开发者文档:http://velocity.apache.org/engine/devel/developer-guide.html
http://velocity.apache.org/engine/devel/user-guide.html
模板语言:http://velocity.apache.org/engine/devel/vtl-reference-guide.html
1、Velocity如何工作:
(1)、初始化Velocity,一个应用可以创建一个Singleton对象Velocity或者为每一个实现创建VelocityEngine对象;Initialize Velocity.
(2)、创建一个Context对象(VelocityContext);Create a Context object
(3)、把数据对象添加到Context中;Add your data objects to the Context.
(4)、选择一个模板;Choose a template.
(5)、合并模板与数据产生输出流。'Merge' the template and your data to produce the ouput.
2、单例模式:org.apache.velocity.app.Velocity
import java.io.StringWriter;
import org.apache.velocity.Template;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.Velocity;
import org.apache.velocity.exception.MethodInvocationException;
import org.apache.velocity.exception.ParseErrorException;
import org.apache.velocity.exception.ResourceNotFoundException;
Velocity.init();
VelocityContext context = new VelocityContext();
context.put("name", new String("Velocity" ));
Template template = null;
try {
template = Velocity.getTemplate( "mytemplate.vm");
} catch (ResourceNotFoundException
rnfe) {
// couldn't find the template
} catch (ParseErrorException
pee) {
// syntax error: problem parsing the template
} catch (MethodInvocationException
mie) {
// something invoked in the template
// threw an exception
} catch (Exception
e) {
}
StringWriter sw = new StringWriter();
template.merge(context, sw);
3、非单例模式:org.apache.velocity.app.VelocityEngine
VelocityEngine velocityEngine = new VelocityEngine();
velocityEngine.init();
VelocityContext context = new VelocityContext();
context.put("name", new String("Velocity" ));
Template template = null;
try {
template = velocityEngine.getTemplate( "mytemplate.vm");
} catch (ResourceNotFoundException
rnfe) {
// couldn't find the template
} catch (ParseErrorException
pee) {
// syntax error: problem parsing the template
} catch (MethodInvocationException
mie) {
// something invoked in the template
// threw an exception
} catch (Exception
e) {
}
StringWriter sw = new StringWriter();
template.merge(context, sw);
4、Context:VelocitContext
VelocityContext提供两个最主要的方法:
public Object put(String key, Object value);
public Object get(String key);
(1)、使用#foreach()支持迭代对象;Support for Iterative Objects for #foreach()
支持类型:Object[],java.util.Collection,java.util.Map,java.util.Iterator,java.util.Enumeration
(2)、支持类对象。Support
for "Static Classes"
context.put("Math",
Math. class);
在模板中$Math可以使用java.lang.Math静态方法
5、使用Velocity
Velocity有5个方法:
- setProperty(String key, Object o):设置key的值
- Object getProperty(String key):根据key获取值
- init():使用默认的properties配置文件初始化
- init(Properties p):根据Properties对象设置参数初始化
- init(String filename):根据properties文件初始化
默认properties配置文件所在位置:org/apache/velocity/runtime/defaults/velocity.properties,相关配置见官方文档