Show Jdbc Resultset in HTML in Jsp Page Using MVC and Dao Pattern

Show JDBC ResultSet in HTML table in JSP page using MVC pattern - NullPointerException

You are getting this error because the init() method on your UsuarioDAO is never called and this line

List<Usuario> retorno = usrDAO.list();

returns null.
Try to usrDAO.init() before calling the list.

The reason probably because UsuarioDAO is not a httpServlet so the init() method is not running on creation

How do I make a Java ResultSet available in my jsp?

Model (Row):

public class Row { 
    private String name;
    // Add/generate constructor(s), getters and setters.
}

DAO:

public List<Row> list() throws SQLException {
    Connection connection = null;
    Statement statement = null;
    ResultSet resultSet = null;
    List<Row> rows = new ArrayList<Row>();

    try {
        connection = database.getConnection();
        statement = connection.createStatement();
        resultSet = statement.executeQuery(SQL_LIST);
        while (resultSet.next()) {
            Row row = new Row();
            row.setName(resultSet.getString("name"));
            // ...
            rows.add(row);
        }
    } finally {
        if (resultSet != null) try { resultSet.close(); } catch (SQLException logOrIgnore) {}
        if (statement != null) try { statement.close(); } catch (SQLException logOrIgnore) {}
        if (connection != null) try { connection.close(); } catch (SQLException logOrIgnore) {}
    }

    return rows;
}

Controller (servlet):

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    try {
        List<Row> rows = someDAO.list();
        request.setAttribute("rows", rows);
    } catch (SQLException e) {
        request.setAttribute("error", "Retrieving rows failed.");
        e.printStackTrace();
    }
    request.getRequestDispatcher("page.jsp").forward(request, response);
}

View (page.jsp):

<c:forEach items="${rows}" var="row">
    <c:out value="${row.name}" />
    ...
</c:forEach>
<c:if test="${not empty error}">Error: ${error}</c:if>

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