我正在做一个像这样的非常基本的插入:

try
{
    DB mongoDb = _mongo.getDB(_databaseName);
    DBCollection collection = mongoDb.getCollection(_collectionName);
    collection.insert(myBasicDBObject);
}
catch (IOException ex)
{
    // Unreachable code
}
catch (MongoException ex)
{
    // Exception never thrown
}
catch (Exception ex)
{
    // Handle exception
}

假设由于某种原因 _databaseName 不正确，因此驱动程序无法连接到数据库。插入操作失败，显然有 3 件事:

• 它从不抛出 MongoException
• 我可以在“catch” block 中捕获的唯一异常是一个通用的“java 空指针异常”
• mongoDb 和集合对象已创建且不为空

但是，在我的 Eclipse 控制台中，我可以清楚地看到更详细的异常消息，例如:

java.io.IOException: couldn't connect to [/127.0.0.1:27017] bc:java.net.ConnectException: Connection refused: connect

有没有办法捕获这个异常？

谢谢

编辑

不幸的是，NullPointerException 不包含堆栈跟踪，只有微不足道的“java.lang.NullPointerException”。但是，在抛出 NullPointerException 之前，这是我在控制台中看到的内容:

2011-08-05 10:06:52 com.mongodb.DBTCPConnector fetchMaxBsonObjectSize
ATTENTION: Exception determining maxBSON size using0
java.io.IOException: couldn't connect to [/127.0.0.1:27017]     bc:java.net.ConnectException: Connection refused: connect
at com.mongodb.DBPort._open(DBPort.java:206)
at com.mongodb.DBPort.go(DBPort.java:94)
at com.mongodb.DBPort.go(DBPort.java:75)
at com.mongodb.DBPort.findOne(DBPort.java:129)
at com.mongodb.DBPort.runCommand(DBPort.java:138)
at com.mongodb.DBTCPConnector.fetchMaxBsonObjectSize(DBTCPConnector.java:419)
at com.mongodb.Mongo.getMaxBsonObjectSize(Mongo.java:541)
at com.mongodb.DBApiLayer$MyCollection.insert(DBApiLayer.java:237)
at com.mongodb.DBApiLayer$MyCollection.insert(DBApiLayer.java:210)
at com.mongodb.DBCollection.insert(DBCollection.java:80)
at foo.App.main(App.java:25)

2011-08-05 10:06:53 com.mongodb.DBTCPConnector fetchMaxBsonObjectSize
ATTENTION: Exception determining maxBSON size using0
java.io.IOException: couldn't connect to [/127.0.0.1:27017]     bc:java.net.ConnectException: Connection refused: connect
at com.mongodb.DBPort._open(DBPort.java:206)
at com.mongodb.DBPort.go(DBPort.java:94)
at com.mongodb.DBPort.go(DBPort.java:75)
at com.mongodb.DBPort.findOne(DBPort.java:129)
at com.mongodb.DBPort.runCommand(DBPort.java:138)
at com.mongodb.DBTCPConnector.fetchMaxBsonObjectSize(DBTCPConnector.java:419)
at com.mongodb.DBTCPConnector.checkMaster(DBTCPConnector.java:406)
at com.mongodb.DBTCPConnector.say(DBTCPConnector.java:144)
at com.mongodb.DBTCPConnector.say(DBTCPConnector.java:137)
at com.mongodb.DBApiLayer$MyCollection.insert(DBApiLayer.java:255)
at com.mongodb.DBApiLayer$MyCollection.insert(DBApiLayer.java:210)
at com.mongodb.DBCollection.insert(DBCollection.java:80)
at foo.App.main(App.java:25)

2011-08-05 10:06:54 com.mongodb.DBPortPool gotError
ATTENTION: emptying DBPortPool to 127.0.0.1:27017 b/c of error
java.io.IOException: couldn't connect to [/127.0.0.1:27017]   bc:java.net.ConnectException: Connection refused: connect
at com.mongodb.DBPort._open(DBPort.java:206)
at com.mongodb.DBPort.go(DBPort.java:94)
at com.mongodb.DBPort.go(DBPort.java:75)
at com.mongodb.DBPort.say(DBPort.java:70)
at com.mongodb.DBTCPConnector.say(DBTCPConnector.java:151)
at com.mongodb.DBTCPConnector.say(DBTCPConnector.java:137)
at com.mongodb.DBApiLayer$MyCollection.insert(DBApiLayer.java:255)
at com.mongodb.DBApiLayer$MyCollection.insert(DBApiLayer.java:210)
at com.mongodb.DBCollection.insert(DBCollection.java:80)
at foo.App.main(App.java:25)

这就是我想捕获的，但不幸的是似乎没有办法这样做......

最佳答案

我能够重现该行为，事实上，当您尝试将对象插入无法访问的 MongoDB 实例时，您只能捕获 NullpointerException。恕我直言，这种行为应该在 MongoDB Java 驱动程序中修复，因为它不是很 Java-ish。肮脏的解决方法看起来可能是这样的:

private static void safeInsert(DBCollection c, DBObject o) {
    if (c == null) {
        throw new RuntimeException("collection must not be null");
    }

    if (o == null) {
        throw new RuntimeException("object must not be null");
    }

    try {
        c.insert(o);
    } catch (NullPointerException e) {
        throw new RuntimeException("unable to connect to MongoDB " + c.getFullName(), e);
    }
}

关于java - MongoDB-Java 驱动程序 : Catch exception when insert fails，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/6926352/