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Tuesday, June 16, 2009

Abstract Syntax Tree

Summary

The Abstract Syntax Tree is the base framework for many powerful tools of the Eclipse IDE, including refactoring, Quick Fix and Quick Assist. The Abstract Syntax Tree maps plain Java source code in a tree form. This tree is more convenient and reliable to analyse and modify programmatically than text-based source. This article shows how you can use the Abstract Syntax Tree for your own applications.

By Thomas Kuhn, Eye Media GmbH
Olivier Thomann, IBM Ottawa Lab

Complete Article
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6 comments:

  1. sagarJuly 24, 2011 at 6:52 PM

    Hi Deepak,
    How can i change an Abstract syntax tree of simple java source code and reprint the modified java source code.? Kindly help me.

    ReplyDelete
  2. DeepakJuly 24, 2011 at 7:58 PM

    @Sagar: The article gives the complete details, are you stuck at a particular point ?

    ReplyDelete
  3. sagarAugust 6, 2011 at 8:24 PM

    Hey Hi deepak.
    Thanks for reply. as per the article, I can create abstract syntax tree (ast) for a java source file, and modify ast. But, the reflecting the changes back to the original source code file is not working.
    Kindly refer "Write it down" section of article . It says to declare:
    ITextFileBufferManager bufferManager = FileBuffers.getTextFileBufferManager();
    // get the buffer manager

    But I am getting following Exception at this line.

    Exception in thread "main" java.lang.ExceptionInInitializerError
    at ASTModifier.main(ASTModifier.java:205)
    Caused by: java.lang.IllegalStateException: Workspace is closed.
    at org.eclipse.core.resources.ResourcesPlugin.getWorkspace(ResourcesPlugin.java:340)
    at org.eclipse.core.filebuffers.FileBuffers.(FileBuffers.java:52)
    ... 1 more


    What can be this error? everything else works fine. But for making the changes of ast reflected back to the original source file is not working?
    Kindly help
    thanks

    regards
    sagar

    ReplyDelete
  4. sagarAugust 7, 2011 at 7:32 AM

    Hi deepak, In continuation of the previous problem, I have got a link :
    http://www.programcreek.com/2011/05/java-lang-illegalstateexception-workspace-is-closed/#comment-1939

    It says that: " In brief, this is caused by simply adding dependent jar files to regular java project.

    To use JDT, you need to have the program running as a plug-in (or at least, an OSGi-enabled application) rather than using it as a jar. "

    So, doest it mean I have to create a plug in project , instead of simple java project for using FileBuffers.getTextFileBufferManager() method? But article doesnt point out this issue

    waiting for reply.
    Thanks

    ReplyDelete
  5. DeepakAugust 7, 2011 at 7:45 AM

    Yup, all JDT apis can be used easily from a plug-in. If you have a simple java project, you can use some apis but not all and have to jump through more hoops.

    While the article does not say that use a plug-in, the example project is a plug-in.

    ReplyDelete
  6. sagarAugust 10, 2011 at 10:00 PM

    Alright.thanks deepak. I have come across another issue. I want to insert code inside a method's body using JDT.
    Ex:
    String code= " a = a -1;
    val = false;
    return a; "

    Now , above code string, I want to insert into a method's body.
    for ex: Method b4 inserting is

    public int decrement(int a){

    }

    and method after inserting should be:

    public int decrement(int a){
    a = a -1;
    val = false;
    return a; "
    }
    ----------------
    How this can be done? I am able to find out a particular method, code string is also ready.
    Is there any way I can create block of statements and directly add to a method body?
    or do I have to create individually 3 expressions (for above case) and then add it individually to the method?

    Kindly help
    Thanks

    regards
    sagar

    ReplyDelete