velocity模板引擎學習(2)-velocity tools 2.0

使用velocity後，原來的不少標籤沒法使用了，必須藉助velocity tools來完成，目前velocity tools最新版本是2.0，下面是velocity tools的一些注意事項：

1. 與Spring MVC 3.x/4.x的集成問題

Spring 3.x/4.x只支持1.3.x的velocity tools，要使用2.0必須本身擴展VelocityToolboxView類

 1 package org.springframework.web.servlet.view.velocity;
 2 
 3 import java.util.Map;
 4 
 5 import javax.servlet.http.HttpServletRequest;
 6 import javax.servlet.http.HttpServletResponse;
 7 
 8 import org.apache.velocity.context.Context;
 9 import org.apache.velocity.tools.Scope;
10 import org.apache.velocity.tools.ToolManager;
11 import org.apache.velocity.tools.view.ViewToolContext;
12 import org.springframework.web.servlet.view.velocity.VelocityToolboxView;
13 
14 public class VelocityToolbox2View extends VelocityToolboxView {
15     @Override
16     protected Context createVelocityContext(Map<String, Object> model,
17             HttpServletRequest request, HttpServletResponse response)
18             throws Exception {// Create a
19                                 // ChainedContext
20                                 // instance.
21         ViewToolContext ctx;
22 
23         ctx = new ViewToolContext(getVelocityEngine(), request, response,
24                 getServletContext());
25 
26         ctx.putAll(model);
27 
28         if (this.getToolboxConfigLocation() != null) {
29             ToolManager tm = new ToolManager();
30             tm.setVelocityEngine(getVelocityEngine());
31             tm.configure(getServletContext().getRealPath(
32                     getToolboxConfigLocation()));
33             if (tm.getToolboxFactory().hasTools(Scope.REQUEST)) {
34                 ctx.addToolbox(tm.getToolboxFactory().createToolbox(
35                         Scope.REQUEST));
36             }
37             if (tm.getToolboxFactory().hasTools(Scope.APPLICATION)) {
38                 ctx.addToolbox(tm.getToolboxFactory().createToolbox(
39                         Scope.APPLICATION));
40             }
41             if (tm.getToolboxFactory().hasTools(Scope.SESSION)) {
42                 ctx.addToolbox(tm.getToolboxFactory().createToolbox(
43                         Scope.SESSION));
44             }
45         }
46         return ctx;
47     }
48 }

View Code

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

getResource試試

 

而後在spring mvc的servlet配置文件中參考以下設置：

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

View Code

 

2. 如何獲取當前應用的contextPath

1     <tool>
2         <key>link</key>
3         <scope>request</scope>
4         <class>org.apache.velocity.tools.view.LinkTool</class>
5     </tool>

藉助velocity-tools的LinkTool類，在velocity中直接用${link.contextPath}便可獲得當前的contextPath

 

三、如何獲取url參數

1     <tool>
2         <key>params</key>
3         <scope>request</scope>
4         <class>org.apache.velocity.tools.view.ParameterTool</class>
5     </tool>

而後就能夠用相似$params.returnUrl，來獲取相似 http://xxx.com/login?returnUrl=abc 中的 abc部分

 

