??? JSF作為如今JavaEE標準之一，基于組件的設(shè)計為Java的web開發(fā)帶來了極大的便利性。然而在設(shè)計上，JSF拋棄了傳統(tǒng)的GET請求方式，所有JSF的表單都已post方式提交。這樣雖然在安全性等方面有一定好處，但是也帶來了一些不便，比如，由JSF開發(fā)的web應(yīng)用難以為每個單元定位。
?? 上述單元定位的意思是，比如你開發(fā)了一個project.faces用于動態(tài)顯示project的內(nèi)容。由于是post提交表單，那么一個叫dollyCal的項目和一個叫nirvana的項目將同樣顯示為project.faces，這樣每次用戶都需要通過導航瀏覽自己需要的項目，而不能通過對固定網(wǎng)頁的收藏來一次性瀏覽。
??? 解決上述問題可以通過filter來模擬get請求。
???以下還是以dollyCal舉例：
?? GET請求下url形式為project.faces?name=dollyCal
??? 則通過filter攔截該請求，取出dollyCal字段，然后調(diào)用FacesContext，初始化相應(yīng)的managed-bean，從數(shù)據(jù)庫中讀出dollyCal的相關(guān)信息填充到managed－bean中，再通過dispatcher導航到相應(yīng)頁面即可。這樣用戶可以project.faces?name=dollyCal形式輕松訪問一個項目，方便其收藏和訂閱
???
if?(request?instanceof?HttpServletRequest)?
{
????????????HttpServletRequest?r?=?(HttpServletRequest)?request;
????????????String?s?=?r.getQueryString();
????????????if?(s?!=?null?&&?s.startsWith("project=")?&&?s.length()?>?8)?{
????????????????String?name?=?s.substring(8);
????????????????if?(!PersistenceUtil.validateProject(name))?{
????????????????????FacesContext?fcg?=?getFacesContext(request,response);
????????????????????ProjectViewBean?pjv=(ProjectViewBean)fcg.getApplication().getVariableResolver().resolveVariable(fcg,"pjv");
????????????????????try?{
????????????????????????ProjectBean?p=PersistenceUtil.getProjectByName(name);
????????????????????????pjv.setProject(p);
????????????????????}?catch?(Exception?e)?{
????????????????????????//?TODO?Auto-generated?catch?block
????????????????????????e.printStackTrace();
????????????????????}
????????????????????RequestDispatcher?rd=request.getRequestDispatcher("/projectView.faces");
????????????????????rd.forward(request,?response);
????????????????}
????????????}??? 唯一需要注意的問題是，filter實際上處于JSF的管理區(qū)域之外，因此不能調(diào)用FacesContext.getCurrentInstance方法來獲得JSF上下文，而需要通過request， response來創(chuàng)建當前JSF上下文。再從該上下文中查出managed－bean，進行數(shù)據(jù)填充，
? 以下是完整代碼，說明如下：
?? ProjectViewBean是projectView.faces頁面的managed-bean, 首先解析url中要查詢的項目名稱，從數(shù)據(jù)庫中讀出相應(yīng)信息，再從上下文中查詢出該bean，填充信息即可。這樣再訪問該頁面時就會得到想要的結(jié)果。
package?org.myibm;
import?java.io.IOException;
import?javax.faces.FactoryFinder;
import?javax.faces.context.FacesContext;
import?javax.faces.context.FacesContextFactory;
import?javax.faces.lifecycle.Lifecycle;
import?javax.faces.lifecycle.LifecycleFactory;
import?javax.servlet.Filter;
import?javax.servlet.FilterChain;
import?javax.servlet.FilterConfig;
import?javax.servlet.RequestDispatcher;
import?javax.servlet.ServletContext;
import?javax.servlet.ServletException;
import?javax.servlet.ServletRequest;
import?javax.servlet.ServletResponse;
import?javax.servlet.http.HttpServletRequest;
import?org.myibm.beans.ProjectViewBean;
import?org.myibm.persistence.bean.ProjectBean;
import?org.myibm.utils.PersistenceUtil;
public?class?ParserFilter?implements?Filter?{
????private?FilterConfig?filterConfig?=?null;
????public?void?destroy()?{
????????//?TODO?Auto-generated?method?stub
????????filterConfig?=?null;
????}
????public?void?doFilter(ServletRequest?request,?ServletResponse?response,
????????????FilterChain?chain)?throws?IOException,?ServletException?{
????????//?TODO?Auto-generated?method?stub
????????if?(request?instanceof?HttpServletRequest)?{
????????????HttpServletRequest?r?=?(HttpServletRequest)?request;
????????????String?s?=?r.getQueryString();
