錯(cuò)誤: 找不到或無法加載主類 util.DBHelper
package util;
import java.sql.Connection;
import java.sql.DriverManager;
public class DBHelper {
? ?
private static final String driver = "com.mysql.jdbc.Driver"; //數(shù)據(jù)庫驅(qū)動(dòng)
//連接數(shù)據(jù)庫的URL地址
private static final String url="jdbc:mysql://localhost:3306/t1?useUnicode=true&characterEncoding=UTF-8";?
private static final String username="root";//數(shù)據(jù)庫的用戶名
private static final String password="";//數(shù)據(jù)庫的密碼
? ??
private static Connection conn=null;
//靜態(tài)代碼塊負(fù)責(zé)加載驅(qū)動(dòng)
static?
{
try
{
Class.forName(driver);
}
catch(Exception ex)
{
ex.printStackTrace();
}
}
//單例模式返回?cái)?shù)據(jù)庫連接對(duì)象
public static Connection getConnection() throws Exception
{
if(conn==null)
{
conn = DriverManager.getConnection(url, username, password);
return conn;
}
return conn;
}
public static void main(String[] args) {
try
{
? Connection conn = DBHelper.getConnection();
? if(conn!=null)
? {
? System.out.println("數(shù)據(jù)庫連接正常!");
? }
? else
? {
? System.out.println("數(shù)據(jù)庫連接異常!");
? }
}
catch(Exception ex)
{
ex.printStackTrace();
}
}
}
2016-08-19
是不是項(xiàng)目的Java Build Path中的Libraries中有個(gè)jar包不可用?
2016-08-11
是不是沒有給數(shù)據(jù)庫連接密碼賦值?