Retrieving the specific MongoDB key from DuplicateKeyException that was actually duplicated (Java/Spring)

java, mongodb, spring, spring-data

Solution

Not really, as the Mongo Java Driver already exposes the last error as a constructed String:

`writeResult.getLastError().get("err")` returns something such as:

`insertDocument :: caused by :: 11000 E11000 duplicate key error index: test.person.$username dup key: { : "joe" }`

This is also true for the shell and every driver, I imagine.

A reasonable solution, I think, is to parse such duplicate key exception using a custom exception:

public class DetailedDuplicateKeyException extends DuplicateKeyException {
    public DetailedDuplicateKeyException(String msg) {
        // Instead of just calling super parse the message here.
        super(msg);
    }
}

... a custom exception translator:

public class DetailedDuplicateKeyExceptionTransaltor extends MongoExceptionTranslator {

    @Override
    public DataAccessException translateExceptionIfPossible(RuntimeException ex) {
        if (ex instanceof MongoException.DuplicateKey) {
            return new DetailedDuplicateKeyException(ex.getMessage());
        }
        return super.translateExceptionIfPossible(ex);
    }
}

... and setting the Spring configuration properly:

@Bean
public MongoFactoryBean mongo() {
    MongoFactoryBean mongo = new MongoFactoryBean();
    mongo.setExceptionTranslator(new DetailedDuplicateKeyExceptionTransaltor());
    mongo.setHost("localhost");
    return mongo;
}

EDIT

After inspecting `MongoTemplate` code (1.4.1.RELEASE), it seems that internally a `SimpleMongoDbFactory` is used to retrieve a default `MongoExceptionTranslator`, so the one created with `MongoFactoryBean` is shadowed. Had missed that part.

The solution is to override `SimpleMongoDbFactory` (forget about `MongoFactoryBean`, it's useless in this context):

public class MySimpleMongoDbFactory extends SimpleMongoDbFactory {

    PersistenceExceptionTranslator translator = new       
            DetailedDuplicateKeyExceptionTransaltor();

    public MySimpleMongoDbFactory(Mongo mongo, String databaseName) {
        super(mongo, databaseName);
    }

    @Override
    public PersistenceExceptionTranslator getExceptionTranslator() {
        return translator;
    }
}

Now you can construct a template using the custom `MongoDbFactory`:

`template = new MongoTemplate (new MySimpleMongoDbFactory(new MongoClient(), "test"));`

Had tried, and this one works for me.

Problem

Original source

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