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