Velocity详细说明

2012.01.07 大连 晴

 

这些天真是很忙，也没时间写文章了，放假了，可以细细的品味一些最近的收获和感想，还有很多。。。

慢慢的到了2012，这个注定不平凡的一年，大家都有自己的事业和发展，都有自己对这一年的期望，希望能梦想成真，发展顺利

 

废话就不多说了，马上开始我们的说明

 

Velocity 是jsp等的模版语言，真是强大，但都是写好vm文件，让后解析的，如果是要在jsp等中应用，需要其他的扩展tool，Velocity官网也提供下载

我这里也会说明，让我们慢慢道来

 

1.官网：

http://velocity.apache.org/engine/devel/index.html

 

2.下载Velocity

现在的版本是：1.7 

http://velocity.apache.org/download.cgi

里面包含了2个jar

 

1.velocity-1.7.jar

2.velocity-1.7-dep.jar

 

分别说明一下：

1.velocity-1.7.jar基本jar包，里面包含了开发需要的一切包

2.velocity-1.7-dep.jar包含了上面的包，但还包含了、其他的比如：oro.*,commons-lang.*，org.apache.log.*等

 

我用的是第一个，我不喜欢别人给封装好的东西

 

Velocity plugin for the Eclipse 

Velocity - http://veloeclipse.googlecode.com/svn/trunk/update/

 

下面我们可以写一个main函数调用vm了

jar：

avalon-logkit-2.1.jar

commons-collections-3.2.1.jar

commons-lang-2.4.jar

log4j-1.2.12.jar

velocity-1.7.jar

 

 

package com.chenhailong.velocity;

import java.io.IOException;
import java.io.StringWriter;
import java.util.Date;

import org.apache.velocity.Template;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.VelocityEngine;

/**
 * 
 * @author chenhailong
 * pm 12:02:38
 * com.chenhailong.velocity
 */
public class HelloWorld {

    public static void main(String[] args) throws IOException {
        VelocityEngine ve = new VelocityEngine();
        ve.init();
        Template template = ve.getTemplate("hello.vm");
        VelocityContext context = new VelocityContext();
        context.put("name", "chenhailong");
        context.put("date", new Date().toString());
        StringWriter writer = new StringWriter();
        template.merge(context, writer);
        System.out.println(writer.toString());
        writer.close();
    }
}

 

 

 

Welcome $name to Javayou.com!
today is $date.

 

 

 

好了 这样我们就能运行了

其他例子

 

 

package com.chen.example;

import java.io.BufferedWriter;
import java.io.OutputStreamWriter;
import java.util.ArrayList;

import org.apache.log4j.BasicConfigurator;
import org.apache.log4j.Logger;
import org.apache.velocity.Template;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.Velocity;
import org.apache.velocity.app.VelocityEngine;
import org.apache.velocity.exception.ParseErrorException;
import org.apache.velocity.exception.ResourceNotFoundException;
import org.apache.velocity.runtime.RuntimeConstants;
import org.apache.velocity.runtime.log.Log4JLogChute;

public class Example {
    public static String LOGGER_NAME = "velexample";
    public static VelocityEngine ve = null;

    public Example(String templateFile) {
        try {
            ve = new VelocityEngine();
            //ve.init("bin/velocity.properties");
            ve.init();
            VelocityContext context = new VelocityContext();
            context.put("list", getNames());
            Template template = null;

            try {
                template = Velocity.getTemplate(templateFile);
            } catch (ResourceNotFoundException rnfe) {
                System.out.println("Example : error : cannot find template " + templateFile);
            } catch (ParseErrorException pee) {
                System.out.println("Example : Syntax error in template " + templateFile + ":" + pee);
            }
            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(System.out));

            if (template != null)
                template.merge(context, writer);
            writer.flush();
            writer.close();
        } catch (Exception e) {
            System.out.println(e);
        }
    }

    public ArrayList getNames() {
        ArrayList list = new ArrayList();

        list.add("ArrayList element 1");
        list.add("ArrayList element 2");
        list.add("ArrayList element 3");
        list.add("ArrayList element 4");

        return list;
    }

    public static void main(String[] args) {
        BasicConfigurator.configure();

        Logger log = Logger.getLogger(LOGGER_NAME);
        log.info("Hello from Log4jLoggerExample - ready to start velocity");
        Example t = new Example("example.vm");
        ve.setProperty(RuntimeConstants.RUNTIME_LOG_LOGSYSTEM_CLASS, "org.apache.velocity.runtime.log.Log4JLogChute");
        ve.setProperty(Log4JLogChute.RUNTIME_LOG_LOG4J_LOGGER, LOGGER_NAME);
        log.info("this should follow the initialization output from velocity");
    }
}

 

 

 

#set( $this = "Velocity")

$this is great!

#foreach( $name in $list )
    $name is great!
#end

#set( $condition = true)

#if ($condition)
    The condition is true!
#else
    The condition is false!
#end

 

 

 

runtime.log = velocity_example.log

 

 

基本的velocity的语法和常用的都在上面了，希望对大家有用

 

这里我介绍一下velocity tool 的应用

 

举一个小例子

 

 

<?xml version="1.0" ?>
<test>
	<chen a="1">
		chenhailong
	</chen>
</test>

 

commons-beanutils-1.7.0.jar

commons-collections-3.2.jar

commons-digester-1.8.jar

commons-lang-2.2.jar

commons-logging-1.1.jar

dom4j-1.1.jar

oro-2.0.8.jar

velocity-tools-view-2.0.jar

velocity-1.6.2.jar

 

they are togetder 

tools.xml

 

<?xml version="1.0"?>
<tools>
	<data key="author">chenhailong</data>
	<data key="enter">chenh</data>

	<toolbox scope="application">
		<tool class="org.apache.velocity.tools.generic.XmlTool" key="test"
			file="test.xml" />
	</toolbox>
</tools>

 

web.xml

 

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN" "http://java.sun.com/j2ee/dtds/web-app_2_2.dtd">

<web-app>
	<servlet>
		<servlet-name>velocity</servlet-name>
		<servlet-class>org.apache.velocity.tools.view.VelocityLayoutServlet</servlet-class>
		<init-param>
			<param-name>org.apache.velocity.tools.deprecationSupportMode</param-name>
			<param-value>false</param-value>
		</init-param>
		<init-param>
			<param-name>org.apache.velocity.tools.cleanConfiguration</param-name>
			<param-value>true</param-value>
		</init-param>
		<init-param>
			<param-name>org.apache.velocity.tools.userCanOverwriteTools</param-name>
			<param-value>false</param-value>
		</init-param>
	</servlet>
	<servlet-mapping>
		<servlet-name>velocity</servlet-name>
		<url-pattern>*.vm</url-pattern>
	</servlet-mapping>
</web-app>

 

 

xml.vm

 

$test.chen.text
$test.find('@a')
$test.chen.a
$test.children()
$test.first+$test.last
$enter
$author 

 

 

其他工具基本都是一样的。。。

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