[resolved] The correct way to assign the value of context variables in Java

[Anonymous]

Hi there,
I can't see anywhere in the documentation here in any of the 4.4.x pages where it covers setting context variables from java code.
https://help.talend.com/search/all?query=Using+contexts+and+variables&content-lang=en
I have read it on this forum being said that setting context variables using tJava/tJavaRow using the following syntax is only temporary:

context.TestVar = "Test Value";

" The location context.<var_name> is not permanent and it just holds the value for you to access it easily."
And that you should instead use the following syntax to assign values to context variables from java:

context.setProperty("TestVar ", "Test Value");

I have also read other posts like this one:
https://community.talend.com/t5/Design-and-Development/set-variable-in-context-with-tJava-fails-when...
Saying:
" ...context values are stored in more than one place and tContextDump picks up only those values defined when the job begins so if you set context values dynamically using tJava you need to follow with the following statement so that tContextDump will use the new values:"

context.synchronizeContext();

I can't see this topic discussed anywhere in the Talend documentation.
context.setProperty is a pain to use because it only accepts strings.  So if you want to assigned values to context variables of any other type from tJava or tJavaRow you need to convert them.  Especially painful for dates.
So can we please get an official word from Talend on this?  (or anyone that can point out some documentation that gives a clear answer to the following questions)
QUESTION 1:
Has there been some confusion here in the developer community due to the undocumented need to call  context.synchronizeContext() to get updated context variable values to show in tContextDump that has made people thing that the use of context.setProperty is needed for the assignment of context variables and that values set in java are not permanent?

Excluding the obvious nature of tJavaRow (eg; variables assigned in tJavaRow get overwritten for every iteration), is there an issue with just using:

context.TestDateVar = TalendDate.getCurrentDate();

to assign a variable?

QUESTION 2:
Is there a difference between using:

context.TestVar = "Test Value";

and

context.setProperty("TestVar ", "Test Value");

in regard to the scope and  permanency of the value assigned?

QUESTION 3:
If you are not using tContextDump but only using updated context variable values in other components, do you need to use  context.synchronizeContext(); to ensure these values will be available, or is this only needed for tContextDump?
-------------------------------------------------
For what it's worth, the Talend Open Studio Cookbook has a page on: "Setting the context and globalMap variables
using tJava".  In their examples they set the value of context variables using the following:

context.testValue ="testValue is now initialized";

And make no mention of an issue with scope or  permanency of the value assigned.
https://www.packtpub.com/big-data-and-business-intelligence/talend-open-studio-cookbook
Thank you for your time,
Scott

[Anonymous]

OK, I have recreated the issue and demonstrated it in the attached Job. You will need Talend v6.0 or higher to test this. I am using the ESB version, but it shouldn't stop you from loading this DI Job. A link to the file is here.
Basically I have some context variables set inside the Job (Check the contexts tab to see the values). The first thing I do is change the values. Two of them using the "context.new1 = " method and one using the "context.setProperty(" method. I then dump them to a parameter file. If you check the parameter file you will see that only the context variable that has been set using the "context.setProperty(" method has been changed in time to be sent to the file.

[Anonymous]

rhall,
Thanks for putting in the effort to do this mate.  Unfortunately I am running Jaspersoft ETL Express (Talend 5.6).
Can you post a screen shot of the job and maybe I can recreate it.
Regards,
Scott

[Anonymous]

This will look a little different to what you have (UI update), but you should be able to extrapolate....
Context Tab

Code in tJava

Layout

Edit: Oops, the images didn't upload properly first time. 
I have created a Jira for this: https://jira.talendforge.org/browse/TDI-34112

[Anonymous]

rhall,
Ok great I see what you mean now mate.  So to make this work you just need to put:

context.synchronizeContext();

after you set the variables in the tJava, and you should then get all the updated values.
So it may not be a bug, just poor documentation...
Regards,
Scott

[Anonymous]

The overhead of using synchronizeContext() every time you change a context variable if you have many variables (some of my jobs have almost 50), will be quite high. Particularly if you make a change for every row and you are processing millions of rows. Since synchronizeContext actually performs a "context.setProperty(" on all context variables that are not null, it arguably makes sense to use the setProperty method. 
Since you are not supposed to have to be a Java expert in order to use Talend, I believe that this is a bug. Thanks for bringing this up. I just coded around it without thinking about it in the past.

[Anonymous]

rhall,
Yes  mate you make some really good points there and I am inclined to agree with you.
Let's hope the team get onto this one and get it sorted for us.
Thanks again for your effort in this discussion mate  😉
Regards,
Scott

[Anonymous]

I have another doubt.. How to apply "ALL in One" property in tWriteJSONField.. I know about tXMLMap but I want to perform this property with tWriteJSONField.. so please explain with example. I am beginner in Talend

[Anonymous]

Hi  amolkhandekar92
Before tWriteJSONField,add a new column and set a fixed value such as 1 to it, this column will be group element on tWriteJSONField.

Shong

[Anonymous]

My findings

context.setProperty("mailFileName", "rejected.xlsx");
context.filePath="talend_files_0.1/out/";

//access variable set using setProperty method with getProperty
System.out.println("method1="+context.getProperty("mailFileName"));
System.out.println("method2="+context.filePath);
System.out.println("method3="+context.getProperty("filePath"));
System.out.println("method4="+context.mailFileName);

// after synchronization it outputs right values set without setPropperty and accessed with getProperty. But it //wipes out value set with setProperty after synchronization.
context.synchronizeContext();

System.out.println("method5="+context.getProperty("mailFileName"));
System.out.println("method6="+context.filePath);
System.out.println("method7="+context.getProperty("filePath"));

output

------

method1=rejected.xlsx
method2=talend_files_0.1/out/
method3=
method4=
method5=
method6=talend_files_0.1/out/
method7=talend_files_0.1/out/
method8=

From above scenario i understand that Synchronization sets the values of variables to the latest change made using methos

context.<variable> = value

[Anonymous]

How do I include the value of contexts in tjavarow?

For Example:

This is my job tFileInputDelimited==Main==>tjavarow==main==>tFileOutputJSON

I'm trying to convert a normal text file into a JSON file, this is my text input:

Document,Files (Header)
doc_1, 2 (values)

And my output should be like this:

[{"Document":"doc_1 20180914","Files":1}]

So, My issue is when I try to include the date value through context it projects me a null value like this:

[{"Document":"doc_1 null","Files":1}]

This is the code I'm following in tjavarow to implement it:

output_row.Document = input_row.Document+" "+context.date;
output_row.Files = Integer.parseInt(input_row.Files);

Can Anyone help me with this?