Alter session with native query for a single JPA query - oracle

I'm forced to use a certain NLS_LANGUAGE for accessing a database and don't want to change user.locale to avoid affecting the rest of the application. Is something like this okay to do or can it cause unexpected issues?
Also, how large is the scope of the session? Will this affect this single query only, or each call using the same entityManager, or even the whole application?
#Stateless
#Local
public class myDAOImpl implements MyDAO{
#PersistenceContext(unitName = "MyUnit" )
protected EntityManager em;
public List<Object> getSomeData(){
em.createNativeQuery("alter session set nls_language = 'AMERICAN'").executeUpdate();
Query q = em.createNativeQuery("Select * from my_view");
return q.getResultList();
}
}

Alter session on oracle will affect all future requests on that connection. So if you are using a connection-pool, as you should, this will affect all future sessions that are opened on the same connection.

Related

Spring boot manually commit transaction

In my Spring boot app I'm deleting and inserting a large amount of data into my MySQL db in a single transaction. Ideally, I want to only commit the results to my database at the end, so all or nothing. I'm running into issues where my deletions will be committed before my insertions, so during that period any calls to the db will return no data (not good). Is there a way to manually commit transaction?
My main logic is:
#Transactional
public void saveParents(List<Parent> parents) {
parentRepo.deleteAllInBatch();
parentRepo.resetAutoIncrement();
//I'm setting the id manually before hand
String sql = "INSERT INTO parent " +
"(id, name, address, number) " +
"VALUES ( ?, ?, ?, ?)";
jdbcTemplate.batchUpdate(sql, new BatchPreparedStatementSetter() {
#Override
public void setValues(PreparedStatement ps, int i) throws SQLException {
Parent parent = parents.get(i);
ps.setInt(1, parent.getId());
ps.setString(2, parent.getName());
ps.setString(3, parent.getAddress());
ps.setString(4, parent.getNumber());
}
#Override
public int getBatchSize() {
return parents.size();
}
});
}
ParentRepo
#Repository
#Transactional
public interface ParentRepo extends JpaRepository<Parent, Integer> {
#Modifying
#Query(
value = "alter table parent auto_increment = 1",
nativeQuery = true
)
void resetAutoIncrement();
}
EDIT:
So I changed
parentRepo.deleteAllInBatch();
parentRepo.resetAutoIncrement();
to
jdbcTemplate.update("DELETE FROM output_stream");
jdbcTemplate.update("alter table output_stream auto_increment = 1");
in order to try avoiding jpa's transaction but each operation seems to be committing separately no matter what I try. I have tried TransactionTemplate and implementing PlatformTransactionManager (seen here) but I can't seem to get these operations to commit together.
EDIT: It seems the issue I was having was with the alter table as it will always commit.
I'm running into issues where my deletions will be committed before my insertions, so during that period any calls to the db will return no data
Did you configure JPA and JDBC to share transactions?
If not, then you're basically using two different mechanisms to access the data (EntityManager and JdbcTempate), each of them maintaining a separate connection to the database. What likely happens is that only EntityManager joins the transaction created by #Transactional; the JdbcTemplate operation executes either without a transaction context (read: in AUTOCOMMIT mode) or in a separate transaction altogether.
See this question. It is a little old, but then again, using JPA and Jdbc together is not exactly a common use case. Also, have a look at the Javadoc for JpaTransactionManager.

How to give dynamic value to #Table(name=p+"name") in spring JPA

name of the table should be fixed but in my scenario the last part of the table name is profile based so in local it is X but in dev it is Y and so on till Prod. Is there way to add dynamically the value to the table name.
The question tries to implement a bad practice. Don't do that.
Currently, Spring, Hibernate, and JPA does not support your configuration type.
You can use Hibernate interceptors to change the table in the generated SQL statements.
For your case you can define your table class like this:
#Entity
#org.hibernate.annotations.Proxy(lazy=false)
#Table(name=TableNameReplacer.PLACEHOLDER, schema="MySchema")
#Inheritance(strategy=InheritanceType.SINGLE_TABLE)
public class ProfileData implements Serializable {
and define your Hibernate interceptor in a following way:
public class TableNameReplacer extends EmptyInterceptor {
public static final String TABLE_PLACEHOLDER = "{table_placeholder}";
#Override
public String onPrepareStatement(String sql) {
if (sql.contains(TABLE_PLACEHOLDER )) {
String replacement = "{your logic to fill proper table name}";
sql = sql.replace(TABLE_SUFFIX_PLACEHOLDER, replacement);
}
return super.onPrepareStatement(sql);
}
Using this approach you're free to modify generated SQL and replace the table name there as you wish.
I recommend to use good placeholder value which you're sure will not be a part of actual values being saved to the table (or you can only limit this to select statements if you only read the data).

Hibernate - Table Locked after update

I'm performing an update via a method using Hibernate and the EntityManager.
This update method is called multiple times (within a loop).
It seems like when I execute it the first time, it locks the table and does not free it.
When trying to update the table via SQL Developer after having closed the application, I see the table is still locked because the update is hanging.
What do you see as a solution to this problem? If you need more information, let me know.
Class
#Repository
#Transactional(propagation = REQUIRES_NEW)
public class YirInfoRepository {
#Autowired
EntityManager entityManager;
#Transactional(propagation = REQUIRES_NEW)
public void setSent(String id) {
String query = "UPDATE_QUERY";
Query nativeQuery = entityManager.createNativeQuery(String.format(query, id));
nativeQuery.executeUpdate();
}
}
UPDATE
After having waited more than one hour, I launched the application again and it worked fine once but now again, it hangs.
UPDATE 2 -- I'll give a maximum bounty to whoever helps me solve this
On another place I use an application managed entity manager and it still gives me the same type of errors.
public void fillYirInfo() {
File inputFile = new File("path");
try (InputStream inputStream = new FileInputStream(inputFile);
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream))) {
bufferedReader.lines().skip(1).limit(20).forEach(line -> {
String[] data = line.split(",");
String rnr = data[0];
String linked = data[1];
String email = data.length > 2 ? data[2] : "";
String insuredId = insuredPeopleRepository.getInsuredIdFromNationalId(rnr);
int modifiedCounter = 0;
if (!isNullOrEmpty(insuredId)) {
EntityManager entityManager = emf.createEntityManager();
EntityTransaction transaction = entityManager.getTransaction();
Query nativeQuery = entityManager.createNativeQuery(
"QUERY"
);
transaction.begin();
nativeQuery.executeUpdate();
entityManager.flush();
transaction.commit();
entityManager.close();
}
System.out.println(modifiedCounter + " rows modified");
});
} catch (IOException e) {
e.printStackTrace();
}
}
Try without an update-query:
#Repository
#Transactional(propagation = REQUIRES_NEW)
public class YirInfoRepository {
#Autowired
EntityManager entityManager;
#Transactional(propagation = REQUIRES_NEW)
public void setSent(String id) {
//guessing your class name and method..
final YirInfo yirInfo = entityManager.find(YirInfo.class, id);
yirInfo.setSent();
}
}
Might not be as fast as a single update query, but it's possible to get it reasonably fast, unless the amount of data is huge. This is the preferred way of using Hibernate/JPA, instead of thinking in terms of single values and SQL queries, you work with entities/objects and (sometimes) HQL/JPQL queries.
You are using #Transactional annotation. This means you are using Spring Transaction. Then in your UPDATE 2 you are using transaction by yourself and managed by spring (I guess it's another project or class not managed by Spring).
In any case what I would do is to try to update your records in single spring transaction and I'd not use #Transactional in DAO layer but in service layer. Something like this:
Service layer:
#Service
public class YirInfoService {
#Autowired
YirInfoRepository dao;
#Transactional(propagation = REQUIRES_NEW)
public void setSent(List < String > ids) {
dao.setSents(ids);
}
}
DAO layer:
#Repository
public class YirInfoRepository {
#Autowired
EntityManager entityManager;
//Here you can update by using and IN statement or by doing a cycle
//Let's suppose a bulk operation
public void setSents(List < String > ids) {
String query = "UPDATE_QUERY";
for (int i = 0; i < ids.size(); i++) {
String id = ids.get(i);
Query nativeQuery = entityManager.createNativeQuery(String.format(query, id));
nativeQuery.executeUpdate();
if (i % 20 == 0) {
entityManager.flush();
entityManager.clear();
}
}
}
}
The first thing you have to understand is that for the first example, you are using a native query to update rows in the DB. In this case you are completely skipping Hibernate to do anything for you.
In your second example, you have the same thing, you are updating via an update query. You don't need to flush the entity manager as it's only necessary for transferring the pending changes made to your entity objects within that entity manager.
Plus I don't know how your example works as you are autowiring the entity manager and not using the #PersistenceContext annotation. Make sure you use this one properly because you might have misconfigured the application. Also there is no need to manually create the entity manager when using Spring as it looks in the second example. Just use #PersistenceContext to get an entity manager in your app.
You are also mixing up transaction management. In the first example, it's enough if you put the #Transactional annotation to either of your method or to the class.
For the other example, you are doing manual transaction management which makes no sense in this case. If you are using Spring, you can simply rely on declarative transaction management.
The first thing I'd check here is to integrate datasource-proxy into your connection management and log out how your statements are executed. With this info, you can make sure that the query is sent to the DB side and the DB is executing it very slowly, or you are having a network issue between your app and db.
If you find out that the query is sent properly to the DB, you want to analyze your query, because most probably it's just executed very slowly and needs some optimizations. For this, you can use the Explain plan feature, to find out how your execution plan looks like and then make it faster.

Spring Boot - Change connection dynamically

I have a Spring Boot project with multiple databases of different years and these databases have same tables so the only difference is the year (..., DB2016, DB2017). In the controller of the application i need to return data that belong to "different" years. Moreover in future years other databases will be created (eg. in 2018 there's going to be a db named "DB2018"). So my problem is how to switch the connection among databases without creating a new datasource and a new repository every new year.
In an other question posted by me (Spring Boot - Same repository and same entity for different databases) the answer was to create different datasources and different repositories for every existing database, but in this case i want to return data from existing databases on the basis of the current year. More specifically:
SomeEntity.java
#Entity(name = "SOMETABLE")
public class SomeEntity implements Serializable {
#Id
#Column(name="ID", nullable=false)
private Integer id;
#Column(name="NAME")
private String name;
}
SomeRepository.java
public interface SomeRepository extends PagingAndSortingRepository<SomeEntity, Integer> {
#Query(nativeQuery= true, value = "SELECT * FROM SOMETABLE WHERE NAME = ?1")
List<SomeEntity> findByName(String name);
}
SomeController.java
#RequestMapping(value="/foo/{name}", method=RequestMethod.GET)
public ResponseEntity<List<SomeEntity>> findByName(#PathVariable("name") String name) {
List<SomeEntity> list = autowiredRepo.findByName(name);
return new ResponseEntity<List<SomeEntity>>(list,HttpStatus.OK);
}
application.properties
spring.datasource.url=jdbc:postgresql://localhost:5432/DB
spring.datasource.username=xxx
spring.datasource.password=xxx
So if the current year is 2017 i want something like this:
int currentyear = Calendar.getInstance().get(Calendar.YEAR);
int oldestDbYear = 2014;
List<SomeEntity> listToReturn = new LinkedList<SomeEntity>();
//the method getProperties is a custom method to get properties from a file
String url = getProperties("application.properties", "spring.datasource.url");
props.setProperty("user", getProperties("application.properties","spring.datasource.username"));
props.setProperty("password", getProperties("application.properties","spring.datasource.password"));
for (int i = currentYear, i>oldestDbYear, i--) {
//this is the connection that must be used by autowiredRepo Repository, but i don't know how to do this.
//So the repository uses different connection for every year.
Connection conn = getConnection(url+year,props);
List<SomeEntity> list_of_specific_year = autowiredRepo.findByName(name);
conn.close;
listToReturn.addAll(list_of_specific_year);
}
return listToReturn;
Hope everithing is clear
The thing that is probably most suitable to your needs here is Spring's AbstractRoutingDataSource. You do need to define multiple DataSources but you will only need a single repository. Multiple data sources is not an issue here as there is always a way to create the DataSource beans programatically at run time and register them with the application context.
How it works is you basically register a Map<Object, DataSource> inside your #Configuration class when creating your AbstractRoutingDataSource #Bean and in this case the lookup key would be the year.
Then you need create a class that implements AbstractRoutingDataSource and implement the determineCurrentLookupKey() method. Anytime a database call is made, this method is called in the current context to lookup which DataSource should be returned. In your case it sounds like you simply want to have the year as a #PathVariable in the URL and then as the implementation of determineCurrentLookupKey() grab that #PathVariable out of the URL (e.g in your controller you have mappings like #GetMapping("/{year}/foo/bar/baz")).
HttpServletRequest request = ((ServletRequestAttributes)RequestContextHolder
.getRequestAttributes()).getRequest();
HashMap templateVariables =
(HashMap)request.getAttribute(HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE);
return templateVariables.get("year");
I used this approach when writing a testing tool for a product where there were many instances running on multiple different servers and I wanted a unified programming model from my #Controllers but still wanted it to be hitting the right database for the server/deployment combination in the url. Worked like a charm.
The drawback if you are using Hibernate is that all connections will go through a single SessionFactory which will mean you can't take advantage of Hibernate's 2nd level caching as I understand it, but I guess that depends on your needs.

Spring Boot Data JPA - Modifying update query - Refresh persistence context

I'm working with Spring Boot 1.3.0.M4 and a MySQL database.
I have a problem when using modifying queries, the EntityManager contains outdated entities after the query has executed.
Original JPA Repository:
public interface EmailRepository extends JpaRepository<Email, Long> {
#Transactional
#Modifying
#Query("update Email e set e.active = false where e.active = true and e.expire <= NOW()")
Integer deactivateByExpired();
}
Suppose we have Email [id=1, active=true, expire=2015/01/01] in DB.
After executing:
emailRepository.save(email);
emailRepository.deactivateByExpired();
System.out.println(emailRepository.findOne(1L).isActive()); // prints true!! it should print false
First approach to solve the problem: add clearAutomatically = true
public interface EmailRepository extends JpaRepository<Email, Long> {
#Transactional
#Modifying(clearAutomatically = true)
#Query("update Email e set e.active = false where e.active = true and e.expire <= NOW()")
Integer deactivateByExpired();
}
This approach clears the persistence context not to have outdated values, but it drops all non-flushed changes still pending in the EntityManager. As I use only save() methods and not saveAndFlush() some changes are lost for other entities :(
Second approach to solve the problem: custom implementation for repository
public interface EmailRepository extends JpaRepository<Email, Long>, EmailRepositoryCustom {
}
public interface EmailRepositoryCustom {
Integer deactivateByExpired();
}
public class EmailRepositoryImpl implements EmailRepositoryCustom {
#PersistenceContext
private EntityManager entityManager;
#Transactional
#Override
public Integer deactivateByExpired() {
String hsql = "update Email e set e.active = false where e.active = true and e.expire <= NOW()";
Query query = entityManager.createQuery(hsql);
entityManager.flush();
Integer result = query.executeUpdate();
entityManager.clear();
return result;
}
}
This approach works similar to #Modifying(clearAutomatically = true) but it first forces the EntityManager to flush all changes to DB before executing the update and then it clears the persistence context. This way there won't be outdated entities and all changes will be saved in DB.
I would like to know if there's a better way to execute update statements in JPA without having the issue of the outdated entities and without the manual flush to DB. Perhaps disabling the 2nd level cache? How can I do it in Spring Boot?
Update 2018
Spring Data JPA approved my PR, there's a flushAutomatically option in #Modifying() now.
#Modifying(flushAutomatically = true, clearAutomatically = true)
I know this is not a direct answer to your question, since you already have built a fix and started a pull request on Github. Thank you for that!
But I would like to explain the JPA way you can go. So you would like to change all entities which match a specific criteria and update a value on each. The normal approach is just to load all needed entities:
#Query("SELECT * FROM Email e where e.active = true and e.expire <= NOW()")
List<Email> findExpired();
Then iterate over them and update the values:
for (Email email : findExpired()) {
email.setActive(false);
}
Now hibernate knows all changes and will write them to the database if the transaction is done or you call EntityManager.flush() manually. I know this won't work well if you have a big amount of data entries, since you load all entities into memory. But this is the best way, to keep the hibernate entity cache, 2nd level caches and the database in sync.
Does this answer say "the `#Modifying´ annotation is useless"? No! If you ensure the modified entities are not in your local cache e.g. write-only application, this approach is just the way to go.
And just for the record: you don't need #Transactional on your repository methods.
Just for the record v2: the active column looks as it has a direct dependency to expire. So why not delete active completely and look just on expire in every query?
As klaus-groenbaek said, you can inject EntityManager and use its refresh method :
#Inject
EntityManager entityManager;
...
emailRepository.save(email);
emailRepository.deactivateByExpired();
Email email2 = emailRepository.findOne(1L);
entityManager.refresh(email2);
System.out.println(email2.isActive()); // prints false

Resources