技術標籤：bug系列javamysql

最近與第三方對接資料的時候，通過navicat等工具的時候是能夠正常訪問資料庫的，但通過java程式碼訪問對方提供的資料庫，總是錯誤，通過各種嘗試，總算解決了，特記錄一下，希望能幫助同樣遇到此問題的同行
（1）第一次通過程式碼訪問時出現了以下錯誤:

    Exception in thread "main" 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:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.
 
newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1116)
    at com.mysql.jdbc.MysqlIO.<
 
init>(MysqlIO.java:344)
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2332)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2369)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2153)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:792)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
    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:525)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:381)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)
    at java.sql.DriverManager.getConnection(DriverManager.java:579)
    at java.sql.DriverManager.getConnection(DriverManager.java:243)
    at javaapplication3.JavaApplication3.main(JavaApplication3.java:32)

解決辦法:

大部分網上給的解決方案都是修改連線接超時的引數，但是我按照網上的方法都試了依然不行

同樣的一套程式碼使用我本地的資料庫進行測試的時候是正常的，但是現在外網的資料庫出現這種問題，
最後沒有辦法，我對比了一下兩個庫的版本號，左邊是我本地的，右邊是第三方提供的外網資料庫

目前程式裡使用的mysql的驅動jar包版本為

於是，我嘗試著將mysql的驅動jar包版本提升一下，換成一下jar包

（2）換了jar包後出現了以下新的錯誤，第一個問題算是解決了，可是出現了新的問題

```java
Tue Feb 09 20:08:38 CST 2021 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server. Attempted reconnect 3 times. Giving up.
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
	at java.lang.reflect.Constructor.newInstance(Unknown Source)
	at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
	at com.mysql.jdbc.Util.getInstance(Util.java:408)
	at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:919)
	at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:898)
	at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:887)
	at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:861)
	at com.mysql.jdbc.ConnectionImpl.connectWithRetries(ConnectionImpl.java:2105)
	at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2030)
	at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:778)
	at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
	at java.lang.reflect.Constructor.newInstance(Unknown Source)
	at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
	at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:386)
	at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:330)
	at java.sql.DriverManager.getConnection(Unknown Source)
	at java.sql.DriverManager.getConnection(Unknown Source)
	at com.ccb.commons.util.MYSQLJDBCUtil.getConnection(MYSQLJDBCUtil.java:40)
	at com.ccb.commons.util.MYSQLJDBCUtil.main(MYSQLJDBCUtil.java:95)

解決辦法:
我的連結地址配置是這樣的
url = “jdbc:mysql://127.0.0.1:39603/test?useUnicode=true&characterEncoding=utf8&autoReconnect=true&failOverReadOnly=false”;
於是將地址換成了一下
url = “jdbc:mysql://127.0.0.1:39603/test?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=true&serverTimezone=GMT%2B8”;

(3)第二個問題解決了，又出現了以下錯誤

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

The last packet successfully received from the server was 619 milliseconds ago.  The last packet sent successfully to the server was 595 milliseconds ago.
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
	at java.lang.reflect.Constructor.newInstance(Unknown Source)
	at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
	at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:990)
	at com.mysql.jdbc.ExportControlled.transformSocketToSSLSocket(ExportControlled.java:201)
	at com.mysql.jdbc.MysqlIO.negotiateSSLConnection(MysqlIO.java:4914)
	at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1663)
	at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1224)
	at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2199)
	at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2230)
	at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2025)
	at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:778)
	at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
	at java.lang.reflect.Constructor.newInstance(Unknown Source)
	at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
	at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:386)
	at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:330)
	at java.sql.DriverManager.getConnection(Unknown Source)
	at java.sql.DriverManager.getConnection(Unknown Source)
	at com.ccb.commons.util.MYSQLJDBCUtil.getConnection(MYSQLJDBCUtil.java:40)
	at com.ccb.commons.util.MYSQLJDBCUtil.main(MYSQLJDBCUtil.java:95)
Caused by: javax.net.ssl.SSLHandshakeException: java.security.cert.CertificateException: java.security.cert.CertPathValidatorException: Path does not chain with any of the trust anchors
	at sun.security.ssl.Alerts.getSSLException(Unknown Source)
	at sun.security.ssl.SSLSocketImpl.fatal(Unknown Source)
	at sun.security.ssl.Handshaker.fatalSE(Unknown Source)
	at sun.security.ssl.Handshaker.fatalSE(Unknown Source)
	at sun.security.ssl.ClientHandshaker.serverCertificate(Unknown Source)
	at sun.security.ssl.ClientHandshaker.processMessage(Unknown Source)
	at sun.security.ssl.Handshaker.processLoop(Unknown Source)
	at sun.security.ssl.Handshaker.process_record(Unknown Source)
	at sun.security.ssl.SSLSocketImpl.readRecord(Unknown Source)
	at sun.security.ssl.SSLSocketImpl.performInitialHandshake(Unknown Source)
	at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
	at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
	at com.mysql.jdbc.ExportControlled.transformSocketToSSLSocket(ExportControlled.java:186)
	... 19 more
Caused by: java.security.cert.CertificateException: java.security.cert.CertPathValidatorException: Path does not chain with any of the trust anchors
	at com.mysql.jdbc.ExportControlled$X509TrustManagerWrapper.checkServerTrusted(ExportControlled.java:302)
	at sun.security.ssl.AbstractTrustManagerWrapper.checkServerTrusted(Unknown Source)
	... 28 more
Caused by: java.security.cert.CertPathValidatorException: Path does not chain with any of the trust anchors
	at sun.security.provider.certpath.PKIXCertPathValidator.engineValidate(Unknown Source)
	at java.security.cert.CertPathValidator.validate(Unknown Source)
	at com.mysql.jdbc.ExportControlled$X509TrustManagerWrapper.checkServerTrusted(ExportControlled.java:295)
	... 29 more

解決辦法:
看提示ssl的問題，於是將url地址中的useSSL=true改成useSSL=false
最後終於成功了

總結解決方案
（1）首先確定jdbc.url地址是正確的
（2）修改wait_timeout和interactive_timeout ，參考連結https://blog.csdn.net/JustinQin/article/details/78630100
（3）修改mysql驅動版本，將版本提升，所以建議如果修改timeout不成功的話，一定要將驅動版本升級一下再試試