项目的js库只加载一次

使用struts2开发portlet时，需要在jsp页面上加载现有的js库进行交互。这个portlet可能在页面上重复使用，这就要求确保页面上的多个portlet中同样的js文件只会加载一次。经过研究，发现可以通过扩展Jsr286Dispatcher类，然后重写doHeaders方法实现，代码如下：

Java代码
    @Override
    protected void doHeaders(RenderRequest request, RenderResponse response) {
        super.doHeaders(request, response);

//        if (request.getPortalContext().getProperty(PortalContext.MARKUP_HEAD_ELEMENT_SUPPORT) == null) {
//          logger.warn("The Portal Server does not support adding markup to the header. This may lead to portlets that do not work properly.");
//      } else {
            for (String cssFile : styles) {
                Element htmlHeader = response.createElement("link");
                htmlHeader.setAttribute("rel", "stylesheet");
                htmlHeader.setAttribute("type", "text/css");
                htmlHeader.setAttribute("href", response.encodeURL(request.getContextPath() + cssFile));

                response.addProperty(MimeResponse.MARKUP_HEAD_ELEMENT, htmlHeader);
                logger.debug("Added {} CSS file to the portal header.", cssFile);
            }

            for (String javascriptFile : scripts) {
                Element htmlHeader = response.createElement("script");
                htmlHeader.setAttribute("src", response.encodeURL(request.getContextPath() + javascriptFile));
                htmlHeader.setAttribute("type", "text/javascript");

                response.addProperty(MimeResponse.MARKUP_HEAD_ELEMENT, htmlHeader);
                logger.debug("Added {} Javascript file to the portal header.", javascriptFile);
            }
//      }
    }
运行后发现doHeaders方法不执行，然后查阅Jsr286Dispatcher类的源代码和GenericPortlet类的源代码，发现struts2已经修改了render方法，不再执行调用doHeaders的方法，所以我又重写了render方法，整体代码如下：
Java代码
/**
*
*/
package com.lily.dap.web.portlet.dispatcher;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.portlet.MimeResponse;
//import javax.portlet.PortalContext;
import javax.portlet.PortletConfig;
import javax.portlet.PortletException;
import javax.portlet.RenderRequest;
import javax.portlet.RenderResponse;

import org.apache.struts2.portlet.dispatcher.Jsr286Dispatcher;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.w3c.dom.Element;

/**
* 支持加载js脚本文件、css样式文件
*
* @author zouxuemo
*
*/
public class Dispatcher extends Jsr286Dispatcher {
    protected final Logger logger = LoggerFactory.getLogger(getClass());

    private List<String> scripts = new ArrayList<String>();

    private List<String> styles = new ArrayList<String>();

    @Override
    public void init(PortletConfig cfg) throws PortletException {
        super.init(cfg);

        String s = cfg.getInitParameter("scripts");
        if (s != null) {
            String[] tmp = s.split(" ");
            for (String script : tmp) {
                script = script.trim();
                if (script.charAt(0) != '/')
                    script = '/' + script;

补充：web前端 , JavaScript ,