != null) {
            super.setName(s);
        }

        if ((s = eval.evalString("target", _target)) != null) {
            super.setTarget(s);
        }
    }
}