《Java程序设计》实验报告（六）之在JSP中操作数据库

实验内容及步骤： 对试题表通过DAO类来操作数据库代码： 代码： package lyx.study.jsp.dao; import lyx.study.jsp.entity.Course; import java.sql.*; import java.util.ArrayList; import java.util.List; public class CourseDao {     private Connection conn ;     private PreparedStatement pstmt;     private ResultSet rs;     public List selectAll()     {         try {             Class.forName("com.mysql.cj.jdbc.Driver");             conn = DriverManager.getConnection(                     "jdbc:mysql://localhost:3306/mysql" +                          "?serverTimezone=UTC&useUnicode" +                           "=true&characterEncoding=utf8&useSSL=true",                     "root",                     "root");             String sql = "select * from course";             pstmt = conn.prepareStatement(sql);             //执行查询用executeQuery()             rs = pstmt.executeQuery();             Course course = null;             List courseList = new ArrayList<>();             while(rs.next())             { 实验内容及步骤：                 course = new Course(                         rs.getInt(1),                         rs.getString(2),                         rs.getString(3),                         rs.getDouble(4),                         rs.getString(5),                         rs.getString(6)                 );                 courseList.add(course);             }             return courseList;         }catch (ClassNotFoundException cfe)         {             cfe.printStackTrace();             System.out.println("数据库驱动加载失败!");         }catch (SQLException sqle)         {             sqle.printStackTrace();             System.out.println("获取数据库链接失败!");         }         return null;     }     public Integer insertCourse(Course course)     {         try {             Class.forName("com.mysql.cj.jdbc.Driver");             conn = DriverManager.getConnection(                     "jdbc:mysql://localhost:3306/mysql",                     "root",                     "root");             String sql = "insert into course values(?,?,?,?,?,?)";             pstmt = conn.prepareStatement(sql);             //执行查询用executeQuery()             pstmt.setInt(1,course.getCid());             pstmt.setString(2,course.getCno());             pstmt.setString(3,course.getCname());             pstmt.setDouble(4,course.getCscore());             pstmt.setString(5, course.getCtno());             pstmt.setString(6,course.getCtype()); 实验内容及步骤：              int count =  pstmt.executeUpdate();             return count;         }catch (ClassNotFoundException cfe)         {             cfe.printStackTrace();             System.out.println("数据库驱动加载失败!");         }catch (SQLException sqle)         {             sqle.printStackTrace();             System.out.println("获取数据库链接失败!");         }         return 0;     } } package lyx.study.jsp.entity; import java.util.Objects; public class Course {     private Integer cid;     private String cno;     private String cname;     private Double cscore;     private String ctno;     private String ctype;     public Course()     {     }     public Course(Integer cid, String cno, String cname, Double cscore, String ctno, String ctype)     {         this.cid = cid;         this.cno = cno;         this.cname = cname;         this.cscore = cscore;         this.ctno = ctno;         this.ctype = ctype;     }     public Integer getCid()     {         return cid; 实验内容及步骤：      }     public void setCid(Integer cid)     {         this.cid = cid;     }     public String getCno()     {         return cno;     }     public void setCno(String cno)     {         this.cno = cno;     }     public String getCname()     {         return cname;     }     public void setCname(String cname)     {         this.cname = cname;     }     public Double getCscore()     {         return cscore;     }     public void setCscore(Double cscore)     {         this.cscore = cscore;     }     public String getCtno()     {         return ctno;     }     public void setCtno(String ctno)     {         this.ctno = ctno;     }     public String getCtype()     {         return ctype;     }     public void setCtype(String ctype) 实验内容及步骤：      {         this.ctype = ctype;     }     @Override     public boolean equals(Object o) {         if (this == o) return true;         if (!(o instanceof Course)) return false;         Course course = (Course) o;         return Objects.equals(cid, course.cid) &&                 Objects.equals(cno, course.cno) &&                 Objects.equals(cname, course.cname) &&                 Objects.equals(cscore, course.cscore) &&                 Objects.equals(ctno, course.ctno) &&                 Objects.equals(ctype, course.ctype);     }     @Override     public int hashCode()     {         return Objects.hash(cid, cno, cname, cscore, ctno, ctype);     } } package lyx.study.jsp.service; import lyx.study.jsp.dao.CourseDao; import lyx.study.jsp.entity.Course; import java.util.List; public class CourseService {     private CourseDao courseDao;     public CourseService()     {         courseDao = new CourseDao();     }     //处理查询所有课程的业务     public List allCourse()     {         return courseDao.selectAll();     }     public Integer addCourse(Course course)     { 实验内容及步骤：          return courseDao.insertCourse(course);     } } package lyx.study.jsp.Servlet; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; @WebServlet("/addCourse") public class AddCourseServlet extends HttpServlet {     @Override     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException     {         resp.sendRedirect(req.getContextPath() + "/addCourse.jsp");     }     @Override     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException     {         doGet(req,resp);     } } package lyx.study.jsp.Servlet; import lyx.study.jsp.entity.Course; import lyx.study.jsp.service.CourseService; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; import java.util.List; public class AllCourseServlet extends HttpServlet 实验内容及步骤：  {     @Override     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {         resp.setContentType("text/html;charset=utf-8");         CourseService courseService = new CourseService();         List courseList = courseService.allCourse();         //用的请求作用域：在一次请求内，数据可以用请求域（request）进行流转         req.setAttribute("courseList",courseList);      req.getRequestDispatcher("allCourse.jsp").forward(req,resp);     }     @Override     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException     {         doGet(req,resp);     } } package lyx.study.jsp.Servlet; import lyx.study.jsp.entity.Course; import lyx.study.jsp.service.CourseService; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; @WebServlet("/saveCourse") public class SaveCourseServlet extends HttpServlet {     @Override     protected void doGet(HttpServletRequest req, HttpServletResponse resp)             throws ServletException, IOException     {         String cno = req.getParameter("cno"); 实验内容及步骤：          String cname = req.getParameter("cname");         String cscore = req.getParameter("cscore");         String ctno = req.getParameter("ctno");         String ctype = req.getParameter("ctype");         Course course = new Course(                 0 ,                 cno ,                 cname,                 Double.parseDouble(cscore),                 ctno,                 ctype);         CourseService courseService = new CourseService();         Integer i = courseService.addCourse(course);         if (i > 0){             System.out.println("添加成功！");         }     }     @Override     protected void doPost(HttpServletRequest req, HttpServletResponse resp)             throws ServletException, IOException     {         doGet(req,resp);     } }          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"          version="4.0">             allCourse         lyx.study.jsp.Servlet.AllCourseServlet     实验内容及步骤：              allCourse         /allCourse       添加Course信息！ method="get">   课程编号：   课程名称：   课程学分：   课程教师编号：   课程类型：         添加课程 <%     List courseList = (List)request.getAttribute("courseList");     if (courseList != null){ %>         实验内容及步骤：                          a                                         <%         for(Course course:courseList){     %>                                                     <%             }         }     %>     课程id 课程编号 课程名称 课程学分 课程教师编号 课程类型 <%=course.getCid()%> <%=course.getCno()%> <%=course.getCname()%> <%=course.getCscore()%> <%=course.getCtno()%> <%=course.getCtype()%> 运行结果：
实验内容及步骤：
你的问题： 遇到SQL语句错误、连接池配置错误等问题。 定义 DAO 接口时，出现实现类与接口的方法定义不一致的问题