com.mongodb.MongoSocketOpenException: Exception opening socket

at com.mongodb.connection.SocketStream.open(SocketStream.java:63) ~[mongodb-driver-core-3.4.3.jar:na]
at com.mongodb.connection.InternalStreamConnection.open(InternalStreamConnection.java:115) ~[mongodb-driver-core-3.4.3.jar:na]
at com.mongodb.connection.DefaultServerMonitor$ServerMonitorRunnable.run(DefaultServerMonitor.java:113) ~[mongodb-driver-core-3.4.3.jar:na]
at java.lang.Thread.run(Thread.java:748) [na:1.8.0_161]

Caused by: java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method) ~[na:1.8.0_161]
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85) ~[na:1.8.0_161]
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) ~[na:1.8.0_161]
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[na:1.8.0_161]
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[na:1.8.0_161]
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172) ~[na:1.8.0_161]
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_161]
at java.net.Socket.connect(Socket.java:589) ~[na:1.8.0_161]
at com.mongodb.connection.SocketStreamHelper.initialize(SocketStreamHelper.java:57) ~[mongodb-driver-core-3.4.3.jar:na]
at com.mongodb.connection.SocketStream.open(SocketStream.java:58) ~[mongodb-driver-core-3.4.3.jar:na]
... 3 common frames omitted

网上搜索了一下解决方案

1. 说是 springboot 自动配置了支持 mongodb。在启动 springboot 时会自动实例化一个 mongo 实例。 要加上
@SpringBootApplication(exclude = MongoAutoConfiguration.class)，但是我的不行，原文链接如下。

http://blog.csdn.net/xuyw10000/article/details/72918360

2. 说在配置文件里把初始的 mongodb 取消掉就好了（不懂怎么取消）

.http://www.cnblogs.com/zhuangfei/p/7338488.html

3. 最后发现我用的 idea，spring initializr 选择的依赖是 testCompile 的，在运行环境下没有

 这是 springboot 默认的

testCompile('de.flapdoodle.embed:de.flapdoodle.embed.mongo')

打包成 jar 在 Linux 下运行报错

改成

compile('de.flapdoodle.embed:de.flapdoodle.embed.mongo')

 正常运行