Scripting language for "end user" in a Java app

Question

We have a Java application and we want to provide the ability for end users to write 'business rules'. These rules will be evaluated when entities are created, updated or deleted.

I am looking for a language to write these business rules. Considerations are:

Configurable security - end user should not be able to call things like new File("some secret file") or call an internal API
Easy to read and understand
Easy to manipulate lists and maps
Ability to provide a syntax checker

Any suggestions?

@Dev: -rw-r--r-- 1 root root 2168 2011-04-13 04:43 /etc/passwd is readable whole world, and has to be, to allow login. — user unknown
– user unknown, Commented Mar 18, 2012 at 5:22

Aravind Yarram · Accepted Answer · 2012-03-18 03:37:08Z

2

Use either a business rules engine (like Drools) or build your own vocabulary or DSL using Groovy or xText.

answered Mar 18, 2012 at 3:37

Aravind Yarram

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Mikko Ohtamaa · Accepted Answer · 2012-03-18 06:06:17Z

1

Python can be made quite English readable and is available to Java as Jython package. List syntaxes in Python are very flexible and it has much syntatic suger for use cases like this. Jython is well established project and already used in business application scripting.

http://www.jython.org/

Sandboxing can be provided on Java level using JVM internal security manager mechanisms. This is what Java applets use.

Python has a syntax checker called pylint.

answered Mar 18, 2012 at 6:06

Mikko Ohtamaa

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adammtlx · Accepted Answer · 2012-03-18 03:42:20Z

0

You could also try ANTLR. It's a little more complicated, but there's a lot of flexibility.

answered Mar 18, 2012 at 3:42

adammtlx

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wks · Accepted Answer · 2012-03-18 09:35:49Z

0

You can also base your DSL on XML, JSON, YAML or even LISP's s-exp.

Some examples:

Using YAML:

- action:  reject
  pattern: http://www\.example\.com/.+
- action:  allow
  pattern: http://www\.example\.net/.+

Another YAML example:

- xpath-select: /a[1]/b/c[@p1=v1]/d
  as: x
- xpath-select: /e/f/g
  as: y
- yield: "${x}+${y}"

Using XML:

<select value="*" from="mytable">
    <criteria property="name" op="eq" value="foo" />
    <criteria property="age" op="ge" value="18" />
</select>

XML, JSON, YAML are data formats. You have to interprete these data by yourself, but it prevents arbitrary objects to be created. Using a well-known data format also relieves you from having to write your own parsers. There are existing parsers available in Java.

edited Mar 18, 2012 at 9:35

answered Mar 18, 2012 at 6:23

wks

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