Im trying to use the findDistinct function from mongoTemplate but i always retrieve an empty result list.
Can you help me out to spot the problem ? Or maybe you have a simpliest way to do it
NB:
I do have data in my collection
(on a basic find, i fetch more than 300 results in the list but all of this result are the same excepting on one key, i want all the distinct object from their NAME value for instance )
I tryied this :
List<DiffusionListImpl> list = new ArrayList<>();
try{
query = new Query(Criteria.where("CUSTOMERNUMBER").is(1));
list = mongoTemplate.findDistinct(query, KeyWhereIWantTheDistinct, collectionName,
KlassResultModel.class);
} catch (MongoException e) {
logger.error("MongoException: " + e);
} catch (Exception e) {
logger.error("Error: " + e);
}
return list;
My bad, i misread the documentation.
But i find it akward to have this kind of comportement of this function.
I have to make a call to the DB to fetch a list of distinct value and then make another Call of the same DB to retrieve the object.
Is there any way to do it in one call? (Performance issue)
It can be done in one DB call, use below code.
final List<DiffusionListImpl> result =
IteratorUtils.toList(this.mongoTemplate.getCollection("collectionName")
.distinct("fieldName", query.getQueryObject(), DiffusionListImpl.class)
.iterator());
for IteratorUtils you can use apache
import org.apache.commons.collections4.IteratorUtils;
Related
I'm creating an API that return Vaccination Info of people. The code below is that I'm getting list of vaccination IDs. If people injected 1 or more, the API working fine, I get a list as expected. Vice versa, if they haven't injected, the data on server is null. In that case, when I make an API call I will get the error that vaccinationInfoList is null, but it's still have the size 1. I tried as below to locate the error but it's cannot catch any exception.
try {
Response<List<Vaccination_info>> res = call.execute();
Log.v("RES" , String.valueOf(res));
if (res.body() != null){
try {
vaccinationInfoList = res.body();
}
catch (Exception n){
Log.v("ExceptionN" , String.valueOf(n));
}
} else {
Log.v("NULL" , "NULL");
}
} catch (IOException e) {
e.printStackTrace();
}
Log.v("VACC", String.valueOf(vaccinationInfoList.size()));
Can someone recommend me a solution or a different aproach? Thanks so much
If you have access and can change api response so change response from null to empty array list []
If not You can use com.google.gson.JsonElement
I am currently working over CSV exports. I am fetching header from properties file with below code -
String[] csvHeader = exportables.get(0).getCSVHeaderMap(currentUser).keySet().stream().
map(s ->messageSource.getMessage("report."+s, null, locale)).toArray(String[]::new);
The above code works well. But i need to find a way to handle exception and also fetch data from another file, if it is not found in above file. I am expecting to use somewhat below code -
try{
exportables.get(0).getCSVHeaderMap(currentUser).keySet().stream().
map(s ->messageSource.getMessage("report."+s, null, locale)).toArray(String[]::new);
}catch(NoSuchMessageException e){
// code to work over lacking properties
}
I want to catch the 's' element in catch block (or in other good way). So that i can fetch it from another file and also add its return to current csvHeader.
One way is to make for each element a try catch block like:
exportables.get(0).getCSVHeaderMap(currentUser).keySet().stream().
map(s -> {
String result;//Put the class to which you map
try{
result = messageSource.getMessage("report."+s, null, locale);
}catch(NoSuchMessageException e){
// code to work over lacking properties here you have access to s
}
return result;
}
).toArray(String[]::new);
Another solution will be to check for specific problems and then there is no need to catch exceptions. For example if s is null and then you want to get the data from another place:
exportables.get(0).getCSVHeaderMap(currentUser).keySet().stream().
map(s -> {
String result;//Put the class to which you map
if(null == s)// Some condition that you want to check.
{
//get info from another place
//result = ....
}
else
{
result = messageSource.getMessage("report."+s, null, locale);
}
return result;
}
).toArray(String[]::new);
If we wanna get an object ID we should do this:
String objectId = gameScore.getObjectId();
but what if we wanna get an object ID by a query? Like this:
ParseQuery<ParseObject> query = ParseQuery.getQuery("mytable");
query.whereEqualTo("Title", "Adrians Book");
List<ParseObject> results = null;
try {
results = query.find();
if(!results.isEmpty()) {
String objectId = results.getObjectId();
}
} catch (com.parse4cn1.ParseException e) {
Dialog.show("Err", "Something went wrong.", "OK", null);
}
Sounds interesting don't you think? I wish it could be possible. As you can see in this example the query will get a value from a specific object in the table which could track for the object ID then returning it as well. ParseQuery class should be implemented with getObjectId(). Because by this way applications always could have access to object IDs from the query even after applications get restarted so in the first example the gameScore which is actually an instance of ParseObject would lost reference to the Database after restarting. Getting object IDs by the query it would be able to program applications to get object IDs automatically without the need of doing it manually nor depending on instances of ParseObject.
