在dwr.xml中有，<creator>标签负责公开用于Web远程的类和类的方法，实际上最后调用的就是本包下面的script创建类。
creator类型在1.1版本的时候有如下几种，现在是3.0版本了，我查了下源码，种类好像比下面要多（查XXXCreator有多少个）。
new: 用Java的new关键字创造对象。
none: 它不创建对象，看下面的原因。 (v1.1+)
scripted: 通过BSF使用脚本语言创建对象，例如BeanShell或Groovy。
spring: 通过Spring框架访问Bean。
jsf: 使用JSF的Bean。 (v1.1+)
struts: 使用Struts的FormBean。 (v1.1+)
pageflow: 访问Beehive或Weblogic的PageFlow。 (v1.1+)
creator是在什么时候调用的呢？
实际上，在Serlvet加载的时候有个doPost方法，doPost方法调用handle，handle再调用remotor，remotor最终调用相应的creator,比如NewCreator，creator实际上是执行创建script字符串的工作。
举例来说，我们想在html中某个地方直接显示当前时间的long值，那么我们就可以调用java.util.Date类的getTime()方法。dwr.xml中写法如下：
<dwr>
<allow>
<create creator="new" javascript="JDate">
<param name="class" value="java.util.Date"/>
</create>
<create creator="new" javascript="Demo">
<param name="class" value="your.java.Bean"/>
</create>
</allow>
</dwr>
我们知道这样所有的/dwr/*所有请求都由这个servlet来处理，那么实际上，浏览器加载
<script type='text/javascript' src='dwr/interface/JDate.js'></script>时，实际上是在触发servlet，这次触发属于系统触发，不做事的，只有执行javascript调用方法时如：
function getServerDateTime()
{
JDate.getTime(handleGetTime);
}
function handleGetTime(dateTime){
DWRUtil.setValue("date", dateTime);
}
才会触发下面
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException
{
doPost(req, resp);
}
doGet会调用到doPost
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
{
try
{
webContextBuilder.set(request, response, getServletConfig(), getServletContext(), container);
UrlProcessor processor = container.getBean(UrlProcessor.class);
processor.handle(request, response);
}
finally
{
webContextBuilder.unset();
}
}
在proccessor中我们看到如下代码
public void handle(HttpServletRequest request, HttpServletResponse response) throws IOException
{
try
{
String pathInfo = request.getPathInfo();
contextPath = request.getContextPath();
if (pathInfo == null || pathInfo.length() == 0 || "/".equals(pathInfo))
{
response.sendRedirect(contextPath + request.getServletPath() + indexHandlerUrl);
}
else
{
// Loop through all the known URLs
for (Entry<String, Object> entry : urlMapping.entrySet())
{
String url = entry.getKey();
// If this URL matches, call the handler
if (pathInfo.startsWith(url))
{
Handler handler = (Handler) entry.getValue();
handler.handle(request, response);
return;
}
}
notFoundHandler.handle(request, response);
}
}
catch (Exception ex)
{
exceptionHandler.setException(ex);
exceptionHandler.handle(request, response);
}
}
这些handle有多种
1，
/**
* A Handler that supports requests for auth.js
*/
public class AuthHandler extends JavaScriptHandler
2，
/**
* A Handler that supports requests for engine.js
* @author Joe Walker [joe at getahead dot ltd dot uk]
*/
public class EngineHandler extends JavaScriptHandler
3，
/**
* A Handler that supports requests for util.js
* @author Joe Walker [joe at getahead dot ltd dot uk]
*/
public class GiHandler extends JavaScriptHandler
4，
/**
* A handler for interface generation requests
* @author Joe Walker [joe at getahead dot ltd dot uk]
*/
public class InterfaceHandler extends JavaScriptHandler
上面三种都是系统范围的handle，对于我们自己编写的类，应该是触发InterfaceHandler 。
我们再看如下关系
public abstract class CachingFileHandler implements Handler
public abstract class TemplateHandler extends CachingFileHandler
public abstract class JavaScriptHandler extends TemplateHandler
public class InterfaceHandler extends JavaScriptHandler
逐级往上继承
InterfaceHandler，我们看到如下代码，
执行顺序-4，里面调用了远程remoter
protected String generateTemplate(HttpServletRequest request, HttpServletResponse response) throws IOException
{
String scriptName = request.getPathInfo();
scriptName = scriptName.replace(interfaceHandlerUrl, "");
