package com.yangwansheng.test.util;import java.sql.*;public class MysqlJdbcUtil {private static String driver = "com.mysql.jdbc.Driver";//驱动//数据库private static String url = "jdbc:mysql://localhost:3306/worksql?useUnicode=true&characterEncoding=UTF-8";private static String user = "YangWanSheng";//用户名private static String pwd = "Wansheng";//密码private static Connection conn = null;//连接对象private static Statement stat = null;//执行语句对象//打开数据库连接public static void open() {try {//加载驱动Class.forName("com.mysql.jdbc.Driver");//打开连接--实例化数据库连接对象conn = DriverManager.getConnection(url, user, pwd);} catch (Exception e) {e.printStackTrace();}}//关闭数据库连接对象，释放内存public static void close() {try {//判断数据库是否处于连接中if (conn != null && conn.isClosed()) {conn.close();}if (stat != null) {stat.close();}} catch (Exception e) {e.printStackTrace();}}/**** 查询所有数据*/public static ResultSet executeQuery(String sql) {try {open();stat = conn.createStatement();return stat.executeQuery(sql);} catch (Exception e) {e.printStackTrace();}return null;}/*** 条件查询、分页查询* @param sql 数据库执行语句* @param o 参数* @return 反回一个集合命令*/public static ResultSet executeQuery(String sql,Object... o){try {open();PreparedStatement pst=conn.prepareStatement(sql);for(int i=0;i<o.length;i++)pst.setObject(i+1, o[i]);return pst.executeQuery();} catch (SQLException e) {e.printStackTrace();}return null;}/**执行增、删、改*/public static int executUpeate(String sql, Object... obj) {try {open();PreparedStatement pst = conn.prepareStatement(sql);for (int i = 0; i < obj.length; i++) {pst.setObject(i + 1, obj[i]);}stat = pst;return pst.executeUpdate();} catch (Exception e) {e.printStackTrace();}return 0;}
}

package com.yangwansheng.test.bo;public class StudentCourse {private int id;private String Sno;private String Cno;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getSno() {return Sno;}public void setSno(String sno) {Sno = sno;}public String getCno() {return Cno;}public void setCno(String cno) {Cno = cno;}public StudentCourse(int id, String sno, String cno) {this.id = id;Sno = sno;Cno = cno;}public StudentCourse(){}@Overridepublic String toString() {return "StudentCourse{" +"id=" + id +", Sno='" + Sno + '\'' +", Cno='" + Cno + '\'' +'}';}
}

package com.yangwansheng.test.dao;import com.yangwansheng.test.bo.StudentCourse;
import com.yangwansheng.test.util.MysqlJdbcUtil;import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;public class StudentCourseDao {/**查询所有的学生选课表的信息*/public List<StudentCourse> getAllStudentCourse(){List<StudentCourse> list = new ArrayList<>();String sql = "SELECT `StudentCourse`.id, `Course`.Cname, `Student`.Sname FROM `StudentCourse`";sql +=" LEFT JOIN `Course` ON `StudentCourse`.Cno = `Course`.Cno ";sql +=" LEFT JOIN `Student` ON `StudentCourse`.Sno = `Student`.Sno LIMIT 0,5";ResultSet rs = MysqlJdbcUtil.executeQuery(sql);try{while (rs.next()){StudentCourse stucou = new StudentCourse(rs.getInt("id"),rs.getString("Cname"),rs.getString("Sname"));list.add(stucou);}return list;}catch (Exception e){e.printStackTrace();}finally {MysqlJdbcUtil.close();}return null;}/*** 分页查询* @param state* @param end* @return*/public List<StudentCourse> getPageStudentCourse(int state, int end){List<StudentCourse> list = new ArrayList<>();String sql = "SELECT `StudentCourse`.id, `Course`.Cname, `Student`.Sname FROM `StudentCourse`";sql +=" LEFT JOIN `Course` ON `StudentCourse`.Cno = `Course`.Cno ";sql +=" LEFT JOIN `Student` ON `StudentCourse`.Sno = `Student`.Sno LIMIT ?,?";ResultSet rs = MysqlJdbcUtil.executeQuery(sql,state,end);try{while (rs.next()){StudentCourse stucou = new StudentCourse(rs.getInt("id"),rs.getString("Cname"),rs.getString("Sname"));list.add(stucou);}return list;}catch (Exception e){e.printStackTrace();}finally {MysqlJdbcUtil.close();}return null;}//修改public int updateSc(int id ,String Cno){String sql ="update StudentCourse set Cno = ? where id=? ";int i = MysqlJdbcUtil.executUpeate(sql,Cno,id);return i;}/*** 添加* @return 大于一添加成功*/public int addSc(String sno, String con){String sql ="insert into StudentCourse(Sno,Cno) VALUES(?,?);";int i = MysqlJdbcUtil.executUpeate(sql,sno,con);return i;}/*** 删除* @param id * @return 大于1执行成功*/public int delSc(int id){String sql ="delete from StudentCourse where id=?;";int i = MysqlJdbcUtil.executUpeate(sql,id);return i;}
}

package com.yangwansheng.test.test;import com.yangwansheng.test.bo.StudentCourse;
import com.yangwansheng.test.dao.StudentCourseDao;public class MysqlTest {public static void main(String[] args) {StudentCourseDao SCdao = new StudentCourseDao();System.out.println(SCdao.getAllStudentCourse());}
}