#Shai Almog: Thank you very much for taking your time to look at the ParseQuery documentation.
I accidentally figured out how to get this done!
ParseQuery<ParseObject> query = ParseQuery.getQuery("mytable");
query.whereEqualTo("Title", "Adrians Book");
List<ParseObject> results = null;
try {
results = query.find();
if(!results.isEmpty()) {
String objectId = results.get(0).getObjectId();
System.out.println(objectId);
}
} catch (com.parse4cn1.ParseException e) {
Dialog.show("Err", "Something went wrong.", "OK", null);
}
Yep, after adding the method .get(index) it allows you to access the method .getObjectId() since results is a list of a ParseObject, then the respective objectId of your query result will be printed in the console! I'm pretty glad it's working because I won't need to serialize each object for now which would be a pain.
Also if you wanna set an instance of ParseObject with an existing objectId in case you need to update something in your Database, you can use this example:
ParseObject po = ParseObject.create("mytable");
po.setObjectId(//YOUR DESIRED OBJECTID HERE, AS LONG AS IT EXISTS IN THE DATABASE);
As far as I know you need to get the whole object then query it's ID. I don't see a query id method here https://github.com/sidiabale/parse4cn1/blob/41fe491699e604fc6de46267479f47bc422d8978/src/com/parse4cn1/ParseQuery.java
{
"question":"what is your color?",
"choices":[{"option":"yello"},{"option":"blue"}],
"creation-date":"2014-04-13",
"expiry date":"2014-04-14"
}
In order to retrive list of polls
public List<Poll> getPolls()
{
try {
mongoClient=new MongoClient("NavDeep",27017);
db=mongoClient.getDB("sms-voting");
collection=db.getCollection("pollsCollection");
} catch(Exception e){
e.printStackTrace();
}
List<Poll> polls = new ArrayList<Poll>();
DBCursor cursor=collection.find();
while(cursor.hasNext())
{
DBObject object = cursor.next();
what should i write in order to retrieve List<Poll>????
}
}
mongoClient.close();
return polls;
}
but i am getting null pointer exception near BasicDBList pollList=(BasicDBList)object.get("pollsCollection");
Can any body please Help me out.What should i actually write inside get()??
Thnks,
deepthi
I think the problem could be that you're doing cursor.next() twice in the lines above, pulling two records at a time.
What if you try:
polls.add(object)
instead of
polls.add(cursor.next())
Rather than iterating the cursor you appear to want the .toArray() method:
DBCursor cursor = collection.find();
List<DBObject> list = cursor.toArray();
Generally cursors are a good idea, and you probably should be building any array type results from within that loop. But this is a way to change the cursor.
I need to insert a list of objects with a predefined _id (Long) into a collection.
insert(object) method for a single object from AdvancedDatastore works great. The trouble begins when i try to use the insert() method which accepts an Iterable. Here is a sample piece of code:
try {
advancedDatastore.insert("collection_name", feeds, WriteConcern.ERRORS_IGNORED);
} catch (Exception e) {
e.printStackTrace();
}
I guess that this code is supposed to ignore errors (an object with a duplicate id already exists in the collection) and just continue with the next item, but it does not. And no exception is raised.
Thanks!
Update:
This code inserts all the elements, but "1" is not printed out.
try {
System.err.println(0);
advancedDatastore.insert("collection_name", feeds, WriteConcern.ERRORS_IGNORED.continueOnErrorForInsert(true));
System.err.println(1);
} catch (Exception e) {
e.printStackTrace();
}
Update2:
Sorry, the code completes properly and "1" is printed out, but it takes tremendously more time than single inserts. In my case 35_000 inserts 1 by one - 3 seconds, in batch - 100+ seconds
Update3:
So far the best way to deal with the issue for me is to use native java driver for mongodb.
1st I convert my object list to DBObject list:
final List<DBObject> dbObjects = new ArrayList<DBObject>();
for (MyObject object: objectList) {
dbObjects.add(morphia.toDBObject(object));
}
Then I insert through mongo DB instance:
db.getCollection("collection_name").insert(dbObjects, WriteConcern.UNACKNOWLEDGED.continueOnErrorForInsert(true));
Performace for inserting 150_000 objects:
Native DB insert: 2-3 seconds
via Morphia's insert(object): 15+ seconds
via Morphia's insert(Iterable): 400+ seconds
A better way would be appreciated.
It works to me in this way
final List<DBObject> dbObjects = new ArrayList<DBObject>();
try {
TypedQuery<RegistroCivil> consulta = em.createQuery("select p from RegistroCivil p", RegistroCivil.class);
List<RegistroCivil> lista = consulta.getResultList();
for (RegistroCivil object : lista) {
dbObjects.add(morphia.toDBObject(object));
}
long start = System.currentTimeMillis();
ds.getCollection(RegistroCivil.class).insert(dbObjects);
//ds.save(lista);
long end = System.currentTimeMillis();
tmongo = end - start;