javax.servlet.ServletException: 实例化 servlet 时出错 class java.UserScoresServlet

Question

我一直在研究与此类似的主题，但 none 的解决方案有效。我正在尝试使用 Eclipse 在 Web 应用程序中映射一个简单的 HttpServlet，但是当从调用 servlet 上的 html 页面提交表单时出现以下错误。

HTTP Status 500 - Error instantiating servlet class java.UserScoresServlet

type Exception report

message Error instantiating servlet class java.UserScoresServlet

description The server encountered an internal error that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: Error instantiating servlet class java.UserScoresServlet
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
    java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    java.lang.Thread.run(Thread.java:748)
root cause

java.lang.ClassNotFoundException: java.UserScoresServlet
    org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1714)
    org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1559)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
    java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    java.lang.Thread.run(Thread.java:748)
note The full stack trace of the root cause is available in the Apache Tomcat/7.0.34 logs.

我已经尝试使用@WebServlet 注释和Web.xml 文件进行映射，但均无济于事。我试图使用一个或另一个，而不是同时使用两者。使用 JSP 和 HTML 页面时，我的映射工作正常。我的XML文件映射如下，位于WEB-INF目录下

<display-name>GetUserScores</display-name>
  <servlet>
    <servlet-name>GetUserScores</servlet-name>
    <servlet-class>java.UserScoresServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>GetUserScores</servlet-name>
    <url-pattern>/GetUserScores</url-pattern>
  </servlet-mapping>
</web-app>

服务器class如下。正如我上面提到的，我一直在做注释，或者 web.xml，而不是两者。两者都抛出相同的异常。

package java;

import java.io.IOException;
import java.score.jpa.Score;
import java.score.jpa.ScoreService;
import java.user.jpa.User;
import java.user.jpa.UserService;
import java.util.List;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class UserScoresServlet
 */
@WebServlet(name = "GetUserScores", urlPatterns = "/GetUserScores")
public class UserScoresServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private UserService userService;
    private ScoreService scoreService;
    /**
     * @see HttpServlet#HttpServlet()
     */
    public UserScoresServlet() {
    super();
    userService = new UserService();
    scoreService = new ScoreService();
}

/**
 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
 */
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String firstName = (String)request.getParameter("firstName");
    String lastName = (String)request.getParameter("firstName");
    User user = userService.findUserByFirstAndLastName(firstName, lastName);
    if (user != null){
        List<Score> scoreList = scoreService.findAllScoresByUser(user);
        request.setAttribute("scoreList", scoreList);
    }
    gotoPage("/scores", request, response);
}

private void gotoPage(String address, HttpServletRequest request,
        HttpServletResponse response) throws ServletException, IOException {
    RequestDispatcher dispatcher = getServletContext().getRequestDispatcher(address);
    dispatcher.forward(request, response);
}

/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
}

}

文件结构见照片：File Structure Image

任何人都可以提供任何帮助，这将是一个很大的帮助。我彻底搜索了这个网站并尝试了所有类似问题的建议，但都无济于事。感谢您的帮助。

Answer 1

如 JLS 中所述，您不应使用 java 作为开发包的名称：

Names of packages intended only for local use should have a first identifier that begins with a lowercase letter, but that first identifier specifically should not be the identifier java; package names that start with the identifier java are reserved for package of the Java SE platform

在您的代码中注明：

package java;

import java.io.IOException;
import java.score.jpa.Score;
import java.score.jpa.ScoreService;
import java.user.jpa.User;
import java.user.jpa.UserService;
import java.util.List;

//rest of code...

将您的包裹名称更改为其他名称。

javax.servlet.ServletException: 实例化 servlet 时出错 class java.UserScoresServlet

javax.servlet.ServletException: Error instantiating servlet class java.UserScoresServlet

java

servlets

tomcat7

servlet-3.0