DWR之HelloWorld_allocate exception for servlet helloworld-优快云博客

1、新建一web项目

2、选中项目右键——属性——Java Build Path ——Libraries——Add External Jars 添加dwr.jar和 commons-logging.jar包

3、web.xml中添加如下代码：

<servlet>
  <servlet-name>dwr-invoker</servlet-name>
  <servlet-class>org.directwebremoting.servlet.DwrServlet</servlet-class>
  <init-param>
   <param-name>debug</param-name>
   <param-value>true</param-value>
  </init-param>
</servlet>
<servlet-mapping>
  <servlet-name>dwr-invoker</servlet-name>
  <url-pattern>/dwr/*</url-pattern>
</servlet-mapping>

4、在WEB-INF目录下新建dwr.xml，输入以下内容：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE dwr PUBLIC "-//GetAhead Limited//DTD Direct Web Remoting 2.0//EN"
"http://www.getahead.ltd.uk/dwr/dwr20.dtd">
<dwr>
<allow>
  <create javascript="service" creator="new">
   <param name="class" value = "helloWorld.Service"></param>
  </create>
</allow>
</dwr>

5、在src目录下添加Service.class文件

package helloWorld;

public class Service {
public String sayHello(String yourName)
{
//可以是访问数据库的复杂代码
return "Hello World" + yourName;
}
}

6、启动服务运行，访问地址http://127.0.0.1:8080/demo_dwr/dwr/

常见错误：

2008-8-28 9:29:47 org.apache.catalina.core.StandardWrapperValve invoke

严重: Allocate exception for servlet dwr-invoker

java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory

at org.directwebremoting.dwrp.PollHandler.<clinit>(PollHandler.java:443)

at java.lang.Class.forName0(Native Method)

at java.lang.Class.forName(Class.java:169)

at org.directwebremoting.impl.ContainerUtil.class$(ContainerUtil.java:97)