Java Implementation of "Classical" Flow-Based Programming (FBP)
General web site on Flow-Based Programming: https://jpaulm.github.io/fbp/ .
Latest release is
v4.1.9. The jar file -
javafbp-4.1.9.jar - can be obtained from the Releases folder, from
build/libs, or from Maven. Note: The Maven 'shield' below will show the new release for a little while before it actually becomes available. After clicking on the Maven shield below, select
This implementation is a kit for building JavaFBP projects. For a number of sample networks, go to https://github.com/jpaulm/javafbp/tree/master/src/main/java/com/jpaulmorrison/fbp/resourcekit/examples .
For your own projects, include the JavaFBP jar file in the Build Path property for the project.
General web site for "classical" FBP:
In computer programming, flow-based programming (FBP) is a programming paradigm that defines applications as networks of "black box" processes, which exchange data across predefined connections by message passing, where the connections are specified externally to the processes. These black box processes can be reconnected endlessly to form different applications without having to be changed internally. FBP is thus naturally component-oriented.
FBP is a particular form of dataflow programming based on bounded buffers, information packets with defined lifetimes, named ports, and separate definition of connections.
JavaFBP Syntax and Component API:
An automatically generated Javadoc can also be browsed at http://jpaulm.github.io/javafbp/ . Unfortunately this isn't very useful for someone planning to use JavaFBP components, so we have built an FBP-specific Component Attributes List, which can be displayed by clicking on http://htmlpreview.github.io/?https://github.com/jpaulm/javafbp/blob/master/compList.html - see below.
Two components are available for reading and writing MySQL tables, respectively:
core.components.jdbc. These dynamically load the most recent MySQL jar file, and use reflection to execute SQL services.
If you get a message saying "No suitable driver found", try restarting the MySQL service in
There is also a small GitHub project called
javafbp-websockets, which contains two generalized components supporting WebSockets ( https://developer.mozilla.org/en-US/docs/Web/API/WebSockets_API ), and a simple test component and network - it can be found at https://github.com/jpaulm/javafbp-websockets .
Running a network
Default connection size
JavaFBP recommends using a small connection size for debugging, and a larger one for production. In the latest version of JavaFBP, this is specified in the
<user>.JavaFBPProperties.xml file - tag.
Running on DOS
You will have downloaded the JavaFBP jar file earlier, so do a
gradle build for your project, to make sure the compiled classes (
.class files) are in the 'bin' directory.
Now position the current directory to your own project, using
cd, and enter the following into the DOS window:
java -cp "<JavaFBP directory>/javafbp-x.y.z.jar;." <program class name>
x.y.z is the version of the JavaFBP jar file. Note the final ;.... or you can place .; in front of the jar file name.
Program class name must be the fully qualified network name.
You must also make sure that
java can find any class files that yor main line needs, by specifying the nwecssary jar files, and class directories using the
Here is a test command you can run, using networks and components provided by the JavaFBP project:
cd command to your downloaded JavaFBP project, then enter
java -cp .;build/libs/javafbp-x.y.z.jar com.jpaulmorrison.fbp.resourcekit.examples.networks.Copy1
For your own project, you will probably have to add more directories to the
classpath parameter - remember to provide the whole directory name.
Running on *nix
Replace the ';' in the
-cp parameter with ":" for *nix.
Running in Eclipse
Properties/Java Build Path for your project; click on
Add External Jars, add your JavaFBP jar file to the list, and then hit
Debug for your project.
Checking your setup
Here is a simple command-line test that can be run to test that everything is working.
Position to the
javafbp directory; then enter
java -cp "build/libs/javafbp-x.y.z.jar;." com.jpaulmorrison.fbp.resourcekit.examples.networks.MergeandSort
x.y.z is the current version number of JavaFBP.
Here is a picture of MergeandSort, drawn using DrawFBP:
This network contains 4 processes:
- 2 occurrences of GenerateTestData,
- a Sort process - a very simple-minded Sort, which can only handle up to 9,999 information packets
- a text display component, which invokes Java Swing to display the sorted data in a scroll pane.
The outputs of the two GenerateTestData processes are merged on a "first come, first served" basis. During the run you should see a scroll pane with the sorted data scrolling down.
At the end of the run, you should see:
Run complete. Time: x.xxx seconds Counts: C: 150, D: 153, S: 300, R (non-null): 304, DO: 0
where the counts are respectively: creates, normal drops, sends, non-null receives, and drops done by "drop oldest".
Care must be taken if combining
LoadBalance (with substreams) and
SubstreamSensitiveMerge in a divergent-convergent pattern - this pattern is one of the warning signals for deadlocks anyway. The problem is described in more detail under https://github.com/jpaulm/javafbp/issues/8.
Tracing and other options
To trace JavaFBP services and/or lock usage, set the appropriate parameter(s) in
JavaFBPProperties.xml in the user directory to
<?xml version="1.0"?> <properties> <tracing>true</tracing> <tracelocks>false</tracelocks> <defaultcapacity>...</defaultcapacity> (as of v4.1.3) </properties>
These traces will appear in the project directory (in GitHub if running Eclipse) under the name
xxxx is the name of the network being run. Subnets have their own trace output files.
defaultcapacity are as follows:
- PRODUCTION (currently 10)
- DEBUG (currently 1)
- any number
defaultcapacitynot specified - defaults to DEBUG value
Two other options are also supported in the properties file:
deadlocktest(defaults to true, so you might set it to
forceconsole(used if immediate console output is required during debugging - normally, console output is sent to a file)