多搜索JDBC

Question

我有一个包含表格和不同文本字段的表单。我想进行多参数搜索，但我的方法searchPlayer仅在填写了所有文本字段时才有效。即使我没有填充一个字段（但其他字段已填满），它也无法工作并返回空表。 如果我填写了一些字段，但是不是所有字段，我应该改变什么才能使搜索成为可能？

private static String SEARCH_PLAYER = 
    "SELECT * FROM fbdb.Players WHERE Number_of_player= ? "
     + "and Full_name LIKE ? "
     + "and Playing_position LIKE ? "
     + "and Height LIKE ? and Weight LIKE ? "
     + "and Nationality LIKE ? and Date_birth LIKE ?";

public String ifnull(String s){
    if (s==null){
        return "%";
    }
    return s;
}

public JTable searchPlayer(JTable table, JTextField tfNumOfPlayer,
                           JTextField tfNamePlayer,
                           JTextField tfPlayingPosition,
                           JTextField tfHeight,
                           JTextField tfWeight,
                           JTextField tfNationality,
                           JTextField tfDateBirth) throws SQLException {

    PreparedStatement pstm = con.prepareStatement(SEARCH_PLAYER);

    pstm.setString (1, ifnull(tfNumOfPlayer.getText()));    
    pstm.setString (2, ifnull(tfNamePlayer.getText()));
    pstm.setString (3, ifnull(tfPlayingPosition.getText()));
    pstm.setString (4, ifnull(tfHeight.getText()));
    pstm.setString (5, ifnull(tfWeight.getText()));
    pstm.setString (6, ifnull(tfNationality.getText()));
    pstm.setString (7, ifnull(tfDateBirth.getText()));

    ResultSet rs=pstm.executeQuery();
    ResultSetMetaData rsmd = rs.getMetaData();
    Vector<Object> data = new Vector<Object>();
    Vector<String> columnNames = new Vector<String>();

    for (int n = 1; n <= rsmd.getColumnCount(); n++) {
        columnNames.add(rsmd.getColumnName(n));
    }

    while (rs.next()){
        Vector<Object> row = new Vector<Object>(); 
       for (int n = 1; n <= rsmd.getColumnCount(); n++) {
           row.add(rs.getObject(n));
       }
       data.add(row); 
    }
    DefaultTableModel dtm = new DefaultTableModel(data,columnNames);
    table.setModel(dtm);
    return table;    
}