velocity模板引擎学习(2)-velocity tools 2.0

使用velocity后，原来的很多标签无法使用了，必须借助velocity tools来完成，目前velocity tools最新版本是2.0，下面是velocity tools的一些注意事项：

1. 与Spring MVC 3.x/4.x的集成问题

Spring 3.x/4.x只支持1.3.x的velocity tools，要使用2.0必须自己扩展VelocityToolboxView类

 package org.springframework.web.servlet.view.velocity;

 import java.util.Map;

 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 import org.apache.velocity.context.Context;
 import org.apache.velocity.tools.Scope;
 import org.apache.velocity.tools.ToolManager;
 import org.apache.velocity.tools.view.ViewToolContext;
 import org.springframework.web.servlet.view.velocity.VelocityToolboxView;

 public class VelocityToolbox2View extends VelocityToolboxView {
     @Override
     protected Context createVelocityContext(Map<String, Object> model,
             HttpServletRequest request, HttpServletResponse response)
             throws Exception {// Create a
                                 // ChainedContext
                                 // instance.
         ViewToolContext ctx;

         ctx = new ViewToolContext(getVelocityEngine(), request, response,
                 getServletContext());

         ctx.putAll(model);

         if (this.getToolboxConfigLocation() != null) {
             ToolManager tm = new ToolManager();
             tm.setVelocityEngine(getVelocityEngine());
             tm.configure(getServletContext().getRealPath(
                     getToolboxConfigLocation()));
             if (tm.getToolboxFactory().hasTools(Scope.REQUEST)) {
                 ctx.addToolbox(tm.getToolboxFactory().createToolbox(
                         Scope.REQUEST));
             }
             if (tm.getToolboxFactory().hasTools(Scope.APPLICATION)) {
                 ctx.addToolbox(tm.getToolboxFactory().createToolbox(
                         Scope.APPLICATION));
             }
             if (tm.getToolboxFactory().hasTools(Scope.SESSION)) {
                 ctx.addToolbox(tm.getToolboxFactory().createToolbox(
                         Scope.SESSION));
             }
         }
         return ctx;
     }
 }

注：31行tm.configure(getServletContext().getRealPath(getToolboxConfigLocation()));这里，在某些容器，比如weblogic中，getRealPath可能取不到值，可改成

getResource试试

然后在spring mvc的servlet配置文件中参考如下设置：

 <bean
                     class="org.springframework.web.servlet.view.velocity.VelocityViewResolver">
                     <property name="order" value="0" />
                     <property name="cache" value="true" />
                     <property name="prefix" value="" />
                     <property name="suffix" value=".vm" />
                     <property name="toolboxConfigLocation" value="/WEB-INF/toolbox.xml" />
                     <property name="contentType" value="text/html;charset=UTF-8" />
                     <property name="viewClass" value="org.springframework.web.servlet.view.velocity.VelocityToolbox2View"></property>
                 </bean>

2. 如何获取当前应用的contextPath

     <tool>
         <key>link</key>
         <scope>request</scope>
         <class>org.apache.velocity.tools.view.LinkTool</class>
     </tool>

借助velocity-tools的LinkTool类，在velocity中直接用${link.contextPath}即可得到当前的contextPath

3、如何获取url参数

     <tool>
         <key>params</key>
         <scope>request</scope>
         <class>org.apache.velocity.tools.view.ParameterTool</class>
     </tool>

然后就可以用类似$params.returnUrl，来获取类似 http://xxx.com/login?returnUrl=abc 中的 abc部分

4、如何与Spring-Security集成

 <sec:authorize access="isAnonymous()">
 ...
     </sec:authorize>

之类的标签无法在velocity中使用，而velocity-tools中也未提供相应的支持，在老外的一篇博客上，看到了解决方案：

 package com.cnblogs.yjmyzz.utils;

 import java.util.Collection;
 import java.util.HashSet;
 import java.util.Set;
 import org.springframework.security.core.GrantedAuthority;
 import org.springframework.security.core.context.SecurityContextHolder;
 import org.springframework.security.core.userdetails.UserDetails;

 public class VelocitySecurityUtil {

     public static String getPrincipal() {

         Object obj = SecurityContextHolder.getContext().getAuthentication()
                 .getPrincipal();

         if (obj instanceof UserDetails) {
             return ((UserDetails) obj).getUsername();
         } else {
             return "anonymous";
         }
     }

