The SAP Java Connector (JCo) has quickly become very popular and deservedly
so. Check out my article in the previous issue of this publication if
you want a product overview. In the meantime, JCo 1.1 has been
released (you can download it from http://service.sap.com/connectors).
In this article I would like to introduce you to the most important new
features in version 1.1.
In JCo 1.0(, the two DLLs jRFC11.dll and jRFC12.dll needed to reside
in the WINNT\SYSTEM32 directory. In JCo 1.1, those DLLs must be in the
same directory as the jCO.jar file itself. This will allow you
to have multiple versions of JCo installed on the same system in the future.
The first release of JCo ran on 32-bit Windows only. Since
more and more (web) server applications are deployed on Unix machines,
many customers contacted SAP about
support for Unix. In response to these requests, JCo 1.1 now is also available
for Linux, Solaris, AIX, and HP-UX.
Queued Remote Function Call (qRFC)
qRFC is relatively new in SAP, but it can be added to older SAP releases
by applying a hot package. qRFC is basically
an extension of transactional RFC (tRFC), and offers the following main
- Within a queue, items are guaranteed to be processed in
the specified order (serialization). This is true even if multiple processes
are writing to a queue. With plain tRFC, we
would not know the sequence in which the individual
calls would be processed.
- System administrators have full control over the queues, being able
to specify when a queue should be activated.
This allows processing of not-so-urgent input to be
postponed until off-peak hours.
JCo 1.0( already supported outbound qRFC
(since there is no difference between tRFC and qRFC on the server side),
i.e., you could write a server program that accepted qRFC messages from
SAP. Now, in 1.1, inbound qRFC can be used as well. JCo offers the following,
extended version of the execute() method:
public void execute(JCO.Function function,
The tid parameter needs to be
set to the Transaction ID (usually a GUID acquired via the createTID()
method of the JCO.Client class1). The queue_name parameter
is set to whatever queue name you have selected (or have been told to
use). Here is some sample code for a qRFC inbound call:
JCO.Function function =
JCO.Table table =
table.setValue("Some test data", "LINE");
String tid = mConnection.createTID();
mConnection.execute(function, tid, "WBK");
By the way: in most cases, you should consider
qRFC instead of tRFC in your applications. Refer to SAP's documentation
for more details on qRFC.
When debugging an application, it is often advantageous to be able to
quickly check the parameters being passed to and from SAP. JCo offers
method writeHTML() to create an HTML file based on an object
of type JCO.Function, JCO.ParameterList, JCO.Structure, or JCO.Table.
In JCo 1.0(, only the first 100 rows (and the last row)
of a table would be included, which saved space (and prevented the browser
from aborting due to a very large HTML file), but did not allow you to
view all data. JCo 1.1 comes with a new global property,
jco.html.table_max_rows, that can be used to control the maximum
number of rows put into the HTML file. Here is some sample code:
JCO.Function function =
JCO.Table codes =
String oldMaxRows =
Our code is polite enough to store the old
the property before changing it. Then, after the call to writeHTML(),
we restore the old value so that other users are not affected more than
necessary (remember: the property is global within the Java Virtual Machine!).
Figure 1 shows a screen shot of the beginning of the HTML page.
||A Table Parameter Displayed in an HTML Page
XML Output and Input
In JCo 1.1, you can now create an XML representation of an object
of type JCO.ParameterList, JCO.Structure, or JCO.Table
by using method toXML(). Also, you can load data into a variable
from an XML string by using method fromXML(). Here are the method
void fromXML(java.lang.String data)
java.lang.String toXML(int index)
java.lang.String toXML(java.lang.String field_name)
The following source code snippet demonstrates the toXML() method:
JCO.Structure returnStructure =
String xml = returnStructure.toXML();
Figure 2 shows you the XML string for the Return
parameter of a successful BAPI call.
||An XML String Representing the Return Parameter
Auto-Reset of Pooled Connections
There are two flavors of getClient(), the method used
to retrieve a connection from a connection pool. Compare the following
two lines of sample code:
The second parameter of the second flavor
of getClient() specifies whether the connection should be reset
(equivalent to "/n" in SAPGUI). The first flavor uses a default
of false. This is dangerous, since it assumes that all client
programs using the pool are totally stateless.
JCO.Client mConnection = JCO.getClient("ARASOFT")
JCO.Client mConnection = JCO.getClient("ARASOFT". true);
The only reason for the existence of the
second parameter is that 3.1 does not support connection resetting via
RFC. It was very easy to use this parameter incorrectly, though, and if
you are running 4.0 or later you should definitely always use true (and
hence never the first flavor of getClient()!).
1.1 now automatically resets the connection (when it is returned
to the pool) if you are connected to a 4.0 or later SAP system. This makes
life easier for the application programmer using those versions of SAP.
Only if you are still running R/3 3.1 do you still have to choose between
speed (no reset of the connection, but everything needs to be stateless)
and integrity (since 3.1 does not support reset, the connection is closed
and re-opened when you set the second parameter to true).
There are some additional enhancements, like support for complex data
types (required if you want to interface with CRM), a new ServerErrorListener
interface to build more stable server components, etc.
For a complete list of all these enhancements,
refer to the Release Notes of JCo 1.1, included in the
G. Schuessler is the founder of ARAsoft (www.arasoft.de),
a company offering products, consulting, custom development, and training
to a worldwide base of customers. The company specializes in integration
between SAP and non-SAP components and applications. ARAsoft offers various
products for BAPI-enabled programs on the Windows and Java platforms.
These products facilitate the development of desktop and Internet applications
that communicate with R/3. Thomas is the author of SAP's CA925 "Developing
BAPI-enabled Web Applications with Visual Basic" and CA926 "Developing
BAPI-enabled Web Applications with Java" classes, which he teaches in
Germany and in English-speaking countries. Thomas is a regularly featured
speaker at SAP TechEd and SAPPHIRE conferences. Prior to founding ARAsoft
in 1993, he worked with SAP AG and SAP America for seven years. Thomas
can be contacted at email@example.com
or at firstname.lastname@example.org.
SAP has decided to spell "JCo" with a lower-case "o", but in Java source
code you need to use "JCO" since Java is case-sensitive, hence the mixed
spelling in this article.