java报错Communications link failure 该如何解决？

问题描述

就是普通的查询mysql数据库的代码：

错误栈如下：

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failureThe 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:57) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:526) at com.mysql.jdbc.Util.handleNewInstance(Util.java:406) at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074) at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2209) at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:776) at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46) at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:526) at com.mysql.jdbc.Util.handleNewInstance(Util.java:406) at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:352) at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:284) at java.sql.DriverManager.getConnection(DriverManager.java:571) at java.sql.DriverManager.getConnection(DriverManager.java:215) at testHttpConnection.util.DBUtil.getConn(DBUtil.java:26) at testHttpConnection.TestMysql.main(TestMysql.java:23)Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failureThe 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:57) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:526) at com.mysql.jdbc.Util.handleNewInstance(Util.java:406) at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074) at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:675) at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1078) at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2137) ... 13 moreCaused by: java.net.SocketException: Permission denied: recv failed at java.net.SocketInputStream.socketRead0(Native Method) at java.net.SocketInputStream.read(SocketInputStream.java:152) at java.net.SocketInputStream.read(SocketInputStream.java:122) at com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:113) at com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:160) at com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:188) at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2494) at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:599) ... 15 more

问题解答

我来分享下我之前出现这个错误的解决办法吧，和1楼不一样：

eclipse中，设置“Default VM arguments”添加：“-Djava.net.preferIPv4Stack=true”

具体错误原因嘛，好像是由于jvm中的配置改变，导致jvm无法通过网络获取部分信息

这个应该能解决你的问题: Communications link failure的解决办法

使用Connector/J连接MySQL数据库，程序运行较长时间后就会报以下错误：Communications link failure，The last packet successfully received from the server was millisecond ago.The last packet successfully sent to the server was millisecond ago。

其中错误还会提示你修改wait_timeout或是使用Connector/J的autoReconnect属性避免该错误。后来查了一些资料，才发现遇到这个问题的人还真不少，大部分都是使用连接池方式时才会出现这个问题，短连接应该很难出现这个问题。这个问题的原因：MySQL服务器默认的“wait_timeout”是28800秒即8小时，意味着如果一个连接的空闲时间超过8个小时，MySQL将自动断开该连接，而连接池却认为该连接还是有效的(因为并未校验连接的有效性)，当应用申请使用该连接时，就会导致上面的报错。修改MySQL的参数，wait_timeout最大为31536000即1年，在my.cnf中加入：[mysqld]wait_timeout=31536000interactive_timeout=31536000重启生效，需要同时修改这两个参数。