服务器异常 
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org.springframework.dao.DataAccessResourceFailureException: Timed out after 4000 ms while waiting to connect. Client view of cluster state is {type=Unknown, servers=[{address=ebs-23307:27017, type=Unknown, state=Connecting, exception={com.mongodb.MongoException$Network: Exception opening the socket}, caused by {java.net.ConnectException: 拒绝连接}}]; nested exception is com.mongodb.MongoTimeoutException: Timed out after 4000 ms while waiting to connect. Client view of cluster state is {type=Unknown, servers=[{address=ebs-23307:27017, type=Unknown, state=Connecting, exception={com.mongodb.MongoException$Network: Exception opening the socket}, caused by {java.net.ConnectException: 拒绝连接}}]
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