Question

我对Class.forName("com.mysql.jdbc.Driver")有疑问;

我想为它创建单独的SQL维护和GUI类。当我直接输入Class.forName("com.mysql.jdbc.Driver");文件时，一切正常。当我尝试为SQL maitenance创建单独的类时，它会抛出一堆异常。

public static void main(String[] args) {

    Connection conn = null;

    SqlMaitanance DB1 = new SqlMaitanance();
    DB1.createDB("XD");
}


//Class for SQL maitanance

public class SqlMaitanance extends Example {

//Variables

public static String dataBaseName = "DBFROMMETHOD";
public static String dbTableName;


public static ResultSetMetaData rsmd = null;
public static ResultSet rs = null;
public static Statement stmt = null;
public static Connection conn = null;
public static final String JdbcDriver = "com.mysql.jbdc.Driver";
public static final String UserName = "root";
public static final String Password = "Herflik$00121";

public static final String Url = "jdbc:mysql://localhost/" + dataBaseName;

//Constructor

public SqlMaitanance() {


    createDB(this.dataBaseName);


}

//Methods

public static void createDB(String dataBaseName){

    String crtTable = "CREATE DATABASE " + dataBaseName;
    try{


        conn = DriverManager.getConnection(Url,UserName,Password);

        stmt = conn.createStatement();
        stmt.executeUpdate(crtTable);
        rs.close();
    }
    catch(SQLException e){
    //Handle exceptions for ClassforName

    e.printStackTrace();

    }
    finally{

        try{
            if(stmt!=null)
                conn.close();
        }catch(SQLException se){
        }// do nothing
        try{
            if(conn!=null)
                conn.close();
        }catch(SQLException se){
            se.printStackTrace();
        }//end finally try
    }


}

抛出错误：

Thu Dec 14 22:35:47 CET 2017 WARN：在没有的情况下建立SSL连接不建议使用服务器的身份验证。根据MySQL 5.5.45 +，5.6.26 +和5.7.6+要求如果未设置显式选项，则必须默认建立SSL连接。为了合规使用SSL的现有应用程序验证verifyServerCertificate property设置为'false'。您需要显式禁用SSL 通过设置useSSL = false，或设置useSSL = true并为其提供truststore 服务器证书验证。 com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException：未知数据库'dbfrommethod'在 sun.reflect.NativeConstructorAccessorImpl.newInstance0（本机方法）在 sun.reflect.NativeConstructorAccessorImpl.newInstance（NativeConstructorAccessorImpl.java:62）在 sun.reflect.DelegatingConstructorAccessorImpl.newInstance（DelegatingConstructorAccessorImpl.java:45） at java.lang.reflect.Constructor.newInstance（Constructor.java:423）在com.mysql.jdbc.Util.handleNewInstance（Util.java:425）at com.mysql.jdbc.Util.getInstance（Util.java:408）at com.mysql.jdbc.SQLError.createSQLException（SQLError.java:944）at at com.mysql.jdbc.MysqlIO.checkErrorPacket（MysqlIO.java:3973）at at com.mysql.jdbc.MysqlIO.checkErrorPacket（MysqlIO.java:3909）at at com.mysql.jdbc.MysqlIO.checkErrorPacket（MysqlIO.java:873）at at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication（MysqlIO.java:1710）在com.mysql.jdbc.MysqlIO.doHandshake（MysqlIO.java:1226）at com.mysql.jdbc.ConnectionImpl.coreConnect（ConnectionImpl.java:2188）在 com.mysql.jdbc.ConnectionImpl.connectOneTryOnly（ConnectionImpl.java:2219）在 com.mysql.jdbc.ConnectionImpl.createNewIO（ConnectionImpl.java:2014）在com.mysql.jdbc.ConnectionImpl。（ConnectionImpl.java:776）at com.mysql.jdbc.JDBC4Connection。（JDBC4Connection.java:47）at sun.reflect.NativeConstructorAccessorImpl.newInstance0（本机方法）在 sun.reflect.NativeConstructorAccessorImpl.newInstance（NativeConstructorAccessorImpl.java:62）在 sun.reflect.DelegatingConstructorAccessorImpl.newInstance（DelegatingConstructorAccessorImpl.java:45） at java.lang.reflect.Constructor.newInstance（Constructor.java:423）在com.mysql.jdbc.Util.handleNewInstance（Util.java:425）at com.mysql.jdbc.ConnectionImpl.getInstance（ConnectionImpl.java:386）at at com.mysql.jdbc.NonRegisteringDriver.connect（NonRegisteringDriver.java:330）在java.sql.DriverManager.getConnection（DriverManager.java:664）at java.sql.DriverManager.getConnection（DriverManager.java:247）at SqlMaitanance.createDB（SqlMaitanance.java:40）at SqlMaitanance。（SqlMaitanance.java:27）at Example.main（Example.java:24）

Answer 1

好的，我明白了。我犯了很多错误。我查看了我的代码并更正了它。这是工作答案

import javax.swing.plaf.nimbus.State;
import java.sql.*;

public class SqlMaitanance {

//Variables

public static String dataBaseName;
public static String dbTableName;


public static ResultSetMetaData rsmd = null;
public static ResultSet rs = null;
public static Statement stmt = null;
public static Connection conn = null;
public static final String JdbcDriver = "com.mysql.jbdc.Driver";
public static final String UserName = "root";
public static final String Password = "Herflik$00121";

public static String Url;

//Constructor

构造函数保持为空而不引用dataBaseName变量

public SqlMaitanance() {


}

//Methods

方法应该有局部变量

public static void createDB(String dbN){

我无法连接到不存在的DB因此我有支持URL

    Url = "jdbc:mysql://localhost/";
    String crtTable = "CREATE DATABASE " + dbN;

    try{

        Class.forName("com.mysql.jdbc.Driver");
        conn = DriverManager.getConnection(Url,UserName,Password);

        stmt = conn.createStatement();
        stmt.executeUpdate(crtTable);
        rs.close();
    }
    catch(SQLException e){
    //Handle exceptions for ClassforName

    e.printStackTrace();

    }
    catch(ClassNotFoundException e){

        e.getException();
    }
    finally{

        try{
            if(stmt!=null)
                conn.close();
        }catch(SQLException se){
        }// do nothing
        try{
            if(conn!=null)
                conn.close();
        }catch(SQLException se){
            se.printStackTrace();
        }//end finally try
    }


}

public static void createTable(){


}



}

抱歉格式错误。

方法中的Class.forName（“com.mysql.jdbc.Driver”）

1 个答案: