Connector / J 8.0驱动程序中的错误

Question

package abc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import com.mysql.cj.jdbc.PreparedStatement;

public class Test {

    public static void main(String[] args) throws ClassNotFoundException, SQLException, InstantiationException, IllegalAccessException {
        Class.forName("com.mysql.cj.jdbc.Driver").newInstance();
        Connection conn = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/tts?autoReconnect=true&useSSL=false", "root", "root");

        String sql = "select * from exceldata limit 0,20";

        PreparedStatement ps = (PreparedStatement) conn.prepareStatement(sql);
        ResultSet rs = ps.executeQuery();

        while (rs.next()) {
            System.out.println(rs.getString("fname"));
        }
    }
}

我在这里创建了一个简单的程序，请帮助并检查它为什么没有在限制0,10上运行。 请不要在这里我使用mysql的新驱动程序（Connector / J 8.0）。

Answer 1

我无法重现这个问题：

<强>的MySQL ：

mysql> SELECT VERSION();
+-----------+
| VERSION() |
+-----------+
| 5.7.19    |
+-----------+
1 row in set (0.00 sec)

mysql> USE `tts`;
Database changed

mysql> DROP TABLE IF EXISTS `exceldata`;
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TABLE IF NOT EXISTS `exceldata` (
    ->   `id` BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    ->   `fname` VARCHAR(100),
    ->   `mobile` CHAR(10),
    ->   `email` VARCHAR(100)
    -> );
Query OK, 0 rows affected (0.00 sec)

mysql> DESC `exceldata`;
+--------+--------------+------+-----+---------+----------------+
| Field  | Type         | Null | Key | Default | Extra          |
+--------+--------------+------+-----+---------+----------------+
| id     | bigint(20)   | NO   | PRI | NULL    | auto_increment |
| fname  | varchar(100) | YES  |     | NULL    |                |
| mobile | char(10)     | YES  |     | NULL    |                |
| email  | varchar(100) | YES  |     | NULL    |                |
+--------+--------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

mysql> INSERT INTO `exceldata`
    ->   (`fname`, `mobile`, `email`)
    -> VALUES
    ->   ('fname 1', 'mobile 1', 'email 1'),
    ->   ('fname 2', 'mobile 2', 'email 2'),
    ->   ('fname 3', 'mobile 3', 'email 3'),
    ->   ('fname 4', 'mobile 4', 'email 4'),
    ->   ('fname 5', 'mobile 5', 'email 5'),
    ->   ('fname 6', 'mobile 6', 'email 6'),
    ->   ('fname 7', 'mobile 7', 'email 7'),
    ->   ('fname 8', 'mobile 8', 'email 8'),
    ->   ('fname 9', 'mobile 9', 'email 9'),
    ->   ('fname 10', 'mobile 10', 'email 10'),
    ->   ('fname 11', 'mobile 11', 'email 11'),
    ->   ('fname 12', 'mobile 12', 'email 12');
Query OK, 12 rows affected (0.00 sec)
Records: 12  Duplicates: 0  Warnings: 0

mysql> SELECT
    ->   `id`,
    ->   `fname`,
    ->   `mobile`,
    ->   `email`
    -> FROM
    ->   `exceldata`;
+----+----------+-----------+----------+
| id | fname    | mobile    | email    |
+----+----------+-----------+----------+
|  1 | fname 1  | mobile 1  | email 1  |
|  2 | fname 2  | mobile 2  | email 2  |
|  3 | fname 3  | mobile 3  | email 3  |
|  4 | fname 4  | mobile 4  | email 4  |
|  5 | fname 5  | mobile 5  | email 5  |
|  6 | fname 6  | mobile 6  | email 6  |
|  7 | fname 7  | mobile 7  | email 7  |
|  8 | fname 8  | mobile 8  | email 8  |
|  9 | fname 9  | mobile 9  | email 9  |
| 10 | fname 10 | mobile 10 | email 10 |
| 11 | fname 11 | mobile 11 | email 11 |
| 12 | fname 12 | mobile 12 | email 12 |
+----+----------+-----------+----------+
12 rows in set (0.00 sec)

Java （文件：Test.java）：

package abc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import com.mysql.cj.jdbc.Driver;
import com.mysql.cj.jdbc.PreparedStatement;

public class Test {
  public static void main(String[] args) throws ClassNotFoundException,
                                                SQLException,
                                                InstantiationException,
                                                IllegalAccessException {
    Driver driver = (Driver) Class.forName("com.mysql.cj.jdbc.Driver").newInstance();
    Connection conn = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/tts?autoReconnect=true&useSSL=false",
                      System.getProperty("mysql.user"), System.getProperty("mysql.password"));

    System.out.println("Java version: " + System.getProperty("java.version"));
    System.out.println("Connection: " + conn.getClass().getName());
    System.out.println("JDBC driver: " + driver.getMajorVersion() + "." + driver.getMinorVersion());

    String sql = "select * from exceldata limit 0,10";

    PreparedStatement ps = (PreparedStatement) conn.prepareStatement(sql);
    ResultSet rs = ps.executeQuery();

    while (rs.next()) {
      System.out.println(rs.getString("fname"));
    }
  }
}

命令行：

$ javac -d . -cp ./mysql-connector-java-8.0.7-dmr-bin.jar Test.java
$ java -cp .:./mysql-connector-java-8.0.7-dmr-bin.jar abc.Test
Java version: 1.8.0_131
Connection: com.mysql.cj.jdbc.ConnectionImpl
JDBC driver: 8.0
fname 1
fname 2
fname 3
fname 4
fname 5
fname 6
fname 7
fname 8
fname 9
fname 10