Question

我正在尝试获取数据库的结果并在线打印但我做错了。我正在使用xampp来托管MySQL中的数据库。我不知道问题是在我的java代码还是在我的HTML中。我尝试了下面的代码，但是当我访问网站并按下返回结果的按钮时，它无法正常工作。所以我无法理解我的问题是与数据库的连接还是HTML代码。这是java代码

  public class CloudServlet extends HttpServlet {
    public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        resp.setContentType("text/plain");
        PrintWriter out;
        out=null;

        String docType=
                "!DOCTYPE HTML PUBLIC\"-//W3C//DTD HTML 4.1"+ "transitional//EN\"\n";

        String title="results";
        String driver="com.mysql.jdbc.Driver";
        String url="jdbc:mysql://localhost:3306/mydb";

        String query = "Select * FROM TRENDS ORDER BY NUM DESC"; 

        showTable(url,query, out);
        resp.getWriter();

    }
    public void showTable(String url,String query, PrintWriter out){

        int num=0;
        String Name=null;

        try {

            Class.forName("com.mysql.jdbc.Driver");
            Connection con = DriverManager.getConnection (url);
            Statement stmt = con.createStatement();
            ResultSet rs = stmt.executeQuery(query);
            while (rs.next()) {

                StringBuilder sb = new StringBuilder();
                sb.append("");
                sb.append(rs.getInt(2));
                String strI = sb.toString();
                Name = rs.getString(1);
                out.print(strI+Name);
            }
        }catch(ClassNotFoundException e) {
            e.printStackTrace();
        }
        catch(SQLException e) {
            e.printStackTrace();
        }

    }

Answer 1

尝试放置ServletOutputStream out = resp.getOutputStream();而不是PrintWriter。

Answer 2

public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
    resp.setContentType("text/plain");
    PrintWriter out;
    out = null;

    String docType = "!DOCTYPE HTML PUBLIC\"-//W3C//DTD HTML 4.1" + "transitional//EN\"\n";

    String title = "results";
    String driver = "com.mysql.jdbc.Driver";
    String url = "jdbc:mysql://localhost:3306/mydb";
    String query = "Select * FROM TRENDS ORDER BY NUM DESC";

    // if you do not perform this step,the parameter "out" in the showTable is null
    // and may throws NullPointerException
    out = resp.getWriter();
    showTable(url, query, out);

    // I think your problem is in this line
    // resp.getWriter();
}

如何将MySQL数据库的结果加载到网站

2 个答案: