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关于velocity与SpringMVC的配置请参考前一篇文章，此处不再介绍。velocity作为Java模版引擎的主要目的是为了允许任何人使用简单而强大的模板语言来引用定义在Java代码中的对象。在velocity文件中可以给该页面指定模版布局，从而节省了大量的时间去写通用的模版布局。可以定义变量，与Java方法进行交互。
#set($layout=‘layout/yourlayout.vm‘)
那么如何定义一个layout，看下面的例子：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <HEAD> <TITLE>$!page_title 测试layout页面</TITLE> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/> <meta http-equiv="Content-Language" content="zh-CN"/> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/> <meta http-equiv="Content-Language" content="zh-CN"/> <link href="/resources/lib/font-awesome/css/font-awesome.min.css" tppabs="/resources/lib/font-awesome/css/font-awesome.min.css" rel="stylesheet" type="text/css"/> <link href="/resources/lib/bootstrap/css/bootstrap.min.css" tppabs="/resources/lib/bootstrap/css/bootstrap.min.css" rel="stylesheet" type="text/css"/> </HEAD> <BODY> $screen_content <script src="/resources/lib/jquery-1.10.2.min.js" tppabs="/resources/lib/jquery-1.10.2.min.js" type="text/javascript"></script> <script src="/resources/lib/jquery-migrate-1.2.1.min.js" tppabs="/resources/lib/jquery-migrate-1.2.1.min.js" type="text/javascript"></script> </BODY> </HTML>
那么$screen_content所在的位置即是你所打开页面将要占用的位置。
#set($var=‘xxxx‘) ##输出上面的变量直接使用$var
#foreach($ele in $list) <span>output element:$ele</span> #end
#if($var==‘xxxx‘) <span>it is right</span> #elseif($var==‘‘) <span>sorry</span> #else <span>it is wrong</span> #end
类似于JSP，velocity也有自己的内置对象，如$request,$response,$session这样以来我们就可以将Java对象request和response以及session里的东西轻而易举的展现在web页面里。
velocity同时也支持自定义标签，或者称为指令。如果查看velocity的源码就会发现有个directive.properties
directive.1=org.apache.velocity.runtime.directive.Foreach directive.2=org.apache.velocity.runtime.directive.Include directive.3=org.apache.velocity.runtime.directive.Parse directive.4=org.apache.velocity.runtime.directive.Macro directive.5=org.apache.velocity.runtime.directive.Literal directive.6=org.apache.velocity.runtime.directive.Evaluate directive.7=org.apache.velocity.runtime.directive.Break directive.8=org.apache.velocity.runtime.directive.Define directive.9=org.apache.velocity.runtime.directive.Stop
这里正是velocity当前所提供的9个标签（指令），下面我们新添加一个指令say
<body>
#say("hello")
</body>
java代码实现
import java.io.IOException;
import java.io.Serializable;
import java.io.StringWriter;
import java.io.Writer;
import java.util.HashMap;
import java.util.Map;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.VelocityEngine;
import org.apache.velocity.context.InternalContextAdapter;
import org.apache.velocity.exception.MethodInvocationException;
import org.apache.velocity.exception.ParseErrorException;
import org.apache.velocity.exception.ResourceNotFoundException;
import org.apache.velocity.runtime.directive.Directive;
import org.apache.velocity.runtime.parser.node.Node;
import org.apache.velocity.runtime.parser.node.SimpleNode;
import org.springframework.beans.factory.annotation.Autowired;
import com.alibaba.citrus.service.template.TemplateService;
import com.alibaba.click.util.HostUtil;
public class Say extends Directive{
@Autowired
TemplateService templateService;
private static final VelocityEngine velocityEngine = new VelocityEngine();
@Override
public String getName() {
return "say";
}
@Override
public int getType() {
return LINE;
}
@Override
public boolean render(InternalContextAdapter context, Writer writer,
Node node) throws IOException, ResourceNotFoundException,
ParseErrorException, MethodInvocationException {
SimpleNode sn = (SimpleNode) node.jjtGetChild(0);
writer.write((String)sn.value(context));
return true;
}
}
接下来就可以在velocity.properties文件里添加上
say=cn.buglife.demo.msv.directive.Say
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原文地址：http://my.oschina.net/crazyharry/blog/363698
