使用ServletContextlistener的ClassNotFoundException

Question

每当我尝试将上下文参数从we.XML获取到ServletContextListener类中时，我都会得到一个异常，我真的很难理解它为什么不能工作，以下是Apache Tomcat 7.0.11日志中的异常：

 Oct 21, 2011 1:24:23 PM org.apache.catalina.core.StandardContext listenerStart
SEVERE: Error configuring application listener of class alaa.ServletContextListener
java.lang.ClassNotFoundException: alaa.ServletContextListener
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1676)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1521)
at   
   org.apache.catalina.core.DefaultInstanceManager.loadClass(DefaultInstanceManager.java:415)
at      

at    org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:118)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4618)
at org.apache.catalina.core.StandardContext$1.call(StandardContext.java:5184)
at org.apache.catalina.core.StandardContext$1.call(StandardContext.java:5179)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)

这是我的web.xml的一部分：

 <context-param>
    <param-name>catName</param-name>
    <param-value>meshmesh</param-value>
</context-param>
<context-param>
    <param-name>catBreed</param-name>
    <param-value>egyptian</param-value>
</context-param>  
<listener>
   <listener-class>alaa.CatLisenter</listener-class>
</listener>
<session-config>
      <session-timeout>
        30
      </session-timeout>
</session-config>

这是我的ServletContextListener.java：

package alaa;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
public class CatLisenter implements ServletContextListener {

@Override
public void contextInitialized(ServletContextEvent sce) {
    ServletContext sc = sce.getServletContext();
    String name = sc.getInitParameter("catName");

    String breed = sc.getInitParameter("catBreed");

    Cat maCat = new Cat();
    maCat.setName(name);
    maCat.setBreed(breed);

    sc.setAttribute("cat", maCat);
}

@Override
public void contextDestroyed(ServletContextEvent sce) {
    throw new UnsupportedOperationException("Not supported yet.");
}   
}



Here's Cat.java : 





package alaa;

public class Cat {
private String name;
private String breed;


public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public String getBreed() {
    return breed;
}


public void setBreed(String breed) {
    this.breed = breed;
}
 }

many thanks 

Answer 1

尝试清除tomcat工作目录并进行清理。在此之后，发布您的项目并再次运行。

Answer 2

我的猜测是，您已经将servlet-api jar打包到webapp (在WEB-INF/lib)文件夹中，这会导致冲突，因为servlet-api已经存在于容器中。在部署webapp时，请确保没有在webapp中包含任何servlet-api或jsp-api (或Java EE api) jars。

Answer 3

我在Tomcat7环境中运行JUnit时遇到了同样的问题，我解决了这个问题，在maven (pom.xml)中添加了一个依赖项，如下所示：

    <dependency>
        <groupId>org.apache.tomcat</groupId>
        <artifactId>tomcat-servlet-api</artifactId>
        <version>7.0.54</version>
        <scope>provided</scope>
    </dependency>