Question

我有一项需要创建的练习：

JSP - 显示servlet转发的数据
一个servlet - 从DAO类获取数据并转发到JSP
DAO类 - 从mariaDB数据库连接和检索数据

问题是我无法在servlet中打开与数据库的连接。当我调试servlet文件时，它在创建新DAO对象的行（我在** ... **下面标记了行）中断了，在DAO文件中，它无法打开与消息的连接＆＃34;没有合适的找到jdbc的驱动程序：mysql：// localhost：3306 / a1605354＆＃34 ;;即使我在构建路径中为mariaDB添加了jdbc驱动程序。

我在帖子的末尾包含了我的项目浏览器的图片。我很困惑，并没有明确地解决问题。真的需要你的帮助！

我有一个名为＆＃34;连接参数＆＃34;的文件。以及连接到mariaDB所需的所有信息：

ConnectionParameter.java

public class ConnectionParameters {

public static final String username = "a1605354"; 
public static final String password = "jaZEMs85o";


private static final String databaseName = username;
public static final String databaseURL = "jdbc:mysql://localhost:3306/" + databaseName;
public static final String jdbcDriver = "org.mariadb.jdbc.Driver";

// PK violation: error code in MariaDB is 1062
public static final int PK_VIOLATION_ERROR = 1062;
}

StudentDAO.java

public class StudentDAO {
private final String username;
private final String password;
private final String databaseURL;

public StudentDAO() throws Exception {
    username = ConnectionParameters.username;
    password = ConnectionParameters.password;
    databaseURL = ConnectionParameters.databaseURL;

    try {
        Class.forName(ConnectionParameters.jdbcDriver);
    } catch (Exception ex) {
        System.out.print(ex.getMessage());
    }
}

private Connection openConnection() throws SQLException {
    Connection dbConnection = DriverManager.getConnection(databaseURL, username, password);
    return dbConnection;
}

private void closeConnection(Connection dbConnection) throws SQLException {
    if (dbConnection != null) {
        dbConnection.close();
    }
}

public ArrayList<Student> getAllStudents() throws SQLException {
    ArrayList<Student> studentList = new ArrayList<Student>();
    Connection dbConnection = null;

    try {
        dbConnection = openConnection();
        String sqlText = "SELECT id, firstname, lastname, streetaddress, postcode, postoffice FROM Student ORDER BY lastname";

        Statement statement = dbConnection.createStatement();

        ResultSet resultSet = statement.executeQuery(sqlText);

        while (resultSet.next()) {
            int id = resultSet.getInt("id");
            String firstname = resultSet.getString("firstname");
            String lastname = resultSet.getString("lastname");
            String streetaddress = resultSet.getString("streetaddress");
            String postcode = resultSet.getString("postcode");
            String postoffice = resultSet.getString("postoffice");

            studentList.add(new Student(id, firstname, lastname, streetaddress, postcode, postoffice));
        }

        return studentList;
    } catch (SQLException sqle) {
        throw sqle;
    } finally {
        closeConnection(dbConnection);
    }
}

StudentListServlet.java

@WebServlet("/StudentListServlet")
public class StudentListServlet extends HttpServlet {
private static final long serialVersionUID = 1L;

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    try {
        **StudentDAO studentDAO = new StudentDAO();**
        ArrayList<Student> studentList = studentDAO.getAllStudents();


        request.setAttribute("studentList", studentList);
        request.getRequestDispatcher("StudentList.jsp").forward(request, response);

    } catch (Exception ex) {
        ex.getMessage();
    }

  }

}

StudentList.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1" %>

<body>
    <h2>List of Students</h2>
    <br/>
    <form action="StudentListServlet" method="GET"></form>
    <table>
        <thead>
            <tr>
                <th>Student ID</th><th>Last Name</th><th>First Name</th><th>Street</th><th>Postcode</th><th>Post Office</th>
            </tr>
        </thead>
        <tbody>
            <c:forEach items="${ studentList }" var="studentListObject">
                <tr>
                    <td><c:out value="${studentListObject.id }" /></td>
                    <td><c:out value="${studentListObject.lastname }" /></td>
                    <td><c:out value="${studentListObject.firstname }" /></td>
                    <td><c:out value="${studentListObject.streetaddress }" /></td>
                    <td><c:out value="${studentListObject.postcode }" /></td>
                    <td><c:out value="${studentListObject.postoffice }" /></td>
                </tr>
            </c:forEach>
        </tbody>
    </table>
</body>

项目资源管理器视图：

找不到JDBC驱动程序（servlet，DAO，mariaDB）

0 个答案: