Running user entered code


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Thread: Running user entered code

  1. #1
    Join Date
    Mar 2006
    Posts
    16

    Running user entered code

    I have an application that allows the user to place boxes of text on a page with special placeholders and then output a pdf where the placeholders are replaced but values from a database. Example: "My name is %NAME%" when composed results in "My name is Bob". Now I need a way to allow the user to enter some form of simple code to create a conditional statement which will be parsed when the document is composed. Example: if (%NAME% == "Joe") { return "Bob" } I have no idea how to even begin to approach this. Does anyone know of a way to turn a user entered string of text into actual Java code that the application will run?

  2. #2
    Join Date
    Feb 2006
    Location
    Cologne - Germany
    Posts
    271
    there are several possibilities.
    one elegant version is using a compiler of Java code at run-time, like http://www.janino.net, which also supports expression evaluation.
    another elegant approach would be to include a scripting language, like the ones listed at http://pnuts.org/~tomatsu/embedding.html.
    the third elegant approach is writing your own little scripting language with jflex, jcup or antlr. but this will assume knowledge on building languages and compilers.

  3. #3
    Join Date
    Mar 2005
    Location
    UK, London
    Posts
    150
    graviton is right, we will need to look into making a compiler, and you need to be able to detect syntax errors. I cant say that this is easy.

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