public void fillTable() { Connection con = null; Student student = null; Room room = new Room(); try { con = dmutil.getCon(); ResultSet rs = roomdao.roomList(con, room); Room room2 = new Room(); room2.setMember("请选择..."); room2.setId(-1 + ""); this.jcb_room.addItem(room2); while (rs.next()) { room = new Room(); room.setId(rs.getInt("id") + ""); room.setMember(rs.getString("member")); room.setLeader(rs.getString("leader")); this.jcb_room.addItem(room); } } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } finally { try { dmutil.closeCon(con); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } }

public void updateCourse(Courses course) { Connection con = null; PreparedStatement pre = null; ResultSet resultSet = null; try { con = DBUtils.getConnection(); String sql = "update td_courses set isbn = ?, tname = ? where isbn = ?"; pre = con.prepareStatement(sql); pre.setString(1, course.getIsbn()); pre.setString(2, course.getTname()); pre.setString(3, course.getIsbn()); pre.execute(); } catch (SQLException e) { e.printStackTrace(); } finally { DBUtils.closeConnection(con, pre, resultSet); } }

这段代码是用于更新数据库中指定 ISBN 号的课程信息的。具体来说，它使用了 JDBC API 来获取一个数据库连接，并通过 PreparedStatement 对象执行了一条 SQL 更新语句。这条 SQL 语句的参数通过 course 参数获取，...

public class ScoreService { public List<Score> getScoreList() { ScoreDao scoreDao = new ScoreDao(); return scoreDao.getScoreList(); } public void addScore(Score score) { ScoreDao scoreDao = new ScoreDao(); scoreDao.addScore(score); } public Score getISBN(String isbn) { Connection con = null; PreparedStatement pre = null; ResultSet resultSet = null; try { con = DBUtils.getConnection(); String sql = "select * from tb_student_buy where isbn = ?"; pre = con.prepareStatement(sql); pre.setString(1, isbn); resultSet = pre.executeQuery(); while (resultSet.next()) { String isbn1 = resultSet.getString("isbn"); Score score = new Score(); score.setIsbn(isbn1); return score; } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } finally { DBUtils.closeConnection(con, pre, resultSet); } return null; } }

这是一个 Java 类，名为 ScoreService，它提供了一些操作成绩信息的方法。其中，getScoreList() 方法用于获取所有的成绩列表，它通过实例化 ScoreDao 对象，调用其 getScoreList() 方法来实现。...

package db; import java.io.IOException; import java.io.InputStream; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.Properties; public class DBCon { Connection con = null; Statement st = null; ResultSet rs = null; String driver=null; String url = null; String username = null; String password = null; public Connection dbCon() { try { InputStream is=DBCon.class.getClassLoader().getResourceAsStream("db.properties"); Properties prop=new Properties(); try { prop.load(is); driver=prop.getProperty("driver"); url=prop.getProperty("url"); username=prop.getProperty("username"); password=prop.getProperty("password"); } catch (IOException e1) { e1.printStackTrace(); } Class.forName(driver); Class.forName("com.mysql.jdbc.Driver"); url = "jdbc:mysql:///sams?useUnicode=true&characterEncoding=utf8"; username = "root"; password = ""; try { con = DriverManager.getConnection(url, username, password); } catch (SQLException e) { e.printStackTrace(); } } catch (ClassNotFoundException e) { e.printStackTrace(); } return con; } /* * 增删改 / public int query(String sql) { int rs = 0; con = dbCon(); try { st = con.createStatement(); rs = st.executeUpdate(sql); } catch (SQLException e) { close(); e.printStackTrace(); } return rs; } / * 查 / public ResultSet find(String sql) { try { con = dbCon(); st = con.createStatement(); rs = st.executeQuery(sql); } catch (SQLException e) { close(); e.printStackTrace(); } return rs; } / * 关闭数据库 */ public void close() { try { if (rs != null) rs.close(); if (st != null) st.close(); if (con != null) con.close(); } catch (SQLException e) { e.printStackTrace(); } } }有错误

public Connection dbCon() { if (con != null) { return con; } try { InputStream is=DBCon.class.getClassLoader().getResourceAsStream("db.properties"); Properties prop=new Properties(); try { ...