     public static boolean isAuthenticated() {
         return !getPrincipal().equals("anonymous");
     }

     public static boolean allGranted(String[] checkForAuths) {
         Set<String> userAuths = getUserAuthorities();
         for (String auth : checkForAuths) {
             if (userAuths.contains(auth))
                 continue;
             return false;
         }
         return true;
     }

     public static boolean anyGranted(String[] checkForAuths) {
         Set<String> userAuths = getUserAuthorities();
         for (String auth : checkForAuths) {
             if (userAuths.contains(auth))
                 return true;
         }
         return false;
     }

     public static boolean noneGranted(String[] checkForAuths) {
         Set<String> userAuths = getUserAuthorities();
         for (String auth : checkForAuths) {
             if (userAuths.contains(auth))
                 return false;
         }
         return true;
     }

     private static Set<String> getUserAuthorities() {
         Object obj = SecurityContextHolder.getContext().getAuthentication()
                 .getPrincipal();
         Set<String> roles = new HashSet<String>();
         if (obj instanceof UserDetails) {
             @SuppressWarnings("unchecked")
             Collection<GrantedAuthority> gas = (Collection<GrantedAuthority>) ((UserDetails) obj)
                     .getAuthorities();
             for (GrantedAuthority ga : gas) {
                 roles.add(ga.getAuthority());
             }
         }
         return roles;
     }

 }

然后修改配置：

     <bean id="velocitySecurityUtil" class="com.cnblogs.yjmyzz.utils.VelocitySecurityUtil" />

     <bean
         class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">
         <property name="order" value="1" />
         ...
         <property name="viewResolvers">
             <list>
                 <bean
                     class="org.springframework.web.servlet.view.velocity.VelocityViewResolver">
                     <property name="order" value="0" />
                     ...
                     <property name="attributesMap">
                         <map>
                             <entry key="sec">
                                 <ref bean="velocitySecurityUtil" />
                             </entry>
                         </map>
                     </property>

                 </bean>
                 ...

页面就能用了：

     #if(${sec.authenticated})
     ...
     #end

注：这个思路也可以用于实现自己的Velocity-Tools类，比如我们创建了一个自己的RequestUtil类

 package com.cnblogs.yjmyzz.utils;
 import javax.servlet.http.HttpServletRequest;
 public class RequestUtil{

     /**
      * 获取当前请求的基地址（例如：http://localhost:8080/ctas/xxx.do 返回 http://localhost:8080/ctas/）
      *
      * @param request
      * @return
      */
     public static String getBaseUrl(HttpServletRequest request) {
         return request.getRequestURL().substring(0,
                 request.getRequestURL().indexOf(request.getContextPath()) + request.getContextPath().length()) + "/";
     }

 }

然后在配置里，加上

     <bean id="requestUtil" class="com.cnblogs.yjmyzz.utils.RequestUtil"/>

     <bean
             class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">
         <property name="order" value="1"/>
        ...
         <property name="viewResolvers">
             <list>
                 ...
                 <bean
                         class="org.springframework.web.servlet.view.velocity.VelocityViewResolver">
                     <property name="order" value="0"/>
                  ...
                     <property name="viewClass"
                               value="com.cnblogs.yjmyzz.utils.VelocityToolbox2View"></property>
                     <property name="attributesMap">
                         <map>
                           ...
                             <entry key="req">
                                 <ref bean="requestUtil"/>
                             </entry>
                         </map>
                     </property>
                 </bean>
               ...
     </bean>

vm页面这样用

 #*取得页面链接基地址*#
 #macro(baseHref)${req.getBaseUrl($request)}#end
 ...
 <base href="#{baseHref}">
 ...
 <script type="text/javascript">
     var baseHref = "#{baseHref}";
 </script>
 ...

顺便提一句：网上有一堆文章和教程，让你在toolbox.xml中添加类似

     <tool>
         <key>req</key>
         <scope>request</scope>
         <class>com.cnblogs.yjmyzz.utils.RequestUtil</class>
     </tool>

在Spring MVC4 + Velocity Tools2的组合下，然而，这并没有什么用，在Spring MVC4 + Velocity-Tools2下，已经不好使了。

最后，Velocity还允许自定义标签（也有人称为自定义指令），支持开发人员定义自己的标签，比如#YourDirective，详情可参考：

编写自定义的 Velocity 指令