java - 组合框 : java. sql.SQLException 中的错误:游标状态无效 - 没有当前行

Question

我一直收到这个错误。

我有一个组合框，里面装满了数据库的元素，我希望它能使选定的选项出现在文本框中，但出现此错误。它只适用于第一个结果:

代码如下:

private void cmbx_vendActionPerformed(java.awt.event.ActionEvent evt) {                                          
    // TODO add your handling code here:
   try{
      String url = "jdbc:informix-sqli://192.168.2.3:1525/cubo:INFORMIXSERVER=myserver;user=infx;password=infx";
    Connection con1 = DriverManager.getConnection(url);  
    System.out.println("Cubo conectada combobox");
    Statement st1= con1.createStatement();
    ResultSet rs1=st1.executeQuery("SELECT * FROM cartsusc WHERE vendedor = '"+this.cmbx_vend.getSelectedItem()+"'");
    rs1.next();
    this.txt_dato.setText(rs1.getString("vendedor"));

    }
    catch(Exception e){
        JOptionPane.showMessageDialog(null, e);
    }
}

Answer 1

检查 ResultSet#next() 以查看是否确实有一行可用。

此外，始终使用 PreparedStatement。它们有助于降低 SQL 注入(inject)攻击的风险。

通常的成语是:

try {
    Connection conn = getConnection();
    try {
        String sql = "SELECT * FROM cartsusc WHERE vendedor = ?";
        PreparedStatement ps = conn.prepareStatement(sql);
        try {
            ps.setString(1, this.cmbx_vend.getSelectedItem());
            ResultSet rs = ps.executeQuery();
            try {
                if (rs.next()) {
                    this.txt_dato.setText(rs1.getString("vendedor"));
                }
            } finally {
                rs.close();
            }
        } finally {
            ps.close();
        }
    } finally {
        conn.close();
    }
} catch (SQLException e) {
    //handle
}

从 Java 7 开始，您可以使用自动关闭资源的 try-with-resources:

String sql = "SELECT * FROM cartsusc WHERE vendedor = ?";
try (
    Connection conn = getConnection();
    PreparedStatement ps = conn.prepareStatement(sql);
    ) {
    ps.setString(1, this.cmbx_vend.getSelectedItem());
    try (ResultSet rs = ps.executeQuery()) {
        if (rs.next()) {
            this.txt_dato.setText(rs1.getString("vendedor"));
        }
    }
} catch (SQLException e) {
    //handle
}