我在eclipse中执行此代码时收到HTTP状态500 - 内部服务器错误。我能否解决我的java项目中的错误[重复]

Question

这个问题在这里已有答案：

• java.lang.ClassNotFoundException:com.mysql.jdbc.Driver [duplicate] 10个答案

如何在Java项目中解决此错误？

    package Com.Admin.Controller;

    import Com.Admin.Dao.Admin_Questions_Dao;
    import Com.Admin.Modal.Questions_Beam;

    import java.io.IOException;
    import java.sql.SQLException;
    import java.util.ArrayList;

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

    @WebServlet("/addQuestions")
    public class Questions extends HttpServlet {

    public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

            String categoryname = request.getParameter("categoryname");
            String str = request.getParameter("category_topic");
            String categorytopic = str.toLowerCase();
            String[] category = request.getParameterValues("category");
            String[] categorytype = request.getParameterValues("categorytype");
            String[] option = request.getParameterValues("option");
            String[] question = request.getParameterValues("question");
            String[] formula_ans = request.getParameterValues("formula_ans");
            String[] shortcut_ans = request.getParameterValues("shortcut_ans");
            String[] option1 = request.getParameterValues("option1");
            String[] option2 = request.getParameterValues("option2");
            String[] option3 = request.getParameterValues("option3");
            String[] option4 = request.getParameterValues("option4");

            ArrayList<Questions_Beam> list = new ArrayList<>(); 

            for(int index=0; index < question.length; index++) {

               list.add(new Questions_Beam(category[index], categorytype[index], option[index], question[index],
                       formula_ans[index], shortcut_ans[index], option1[index], option2[index], option3[index], 
                       option4[index]));    

            }
            //Admin_Questions_Dao obj = new Admin_Questions_Dao();

            try {
                Admin_Questions_Dao.addQuestions(list, categorytopic);
            } 
            catch (ClassNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } 
            catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
    }


}


MODAL CLASS:
package Com.Admin.Modal;

import java.util.Arrays;

public class Questions_Beam {

    public String category ;
    public String categorytype;
    public String option ;
    public String question ;
    public String formula_ans ;
    public String shortcut_ans;
    public String option1;
    public String option2;
    public String option3;
    public String option4;

    public Questions_Beam(String category, String categorytype, String option, String question, String formula_ans,
            String shortcut_ans, String option1, String option2, String option3, String option4) 
    {
        super();
        this.category = category;
        this.categorytype = categorytype;
        this.option = option;
        this.question = question;
        this.formula_ans = formula_ans;
        this.shortcut_ans = shortcut_ans;
        this.option1 = option1;
        this.option2 = option2;
        this.option3 = option3;
        this.option4 = option4;
    }

    @Override
    public String toString() {
        return "Questions_Beam [category=" + category + ", categorytype=" + categorytype + ", option=" + option
                + ", question=" + question + ", formula_ans=" + formula_ans + ", shortcut_ans=" + shortcut_ans
                + ", option1=" + option1 + ", option2=" + option2 + ", option3=" + option3 + ", option4=" + option4
                + "]";
    }
}


DAO LAYER:
package Com.Admin.Dao;

import Com.Admin.Controller.Questions;

import java.sql.*;
import java.util.ArrayList;

import com.mysql.jdbc.Connection;

import Com.Admin.Modal.Questions_Beam;
import Common.DBConnection;

public class Admin_Questions_Dao {

    public static void addQuestions(ArrayList<Questions_Beam> list , String categorytopic) throws ClassNotFoundException, SQLException {
        Connection con = null;
        con = (Connection) DBConnection.getConnection();
        PreparedStatement stmt = null;

        try {
            for (int index=0; index < list.size(); index++) {

                 Questions_Beam data = list.get(index); 

                 stmt = con.prepareStatement("insert into problems on trains values(?,?,?,?,?,?,?,?,?,?)");
                 stmt.setString(1, data.category);
                 stmt.setString(2, data.categorytype);
                 stmt.setString(3, data.option);
                 stmt.setString(4, data.question);
                 stmt.setString(5, data.formula_ans);
                 stmt.setString(6, data.shortcut_ans);
                 stmt.setString(7, data.option1);
                 stmt.setString(8, data.option2);
                 stmt.setString(9, data.option3);
                 stmt.setString(10, data.option4);
                 int result = stmt.executeUpdate();

            }
        }
        catch(SQLException e) {
            e.printStackTrace();
        }
        finally {
            try {
                con.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }

}

结果错误：500 - 内部服务器错误。 ype异常报告

消息Servlet执行引发异常

说明服务器遇到意外情况，无法满足请求。

例外

javax.servlet.ServletException：Servlet执行引发异常org.apache.tomcat.websocket.server.WsFilter.doFilter（WsFilter.java:53）根本原因

java.lang.NoClassDefFoundError：com / mysql / jdbc / Connection Com.Admin.Dao.Admin_Questions_Dao.addQuestions（Admin_Questions_Dao.java:45）Com.Admin.Controller.Questions.doPost（Questions.java:46）javax.servlet.http .HttpServlet.service（HttpServlet.java:660）javax.servlet.http.HttpServlet.service（HttpServlet.java:741）org.apache.tomcat.websocket.server.WsFilter.doFilter（WsFilter.java:53）注意完整服务器日志中提供了根本原因的堆栈跟踪。

Answer 1

我可以看到你的SQL驱动程序类没有类def。这意味着在classpath中mysql类不可用。如果您的应用程序是基于maven添加以下MySQL驱动程序jar依赖https://mvnrepository.com/artifact/mysql/mysql-connector-java如果它不是基于maven下载MySQL驱动程序jar并将其添加到您的lib文件夹。另一个建议请使用适当的标准方式来命名包和类。包名称不应包含大写字母，类和变量应遵循驼峰大小写格式，其中变量名称应以小写字母开头，类名称应以大写字母开头。