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Velocity简单语法及VelocityHelper封装

1.简单替换
##这是注释
Wellcome ${userName}! Now:$date

2.申明变量：
#set( $iAmVariable = "good!" )
Welcome $name to Javayou.com!
today is $date.
$iAmVariable

3.if语句：
#set ($admin = "admin")
#set ($user = "user")
#if ($admin == $user)
Welcome admin!
#else
Welcome user!
#end

4.遍历对象：
#foreach( $product in $list )
<li>$product</li>
#end

5.自定义对象：
#foreach( $s in $students )
<$velocityCount> No:$s.No, Address: $s.Address

#end

6.标签嵌套：
#foreach ($element in $list)
--外部循环--
$velocityCount:This is $element.
--内部循环--
#foreach ($element in $list)
$velocityCount：This is $element.
#end
--内部循环--
--外部循环--
#end

7.调用自定义对象方法：
#foreach( $s in $students )
<$velocityCount> $s.SayHello();

#end

using System.IO;
using NVelocity.App;
using NVelocity.Context;
using NVelocity.Runtime;

namespace NVelocity
{
    /// <summary>
    ///     NVelocity模板工具类 VelocityHelper
    /// </summary>
    public class VelocityHelper
    {
        private IContext _context;
        private VelocityEngine _velocity;
        private string _templateName;

        /// <summary>
        ///     构造函数
        /// </summary>
        /// <param name="templatDir">模板文件夹路径</param>
        /// <param name="templateName">模板文件名</param>
        public VelocityHelper(string templatDir, string templateName)
        {
            Init(templatDir);
            _templateName = templateName;
        }

        /// <summary>
        ///     无参数构造函数
        /// </summary>
        public VelocityHelper()
        {
        }

        /// <summary>
        /// 设置模板文件夹
        /// </summary>
        /// <param name="templatDir"></param>
        public void SetTemplateDirPath(string templatDir)
        {
            Init(templatDir);
        }
        /// <summary>
        /// 设置模板文件
        /// </summary>
        /// <param name="templateName"></param>
        public void SetTemplateFileName(string templateName)
        {
            _templateName = templateName;
        }


        /// <summary>
        ///     初始化NVelocity模块
        /// </summary>
        /// <param name="templatDir">模板文件夹路径</param>
        public void Init(string templatDir)
        {
            //创建VelocityEngine实例对象并设置初始化VelocityEngine 
            _velocity = new VelocityEngine();
            _velocity.SetProperty(RuntimeConstants_Fields.RESOURCE_LOADER, "file");
            _velocity.SetProperty(RuntimeConstants_Fields.FILE_RESOURCE_LOADER_PATH, templatDir);
            _velocity.SetProperty(RuntimeConstants_Fields.INPUT_ENCODING, "utf-8");
            _velocity.SetProperty(RuntimeConstants_Fields.OUTPUT_ENCODING, "utf-8");
            _velocity.Init();

            //为模板变量赋值
            _context = new VelocityContext();
        }

        /// <summary>
        ///     给模板变量赋值
        /// </summary>
        /// <param name="key">模板变量</param>
        /// <param name="value">模板变量值</param>
        public void Put(string key, object value)
        {
            if (_context == null)
            {
                _context = new VelocityContext();
            }
            _context.Put(key, value);
        }

        /// <summary>
        ///     渲染模板
        /// </summary> 
        public string Render()
        {
            if (!string.IsNullOrEmpty(_templateName))
            {
                //从文件中读取模板
                Template template = _velocity.GetTemplate(_templateName);

                //合并模板
                var writer = new StringWriter();
                template.Merge(_context, writer);
                return writer.GetStringBuilder().ToString();
            }
            return "未指定模板文件!";
        }
    }
}

完整Demo下载：http://download.csdn.net/detail/a497785609/5405089