????????????if?(s?!=?null?&&?s.startsWith("project=")?&&?s.length()?>?8)?{
????????????????String?name?=?s.substring(8);
????????????????if?(!PersistenceUtil.validateProject(name))?{
????????????????????FacesContext?fcg?=?getFacesContext(request,response);
????????????????????ProjectViewBean?pjv=(ProjectViewBean)fcg.getApplication().getVariableResolver().resolveVariable(fcg,"pjv");
????????????????????try?{
????????????????????????ProjectBean?p=PersistenceUtil.getProjectByName(name);
????????????????????????pjv.setProject(p);
????????????????????}?catch?(Exception?e)?{
????????????????????????//?TODO?Auto-generated?catch?block
????????????????????????e.printStackTrace();
????????????????????}
????????????????????RequestDispatcher?rd=request.getRequestDispatcher("/projectView.faces");
????????????????????rd.forward(request,?response);
????????????????}
????????????}
????????}
????????try?{
????????????//?System.out.print("filter?begins!");
????????????chain.doFilter(request,?response);
????????????//?System.out.print("filter?works!");
????????}?finally?{
????????}
????}
????public?void?init(FilterConfig?arg0)?throws?ServletException?{
????????//?TODO?Auto-generated?method?stub
????????this.filterConfig?=?arg0;
????}
????private?abstract?static?class?InnerFacesContext?extends?FacesContext?{
????????protected?static?void?setFacesContextAsCurrentInstance(
????????????????FacesContext?facesContext)?{
????????????FacesContext.setCurrentInstance(facesContext);
????????}
????}
????private?FacesContext?getFacesContext(ServletRequest?request,
????????????ServletResponse?response)?{
????????//?Try?to?get?it?first
????????FacesContext?facesContext?=?FacesContext.getCurrentInstance();
????????if?(facesContext?!=?null)
????????????return?facesContext;
????????FacesContextFactory?contextFactory?=?(FacesContextFactory)?FactoryFinder
????????????????.getFactory(FactoryFinder.FACES_CONTEXT_FACTORY);
????????LifecycleFactory?lifecycleFactory?=?(LifecycleFactory)?FactoryFinder
????????????????.getFactory(FactoryFinder.LIFECYCLE_FACTORY);
????????Lifecycle?lifecycle?=?lifecycleFactory
????????????????.getLifecycle(LifecycleFactory.DEFAULT_LIFECYCLE);
????????//?Either?set?a?private?member?servletContext?=
????????//?filterConfig.getServletContext();
????????//?in?you?filter?init()?method?or?set?it?here?like?this:
????????//?ServletContext?servletContext?=
????????//?((HttpServletRequest)request).getSession().getServletContext();
????????//?Note?that?the?above?line?would?fail?if?you?are?using?any?other
????????//?protocol?than?http
????????ServletContext?servletContext?=?((HttpServletRequest)?request)
????????????????.getSession().getServletContext();
????????//?Doesn't?set?this?instance?as?the?current?instance?of
????????//?FacesContext.getCurrentInstance
????????facesContext?=?contextFactory.getFacesContext(servletContext,?request,
????????????????response,?lifecycle);
????????//?Set?using?our?inner?class
????????InnerFacesContext.setFacesContextAsCurrentInstance(facesContext);
????????//?set?a?new?viewRoot,?otherwise?context.getViewRoot?returns?null
????????//?UIViewRoot?view?=
????????//?facesContext.getApplication().getViewHandler().createView(facesContext,
????????//?"yourOwnID");
????????//?facesContext.setViewRoot(view);
????????return?facesContext;
????}
}