在dwr.xml中有，<creator>標簽負責公開用于Web遠程的類和類的方法，實際上最后調用的就是本包下面的script創建類。
creator類型在1.1版本的時候有如下幾種，現在是3.0版本了，我查了下源碼，種類好像比下面要多（查XXXCreator有多少個）。
new: 用Java的new關鍵字創造對象。
none: 它不創建對象，看下面的原因。 (v1.1+)
scripted: 通過BSF使用腳本語言創建對象，例如BeanShell或Groovy。
spring: 通過Spring框架訪問Bean。
jsf: 使用JSF的Bean。 (v1.1+)
struts: 使用Struts的FormBean。 (v1.1+)
pageflow: 訪問Beehive或Weblogic的PageFlow。 (v1.1+)
creator是在什么時候調用的呢？
實際上，在Serlvet加載的時候有個doPost方法，doPost方法調用handle，handle再調用remotor，remotor最終調用相應的creator,比如NewCreator，creator實際上是執行創建script字符串的工作。
舉例來說，我們想在html中某個地方直接顯示當前時間的long值，那么我們就可以調用java.util.Date類的getTime()方法。dwr.xml中寫法如下：
<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>
我們知道這樣所有的/dwr/*所有請求都由這個servlet來處理，那么實際上，瀏覽器加載
<script type='text/javascript' src='dwr/interface/JDate.js'></script>時，實際上是在觸發servlet，這次觸發屬于系統觸發，不做事的，只有執行javascript調用方法時如：
function getServerDateTime()
{
JDate.getTime(handleGetTime);
}
function handleGetTime(dateTime){
DWRUtil.setValue("date", dateTime);
}
才會觸發下面
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException
{
doPost(req, resp);
}
doGet會調用到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中我們看到如下代碼
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);
}
}
這些handle有多種
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
上面三種都是系統范圍的handle，對于我們自己編寫的類，應該是觸發InterfaceHandler 。
我們再看如下關系
public abstract class CachingFileHandler implements Handler
public abstract class TemplateHandler extends CachingFileHandler
public abstract class JavaScriptHandler extends TemplateHandler
public class InterfaceHandler extends JavaScriptHandler
逐級往上繼承
InterfaceHandler，我們看到如下代碼，
執行順序-4，里面調用了遠程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");
}
}
類JavaScriptHandler代碼如下，調用了父類TemplateHandler的generateCachableContent方法
執行順序-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類代碼如下
執行順序-3，里面調用了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類代碼如下，handle方法里面調用了generateCachableContent()方法
執行順序-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);
}
代碼有點繞
我們看到在InterfaceHandler類中
有一行代碼如下：
remoter.generateInterfaceScript(scriptName, contextServletPath);
如果按例子，對于聲明在dwr.xml中的JDate類，scriptName應該是JDate,contextServletPath應該是'dwr/interface/'
執行generateInterfaceScript方法生成相應的字符串，對應于JDate.js
在CachingFileHandler類中的方法handle最后一行如下，
out.println(output);
在這個地方，將返回內容輸出到客戶端。