JavaWeb——升级赛-学生成绩管理系统（2）.java---19.01.03

dao.java

package Dao;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

import DBUtil.Course;
import DBUtil.DBUtil;

public class dao
{
 //添加
 //@param course
 
 public boolean add(Course course)
 {
  String sql="insert into class(name,grade) values('"+course.getName()+"','"+course.getGrade()+"')";
  Connection conn=DBUtil.getConn();//数据库连接，加载驱动
  Statement state=null;//数据库操作
  
  try
  {
   state=conn.createStatement();//实例化Statement对象
   state.executeUpdate(sql);//执行数据库更新操作
  }catch(Exception e)//当try语句中出现异常时，会执行catch中的语句
    {
   e.printStackTrace();//捕获异常的语句
    }
   finally //finally作为异常处理的一部分，它只能用在try/catch语句中，并且附带一个语句块，表示这段语句最终一定会被执行（不管有没有抛出异常），经常被用在需要释放资源的情况下。
   {
    DBUtil.close(state, conn); //close释放资源
   }
  return false;
 }
 
 //删除
 //@param id
 
 public boolean delete(int id)
 {
  String sql="delete from class where id='"+id+"'";
  Connection conn=DBUtil.getConn();
  Statement state=null;
  
  try
  {
   state=conn.createStatement();
   state.executeUpdate(sql);//价格问号？？为什么原版是a=state.executeUpdate(sql)，而只有添加那里没有
  }catch (Exception e)
  {
   e.printStackTrace();
  }
  finally
  {
   DBUtil.close(state, conn);
  }
  return false;
 }
 
 //修改
 //@param name
 
 public boolean update(Course course)
 {
  String sql="update class set name='"+course.getName()+"',place='"+course.getGrade()+"'where id='"+course.getId()+"'";
  Connection conn=DBUtil.getConn();
  Statement state=null;
  
  try
  {
   state=conn.createStatement();
   state.executeUpdate(sql);
  }catch (SQLException e)
  {
   e.printStackTrace();
  }
  finally
  {
   DBUtil.close(state, conn);
  }
  return false;
 }
 
 /**
  * 验证人物名称是否唯一
  * true --- 不唯一
  * @param name
  * @return
  */
 public boolean name(String name) {
  boolean flag = false;
  String sql = "select name from class where name = '" + name + "'";
  Connection conn = DBUtil.getConn();
  Statement state = null;
  ResultSet rs = null;
  
  try {
   state = conn.createStatement();
   rs = state.executeQuery(sql);
   while (rs.next()) {
    flag = true;
   }
  } catch (SQLException e) {
   e.printStackTrace();
  } finally {
   DBUtil.close(rs, state, conn);
  }
  return flag;
 }
 
 /**
  * 通过ID得到类
  * @param id
  * @return
  */
 public Course getCourseById(int id) {
  String sql = "select * from class where id ='" + id + "'";
  Connection conn = DBUtil.getConn();
  Statement state = null;
  ResultSet rs = null;
  Course course = null;
  
  try {
   state = conn.createStatement();
   rs = state.executeQuery(sql);
   while (rs.next()) {
    String name = rs.getString("name");
    int grade = rs.getInt("grade");
    course = new Course(id, name, grade);
   }
  } catch (Exception e) {
   e.printStackTrace();
  } finally {
   DBUtil.close(rs, state, conn);
  }
  
  return course;
 }
 //通过name得到Course
 //@param name
 
 public Course getCourseByName(String name)
 {
  boolean f=false;
  String sql="select name from class where name='"+name+"'";
  Connection conn=DBUtil.getConn(); //Connection是建立与数据库的链接
  Statement state=null;  //Statement算是一个连接的实例，用来执行SQL语句，
  ResultSet rs=null;  //ResultSet是查询后得到的结果集，得到结果后必须执行.next（）方法
  Course course = null;
  
  try
  {
   state=conn.createStatement();
   rs=state.executeQuery(sql);
   while (rs.next()) {
    int id = rs.getInt("id");
    int grade = rs.getInt("grade");
    course = new Course(id, name,grade);
   }
  }
  catch (SQLException e)
  {
   e.printStackTrace();
  }
  finally
  {
   DBUtil.close(rs,state, conn);
  }
  return course;
 }
 
