B4J Question How to create b4j library?

Discussion in 'B4J Questions' started by Shay, Jan 28, 2015.

  1. Shay

    Shay Well-Known Member Licensed User

    How to create b4j library? I didn't see any tutorial for this
    Also which one is the easiest to create b4i, b4a, b4j? (if I never did it before)
  2. Erel

    Erel Administrator Staff Member Licensed User

    It is the same as B4A libraries.

    It is easier to create B4A / B4J libraries.
  3. rwblinn

    rwblinn Well-Known Member Licensed User


    see also here under Libraries > Create B4J Libary
    Erel and ellpopeb4a like this.
  4. Shay

    Shay Well-Known Member Licensed User

    This is nice website
    but I still don't understand how do I take existing Java code (for example I took the jsch library)
    and make it b4J library
    I assume I need to create wrapper, but I have no idea how to do it (I cannot see any tutorial for it)
  5. rwblinn

    rwblinn Well-Known Member Licensed User

    Hi Shay,

    either you wrap the jSch Library or you use JavaObject to access.
    Example lexecuting command 'ls' tested on Raspberry Pi and TinkerForge RED Brick Host.
    YES, its is bit of JavaObject juggle, but works fine - soon InLine Java will come, which makes these kind of code easier :)
    'Example executing ls command on remote host using jSch
    'Ensure     #AdditionalJar: jsch-0.1.51
    Sub ExecuteRemoteCommand
    Dim hostcmd As String = "ls"
    Dim user As String = "<USERNAME>"
    Dim host As String = "<HOST ADDRESS>"
    Dim port As Int = 22
    Dim pw As String = "<PASSWORD>"
    Dim joSch As JavaObject
    'Java: JSch js = new JSch();
    'Java: Session s = js.getSession("myusername", "myremotemachine.mycompany.com", 22);
        Dim joS As JavaObject
        joS = joSch.RunMethod(
    "getSession"Array(user, host, port))
    'Java: s.setPassword("mypassword");
    'Java: Properties config = new Properties();
        Dim joP As JavaObject
        joP = joP.InitializeNewInstance(
    'Java: config.put("StrictHostKeyChecking", "no");
    'Java: s.setConfig(config);
    'Java: s.connect();
    Log("Connected to Host...")
    Log("Invoking Command..." & hostcmd )
    'Java: Channel c = s.openChannel("exec");
        Dim joC As JavaObject = joS.RunMethod("openChannel"Array("exec"))
    "setCommand"Array(hostcmd ))
    'Java: joC.RunMethod("setCommand", Array("ls -l"))
        Log("Invoking Command...Connect")
    Dim joISR As JavaObject
    'Java: BufferedReader reader = new BufferedReader(new InputStreamReader(cE.getInputStream()));
    Dim joBR As JavaObject
    'Java: joBR.RunMethod("readLine", Null)
        Log("Result Command " & hostcmd )
    Dim s As String
    Do While s.Contains("null") = False
            s = joBR.RunMethod(
    If s <> "null" Then Log(s)   
    End Sub
    jmon and B4JExplorer like this.
  6. Shay

    Shay Well-Known Member Licensed User

    Thanks, but some newbie video tutorial is needed for taking any library in java and transfer it to b4j / b4a is needed.
    Also I think the most limiting issue B4X has is the libraries, since if I knew how to write in java, I probably have used standard android/java coding and not b4x

    so I think some "generic" tool is needed for converting any java/android library is needed here, I even willing to pay (which I did in the past) to someone for getting library conversion(but this need to be reasonable price)
  7. giga

    giga Well-Known Member Licensed User

    Is there one in particular you are looking for? I have used SLC in the past which works well.
  8. Erel

    Erel Administrator Staff Member Licensed User

    There is no magic. Creating or wrapping a complex library requires you to understand Java.
  9. Shay

    Shay Well-Known Member Licensed User

    I know, I am just saying, this magic feature (as you did in b4A, and b4I) will take you to the next level ;-)
    but in the meanwhile, can you post some video tutorial on how to do it for someone with basic java skills
    from A to Z (taking existing java library and make it b4a/b4j library)
  10. Erel

    Erel Administrator Staff Member Licensed User

  11. B4JExplorer

    B4JExplorer Active Member Licensed User

    One of the confusions that I originally had about generating a B4J-compatible library, is that the reference to 'coding', meant that we needed the source code, and had to modify that with annotations, in order to make it work. But it's clear now, that we just have to write wrappers for the classes in the jar.


    "soon InLine Java will come, which makes these kind of code easier"

    You mean, in the context of B4A/J? We will be able to insert java snippets inside a B4J module? Sorry, I haven't been reading through all the announcements.

    Thanks for the jsch examples, rwblinn. Having a problem with one of the wrappers for this, and am starting to enjoy using the JavaObject library, more & more.
  12. rwblinn

    rwblinn Well-Known Member Licensed User


    as a followup using InLine Java, find the previous example converted using B4J 2.80. Tested again under Raspian and Debian.
    Pretty simple to use and a really cool feature of B4A / B4J.
    Note that the returned Java List is straight used as a B4J List.

    Sub Process_Globals
    Public NativeMe As JavaObject

    Sub AppStart (Form1 As Form, Args() As String)
      MainForm = Form1
      NativeMe = Me
    Dim l As List = NativeMe.RunMethod("jschexeccmd"Array("username""hostaddress""password""hostcommand"))
    Log("Result (Lines:" & l.Size & ")")
    For i = 0 To l.Size - 1
    End Sub

    #If JAVA
    import java.util.*;
    import java.io.*;
    import com.jcraft.jsch.*;

    public static List<Object> jschexeccmd(String user, String host, String pw, String cmd) {
        List<Object> listJava = new ArrayList<Object>();
            JSch js = new JSch();
            Session s = js.getSession(user, host, 22);
            Properties config = new Properties();
            config.put("StrictHostKeyChecking", "no");
            Channel c = s.openChannel("exec");
            ChannelExec ce = (ChannelExec) c;
            BufferedReader reader = new BufferedReader(new InputStreamReader(ce.getInputStream()));
            String line;
            while ((line = reader.readLine()) != null) {
        catch(Exception e){
        return listJava;
    #End If
    Erel, B4JExplorer and inakigarm like this.
  13. B4JExplorer

    B4JExplorer Active Member Licensed User

    Whooooa! This is completely unexpected. I badly need inline code, it'll save tons of Java - B4x translation time. (Also, thanks for the sample above rwblinn, that will also save time trying to figure out how to use it, inside B4J).

    Also, just noticed in the announcements, that they have a Groovy-style String feature, in the beta.

    I feel like a real nerd, but this is actually exciting.

    So as of last year, they made Web Development much easier, than any other language out there. Now they are shutting down any remaining inconveniences, when working with external Jars.

    Thank You to the developers. What a great gift, for a new year.
    Erel, inakigarm and stevel05 like this.
  14. Kevin Golding

    Kevin Golding Member Licensed User


    I'm trying to find the jsch library (file:jsch-0.1.51.jar) with no success. Any chance of a link to it please?


  15. rwblinn

    rwblinn Well-Known Member Licensed User

    Go Reference jSch .The latest jar here (0.1.53).
    DonManfred and Kevin Golding like this.
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