looks good, looking forward for an updated pull request - Tushar.
On Fri, Jan 15, 2016 at 12:03 PM, Timothy Farkas <[email protected]> wrote: > +1 looks good to me. > > Thanks, > Tim > > On Thu, Jan 14, 2016 at 10:06 AM, Chinmay Kolhatkar < > [email protected] > > wrote: > > > Considering Tim's suggestiom, I'm thinking about modifying the interface > in > > following way: > > > > So there will be 3 interfaces: > > > > public interface Expression<O> > > { > > O execute(Object... obj); > > } > > > > public interface ExpressionEvaluator > > { > > <O> ExpressionEvaluator.Expression<O> createExecutableFunction(String > > expression, Class<?> returnType); > > > > <O> ExpressionEvaluator.Expression<O> createExecutableExpression(String > > expression, Class<?> returnType); > > > > void setExpressionParser(ExpressionParser parser); > > } > > > > public interface ExpressionParser > > { > > String convertToCompilableExpression(String expression, Class<?> > > returnType, boolean containsReturnStatement); > > } > > > > Description of interfaces: > > 1. Expression interface is the final output which will have executable > code > > of expression. > > 2. ExpressionEvaluator interface will be implemented for specific type if > > implementation. For eg. In this case the concrete implementation will be > > JavaExpressionEvaluator which will evaluate quasi-Java expression > > 3. ExpressionParser interface will defined how expression need to be > parsed > > and can be plugin to ExpressionEvaluator interface via > setExpressionParser > > method. > > > > This way, > > 1. One can override parsing logic for specific evaluator. > > 2. Override the expression evaluation logic all together. > > 3. Sticking to a common interface of ExpressionEvaluator & Expression > will > > make the user code not to change even if parser or evaluator changes. > > > > Thoughts? > > > > Thanks, > > Chinmay. > > > > On Thu, Jan 14, 2016 at 2:17 PM, Chinmay Kolhatkar < > > [email protected]> > > wrote: > > > > > I think think is doable. > > > I'll take a look. > > > > > > Thanks, > > > Chinmay. > > > > > > On Thu, Jan 14, 2016 at 1:59 PM, Timothy Farkas <[email protected]> > > > wrote: > > > > > >> Haven't gone though you're PR, so I'm not sure how this would fit in. > > But > > >> I > > >> think introducing an interface like below, and allowing it to be set > may > > >> be > > >> sufficient. > > >> > > >> public interface ExpressionParser > > >> { > > >> public String convertToJavaExpression(String expression); > > >> } > > >> > > >> Thanks, > > >> Tim > > >> > > >> On Thu, Jan 14, 2016 at 12:19 AM, Chinmay Kolhatkar < > > >> [email protected] > > >> > wrote: > > >> > > >> > Ah got it. That's a good point. Maybe its good to separate the > parsing > > >> and > > >> > compilation part of the evaluation. > > >> > And let one override the parsing logic. > > >> > > > >> > I'll see how to incorporate that, but if you have idea about > achieving > > >> it, > > >> > please share it. > > >> > > > >> > Thanks, > > >> > Chinmay. > > >> > > > >> > > > >> > On Thu, Jan 14, 2016 at 1:43 PM, Timothy Farkas < > [email protected]> > > >> > wrote: > > >> > > > >> > > Hey Chinmay, > > >> > > > > >> > > It is possible the user may want to define a syntax radically > > >> different > > >> > > from Java style syntax. I've proposed a syntax similar to yours to > > >> one of > > >> > > our users for expression evaluation but they didn't like it > because > > >> the > > >> > > syntax needs to be something easily validated by a UI. It may be > > >> possible > > >> > > that the user wants expressions to be sent to an operator as json, > > >> > because > > >> > > that is easy to parse and validate in javascript: > > >> > > > > >> > > {"param":"myField1","operation":">","threshold":"1"} > > >> > > > > >> > > If the syntax is pluggable then an implementation of this syntax > > >> could be > > >> > > swapped with with an implementation of the syntax you've already > > >> provided > > >> > > without changing operator code. > > >> > > > > >> > > Thanks, > > >> > > Tim > > >> > > > > >> > > On Wed, Jan 13, 2016 at 11:34 PM, Chinmay Kolhatkar < > > >> > > [email protected] > > >> > > > wrote: > > >> > > > > >> > > > Hi tim, > > >> > > > > > >> > > > I agree with you. The expression here we're talking about is > > really > > >> a > > >> > > > quasi-Java expression. One can do anything which java does. > > >> > > > Only change with java syntax here is how variables are accessed. > > >> > > > > > >> > > > They're by default accessed as ${...}. > > >> > > > > > >> > > > But this is also made configurable via a setter property on > > >> > > > ExpressionEvaluator. The pull request has it. > > >> > > > > > >> > > > If this is what you're talking about then this is taken care of. > > >> > > > > > >> > > > Thanks, > > >> > > > Chinmay. > > >> > > > > > >> > > > > > >> > > > On Thu, Jan 14, 2016 at 1:00 PM, Timothy Farkas < > > >> [email protected]> > > >> > > > wrote: > > >> > > > > > >> > > > > Hi Chinmay, > > >> > > > > > > >> > > > > I think this is a very good first implementation. My only > > concern > > >> is > > >> > > that > > >> > > > > people will get caught up in the details of the syntax for > this > > >> > > > expression > > >> > > > > language. I think a way to avoid that is to make the syntax > > >> > pluggable. > > >> > > > For > > >> > > > > example is there an interface for expression