关于.jar的文件在cmd中无法连接数据库的问题

我使用一个.jar的文件，想在cmd中以“java -jar *.jar”的格式运行，方便system.println()一些信息，该jar包中包含数据库连接内容，在我关闭comodo防火墙和windows防火墙的情况下，该文件无法运行，在我开启comodo防火墙时，会提示是否连接internet(实际上是127.0.0.1的本地连接)，点击同意可正常连接。坑爹的是，我只开启windows防火墙而不开启comodo，系统无任何提示，不能运行此程序，真心不知道是被哪个防火墙拦截的。

另外，如果点击同意之后，后续运行相同程序没有问题会可以继续运行，但是更新之后便必须开启comodo重新同意才可以在cmd中运行该jar包，因此调查一下不开启comodo而jar包被拦截到底是什么原因。

附录：等一段时间后，cmd弹出异常提示如下：

  1 Success loading Mysql Driver!

  2 com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link f

  3 lure

  4 

  5 The last packet sent successfully to the server was 0 milliseconds ago. The dr

  6 er has not received any packets from the server.

  7         at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Metho

  8 

  9         at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstru

 10 orAccessorImpl.java:39)

 11         at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Delegatin

 12 onstructorAccessorImpl.java:27)

 13         at java.lang.reflect.Constructor.newInstance(Constructor.java:513)

 14         at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)

 15         at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java

 16 121)

 17         at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:357)

 18         at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2482)

 19         at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java

 20 519)

 21         at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2304)

 22         at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:834)

 23         at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)

 24         at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Metho

 25 

 26         at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstru

 27 orAccessorImpl.java:39)

 28         at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Delegatin

 29 onstructorAccessorImpl.java:27)

 30         at java.lang.reflect.Constructor.newInstance(Constructor.java:513)

 31         at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)

 32         at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:416)

 33         at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.ja

 34 :346)

 35         at java.sql.DriverManager.getConnection(DriverManager.java:582)

 36         at java.sql.DriverManager.getConnection(DriverManager.java:185)

 37         at ReadAndWriteData_use.getConnection(ReadAndWriteData_use.java:71)

 38         at ReadAndWriteData_use.ConnectMysql(ReadAndWriteData_use.java:46)

 39         at ReadAndWriteData_use.main(ReadAndWriteData_use.java:212)

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

 41         at java.net.PlainSocketImpl.socketConnect(Native Method)

 42         at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)

 43         at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)

 44         at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)

 45         at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)

 46         at java.net.Socket.connect(Socket.java:529)

 47         at java.net.Socket.connect(Socket.java:478)

 48         at java.net.Socket.<init>(Socket.java:375)

 49         at java.net.Socket.<init>(Socket.java:218)

 50         at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.

 51 va:259)

 52         at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:307)

 53         ... 17 more

 54 Success connect Mysql server!

 55 get data error!java.lang.NullPointerException

 56         at ReadAndWriteData_use.ConnectMysql(ReadAndWriteData_use.java:49)

 57         at ReadAndWriteData_use.main(ReadAndWriteData_use.java:212)

 58 开始........

 59 com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link f

 60 lure

 61 

 62 The last packet sent successfully to the server was 0 milliseconds ago. The dr

 63 er has not received any packets from the server.

 64         at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Metho

 65 

 66         at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstru

 67 orAccessorImpl.java:39)

 68         at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Delegatin

 69 onstructorAccessorImpl.java:27)

 70         at java.lang.reflect.Constructor.newInstance(Constructor.java:513)

 71         at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)

 72         at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java

 73 121)

 74         at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:357)

 75         at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2482)

 76         at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java

 77 519)

 78         at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2304)

 79         at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:834)

 80         at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)

 81         at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Metho

 82 

 83         at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstru

 84 orAccessorImpl.java:39)

 85         at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Delegatin

 86 onstructorAccessorImpl.java:27)

 87         at java.lang.reflect.Constructor.newInstance(Constructor.java:513)

 88         at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)

 89         at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:416)

 90         at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.ja

 91 :346)

 92         at java.sql.DriverManager.getConnection(DriverManager.java:582)

 93         at java.sql.DriverManager.getConnection(DriverManager.java:185)

 94         at ReadAndWriteData_use.getConnection(ReadAndWriteData_use.java:71)

 95         at ReadAndWriteData_use.readFile(ReadAndWriteData_use.java:105)

 96         at ReadAndWriteData_use.main(ReadAndWriteData_use.java:218)

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

 98         at java.net.PlainSocketImpl.socketConnect(Native Method)

 99         at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)

100         at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)

101         at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)

102         at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)

103         at java.net.Socket.connect(Socket.java:529)

104         at java.net.Socket.connect(Socket.java:478)

105         at java.net.Socket.<init>(Socket.java:375)

106         at java.net.Socket.<init>(Socket.java:218)

107         at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.

108 va:259)

109         at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:307)

110         ... 17 more

111 step1:getConnection() -> success!

112 Exception in thread "main" java.lang.NullPointerException

113         at ReadAndWriteData_use.readFile(ReadAndWriteData_use.java:107)

114         at ReadAndWriteData_use.main(ReadAndWriteData_use.java:218)

115 Success loading Mysql Driver!