四、如何與Spring-Security集成

1 <sec:authorize access="isAnonymous()">
2 ...
3     </sec:authorize>

View Code

之類的標籤沒法在velocity中使用，而velocity-tools中也未提供相應的支持，在老外的一篇博客上，看到了解決方案：

 1 package com.cnblogs.yjmyzz.utils;
 2 
 3 import java.util.Collection;
 4 import java.util.HashSet;
 5 import java.util.Set;
 6 import org.springframework.security.core.GrantedAuthority;
 7 import org.springframework.security.core.context.SecurityContextHolder;
 8 import org.springframework.security.core.userdetails.UserDetails;
 9 
10 public class VelocitySecurityUtil {
11 
12     public static String getPrincipal() {
13 
14         Object obj = SecurityContextHolder.getContext().getAuthentication()
15                 .getPrincipal();
16 
17         if (obj instanceof UserDetails) {
18             return ((UserDetails) obj).getUsername();
19         } else {
20             return "anonymous";
21         }
22     }
23 
24     public static boolean isAuthenticated() {
25         return !getPrincipal().equals("anonymous");
26     }
27 
28     public static boolean allGranted(String[] checkForAuths) {
29         Set<String> userAuths = getUserAuthorities();
30         for (String auth : checkForAuths) {
31             if (userAuths.contains(auth))
32                 continue;
33             return false;
34         }
35         return true;
36     }
37 
38     public static boolean anyGranted(String[] checkForAuths) {
39         Set<String> userAuths = getUserAuthorities();
40         for (String auth : checkForAuths) {
41             if (userAuths.contains(auth))
42                 return true;
43         }
44         return false;
45     }
46 
47     public static boolean noneGranted(String[] checkForAuths) {
48         Set<String> userAuths = getUserAuthorities();
49         for (String auth : checkForAuths) {
50             if (userAuths.contains(auth))
51                 return false;
52         }
53         return true;
54     }
55 
56     private static Set<String> getUserAuthorities() {
57         Object obj = SecurityContextHolder.getContext().getAuthentication()
58                 .getPrincipal();
59         Set<String> roles = new HashSet<String>();
60         if (obj instanceof UserDetails) {
61             @SuppressWarnings("unchecked")
62             Collection<GrantedAuthority> gas = (Collection<GrantedAuthority>) ((UserDetails) obj)
63                     .getAuthorities();
64             for (GrantedAuthority ga : gas) {
65                 roles.add(ga.getAuthority());
66             }
67         }
68         return roles;
69     }
70 
71 }

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而後修改配置：

 1     <bean id="velocitySecurityUtil" class="com.cnblogs.yjmyzz.utils.VelocitySecurityUtil" />
 2 
 3     <bean
 4         class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">
 5         <property name="order" value="1" />
 6         ...
 7         <property name="viewResolvers">
 8             <list>
 9                 <bean
10                     class="org.springframework.web.servlet.view.velocity.VelocityViewResolver">
11                     <property name="order" value="0" />
12                     ...
13                     <property name="attributesMap">
14                         <map>
15                             <entry key="sec">
16                                 <ref bean="velocitySecurityUtil" />
17                             </entry>
18                         </map>
19                     </property>
20 
21                 </bean>
22                 ...

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頁面就能用了：

1     #if(${sec.authenticated}) 
2     ...
3     #end

View Code

注：這個思路也能夠用於實現本身的Velocity-Tools類，好比咱們建立了一個本身的RequestUtil類

 1 package com.cnblogs.yjmyzz.utils;
 2 import javax.servlet.http.HttpServletRequest;
 3 public class RequestUtil{
 4 
 5     /**
 6      * 獲取當前請求的基地址（例如：http://localhost:8080/ctas/xxx.do 返回 http://localhost:8080/ctas/）
 7      *
 8      * @param request
 9      * @return
10      */
11     public static String getBaseUrl(HttpServletRequest request) {
12         return request.getRequestURL().substring(0,
13                 request.getRequestURL().indexOf(request.getContextPath()) + request.getContextPath().length()) + "/";
14     }
15 
16 }

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而後在配置裏，加上

 1     <bean id="requestUtil" class="com.cnblogs.yjmyzz.utils.RequestUtil"/>
 2 
 3     <bean
 4             class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">
 5         <property name="order" value="1"/>
 6        ...
 7         <property name="viewResolvers">
 8             <list>
 9                 ...
10                 <bean
11                         class="org.springframework.web.servlet.view.velocity.VelocityViewResolver">
12                     <property name="order" value="0"/>
13                  ...
14                     <property name="viewClass"
15                               value="com.cnblogs.yjmyzz.utils.VelocityToolbox2View"></property>
16                     <property name="attributesMap">
17                         <map>
18                           ...
19                             <entry key="req">
20                                 <ref bean="requestUtil"/>
21                             </entry>
22                         </map>
23                     </property>
24                 </bean>
25               ...
26     </bean>

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 vm頁面這樣用

1 #*取得頁面連接基地址*#
2 #macro(baseHref)${req.getBaseUrl($request)}#end
3 ...
4 <base href="#{baseHref}">
5 ...
6 <script type="text/javascript">
7     var baseHref = "#{baseHref}";
8 </script>
9 ...

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順便提一句：網上有一堆文章和教程，讓你在toolbox.xml中添加相似

1     <tool>
2         <key>req</key>
3         <scope>request</scope>
4         <class>com.cnblogs.yjmyzz.utils.RequestUtil</class>
5     </tool>

View Code

在Spring MVC4 + Velocity Tools2的組合下，然而，這並無什麼用，在Spring MVC4 + Velocity-Tools2下，已經很差使了。

最後，Velocity還容許自定義標籤（也有人稱爲自定義指令），支持開發人員定義本身的標籤，好比#YourDirective，詳情可參考：

編寫自定義的 Velocity 指令