如果可以通過終端訪問數據庫，并且可以完成所有的操作，但是ecplise中無法和數據庫建立連接，解決了常見的錯誤后還是報錯，那很有可能是端口不匹配。小編就是把所有常見的錯誤解決后，還存在錯誤，比如

com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.net.ConnectException MESSAGE: Connection refused: connectSTACKTRACE:java.net.ConnectException: Connection refused: connect at java.net.PlainSocketImpl.socketConnect(Native Method) at java.net.PlainSocketImpl.doConnect(Unknown Source) at java.net.PlainSocketImpl.connectToAddress(Unknown Source) at java.net.PlainSocketImpl.connect(Unknown Source) at java.net.SocksSocketImpl.connect(Unknown Source) at java.net.Socket.connect(Unknown Source) at java.net.Socket.connect(Unknown Source) at java.net.Socket.<init>(Unknown Source) at java.net.Socket.<init>(Unknown Source) at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:256) at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:271) at com.mysql.jdbc.Connection.createNewIO(Connection.java:2771) at com.mysql.jdbc.Connection.<init>(Connection.java:1555) at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285) at java.sql.DriverManager.getConnection(Unknown Source) at java.sql.DriverManager.getConnection(Unknown Source) at Test.selectdb(Test.java:151) at Test.main(Test.java:22)** END NESTED EXCEPTION **Last packet sent to the server was 0 ms ago. at com.mysql.jdbc.Connection.createNewIO(Connection.java:2847) at com.mysql.jdbc.Connection.<init>(Connection.java:1555) at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285) at java.sql.DriverManager.getConnection(Unknown Source) at java.sql.DriverManager.getConnection(Unknown Source) at Test.selectdb(Test.java:151) at Test.main(Test.java:22)

折磨了幾十個小時，最后發現Mac 本mysql的默認端口時3307，不是3306.廢話不多說了，說說如何查看端口。

終端輸入：????ps -ef | grep mysql? ?查看mysql的端口

查看安裝文件中的端口：/Library/LaunchDaemons/com.oracle.oss.mysql.mysqld.plist

修改和自己的一樣就可以了。

幾十個小時血的教訓。

總結

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