package com.dao; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.util.ArrayList; import java.util.List; import com.entity.Fyxx; import com.entity.User; import com.util.DBhelper; public class FyxxDao { // 删除方法 public int delete(String id) { int n = 0; Connection con = null; PreparedStatement ps = null; ResultSet rs = null; try { con = DBhelper.getCon(); ps = con.prepareStatement("delete from fyxx where bh like '"+id+"'"); n = ps.executeUpdate(); } catch (Exception e) { e.printStackTrace(); } finally { DBhelper.myClose(con, ps, rs); } return n; } // 增加方法 public int add(Fyxx car) { int n = 0; Connection con = null; PreparedStatement ps = null; ResultSet rs = null; try { con = DBhelper.getCon(); ps = con.prepareStatement( "insert into fyxx values(?,?,now(),?)"); ps.setString(1, car.getBh()); ps.setString(2, car.getLx()); ps.setFloat(3, car.getJe()); n = ps.executeUpdate(); } catch (Exception e) { e.printStackTrace(); } finally { DBhelper.myClose(con, ps, rs); } return n; } // 得到所有 public List<Fyxx> getAll(String mc) { List<Fyxx> ss = new ArrayList<Fyxx>(); ResultSet rs = null; PreparedStatement ps = null; Connection con = null; try { con = DBhelper.getCon(); ps = con.prepareStatement("select * from fyxx where lx like '%"+mc+"%'"); rs = ps.executeQuery(); while (rs.next()) { Fyxx ta = new Fyxx(); ta.setBh(rs.getString(1)); ta.setLx(rs.getString(2)); ta.setJfsj(rs.getDate(3)); ta.setJe(rs.getFloat(4)); ss.add(ta); } } catch (Exception e) { e.printStackTrace(); } finally { DBhelper.myClose(con, ps, rs); } return ss; } }

这是一个 FyxxDao 类，其中包含了一些对数据库 fyxx 表的操作方法，包括删除、增加和查询所有信息。该类使用了 JDBC API 连接数据库，并使用了 DBhelper 类中的方法来获取和关闭连接。在增加和删除方法中，使用了 ...

在(1)内进行代码填空public class Login extends GetConnection( User result=null; public User loginUser(User user) （1）=getConnection(); Statement st=null; ResultSet rs=null;

con = getConnection(); st = con.createStatement(); rs = st.executeQuery(sql); if (rs.next()) { result = new User(rs.getInt("id"), rs.getString("username"), rs.getString("password"), rs.getString...

public static void add() { con = GetDBConnection.connectDB(DBName, userName, password); }利用Java和这个框架写一个增加图书

Connection con = DriverManager.getConnection(url, userName, password); return con; } 3. 编写一个静态方法来添加图书信息，例如： public static void addBook(Book book) throws SQLException { ...

public class LoginHistoryDao { public void addLoginHistory(LoginHistory loginHistory) { Connection con = null; PreparedStatement pre = null; ResultSet resultSet = null; List<LoginHistory>loginHistories = new ArrayList<LoginHistory>(); try { con = DBUtils.getConnection(); String sql = "insert into tb_login_history(user_id, ip, create_time) values(?, ?, ?)"; pre = con.prepareStatement(sql); pre.setInt(1, loginHistory.getUserId()); pre.setString(2, loginHistory.getIp()); pre.setDate(3, new java.sql.Date(loginHistory.getCreateTime().getTime())); pre.execute(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } finally { DBUtils.closeConnection(con, pre, resultSet); } } public List<LoginHistory>getLoginHistoryList() { Connection con = null; PreparedStatement pre = null; ResultSet resultSet = null; List<LoginHistory>loginHistories = new ArrayList<LoginHistory>(); try { con = DBUtils.getConnection(); String sql = "select * from tb_login_history"; pre = con.prepareStatement(sql); resultSet = pre.executeQuery(); while (resultSet.next()) { Integer id = resultSet.getInt("id"); Integer userId = resultSet.getInt("user_id"); String ip = resultSet.getString("ip"); Date createTime= resultSet.getDate("create_time"); LoginHistory loginHistory = new LoginHistory(); loginHistory.setId(id); loginHistory.setUserId(userId); loginHistory.setIp(ip); loginHistory.setCreateTime(createTime); loginHistories.add(loginHistory); } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } finally { DBUtils.closeConnection(con, pre, resultSet); } return loginHistories; } }

这是一个 LoginHistoryDao 类的代码，它包含两个方法：addLoginHistory 和 getLoginHistoryList。第一个方法用于向数据库中添加一条登录历史记录，第二个方法用于从数据库中获取所有的登录历史记录并返回一个 ...

public boolean addStudentBuy(StudentBuy buy) { Connection con = null; PreparedStatement pre = null; ResultSet resultSet = null; try { con = DBUtils.getConnection(); String sql = "insert into tb_student_buy(isbn, book_name, student_no, student_name, create_time) values(?,?,?,?,?)"; pre = con.prepareStatement(sql); pre.setString(1, buy.getIsbn()); pre.setString(2, buy.getBookName()); pre.setString(3, buy.getStudentNo()); pre.setString(4, buy.getStudentName()); pre.setDate(5, new java.sql.Date(buy.getCreateTime().getTime())); return pre.execute(); } catch (SQLException e) { e.printStackTrace(); } finally { DBUtils.closeConnection(con, pre, resultSet); } return false; }

这段代码是用于往数据库中的 tb_student_buy 表中插入一条记录的。具体来说，它使用了 JDBC API 来获取一个数据库连接，并通过 PreparedStatement 对象执行了一条 SQL 插入语句。这条 SQL 语句的参数通过 buy ...

