在spring boot專案中使用了mongodb，當一段時間沒有操作mongodb，下次操作mongodb時就會出現異常。異常如下：

org.springframework.data.mongodb.UncategorizedMongoDbException: Prematurely reached end of stream; nested exception is com.mongodb.MongoSocketReadException: Prematurely reached end of stream
        at org.springframework.data.mongodb.core.MongoExceptionTranslator.translateExceptionIfPossible(MongoExceptionTranslator.java:
 
107)
        at org.springframework.data.mongodb.core.MongoTemplate.potentiallyConvertRuntimeException(MongoTemplate.java:2146)
        at org.springframework.data.mongodb.core.MongoTemplate.executeFindOneInternal(MongoTemplate.java:1928)
        at org.springframework.data.mongodb.core.MongoTemplate.doFindOne(MongoTemplate.java:
 
1736)
        at org.springframework.data.mongodb.core.MongoTemplate.findOne(MongoTemplate.java:606)
        at org.springframework.data.mongodb.core.MongoTemplate.findOne(MongoTemplate.java:601)
        at com.lwli.service.impl.SessionServiceImpl.findOneSessionByCustomerIdAndStatus(SessionServiceImpl.java:
 
51)
        at java.lang.Thread.run(Thread.java:745)
Caused by: com.mongodb.MongoSocketReadException: Prematurely reached end of stream
        at com.mongodb.connection.SocketStream.read(SocketStream.java:88)
        at com.mongodb.connection.InternalStreamConnection.receiveResponseBuffers(InternalStreamConnection.java:494)
        at com.mongodb.connection.InternalStreamConnection.receiveMessage(InternalStreamConnection.java:224)
        at com.mongodb.connection.UsageTrackingInternalConnection.receiveMessage(UsageTrackingInternalConnection.java:96)
        at com.mongodb.connection.DefaultConnectionPool$PooledConnection.receiveMessage(DefaultConnectionPool.java:440)
        at com.mongodb.connection.QueryProtocol.execute(QueryProtocol.java:289)
        at com.mongodb.connection.QueryProtocol.execute(QueryProtocol.java:54)
        at com.mongodb.connection.DefaultServer$DefaultServerProtocolExecutor.execute(DefaultServer.java:168)
        at com.mongodb.connection.DefaultServerConnection.executeProtocol(DefaultServerConnection.java:289)
        at com.mongodb.connection.DefaultServerConnection.query(DefaultServerConnection.java:212)
        at com.mongodb.operation.FindOperation$1.call(FindOperation.java:525)
        at com.mongodb.operation.FindOperation$1.call(FindOperation.java:510)
        at com.mongodb.operation.OperationHelper.withConnectionSource(OperationHelper.java:435)
        at com.mongodb.operation.OperationHelper.withConnection(OperationHelper.java:408)
        at com.mongodb.operation.FindOperation.execute(FindOperation.java:510)
        at com.mongodb.operation.FindOperation.execute(FindOperation.java:81)
        at com.mongodb.Mongo.execute(Mongo.java:836)
        at com.mongodb.Mongo$2.execute(Mongo.java:823)
        at com.mongodb.DBCursor.initializeCursor(DBCursor.java:870)
        at com.mongodb.DBCursor.hasNext(DBCursor.java:142)
        at com.mongodb.DBCursor.one(DBCursor.java:679)
        at com.mongodb.DBCollection.findOne(DBCollection.java:833)
        at com.mongodb.DBCollection.findOne(DBCollection.java:796)
        at com.mongodb.DBCollection.findOne(DBCollection.java:743)
        at org.springframework.data.mongodb.core.MongoTemplate$FindOneCallback.doInCollection(MongoTemplate.java:2197)
        at org.springframework.data.mongodb.core.MongoTemplate$FindOneCallback.doInCollection(MongoTemplate.java:2181)
        at org.springframework.data.mongodb.core.MongoTemplate.executeFindOneInternal(MongoTemplate.java:1925)
        ... 12 more

　　網上搜了下，這個問題原因很多，主要的原因可能有連線超時，讀寫超時等，按照別人的提示，設定了

socketKeepAlive = true;

socketTimeout = 30000;

　　然而並沒有效果，超過一段時間再次訪問mongdb時，任然出現異常。在google搜尋時，發現一篇文章https://studio3t.com/whats-new/how-to-prevent-your-connection-from-dropping-with-hosted-mongodb-instances/，上面提到了一點，當連線閒置一段時間，由於防火牆或者負載均衡的原因，導致連線被關閉，而客戶端並不知道，當客戶端繼續使用這個關閉的連線進行讀寫時就會出錯。

　　解決辦法就是設定連線閒置時間，當超過這個閒置時間客戶端主動關閉連線，下次使用時重新建立連線，這樣可以有效避免連線失效的問題。

　　在spring boot中配置MongoClientOptions的bean。例如將最大閒置時間設為6000ms。

@Configuration
public class WechatMpConfiguration {

    @Bean
    public MongoClientOptions mongoOptions() {
        return MongoClientOptions.builder().maxConnectionIdleTime(6000).build();
    }
}

　　通過上面的設定後，後面沒有再出現Prematurely reached end of stream異常了。