I am making the following query which works and updates the info into the database as expected. But is there a way I can get an output from Single < UpdateResult >?
public Single<UpdateResult> update(UpdateEventRequest request) {
return client.rxUpdateWithParams(
"UPDATE mydb.sample SET sta_cd=?, some_ts=current_timestamp WHERE id=? RETURNING sta_cd",
new JsonArray(Arrays.asList(sta_cd, id)));
}
From the following e variable, I was hoping to get the value "10012". But it doesn't seem possible. Tried with map, flatmap and just see options available in e. The only result data in e is 'keys' which is an empty list and 'updated' which is an integer value of 1. My DB is postgres and was expecting results from from Single < UpdateResult > since am using 'RETURNING' in the query.
I have done the same for an insert operation which works but that is via the method rxQueryWithParams() and that returns a Single < ResultSet > instead. Thus wondering if this is even possible. Been having a look at docs and maybe this is not possible as an update query is returning a Single < UpdateResult > . Looking for advice if this is possible, to return data from an update query or a way around this. Please advice. Thanks.
Single<UpdateResult> result = someClass.update("10012", "78632");
result.subscribe(
e -> {
System.out.println("success: " + e); // I land here as expected
},
error -> {
System.out.println("error: " + error);
}
);
Because you are using RETURNING in these commands, treat these INSERT and UPDATE commands as queries.
Run them through rxQueryWithParams() so you can retrieve the results.
When you run rxUpdateWithParams(), the UpdateResult contains only the number of rows affected.
Related
I have the following method where I am doing db insertions. I want to perform the inserts in a transaction.
Meaning when there are 100 values in records, I wan to insert them all and commit once.
How could I amend the following such that I can get record.value() info for each insert queries below.
This would essentially equate to having andThen() a 100 times but of course I do not want to write andThen() a 100 times nor do I know the number of records which can vary.
To note: Using RX Java 1.
Please advice. Thank you.
public Observable<?> insert(Observable<Record<String, String>> records) {
// I am looking for a way to get this record.value() into the following return block.
records.flatMap(record -> {
String value = record.value();
return null;
});
return client.rxGetConnection()
// making it transactional by setting to false
.flatMap(connection -> connection.rxSetAutoCommit(false)
// was looking to insert above records and flatMap operations here but it is not possible from what I have explored.
.toCompletable()
// .andThen(connection.rxExecute("INSERT (name) VALUES " + record.value()) // trying to achieve this, to be able to get record.value for each insert
.andThen(connection.rxExecute("INSERT (name) VALUES some_value"))
.flatMap(rows -> connection.rxCommit())).toObservable();
}
I want to use this SQL query:
String hql = "select e from " + Terminals.class.getName() + " e WHERE e.merchantId IN :merchant_ids";
TypedQuery<Terminals> query = entityManager.createQuery(hql, Terminals.class).setParameter("merchant_ids", merchant_ids);
List<Terminals> merchants = query.getResultList();
But I get error: the right syntax to use near ') So IN clause list into IN (....) can't be empty. Is there some solution to this problem?
It is allowable and even very fine not executing the query:
if (merchant_ids.isEmpty()) {
return new ArrayList<>();
} else {
String hql = "select e from " + Terminals.class.getName()
+ " e WHERE e.merchantId IN :merchant_ids";
return entityManager.createQuery(hql, Terminals.class)
.setParameter("merchant_ids", merchant_ids)
.getResultList();
}
I do not know what would happen if one would pass null instead of an empty list;
SQL ... IN NULL could do. On the other hand it might do a full table scan in order to return 0 results.
If x IN() would not result in 0 records (when there is an OR ...) then:
if (merchant_ids.isEmpty()) {
merchant_ids.add(-1);
String hql = "select e from " + Terminals.class.getName() + ...
Very often, I used to stuck this kind of case. I couldn't find out a proper solution. Since you are using Spring JPA But I have some workaround to suggest to you.