String contextServletPath = request.getContextPath() + request.getServletPath();
if (scriptName.endsWith(PathConstants.EXTENSION_JS))
{
scriptName = scriptName.replace(PathConstants.EXTENSION_JS, "");
if (!LocalUtil.isJavaIdentifier(scriptName))
{
log.debug("Throwing at request for script with name: '" + scriptName + "'");
throw new SecurityException("Script names may only contain Java Identifiers");
}
return remoter.generateInterfaceScript(scriptName, contextServletPath);
}
else if (scriptName.endsWith(PathConstants.EXTENSION_SDOC))
{
scriptName = scriptName.replace(PathConstants.EXTENSION_SDOC, "");
if (!LocalUtil.isJavaIdentifier(scriptName))
{
log.debug("Throwing at request for script with name: '" + scriptName + "'");
throw new SecurityException("Script names may only contain Java Identifiers");
}
return remoter.generateInterfaceSDoc(scriptName, contextServletPath);
}
else
{
log.debug("Throwing at request for script with unknown extension: '" + scriptName + "'");
throw new SecurityException("Unknown extension");
}
}
类JavaScriptHandler代码如下，调用了父类TemplateHandler的generateCachableContent方法
执行顺序-2
protected String generateCachableContent(HttpServletRequest request, HttpServletResponse response) throws IOException
{
String output = super.generateCachableContent(request, response);
if (debug || compressor == null)
{
return output;
}
try
{
return compressor.compressJavaScript(output);
}
catch (Exception ex)
{
log.warn("Compression system (" + compressor.getClass().getSimpleName() +") failed to compress script", ex);
return output;
}
}
TemplateHandler类代码如下
执行顺序-3，里面调用了generateTemplate方法
protected String generateCachableContent(HttpServletRequest request, HttpServletResponse response) throws IOException
{
String template = generateTemplate(request, response);
Map<String, String> replace = getSearchReplacePairs();
if (replace != null)
{
for (Map.Entry<String, String> entry : replace.entrySet())
{
String search = entry.getKey();
if (template.contains(search))
{
template = template.replace(search, entry.getValue());
}
}
}
return template;
}
/** *//**
* Generate a template to undergo search and replace processing according to
* the search and replace pairs from {@link #getSearchReplacePairs()}.
* @param request The HTTP request data
* @param response Where we write the HTTP response data
* @return A template string containing ${} sections to be replaced
*/
protected abstract String generateTemplate(HttpServletRequest request, HttpServletResponse response) throws IOException;
CachingFileHandler类代码如下，handle方法里面调用了generateCachableContent()方法
执行顺序-1
public void handle(HttpServletRequest request, HttpServletResponse response) throws IOException
{
if (isUpToDate(request))
{
response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
return;
}
String output;
synchronized (scriptCache)
{
String url = request.getPathInfo();
output = scriptCache.get(url);
if (output == null)
{
output = generateCachableContent(request, response);
}
scriptCache.put(url, output);
}
response.setContentType(mimeType);
response.setDateHeader(HttpConstants.HEADER_LAST_MODIFIED, CONTAINER_START_TIME);
response.setHeader(HttpConstants.HEADER_ETAG, ETAG);
PrintWriter out = response.getWriter();
out.println(output);
}
代码有点绕
我们看到在InterfaceHandler类中
有一行代码如下：
remoter.generateInterfaceScript(scriptName, contextServletPath);
如果按例子，对于声明在dwr.xml中的JDate类，scriptName应该是JDate,contextServletPath应该是'dwr/interface/'
执行generateInterfaceScript方法生成相应的字符串，对应于JDate.js
在CachingFileHandler类中的方法handle最后一行如下，
out.println(output);
在这个地方，将返回内容输出到客户端。