DWR 之 org.directwebremoting.create包

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();