com.mysql.jdbc.CommunicationsException: The last packet
successfully received from the server was58129 seconds ago.The last
packet sent successfully to the server was 58129 seconds ago, which is
longer than the server configured value of 'wait_timeout'. You should
consider either expiring and/or testing connection validity before use
in your application, increasing the server configured values for client
timeouts, or using the Connector/J connection property
'autoReconnect=true' to avoid this problem.
查了一下,原來(lái)是mysql超時(shí)設(shè)置的問(wèn)題
如果連接閑置8小時(shí) (8小時(shí)內(nèi)沒(méi)有進(jìn)行數(shù)據(jù)庫(kù)操作), mysql就會(huì)自動(dòng)斷開(kāi)連接, 要重啟tomcat.
解決辦法:
一種. 如果不用hibernate的話, 則在 connection url中加參數(shù): autoReconnect=true
jdbc.url=jdbc:mysql://ipaddress:3306/database?autoReconnect=true&autoReconnectForPools=true
二種。用hibernate的話, 加如下屬性:
<property name="connection.autoReconnect">true</property>
<property name="connection.autoReconnectForPools">true</property>
<property name="connection.is-connection-validation-required">true</property>
三。要是還用c3p0連接池:
<property name="hibernate.c3p0.acquire_increment">1</property>
<property name="hibernate.c3p0.idle_test_period">0</property>
<property name="hibernate.c3p0.timeout">0</property>
<property name="hibernate.c3p0.validate">true</property>
四。最不好的解決方案
使用Connector/J連接MySQL數(shù)據(jù)庫(kù),程序運(yùn)行較長(zhǎng)時(shí)間后就會(huì)報(bào)以下錯(cuò)誤:
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。
其中錯(cuò)誤還會(huì)提示你修改wait_timeout或是使用Connector/J的autoReconnect屬性避免該錯(cuò)誤。
后來(lái)查了一些資料,才發(fā)現(xiàn)遇到這個(gè)問(wèn)題的人還真不少,大部分都是使用連接池方式時(shí)才會(huì)出現(xiàn)這個(gè)問(wèn)題,短連接應(yīng)該很難出現(xiàn)這個(gè)問(wèn)題。這個(gè)問(wèn)題的原因:
MySQL服務(wù)器默認(rèn)的“wait_timeout”是28800秒即8小時(shí),意味著如果一個(gè)連接的空閑時(shí)間超過(guò)8個(gè)小時(shí),MySQL將自動(dòng)斷開(kāi)該連接,而連接池卻認(rèn)為該連接還是有效的(因?yàn)椴⑽葱r?yàn)連接的有效性),當(dāng)應(yīng)用申請(qǐng)使用該連接時(shí),就會(huì)導(dǎo)致上面的報(bào)錯(cuò)。
1.按照錯(cuò)誤的提示,可以在JDBC
URL中使用autoReconnect屬性,實(shí)際測(cè)試時(shí)使用了autoReconnect=true&
failOverReadOnly=false,不過(guò)并未起作用,使用的是5.1版本,可能真像網(wǎng)上所說(shuō)的只對(duì)4之前的版本有效。
2.沒(méi)辦法,只能修改MySQL的參數(shù)了,wait_timeout最大為31536000即1年,在my.cnf中加入:
[mysqld]
wait_timeout=31536000
interactive_timeout=31536000
重啟生效,需要同時(shí)修改這兩個(gè)參數(shù)