Implement EntityManger and create your SQL queries in runtime. So you can populate your where cause and everything.
Like this: entityManager.createNativeQuery(sql.toString())
Implement if-else block. Check if the list is empty or not, if false call actual query (with IN block) or else write another query without IN block.
Again I am telling, this may not be a proper solution. But I see this is proper workaround.
I am not familiar with hibernate but since it is an SQL error, the following should work :
TypedQuery<Terminals> query = entityManager
.createQuery(hql, Terminals.class)
.setParameter("merchant_ids",merchant_ids.size()==0?null:merchant_ids);
But as #Richard Barker mentioned , best solution is to not even execute the query when the list is empty.
You will even save on the unnecessary database call , when you already know that the query is not going to return anything.
I followed #Rambler's suggestion and created a method to return a null:
public static <T> Collection<T> nullIfEmpty(Collection<T> collection) {
return (collection == null || collection.isEmpty()) ? null : collection;
}
This was easier to add in place, but I agree that it is better to not make the call to the database.
I have a JAVA RESTful API built using NetBeans. I've created a custom method to retrieve data using a field that isn;t the Primary Key. If I run this SQL command on the Database itself, I get data however if I run it via the API I get 0 results.
Here is the Named Query:
#NamedQuery(name = "KeywordsView.findByCharId", query = "SELECT k FROM KeywordsView k WHERE k.charId = :charId")
The method calling this query:
#GET
#Path("findcharid/{charId}")
#Produces({MediaType.APPLICATION_JSON})
public List<KeywordsView> findByCharId(#PathParam("CharId") Integer charId){
return getEntityManager().createNamedQuery("KeywordsView.findByCharId", KeywordsView.class).setParameter("charId", charId).getResultList();
}
I've debugged the URL and it is calling and running the URL as expected.
Anything clearly wrong?
The charId value is null due to the case not match for the "CharId" in #PathParam("CharId") with {charId} in #Path("findcharid/{charId}"). And this make no result as null comparison is always false.
#GET
#Path("findcharid/{charId}")
#Produces({MediaType.APPLICATION_JSON})
// Should match the case
public List<KeywordsView> findByCharId(#PathParam("CharId") Integer charId){
System.out.println("charId:"+charId);
return getEntityManager().createNamedQuery("KeywordsView.findByCharId", KeywordsView.class).setParameter("charId", charId).getResultList();
}
the selected field k name is similar to the table KeywordsView alias k too, not sure but this could be an issue? maybe the when qry executed it generates an exception and that's why you have 0 result?
try to change your query as below:
#NamedQuery(name = "KeywordsView.findByCharId", query = "SELECT k FROM KeywordsView kv WHERE kv.charId = :charId")
I have now fixed this. It was in my method, there is a sneaky Capital C at "CharId" where is should be "charId".
private ILogin results;
public ILogin authenticate(Login login) {
System.out.println(login);
System.out.println(login.getEmail());
String query = "SELECT email, id FROM Login WHERE email='"
+ login.getEmail() + "' AND password='" + login.getPassword() + "'";
results = getHibernateTemplate().find(query);
System.out.println(results);
return results;
}
How do i change results = getHibernateTemplate().find(query); I get the error in this line. But i want that in ILogin type not of List type. How do i do an Type Conversion here.
The problem isn't the type conversion per se - it's that you've executed a query which may return multiple results, but you only want a single result.
You probably want to check that the resulting list has exactly one value (0 means login not found; more than 1 probably means there's a problem in your data somewhere) and then return that first value (return (ILogin) list.get(0);).
As a slightly separate matter, you shouldn't be including the data directly in your query like that, IMO. Use query parameters, which is pretty easy in Hibernate:
String query = "SELECT email, id FROM Login WHERE email=? AND password=?";
Object[] parameters = { login.getEmail(), login.getPassword() };
List results = getHibernateTemplate().find(query, parameters);
if (results.size() != 1) {
// Probably throw an exception
}
// I'm assuming your mapping has been set up appropriately such that
// the returned value will *be* an `ILogin`.
return (ILogin) results.get(0);
Finally, you almost certainly don't want results to be an instance variable - it should probably be a local variable, as per my example above.
