public String chaBookname(int id) throws Exception{ Connection con=DbUtil.getConnection(); Statement stm=con.createStatement(); String sql="select * from book where id='"+id+"'"; ResultSet rs=DataB.query(sql, stm); if(rs.next()) { return rs.getString("book_name"); } return null; } public void initJTable() { String []colNames= {"编号", "教室编号","状态","借阅时间","归还时间"}; String [][]tableValues={}; tableModel=new DefaultTableModel(tableValues,colNames); table=new JTable(tableModel); table.setSelectionBackground(Color.YELLOW); table.setSelectionForeground(Color.RED); table.setRowHeight(30); } }

这段代码还是没有任何注释，不过我可以为您解释一下这两个方法的功能和实现思路。

第一个方法名为`chaBookname`，是一个查询数据库的方法。它接收一个`int`类型的参数`id`，表示要查询的书籍的编号。该方法通过调用`DbUtil.getConnection()`方法获取一个数据库连接，然后使用该连接创建一个`Statement`对象，执行一条SQL查询语句，查询`book`表中`id`等于传入参数`id`的书籍记录。查询结果通过调用`DataB.query()`方法获取，如果查询结果不为空，通过调用`ResultSet`对象的`getString()`方法获取该书籍记录中的`book_name`字段值，并返回该字段值；否则返回`null`。

第二个方法名为`initJTable`，是一个初始化`JTable`控件的方法。该方法首先定义了两个数组变量`colNames`和`tableValues`，分别表示表头和表格数据模型。然后使用这两个数组变量创建一个`DefaultTableModel`对象，该对象表示表格的数据模型。接着使用该数据模型创建一个`JTable`对象，并设置表格的一些样式属性，如选中行的背景色和前景色，行高等。

相关问题

javaweb实现数据库增删改查的小项目代码

很抱歉，作为AI语言模型，我无法提供完整的JavaWeb项目代码。但是，我可以给你一些指导，帮助你实现JavaWeb项目中的增删改查功能。

下面是一个简单的示例代码，实现了一个简单的学生信息管理系统，包括增加学生信息、删除学生信息、修改学生信息和查询学生信息等功能。

首先是数据库连接的代码：

public class DBUtil {

    private static final String URL = "jdbc:mysql://localhost:3306/test?useSSL=false&serverTimezone=UTC";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "root";

    public static Connection getConnection() {
        Connection conn = null;
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return conn;
    }

    public static void close(Connection conn, Statement stmt, ResultSet rs) {
        try {
            if (rs != null) {
                rs.close();
            }
            if (stmt != null) {
                stmt.close();
            }
            if (conn != null) {
                conn.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

接下来是学生信息的实体类：

public class Student {

    private int id;
    private String name;
    private int age;
    private String address;

    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 getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}

然后是增加学生信息的Servlet代码：

public class AddStudentServlet extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int id = Integer.parseInt(request.getParameter("id"));
        String name = request.getParameter("name");
        int age = Integer.parseInt(request.getParameter("age"));
        String address = request.getParameter("address");

        Connection conn = null;
        PreparedStatement stmt = null;

        try {
            conn = DBUtil.getConnection();
            String sql = "insert into student(id, name, age, address) values (?, ?, ?, ?)";
            stmt = conn.prepareStatement(sql);
            stmt.setInt(1, id);
            stmt.setString(2, name);
            stmt.setInt(3, age);
            stmt.setString(4, address);
            stmt.executeUpdate();
            response.sendRedirect("index.jsp");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(conn, stmt, null);
        }
    }
}

接下来是删除学生信息的Servlet代码：

public class DeleteStudentServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int id = Integer.parseInt(request.getParameter("id"));

        Connection conn = null;
        PreparedStatement stmt = null;

        try {
            conn = DBUtil.getConnection();
            String sql = "delete from student where id=?";
            stmt = conn.prepareStatement(sql);
            stmt.setInt(1, id);
            stmt.executeUpdate();
            response.sendRedirect("index.jsp");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(conn, stmt, null);
        }
    }
}

然后是修改学生信息的Servlet代码：

public class EditStudentServlet extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int id = Integer.parseInt(request.getParameter("id"));
        String name = request.getParameter("name");
        int age = Integer.parseInt(request.getParameter("age"));
        String address = request.getParameter("address");

        Connection conn = null;
        PreparedStatement stmt = null;

        try {
            conn = DBUtil.getConnection();
            String sql = "update student set name=?, age=?, address=? where id=?";
            stmt = conn.prepareStatement(sql);
            stmt.setString(1, name);
            stmt.setInt(2, age);
            stmt.setString(3, address);
            stmt.setInt(4, id);
            stmt.executeUpdate();
            response.sendRedirect("index.jsp");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(conn, stmt, null);
        }
    }
}

最后是查询学生信息的Servlet代码：

public class QueryStudentServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        List<Student> studentList = new ArrayList<>();

        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;

        try {
            conn = DBUtil.getConnection();
            String sql = "select * from student";
            stmt = conn.createStatement();
            rs = stmt.executeQuery(sql);
            while (rs.next()) {
                Student student = new Student();
                student.setId(rs.getInt("id"));
                student.setName(rs.getString("name"));
                student.setAge(rs.getInt("age"));
                student.setAddress(rs.getString("address"));
                studentList.add(student);
            }
            request.setAttribute("studentList", studentList);
            request.getRequestDispatcher("index.jsp").forward(request, response);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(conn, stmt, rs);
        }
    }
}

以上代码仅供参考，具体实现可以根据自己的需求进行修改和扩展。

javaweb学生信息管理系统用到的核心代码

以下是一个简单的JavaWeb学生信息管理系统的核心代码，包括数据库连接、查询和更新操作：

1. 数据库连接代码：

public class DBUtil {
    private static final String DRIVER = "com.mysql.jdbc.Driver";
    private static final String URL = "jdbc:mysql://localhost:3306/student";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "123456";

    public static Connection getConnection() throws ClassNotFoundException, SQLException {
        Class.forName(DRIVER);
        Connection conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
        return conn;
    }
}

2. 查询数据库中所有学生信息的代码：

public class StudentDao {
    public List<Student> getAllStudents() {
        List<Student> students = new ArrayList<Student>();
        String sql = "select * from student";
        try {
            Connection conn = DBUtil.getConnection();
            Statement stmt = conn.createStatement();
            ResultSet rs = stmt.executeQuery(sql);
            while (rs.next()) {
                Student student = new Student();
                student.setId(rs.getInt("id"));
                student.setName(rs.getString("name"));
                student.setAge(rs.getInt("age"));
                student.setGender(rs.getString("gender"));
                student.setMajor(rs.getString("major"));
                students.add(student);
            }
            rs.close();
            stmt.close();
            conn.close();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return students;
    }
}

3. 向数据库中插入学生信息的代码：

public class StudentDao {
    public boolean addStudent(Student student) {
        boolean result = false;
        String sql = "insert into student(name, age, gender, major) values(?, ?, ?, ?)";
        try {
            Connection conn = DBUtil.getConnection();
            PreparedStatement stmt = conn.prepareStatement(sql);
            stmt.setString(1, student.getName());
            stmt.setInt(2, student.getAge());
            stmt.setString(3, student.getGender());
            stmt.setString(4, student.getMajor());
            int rows = stmt.executeUpdate();
            if (rows > 0) {
                result = true;
            }
            stmt.close();
            conn.close();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return result;
    }
}