mysql connection refused

[qq_24853685]

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:408)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:404)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:988)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:341)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2251)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2284)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2083)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:806)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:408)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:404)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:410)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:328)
at java.sql.DriverManager.getConnection(DriverManager.java:664)
at java.sql.DriverManager.getConnection(DriverManager.java:247)
at com.hibernate.TestMysql.main(TestMysql.java:35)
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:345)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:211)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:300)
... 15 more
Exception in thread "main" java.lang.NullPointerException

[gikod]

这就是原因：

Caused by: java.net.ConnectException: Connection refused: connect

Socket连不上，具体原因有可能是 1 MySQL服务没启动 2 MySQL连接信息不对 3 网络有问题 首先用mysql -u <username> -p 连接试试，看看服务器和网络是否正常

[ACMAIN_CHM]

先尝试直接用MYSQL自带的MYSQL客户端工具连接一下试试。可能的原因有很多。如果MYSQL自带工具可以，则需要检查程序代码和以驱动 参考下贴中的检查方法并贴出你的检查结果(#43楼) http://topic.csdn.net/u/20090920/22/14d4f597-b7d4-4c24-b0db-abb2956e66c3.html [收集]mysql 无法联接故障现象及原因

[qq_24853685]

自带的客户端可以连接，代码如2楼我看了很多遍，也找不到问题，驱动我换了2个版本了，都不行！

[qq_24853685]

我在cmd中试了一下mysql -u <root> -p 显示系统找不到指定的文件

[qq_24853685]

自带的客户端可以连接，代码如2楼我看了很多遍，也找不到问题，驱动我换了2个版本了，都不行！

[qq_24853685]

public class TestMysql { public static void main(String[] args) { Connection conn = null; Statement stmt = null; ResultSet rs = null; String url = null; String user = null; String password ; String sql = null; try { Class.forName("com.mysql.jdbc.Driver"); //加载mysq驱动 } catch (ClassNotFoundException e) { System.out.println("驱动加载错误"); e.printStackTrace();//打印出错详细信息 } try { url = "jdbc:mysql://localhost/mydb"; user = "root"; password = "123456"; conn = DriverManager.getConnection(url,user,password); } catch (SQLException e) { System.out.println("数据库链接错误"); e.printStackTrace(); } try { stmt = conn.createStatement(); sql = "select * from dept";//dept这张表有deptno，deptname和age这三个字段 rs = stmt.executeQuery(sql);//执行sql语句 while(rs.next()) { System.out.print(rs.getInt("deptno") + " "); System.out.print(rs.getString("deptname") + " "); System.out.println(rs.getInt("age") + " "); } } catch (SQLException e) { System.out.println("数据操作错误"); e.printStackTrace(); } //关闭数据库 try { if(rs != null) { rs.close(); rs = null; } if(stmt != null) { stmt.close(); stmt = null; } if(conn != null) { conn.close(); conn = null; } } catch(Exception e) { System.out.println("数据库关闭错误"); e.printStackTrace(); } } }

[qq_24853685]

不知道怎么处理这个问题，哪位大神帮忙看一下

[zhu19774279]

把代码用论坛自带的代码工具贴出来，你上面说35行报错，我都找不到35行是哪一行。 另外把conn输出一下，看看是不是null