php小编子墨为您解答修复"java.lang.nosuchmethodexception: servlets.myservlet.
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.<init>()
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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<html>
<body>
<h2>hello world!</h2>
<form action="myservlet" method="get">
<input type="submit" value="enter">
</form>
</body>
</html>
myservlet.java
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
<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>org.example</groupid>
<artifactid>baseproject</artifactid>
<packaging>war</packaging>
<version>1.0-snapshot</version>
<name>baseproject 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>jakarta.servlet</groupid>
<artifactid>jakarta.servlet-api</artifactid>
<version>6.0.0</version>
<scope>provided</scope>
</dependency>
</dependencies>
<build>
<finalname>baseproject</finalname>
</build>
</project>
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：
<!DOCTYPE web-app PUBLIC
"-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd" >
<web-app>
<display-name>Archetype Created Web Application</display-name>
<servlet>
<servlet-name>MyServlet</servlet-name>
<servlet-class>Servlets.MyServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>MyServlet</servlet-name>
<url-pattern>/MyServlet</url-pattern>
</servlet-mapping>
</web-app>
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();
} 
