如何修复 java.lang.NoSuchMethodException: Servlets.MyServlet.() at java.base/java.lang.Class.getConstructor0

php小编子墨为您解答修复"java.lang.nosuchmethodexception: servlets.myservlet.() at java.base/java.lang.class.getconstructor0"的方法。这个错误通常发生在java程序中，表示找不到指定的构造方法。要解决这个问题，可以检查代码中的构造方法是否存在、参数是否正确，还可以检查类路径是否正确配置。另外，还可以考虑升级java版本或者使用其他可用的构造方法。通过这些方法，您应该能够成功修复这个错误并使程序正常运行。

问题内容

我在 jsp 页面中有一个表单，我正在尝试连接到 servlet myservlet。我使用的是 tomcat 10.x。我不断收到以下错误：

http status 500 – internal server error

type exception report

message error instantiating servlet class [servlets.myservlet]

description the server encountered an unexpected condition that prevented it from fulfilling the request.

exception

jakarta.servlet.servletexception: error instantiating servlet class [servlets.myservlet]
    org.apache.catalina.authenticator.authenticatorbase.invoke(authenticatorbase.java:482)
    org.apache.catalina.valves.errorreportvalve.invoke(errorreportvalve.java:93)
    org.apache.catalina.valves.abstractaccesslogvalve.invoke(abstractaccesslogvalve.java:673)
    org.apache.catalina.connector.coyoteadapter.service(coyoteadapter.java:340)
    org.apache.coyote.http11.http11processor.service(http11processor.java:391)
    org.apache.coyote.abstractprocessorlight.process(abstractprocessorlight.java:63)
    org.apache.coyote.abstractprotocol$connectionhandler.process(abstractprotocol.java:896)
    org.apache.tomcat.util.net.nioendpoint$socketprocessor.dorun(nioendpoint.java:1744)
    org.apache.tomcat.util.net.socketprocessorbase.run(socketprocessorbase.java:52)
    org.apache.tomcat.util.threads.threadpoolexecutor.runworker(threadpoolexecutor.java:1191)
    org.apache.tomcat.util.threads.threadpoolexecutor$worker.run(threadpoolexecutor.java:659)
    org.apache.tomcat.util.threads.taskthread$wrappingrunnable.run(taskthread.java:61)
    java.base/java.lang.thread.run(thread.java:1589)
root cause

java.lang.nosuchmethodexception: servlets.myservlet.()
    java.base/java.lang.class.getconstructor0(class.java:3641)
    java.base/java.lang.class.getconstructor(class.java:2324)
    org.apache.catalina.authenticator.authenticatorbase.invoke(authenticatorbase.java:482)
    org.apache.catalina.valves.errorreportvalve.invoke(errorreportvalve.java:93)
    org.apache.catalina.valves.abstractaccesslogvalve.invoke(abstractaccesslogvalve.java:673)
    org.apache.catalina.connector.coyoteadapter.service(coyoteadapter.java:340)
    org.apache.coyote.http11.http11processor.service(http11processor.java:391)
    org.apache.coyote.abstractprocessorlight.process(abstractprocessorlight.java:63)
    org.apache.coyote.abstractprotocol$connectionhandler.process(abstractprotocol.java:896)
    org.apache.tomcat.util.net.nioendpoint$socketprocessor.dorun(nioendpoint.java:1744)
    org.apache.tomcat.util.net.socketprocessorbase.run(socketprocessorbase.java:52)
    org.apache.tomcat.util.threads.threadpoolexecutor.runworker(threadpoolexecutor.java:1191)
    org.apache.tomcat.util.threads.threadpoolexecutor$worker.run(threadpoolexecutor.java:659)
    org.apache.tomcat.util.threads.taskthread$wrappingrunnable.run(taskthread.java:61)
    java.base/java.lang.thread.run(thread.java:1589)
note the full stack trace of the root cause is available in the server logs.

apache tomcat/10.1.18

我知道它没有在给定位置找到 servlet（？），但我不确定如何解决该问题。任何帮助将不胜感激。

这是我的文件：

index.jsp

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myservlet.java

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package servlets;

import jakarta.servlet.servletexception;
import jakarta.servlet.annotation.webservlet;
import jakarta.servlet.http.httpservlet;
import jakarta.servlet.http.httpservletrequest;
import jakarta.servlet.http.httpservletresponse;

import java.io.ioexception;

@webservlet("/myservlet")
public class myservlet extends httpservlet {

    myservlet(){
        super();
    }

    @override
    protected void doget(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
        super.doget(req, resp);
    }

    @override
    protected void dopost(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
        super.dopost(req, resp);
    }
}

pom.xml

  4.0.0
  org.example
  baseproject
  war
  1.0-snapshot
  baseproject maven webapp
  http://maven.apache.org
  
    
      junit
      junit
      3.8.1
      test
    
    
      jakarta.servlet
      jakarta.servlet-api
      6.0.0
      provided
    
  
  
    baseproject
  

我尝试从 myservlet.java 中删除 '@webservlet("/myservlet")' 并手动将 servlet 和 servlet 映射添加到 web.xml，如下所示：

  Archetype Created Web Application
  
  
    MyServlet
    Servlets.MyServlet
  

  
    MyServlet
    /MyServlet
  

但是，这仍然导致 500 错误。

解决方法

公开 servlet 的构造函数，以便 tomcat 可以运行它。

public MyServlet() {
    super();
}