我正在尝试用Java创建自定义的MySQL类,但是我遇到了一些例外,这是我的代码:
I'm trying to make a custom MySQL class in Java but I'm getting a few exceptions, here's my code:
MySQL.java:
MySQL.java:
package evomon; import java.sql.*; public class MySQL { private static String hostname; private static String username; private static String password; private static String database; public MySQL(String host, String user, String pass, String db) { hostname = host; username = user; password = pass; database = db; } public static void Error(Exception ex) { System.out.println("Fatal Error: "+ex.getMessage()); } public static void SQLError(SQLException ex) { System.out.println("Fatal SQL Error: "+ex.getMessage()); } private static Connection connect() { try { Class.forName("com.mysql.jdbc.Driver").newInstance(); } catch(Exception e){ Error(e); } String url = "jdbc:mysql://"+hostname+":3306/"+database; Connection conn = null; try { conn = DriverManager.getConnection(url, username, password); } catch(SQLException ex){ SQLError(ex); } return conn; } public static ResultSet result(String query) { Connection conn = connect(); PreparedStatement pst = null; ResultSet rs = null; try { pst = conn.prepareStatement(query); rs = pst.executeQuery(); } catch(SQLException ex){ SQLError(ex); } return rs; } public static void main(String args[]){}}
Test.java:
Test.java:
package evomon; import java.sql.*; public class Test { public static void main(String args[]) { MySQL mysql = new MySQL("localhost", "root", "******", "souljaz"); ResultSet res = mysql.result("SELECT * FROM users"); }}
运行Test时,我会在控制台中收到以下错误消息:
When I run Test I get these error messages in the console:
Fatal Error: com.mysql.jdbc.Driver Fatal SQL Error: No suitable driver found for jdbc:mysql://localhost:3306/souljaz Exception in thread "main" java.lang.NullPointerException at evomon.MySQL.result(MySQL.java:58) at evomon.Test.main(Test.java:8)我对Java很陌生,请帮助.谢谢.
I'm quite new to Java so help appreciated. thanks.
推荐答案下载最新版本的 Connector/J ,并将其包含在您的类路径中.如果使用的是IDE,则只需将jar包含在引用的库中即可.如果您要手动完成所有操作,请参阅此官方指南:
Download the lastest version of Connector/J and included it in your Classpath. If you are using an IDE this is only a matter of including the jar in your referenced libraries. If you are doing everything by hand, refer to this official guide:
java -cp "bin;lib/mysql-connector-java-5.1.30-bin" evomon.Test更新:
在Eclipse中:在Package Explorer中右键单击您的项目,然后:
In Eclipse: Right click your project in Package Explorer, then:
Properties -> Java Build Path -> Add JARS... (if lib is in the project) or Add External JARS... (if it is external)更多推荐
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