javaweb 入门级难题，在网上找了很久未果，请高手们指教！！

[辣辣刺刺]

准备学习一下微信公众号，开始的servlet的doGet方法都是可以执行成功，后来把doPost方法加上启动就报错了，下面是代码

package com.lxd.servlet;

import com.lxd.po.TextMessage;
import com.lxd.util.CheckUtil;
import com.lxd.util.MessageUtil;
import org.dom4j.DocumentException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Date;
import java.util.Map;

/**
 * Created by "辣辣刺刺" on 2018-03-31.
 */
public class weixinServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String signature = req.getParameter("signature");
        String timestamp = req.getParameter("timestamp");
        String nonce = req.getParameter("nonce");
        String echostr = req.getParameter("echostr");
        PrintWriter out = resp.getWriter();
        if (CheckUtil.checkSignature(signature, timestamp, nonce)) {
            out.print(echostr);
        }
    }


    @Override
    protected void doPost(HttpServletRequest rep,HttpServletResponse resp) throws ServletException, IOException {
        rep.setCharacterEncoding("UTF-8");
        resp.setCharacterEncoding("UTF-8");
        PrintWriter out = resp.getWriter();
        try{
            Map<String,String> map = MessageUtil.xmlToMap(rep);
            String toUserName = map.get("ToUserName");
            String fromUserName = map.get("FromUserName");
            String msgType = map.get("MsgType");
            String content = map.get("Content");
            String message = null;

            if("text".equals(msgType)){
                TextMessage text=new TextMessage();
                text.setCreateTime(new Date().toString());
                text.setFromUserName(fromUserName);
                text.setToUserName(toUserName);
                text.setMsgType("text");
                text.setContent("你发送的内容是："+content);
                message = MessageUtil.textMessageToXml(text);
                System.out.println(message);
            }
            out.print(message);
        }catch (DocumentException e){
            e.printStackTrace();
        }finally {
            out.close();
        }
    }
}

下面是报的错误
WARNING: Unknown version string [3.1]. Default version will be used.
四月 02, 2018 9:41:56 下午 org.apache.catalina.core.ContainerBase addChildInternal
SEVERE: ContainerBase.addChild: start:
org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/wechat]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:162)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:899)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:875)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:652)
at org.apache.catalina.startup.HostConfig.manageApp(HostConfig.java:1863)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:301)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:792)
at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:618)
at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:565)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:301)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:792)
at javax.management.remote.rmi.RMIConnectionImpl.doOperation(RMIConnectionImpl.java:1486)
at javax.management.remote.rmi.RMIConnectionImpl.access$300(RMIConnectionImpl.java:96)
at javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1327)
at javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1419)
at javax.management.remote.rmi.RMIConnectionImpl.invoke(RMIConnectionImpl.java:847)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:322)
at sun.rmi.transport.Transport$1.run(Transport.java:177)
at sun.rmi.transport.Transport$1.run(Transport.java:174)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:173)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:553)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:808)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:667)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:722)
Caused by: java.lang.NoClassDefFoundError: org/dom4j/DocumentException
at java.lang.Class.getDeclaredFields0(Native Method)
at java.lang.Class.privateGetDeclaredFields(Class.java:2317)
at java.lang.Class.getDeclaredFields(Class.java:1762)
at org.apache.catalina.util.Introspection.getDeclaredFields(Introspection.java:106)
at org.apache.catalina.startup.WebAnnotationSet.loadFieldsAnnotation(WebAnnotationSet.java:270)
at org.apache.catalina.startup.WebAnnotationSet.loadApplicationServletAnnotations(WebAnnotationSet.java:139)
at org.apache.catalina.startup.WebAnnotationSet.loadApplicationAnnotations(WebAnnotationSet.java:65)
at org.apache.catalina.startup.ContextConfig.applicationAnnotationsConfig(ContextConfig.java:417)
at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:891)
at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:388)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5522)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)

[一个人的幽默]

楼上回的很清楚了，但是我记得还有一个问题

rep.setCharacterEncoding("UTF-8");resp.setCharacterEncoding("UTF-8");

虽然不记得具体的，但是rep和resp设置中文应该是不一样的

[Defonds]

Caused by: java.lang.NoClassDefFoundError: org/dom4j/DocumentException 提示的很清楚了。 看看 dom4j 的包导进来了没

[真-酸辣土豆丝]

org/dom4j/DocumentException包的版本不对，去pom文件加上下面的： <dependency> <groupId>dom4j</groupId> <artifactId>dom4j</artifactId> <version>1.6.1</version> </dependency>