 //查找
 //@param name
 
 public List<Course>search(String name,int grade)
 {
  String sql="select * from class where";
  if (name!=" ")
  {
   sql+="name like'%"+name+"%'";
  }
  if (grade!=' ')
  {
   sql+="name like'%"+grade+"%'";
  }
  List<Course>list=new ArrayList<>();
  Connection conn=DBUtil.getConn();
  Statement state=null;
  ResultSet rs=null;
  
  try
  {
   state=conn.createStatement();
   rs=state.executeQuery(sql);
   Course bean=null;
   while (rs.next())
   {
    int id=rs.getInt("id");
    String name1=rs.getString("name");
    int grade1=rs.getInt("grade");
    bean=new Course(id,name1,grade1);
    list.add(bean);   }
  }
  catch (SQLException e) {
   e.printStackTrace();
  } finally {
   DBUtil.close(rs, state, conn);
  }
  return list;

 }
 
 //全部数据
 
 public List<Course>list()
 {
  String sql="select * from course";
  List<Course>list=new ArrayList<>();
  Connection conn=DBUtil.getConn();
  Statement state=null;
  ResultSet rs=null;
  
  try
  {
   state=conn.createStatement();
   rs=state.executeQuery(sql);
   Course bean=null;
   while (rs.next())
   {
    int id=rs.getInt("id");
    String name=rs.getString("name");
    int grade=rs.getInt("grade");
    bean=new Course(id,name,grade);
   }
  }
  catch (SQLException e) {
   e.printStackTrace();
  } finally {
   DBUtil.close(rs, state, conn);
  }
  
  return list;
 }
}

 

 

Course.java

 

package DBUtil;

public class Course
{
 private int id;
 private String name;
 private int grade;
 public int getId()
 {
  return id;
 }
 public void setId(int id)
 {
  this.id = id;
 }
 public String getName()
 {
  return name;
 }
 public void setName(String name)
 {
  this.name = name;
 }
 public int getGrade()
 {
  return grade;
 }
 public void setGrade(int grade)
 {
  this.grade = grade;
 }
 public Course(int id, String name, int grade) {
  this.id = id;
  this.name = name;
  this.grade = grade;
 }
 
 public Course(String name, int grade) {
  this.name = name;
  this.grade = grade;
 }
}

 

DBUtil.java

 

package DBUtil;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

/**
 * 数据库连接工具
 * @author Hu
 *
 */
public class DBUtil {
 //联结字符串                                              //数据库名test
 public static String db_url = "jdbc:mysql://localhost:3306/test?&useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC";
 //数据库用户名
 public static String db_user = "root";
 //数据库密码名
 public static String db_pass = "root";
 
 public static Connection getConn () {
  
  //声明与数据库的连接并实例化为null
  Connection conn = null;
  
  try {
   //驱动程序名
   Class.forName("com.mysql.cj.jdbc.Driver");//连接数据库
   //具体地连接到数据库——联接字符串（数据库名），联接用户名，联接密码名
   conn = DriverManager.getConnection(db_url, db_user, db_pass);
  } catch (Exception e) {
   e.printStackTrace();
  }
  
  return conn;
 }
 
 /**
  * 关闭连接
  * @param state
  * @param conn
  */
 public static void close (Statement state, Connection conn) {
  if (state != null) {
   try {
    state.close();
   } catch (SQLException e) {
    e.printStackTrace();
   }
  }
  
  if (conn != null) {
   try {
    conn.close();
   } catch (SQLException e) {
    e.printStackTrace();
   }
  }
 }
 
 public static void close (ResultSet rs, Statement state, Connection conn) {
  if (rs != null) {
   try {
    rs.close();
   } catch (SQLException e) {
    e.printStackTrace();
   }
  }
  
  if (state != null) {
   try {
    state.close();
   } catch (SQLException e) {
    e.printStackTrace();
   }
  }
  
  if (conn != null) {
   try {
    conn.close();
   } catch (SQLException e) {
    e.printStackTrace();
   }
  }
 }

}

 

servlet.java

 

package Servlet;

import java.io.IOException;
import java.util.List;

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 DBUtil.Course;
import Dao.service;

@WebServlet("/servlet")
public class servlet extends HttpServlet
{
 private static final long serialVersionUID = 1L;
 
 service service1=new service();
 
