java - 如何解决 Servlet 执行抛出异常？

Question

我一直在做一个使用jsp、servlets和tomcat上传文件的项目。

但是，我一直收到以下错误:

type Exception report

message Servlet execution threw an exception

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

exception

javax.servlet.ServletException: Servlet execution threw an exception
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause

java.lang.NoClassDefFoundError: database/Db_Connection
    controller.UploadFileController.doPost(UploadFileController.java:52)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
note The full stack trace of the root cause is available in the Apache Tomcat/8.0.24 logs.

我的 servlet 代码是:

        package controller;

        import java.io.IOException;
        import java.io.InputStream;
        import java.sql.Connection;
        import java.sql.PreparedStatement;
        import javax.servlet.ServletException;
        import javax.servlet.annotation.MultipartConfig;
        import javax.servlet.annotation.WebServlet;
        import javax.servlet.http.HttpServlet;
        import javax.servlet.http.HttpServletRequest;
        import javax.servlet.http.HttpServletResponse;
        import javax.servlet.http.Part;
        import database.Db_Connection;
        import java.io.PrintWriter;
        import java.util.Random;
        import javax.servlet.RequestDispatcher;

        @WebServlet("/uploadServlet")
        @MultipartConfig(maxFileSize = 16177215)

        public class UploadFileController extends HttpServlet 
      {
       @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException 
    {
                response.setContentType("text/html;charset=UTF-8");
                PrintWriter out = response.getWriter();

                InputStream inputStream = null;

                Random rand = new Random();
                int  n = rand.nextInt(9999) + 1;
                String idTemp=(String.valueOf(n));


                String title=(request.getParameter("title"));
                Part filePart = request.getPart("file_uploaded");

                if (filePart != null) 
                {
                    System.out.println(filePart.getName());
                    System.out.println(filePart.getSize());
                    System.out.println(filePart.getContentType());

                    inputStream = filePart.getInputStream();
                }

                try 
                {
                    Db_Connection dbconn=new Db_Connection();
                    Connection conn= dbconn.Connection();

                    String sql = "INSERT INTO files (id, title, file1) values (?, ?, ?)";
                    PreparedStatement statement = conn.prepareStatement(sql);
                    statement.setString(1, idTemp);
                    statement.setString(2, title);

                    if (inputStream != null) 
                    {
                        statement.setBinaryStream(3, inputStream, (int) filePart.getSize());
                    }

                    int row = statement.executeUpdate();
                    if (row > 0) 
                    {
                        out.println("File uploaded!!!");

                        conn.close();

                        RequestDispatcher rs = request.getRequestDispatcher("upload_form.jsp");
                        rs.include(request, response);
                    }
                    else
                    {
                        out.println("Couldn't upload your file!!!");

                        conn.close();

                        RequestDispatcher rs = request.getRequestDispatcher("upload_form.jsp");
                        rs.include(request, response);
                    }    

                }catch(Exception e){e.printStackTrace();}     
    }   
}

我们使用以下命令在 oracle 10g 中创建了一个数据库

   create table files(id number(10), title varchar(20),file1 varchar(20));

我们尝试上传的文件大小为 5 字节。我也完成了数据库连接。你能帮我解决这个错误吗？

Answer 1

在类路径中包含包含 database/Db_Connection 的 jar 文件