如何将数据从主文件插入数据库

Question

我的java项目中有两个文件：MysqlConnect和Main。我想从Main类运行查询。有可能吗？

这是MysqlConnect文件：

public class MysqlConnect {
public Connection conn = null;
public String url = "jdbc:mysql://localhost:3306/";
public String dbName = "jdbctutorial";
public String driver = "com.mysql.jdbc.Driver";
public String userName = "birthday";
public String password = "123456";
public Statement stmt;
public String query = "";
public int rs;
public void crearedatabase() {
    try {
        Class.forName(driver).newInstance();
        conn = DriverManager
                .getConnection(url + dbName, userName, password);
        // System.out.println("Connected to the database");
        Statement stmt = conn.createStatement();
    } catch (Exception e) {
        System.out.println("Baza de date nu a fost creata");
    }
}
public void executeSql() {
    try {
        rs = stmt.executeUpdate(query);
    } catch (Exception e) {
        System.out.println("Mysql Error");
    }
}
}

这是主文件:

public class Main {
public static void main(String[] args) throws SQLException
{

MysqlConnect sqlconnect = new MysqlConnect();   
sqlconnect.crearedatabase();
sqlconnect.query="INSERT INTO `jdbctutorial`.`persons` (`id`, `nume`, `prenume`, `data`) VALUES (NULL, 'xxxx', 'xxxx', '1990-12-12');";
sqlconnect.executeSql();
}
}

错误（异常）在try/catch 的MysqConnection上

rs = stmt.executeUpdate(query);

Answer 1

将语句对象分配给名为stmt的局部变量，而不是具有相同名称的对象字段。更换此

Statement stmt = conn.createStatement();

有了这个：

this.stmt = conn.createStatement();

this在这里没有必要，但在那里有它是一个很好的做法。