The dummy way is to use getHibernateTemplate().find(query).get(0); but this will result in exception in case when no such login found.
As Jon said, check your query for emptiness.
I assume spring :).
List resultsList = getHibernateTemplate().find(query);
if ( resultsList.size() == 1 ) {
results = (ILogin)resultsList.get(0);
} else {
// error no entity or mutiple entities
}
return results.
This should work.
I like the idea of Named Queries in JPA for static queries I'm going to do, but I often want to get the count result for the query as well as a result list from some subset of the query. I'd rather not write two nearly identical NamedQueries. Ideally, what I'd like to have is something like:
#NamedQuery(name = "getAccounts", query = "SELECT a FROM Account")
.
.
Query q = em.createNamedQuery("getAccounts");
List r = q.setFirstResult(s).setMaxResults(m).getResultList();
int count = q.getCount();
So let's say m is 10, s is 0 and there are 400 rows in Account. I would expect r to have a list of 10 items in it, but I'd want to know there are 400 rows total. I could write a second #NamedQuery:
#NamedQuery(name = "getAccountCount", query = "SELECT COUNT(a) FROM Account")
but it seems a DRY violation to do that if I'm always just going to want the count. In this simple case it is easy to keep the two in sync, but if the query changes, it seems less than ideal that I have to update both #NamedQueries to keep the values in line.
A common use case here would be fetching some subset of the items, but needing some way of indicating total count ("Displaying 1-10 of 400").
So the solution I ended up using was to create two #NamedQuerys, one for the result set and one for the count, but capturing the base query in a static string to maintain DRY and ensure that both queries remain consistent. So for the above, I'd have something like:
#NamedQuery(name = "getAccounts", query = "SELECT a" + accountQuery)
#NamedQuery(name = "getAccounts.count", query = "SELECT COUNT(a)" + accountQuery)
.
static final String accountQuery = " FROM Account";
.
Query q = em.createNamedQuery("getAccounts");
List r = q.setFirstResult(s).setMaxResults(m).getResultList();
int count = ((Long)em.createNamedQuery("getAccounts.count").getSingleResult()).intValue();
Obviously, with this example, the query body is trivial and this is overkill. But with much more complex queries, you end up with a single definition of the query body and can ensure you have the two queries in sync. You also get the advantage that the queries are precompiled and at least with Eclipselink, you get validation at startup time instead of when you call the query.
By doing consistent naming between the two queries, it is possible to wrap the body of the code to run both sets just by basing the base name of the query.
Using setFirstResult/setMaxResults do not return a subset of a result set, the query hasn't even been run when you call these methods, they affect the generated SELECT query that will be executed when calling getResultList. If you want to get the total records count, you'll have to SELECT COUNT your entities in a separate query (typically before to paginate).
For a complete example, check out Pagination of Data Sets in a Sample Application using JSF, Catalog Facade Stateless Session, and Java Persistence APIs.
oh well you can use introspection to get named queries annotations like:
String getNamedQueryCode(Class<? extends Object> clazz, String namedQueryKey) {
NamedQueries namedQueriesAnnotation = clazz.getAnnotation(NamedQueries.class);
NamedQuery[] namedQueryAnnotations = namedQueriesAnnotation.value();
String code = null;
for (NamedQuery namedQuery : namedQueryAnnotations) {
if (namedQuery.name().equals(namedQueryKey)) {
code = namedQuery.query();
break;
}
}
if (code == null) {
if (clazz.getSuperclass().getAnnotation(MappedSuperclass.class) != null) {
code = getNamedQueryCode(clazz.getSuperclass(), namedQueryKey);
}
}
//if not found
return code;
}