Question

环境：mac os x 10.10
MongoDB版本：3.0.5
JDK版本：1.8
MongoDB驱动程序：“mongo-java-driver-3.0.2.jar”和 “mongodb的驱动器 - 异步-3.0.2.jar”

问题：

我想连接 mongoDB 并异步插入一些简单数据，因此我使用了“ mongodb-driver-async-3.0.2.jar ”。但我发现我没有连接数据库。代码如下：

public static void main(String[] args) {
        // connect to the local database server,default:127.0.0.1:27017
        MongoClient mongoClient = MongoClients.create();
        // get handle to "testDB" database
        MongoDatabase database = (MongoDatabase) mongoClient.getDatabase("testDB");
        SingleResultCallback<Void> callbackWhenFinished = new SingleResultCallback<Void>() {
            @Override
            public void onResult(final Void result, final Throwable t) {
                System.out.println("Operation Finished!");
            }
        };
        // get a handle to the "test" collection
        MongoCollection<Document> collection = database.getCollection("test");
        collection.insertOne(new Document("lala","hehe"),callbackWhenFinished);
    }

我确定我已经在127.0.0.1:27017启动了数据库服务，并且可以连接shell和非异步方法。错误：

PrimaryServerSelector未从群集描述中选择任何服务器 ClusterDescription {type = UNKNOWN，connectionMode = SINGLE， all = [ServerDescription {address = localhost：27017，type = UNKNOWN，状态= CONNECTING}]}。在超时之前等待30000毫秒

Answer 1

我在我自己的（正在运行的）MongoDB服务器上运行你的代码，我可以看到同样的错误。令我印象深刻的是，错误表示＆＃34;在超时之前等待30000ms＆＃34;但是代码在不到30秒的时间内完成。这提供了一个关于问题的提示。

请记住这是异步的 - 因此您不能期望所有操作在同一个线程上顺序运行。实际发生的是MainActivity方法在您对数据库的调用完成之前完成。

如果您更改代码以等待结果在终止之前返回，则会得到更合理的结果。

代码：

main

结果：

public static void main(String[] args) throws InterruptedException {
    CountDownLatch latch = new CountDownLatch(1);
    // connect to the local database server,default:127.0.0.1:27017
    MongoClient mongoClient = MongoClients.create();
    // get handle to "testDB" database
    MongoDatabase database = (MongoDatabase) mongoClient.getDatabase("testDB");
    SingleResultCallback<Void> callbackWhenFinished = new SingleResultCallback<Void>() {
        @Override
        public void onResult(final Void result, final Throwable t) {
            System.out.println("Operation Finished!");
            latch.countDown();
        }
    };
    // get a handle to the "test" collection
    MongoCollection<Document> collection = database.getCollection("test");
    collection.insertOne(new Document("lala", "hehe"), callbackWhenFinished);

    latch.await();
}

顺便说一句，代码可以进一步简化，特别是因为你说你正在使用Java 8：

Aug 11, 2015 9:31:34 AM com.mongodb.diagnostics.logging.JULLogger log
INFO: Cluster created with settings {hosts=[localhost:27017], mode=SINGLE, requiredClusterType=UNKNOWN, serverSelectionTimeout='30000 ms', maxWaitQueueSize=500}
Aug 11, 2015 9:31:35 AM com.mongodb.diagnostics.logging.JULLogger log
INFO: No server chosen by PrimaryServerSelector from cluster description ClusterDescription{type=UNKNOWN, connectionMode=SINGLE, all=[ServerDescription{address=localhost:27017, type=UNKNOWN, state=CONNECTING}]}. Waiting for 30000 ms before timing out
Aug 11, 2015 9:31:35 AM com.mongodb.diagnostics.logging.JULLogger log
INFO: Opened connection [connectionId{localValue:1, serverValue:4}] to localhost:27017
Aug 11, 2015 9:31:35 AM com.mongodb.diagnostics.logging.JULLogger log
INFO: Monitor thread successfully connected to server with description ServerDescription{address=localhost:27017, type=STANDALONE, state=CONNECTED, ok=true, version=ServerVersion{versionList=[3, 0, 2]}, minWireVersion=0, maxWireVersion=3, electionId=null, maxDocumentSize=16777216, roundTripTimeNanos=1281647}
Aug 11, 2015 9:31:35 AM com.mongodb.diagnostics.logging.JULLogger log
INFO: Opened connection [connectionId{localValue:2, serverValue:5}] to localhost:27017
Operation Finished!

Answer 2

检查Mongo-java-driver和Mongodb-Driver-Async

的版本兼容性

就我而言，我使用的是Mongo-java-driver-3.4.0 和mongodb-driver-async-3.0.4

它解决了这个问题。

无法从java连接到本地monogoDB

2 个答案: