Do synchnorized blocks or methods on Java prevent from multi thread access for every thread?

Hi,

As you read the question, I want to answer it quickly :)

Answer is, it depends. If the synchronized method is marked as "static", yes, it will work for every instances of class, because static methods belong to class, not instance.
For synchronized blocks, if they are in a static method, the same things go for them.

Otherwise, if the method is not static, it will work per instance, one's lock will not affect the other instance's synchronized block.

Have a nice day!

Good Reference Sources for Migration of Commons HttpClient 3.x to HttpComponents HttpClient 4.x

Hi,

I had a task for replacing our Commons HttpClient 3.x dependency to HttpComponents HttpClient 4.x
As the latter one contains many changes over predecessor library, there are many things to be corrected at client side.
So, I used the sources below to accomplish my task, they were very useful, I recommend you to look at these if you have a task like mine :)

http://debuguide.blogspot.in/2013/01/quick-guide-for-migration-of-commons.html

http://www.codingpedia.org/ama/how-to-use-the-new-apache-http-client-to-make-a-head-request/

http://stackoverflow.com/questions/6024376/apache-httpcomponents-httpclient-timeout


Have a good day!

Search on a CLOB column on Oracle DB

Hi,

You can user instr function for searching on a CLOB column.

Ex:

select * from TABLE_NAME where instr(COLUMN_NAME,'SEARCH PARAM') > 0 order by process_date desc

Have a nice day!

Getting RollbackException in Transactional Methods

Hi,

Here is the second problem i have to deal with, RollbackException.
As I search on Google, if you get exception in a transactional method, even if you catch it and not throw, the transaction is marked as rollback only and you cannot commit anything in this transaction.
This may be annoying if you get an ignorable exception, for example NoResultException.
For overcome this, you should take some precautions with Transactional annotation, like this,

@Transactional(rollbackFor=MyException.class, noRollbackFor=MyException2.class)

Specifying rollback and no-rollback situations is the best way to handle this.

Have a nice day!

Link: http://stackoverflow.com/questions/19302196/transaction-marked-as-rollback-only-how-do-i-find-the-cause

About JPA NoResultException

Hi,

Today I looked for NoResultException, wondered when it may occurs, found that,

If you search record with getSingleResult, NoResultException is thrown, because, as written at stackoverflow,

"If getSingleResult() would return null, you could not tell whether the query did not match any row or whether the query matched a row but the selected column contains null as its value"

Otherwise, if you search with query, the return object will be null(or if you cast result to List, it will be empty), so you should deal with null or empty list in this situation.

Link: http://stackoverflow.com/questions/1579560/why-in-jpa-entitymanager-queries-throw-noresultexception-but-find-does-not

Have a nice day !