java - 查询未返回任何结果

Question

Connection con = null;
Statement stmt = null;
Statement resultStmt = null;
ResultSet rs = null;
try {
    // load database driver driver
    System.out.println("Database driver is: " + DataSource.getClassName());
    Class.forName(DataSource.getClassName());

    // connect to database from a given URL with a given username and password
    System.out.println("Database URL is: " + DataSource.getURL());
    con = DriverManager.getConnection(DataSource.getURL(), DataSource.getUserName(), DataSource.getPassword());

    // create an SQL statement object
    stmt = con.createStatement();

    stmt.executeUpdate("INSERT INTO leadcustomer " + "VALUES(1, 'junwei', 'Li', 'heaven road','test@test.com')");

    String SQLStatement = "SELECT * FROM leadcustomer";
    System.out.println("Q1 SQL Statement is: " + SQLStatement);

    rs = resultStmt.executeQuery(SQLStatement);

    while (rs.next()) {
        int customerid = rs.getInt("customerid");
        String fistname = rs.getString("firstname");
        String surname = rs.getString("surname");
        String billAddress = rs.getString("billingAddress");
        String email = rs.getString("email");

        System.out.println("customerid : " + customerid);
        System.out.println("firstname : " + fistname);
        System.out.println("surname : " + surname);
        System.out.println("billingAddress : " + billAddress);
        System.out.println("email : " + email);


        System.out.println(customerid + " : " + fistname + "--" + surname + "--" + billAddress + ":" + email);
    }

    con.close();

    // extract name from first row and print

} catch (SQLException e) {
    // print details of SQL error
    // could be multiple errors chained together
    System.err.println("Error(s) occurred");
    while (e != null) {
        System.err.println("SQLException : " + e.getMessage());
        System.err.println("SQLState : " + e.getSQLState());
        System.err.println("SQLCode : " + e.getErrorCode());
        e = e.getNextException();
        System.err.println();
    }
}

我正在尝试插入数据并在插入后选择表。但它返回错误消息“查询未返回任何结果”

我确实使用executeUpdateandexecuteQuery用于不同的 SQL 语句。

有什么建议吗？

顺便说一句，插入操作运行成功。我唯一想要的就是解决错误并执行select语句打印出表格..

Answer 1

您的 resultStmt 尚未初始化。添加

resultStmt = con.createStatement();

前

rs = resultStmt.executeQuery(SQLStatement);