 //方法选择
 
 protected void service(HttpServletRequest req,HttpServletResponse resp)throws ServletException, IOException
 {
  req.setCharacterEncoding("utf-8");//设置从jsp中请求道德数据的值，也就是设置为中文，防止乱码
  String method=req.getParameter("method");//getParameter()获取的是客户端设置的数据。
  if ("add".equals(method)) {
   add(req, resp);
  } else if ("del".equals(method)) {
   del(req, resp);
  } else if ("update".equals(method)) {
   update(req, resp);
  } else if ("search".equals(method)) {
   search(req, resp);
  } else if ("getcoursebyid".equals(method)) {
   getCourseById(req, resp);
  } else if ("getcoursebyname".equals(method)) {
   getCourseByName(req, resp);
  } else if ("list".equals(method)) {
   list(req, resp);
  }
 }
 
 //添加
 

 private void add(HttpServletRequest req,HttpServletResponse resp)throws IOException, ServletException
 {
  req.setCharacterEncoding("utf-8");
  String name=req.getParameter("name");
  int grade=Integer.parseInt(req.getParameter("grade"));
  Course course=new Course(name,grade);
  
  //添加后消息提示
  if(service1.add(course))
  {
   req.setAttribute("massage", "添加成功");
   req.getRequestDispatcher("add.jsp").forward(req, resp);
  }
  else
  {
   req.setAttribute("massage", "名称重复，请重新录入");
   req.getRequestDispatcher("add.jsp").forward(req, resp);//处理完了，分发到下一个JSP页面或者下一个Action继续处理。
  }
 }
 
 //全部
 
 private void list(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
  req.setCharacterEncoding("utf-8");
  List<Course> courses = service1.list();
  req.setAttribute("courses", courses);
  req.getRequestDispatcher("list.jsp").forward(req,resp);
 }
 
 //通过ID得到Course, 转到detail2.jsp
 
 private void getCourseById(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
  req.setCharacterEncoding("utf-8");
  int id = Integer.parseInt(req.getParameter("id"));
  Course course = service1.getCourseById(id);
  req.setAttribute("course", course);
  req.getRequestDispatcher("detail2.jsp").forward(req,resp);
 }
 
 //通过name查找Course, 转到detail1.jsp
 
 private void getCourseByName(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
  req.setCharacterEncoding("utf-8");
  String name = req.getParameter("name");
  Course course = service1.getCourseByName(name);
  if(course == null) {
   req.setAttribute("message", "查无此人");
   req.getRequestDispatcher("del.jsp").forward(req,resp);
  } else {
   req.setAttribute("course", course);
   req.getRequestDispatcher("detail.jsp").forward(req,resp);
  }
 }
 
 //删除delete
 
 private void del(HttpServletRequest req,HttpServletResponse resp)throws IOException,ServletException
 {
  req.setCharacterEncoding("UTF-8");
  int id=Integer.parseInt(req.getParameter("id"));
  service1.del(id);
  req.setAttribute("message", "删除成功");
  req.getRequestDispatcher("del.jsp").forward(req, resp);
 }
 
 //修改update
 
 private void update(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
  req.setCharacterEncoding("utf-8");
  int id = Integer.parseInt(req.getParameter("id"));
  String name = req.getParameter("name");
  int grade=Integer.parseInt(req.getParameter("grade"));
  Course course = new Course(id, name,grade);  
  service1.update(course);
  req.setAttribute("message", "修改成功");
  req.getRequestDispatcher("servlet?method=list").forward(req,resp);
     //?method=list表示传一个叫做method的参数，他的值是list,你可以在Servlet中用request.getParam...获取到。
 }
 
 //查询
 
 private void search(HttpServletRequest req,HttpServletResponse resp)throws IOException,ServletException
 {
  req.setCharacterEncoding("UTF-8");
  String name=req.getParameter("name");
  int grade=Integer.parseInt(req.getParameter("grade"));
  List<Course>courses=service1.search(name, grade);
  req.setAttribute("Course", courses);
  req.getRequestDispatcher("searchlist.jsp").forward(req, resp);
 }
}

 

结束。

这次挑战赛失败，不过没关系，一点一点地把程序骂了出来并且做了详细的注释。也算颇丰。