500异常：Class com.netease.QueryServlet is not a Servlet

muscleman415 2017-04-14 06:49:49

各位大神，我今天在写一个简单的servlet并用maven部署时，浏览器发请求报500异常：Class com.netease.QueryServlet is not a Servlet
但是同样的源码和web.xml配置放在tomcat里直接启动可以访问，源码和web.xml配置如下
和论坛里类似的问题不一样，我的类是继承了HttpServlet的。不知道问题出在哪额？

package com.netease;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class QueryServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
response.setCharacterEncoding("UTF-8");
PrintWriter writer= response.getWriter();
String title = request.getParameter("title");
if (title==null){
title="默认";
}

Dbquery.dbpoolInit();
Dbquery db=new Dbquery();
String content= db.dbpoolTest(title);
writer.println("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=utf-8\" />");
writer.println("<html><body>");
writer.println("<h1>Poem is "+content+title+"</h1>");
writer.println("</body></html>");

}

}

web.xml配置：
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0">
<display-name>Restaurant</display-name>
<servlet>
<servlet-name>query</servlet-name>
<servlet-class>
com.netease.QueryServlet
</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>query</servlet-name>
<url-pattern>/query</url-pattern>
</servlet-mapping>
</web-app>

控制台抛异常：
java.lang.ClassCastException: com.netease.QueryServlet cannot be cast to javax.servlet.Servlet
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1144)
at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:865)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:136)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1041)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:603)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

...全文

221 4 打赏收藏转发到动态举报

写回复

用AI写文章

4 条回复

切换为时间正序

请发表友善的回复…

发表回复

muscleman415 2017-04-14

打赏
举报

搞定了。这个问题作为一个小白我简单解释下。。由于之前在jre的ext里把servlet-api拷进去了，而pom里添加的依赖又是基于中心仓库的，导致了servlet-api包冲突，就是楼上的大哥说的情况另外调试的时候有一个之前在tomcat里发生的异常今天也在maven里发生了，这里也可以讲一下以免后人踩坑：如果servlet用到了数据库链接，比如mysql connector，那么如果用tomcat直接run，需要事先把mysql的java connector包拷到tomcat的lib里，即使在编译时已经关联了，也要拷，不然会报错用maven管理依赖是同样的道理，需要在pom里配置mysql connector包的依赖，如果不配置依赖，会报同样的错，如何配置依赖可以在网站：http://mvnrepository.com/ 查询

李德胜1995 2017-04-14

打赏
举报

java.lang.ClassCastException: com.netease.QueryServlet cannot be cast to javax.servlet.Servlet一般是没有继承HttpServlet或者Maven的servlet-api冲突了。。把maven工程更新一下试试。。。。

muscleman415 2017-04-14

打赏
举报

求大神解答，在线等！

muscleman415 2017-04-14

打赏
举报

补充一下，我的POM.xml文件如下： <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.netease.restaurant</groupId> <artifactId>Restaurant</artifactId> <packaging>war</packaging> <version>1.0.0-SNAPSHOT</version> <name>Restaurant Maven Webapp</name> <url>http://maven.apache.org</url> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>3.8.1</version> <scope>test</scope> </dependency> <dependency> <groupId>javax.servlet</groupId> <artifactId>javax.servlet-api</artifactId> <version>3.0.1</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-dbcp2</artifactId> <version>2.1.1</version> </dependency> </dependencies> <build> <finalName>Restaurant</finalName> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <configuration> <source>1.6</source> <target>1.6</target> <encoding>UTF-8</encoding> </configuration> </plugin> <plugin> <groupId>org.apache.tomcat.maven</groupId> <artifactId>tomcat7-maven-plugin</artifactId> <version>2.2</version> <configuration> <uriEncoding>UTF-8</uriEncoding> <finalName>Restaurant</finalName> <server>tomcat</server> </configuration> </plugin> </plugins> </build> </project>