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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!
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