public class GetConnection { private Connection con=null; public Connection GetConnection(){ String URL="jdbc:mysql://localhost:3306/day10?&useSSL=false&serverTimezone=UTC";//数据库位置 String USER="root"; String KEY="lzl479894990"; try { Class.forName("com.mysql.cj.jdbc.Driver");//加载驱动，连接数据库， con= DriverManager.getConnection(URL, USER, KEY); } catch (Exception e) { // TODO 自动生成的 catch 块 e.printStackTrace(); } return con; } }

1. 定义了一个 Connection 类型的变量 con，并初始化为 null。 2. 定义了一个 GetConnection 方法，返回值类型为 Connection。 3. 在 GetConnection 方法中，定义了连接 MySQL 数据库的 URL、用户名和密码，并使用...

public class ScoreDao { // public List<Score> getScoreList() { Connection con = null; PreparedStatement pre = null; ResultSet resultSet = null; List<Score> res = new ArrayList<>(); try { con = DBUtils.getConnection(); String sql = "select * from tb_score"; pre = con.prepareStatement(sql); resultSet = pre.executeQuery(); while (resultSet.next()) { Score score = new Score(); score.setIsbn(resultSet.getString("isbn")); score.setCourseName(resultSet.getString("course_name")); score.setClassName(resultSet.getString("class_name")); score.setNum(resultSet.getInt("num")); res.add(score); } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } finally { DBUtils.closeConnection(con, pre, resultSet); } return res; } public boolean addScore(Score score) { Connection con = null; PreparedStatement pre = null; ResultSet resultSet = null; try { con = DBUtils.getConnection(); String sql = "insert into tb_score(isbn, course_name, class_name, num) values(?,?,?,?)"; pre = con.prepareStatement(sql); pre.setString(1, score.getIsbn()); pre.setString(2, score.getCourseName()); pre.setString(3, score.getClassName()); pre.setInt(4, score.getNum()); return pre.execute(); } catch (SQLException e) { e.printStackTrace(); } finally { DBUtils.closeConnection(con, pre, resultSet); } return false; } }

这段代码是一个名为ScoreDao的类，其中包含了两个方法：getScoreList和addScore。getScoreList方法用于从数据库中获取所有的成绩信息，返回一个Score对象列表。addScore方法用于向数据库中插入一条新的成绩信息，...

public List<Student> queryList(String name){ List<Student> list = new ArrayList<Student>(); Connection con = null; PreparedStatement pstmt = null; ResultSet rs = null; try { con = JDBCUtils.getConnection(); List<Object> params = new ArrayList<>(); StringBuffer sb = new StringBuffer("select * from t_student where 1=1 "); if(name != null && !"".equals(name)){ sb.append("and name like ? "); params.add(name); } sb.append("order by create_time desc"); pstmt = con.prepareStatement(sb.toString()); if(params != null && params.size()>0){ for(int i=1; i<params.size(); i++){ pstmt.setObject(i, params.get(i)); } } rs = pstmt.executeQuery(); while(rs.next()){ Student student = new Student(); student.setId(rs.getInt("id")); student.setStuno(rs.getString("stuno")); student.setName(rs.getString("name")); student.setGrade(rs.getString("grade")); student.setCreatTime(rs.getDate("create_time")); student.setUpdateTime(rs.getDate("update_time")); list.add(student); } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally { JDBCUtils.close(con, pstmt, rs); } return list; }

= null && params.size() > 0){ for(int i=0; i(); i++){ pstmt.setObject(i+1, params.get(i)); } } 这样就可以避免这个错误了。同时，你还需要确保参数列表中的参数类型与 SQL 语句中的参数类型匹配，否则...

在(1)内进行简短的代码填空public class Login extends GetConnection( User result=null; public User loginUser(User user) （1）=getConnection(); Statement st=null; ResultSet rs=null;

try (Connection con = getConnection(); Statement st = con.createStatement(); ResultSet rs = st.executeQuery("SELECT * FROM users WHERE username='" + user.getUsername() + "' AND password='" + user....

Liu_Yan_Ban.zip_liujsp_seliulang con

　Connection con=null //连接　PreparedStatement ps=null //命令对象　ResultSet rs=null //结果集　String sql //sql语句方法：　public DBConn():连接数据库　public User checkUser(String username,...

public static Connection con=null;

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在(1)内进行代码填空public class Login extends GetConnection( User result=null; public User loginUser(User user) （1）=getConnection(); Statement st=null; ResultSet rs=null;

public static void add() { con = GetDBConnection.connectDB(DBName, userName, password); }利用Java和这个框架写一个增加图书

在(1)内进行简短的代码填空public class Login extends GetConnection( User result=null; public User loginUser(User user) （1）=getConnection(); Statement st=null; ResultSet rs=null;

Liu_Yan_Ban.zip_liujsp_seliulang con

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