evaluation which > > can > > >> be > > >> > > > > implemented by different syntaxes? This would allow operators > > >> which > > >> > use > > >> > > > > expression evaluation to have the syntax configured via a > > >> property. > > >> > > That > > >> > > > > way if someone discovers a limitation in the syntax down the > > >> line, a > > >> > > new > > >> > > > > syntax can be introduced without breaking backwards > > compatibility > > >> and > > >> > > > > without requiring operator code to be changed. > > >> > > > > > > >> > > > > Thanks, > > >> > > > > Tim > > >> > > > > > > >> > > > > On Wed, Jan 13, 2016 at 10:52 PM, Chinmay Kolhatkar < > > >> > > > > [email protected] > > >> > > > > > wrote: > > >> > > > > > > >> > > > > > Hi All, > > >> > > > > > > > >> > > > > > I'm working on APEXCORE-1972 which adds support for a > > quasi-Java > > >> > > > > Expression > > >> > > > > > Language and its expression evaluator. > > >> > > > > > > > >> > > > > > All the detailed functionality and design details along with > > >> > examples > > >> > > > are > > >> > > > > > present in Jira. > > >> > > > > > > > >> > > > > > I've summarized the ExpressionEvaluator feature & Expression > > >> > language > > >> > > > > > below. > > >> > > > > > > > >> > > > > > The pull request created for this at here: > > >> > > > > > https://github.com/apache/incubator-apex-malhar/pull/170 > > >> > > > > > > > >> > > > > > Please share your thought on this. > > >> > > > > > > > >> > > > > > Thanks, > > >> > > > > > Chinmay. > > >> > > > > > > > >> > > > > > > > >> > > > > > *Summary of functionality of ExpressionEvaluator:* > > >> > > > > > > > >> > > > > > 1. Support quasi-Java Expression which defines a single > > line > > >> > > > > executable > > >> > > > > > expression > > >> > > > > > 2. Support for quasi-Java expression based function code, > > >> which > > >> > > will > > >> > > > > be > > >> > > > > > compiled on the fly and made available for execution. > > >> > > > > > 3. Should support accessing multiple fields from > multiples > > >> input > > >> > > > POJOs > > >> > > > > > while addressing the conversion of private variables to > > >> public > > >> > > > getter > > >> > > > > > method for all levels. > > >> > > > > > 4. Should support nested field support > > >> > > > > > 5. quasi-Java expressions should support operands to be > > >> > mentioned > > >> > > in > > >> > > > > > following ways: > > >> > > > > > - ${input.fieldName} > > >> > > > > > - Access fieldName via a object name. > > >> > > > > > - ${fieldName} > > >> > > > > > - Accessing fieldName directly when a single object > > is > > >> > > > > registered > > >> > > > > > for operation. > > >> > > > > > - ${input} > > >> > > > > > - Accessing object variable directly > > >> > > > > > - ${input.fieldName.internalField} > > >> > > > > > - Accessing nested fields > > >> > > > > > 6. There should be some predefined function provided > to > > >> > > > expression > > >> > > > > > writer which one can directly use in expression for > > invoking > > >> > > certain > > >> > > > > > functionality. > > >> > > > > > 7. These are simple String based, Date time based etc > > >> functions. > > >> > > > > > 8. On-need-basic one should be able to easily update > > >> Expression > > >> > > > > > Evaluator to easily add new predefined functions to be > made > > >> > > > available > > >> > > > > > for > > >> > > > > > expression writer. > > >> > > > > > 9. User of ExpressionEvaluator should be able to add a > > custom > > >> > > method > > >> > > > > > externally to be made available to in expression. > > >> > > > > > 10. Though operands are defined, placeholder for the > > operand > > >> in > > >> > > > > > expression should be allowed to be overridden. By > default, > > >> > > > expression > > >> > > > > > language should support bash type syntax for operand - > {…} > > >> > > > > > 11. The library should not introduce any serialization > > >> related > > >> > > > issues. > > >> > > > > > 12. All the java operators should be supported. > > >> > > > > > > > >> > > > > > > > >> > > > > > > > >> > > > > > *The examples of quasi-Java Expression:* > > >> > > > > > > > >> > > > > > - ${inp.field1} > > >> > > > > > - Will return value of field1 from registered input > > POJO. > > >> > > > > > - ${inp.field1} + ${inp.field2} > > >> > > > > > - Will return sum of field1 & field2 from given POJO > > >> > > > > > - ${field1} + ${field2} > > >> > > > > > - Equivalent to above > > >> > > > > > - ${inpA.field1} > ${inpA.field2} ? ${inpA.field3} : > > >> > > ${inpB.field3} > > >> > > > > > - Executes ternary expression and returns value > > >> accordingly. > > >> > > > Works > > >> > > > > on > > >> > > > > > 2 POJOs. inpA & inpB are two placeholder registered > for > > >> given > > >> > > > POJO > > >> > > > > > with > > >> > > > > > ExpressionEvaluator library. > > >> > > > > > - pow(${inpA.field1}, ${inpB.field2}) > > >> > > > > > - Executes pow function coming from java.lang.Math > > >> library. > > >> > > This > > >> > > > > and > > >> > > > > > other with lot other basic functions is available to > > >> > expression > > >> > > > > > writer out > > >> > > > > > of the box to use in expression. > > >> > > > > > - ${inpA.field1} > 0 ? ${inpB.innerPOJO.field3} : > > >> > > > > > ${inpA.innerPOJO.field3} > > >> > > > > > - Shows how nested POJOs can be accessed in > expression. > > >> The > > >> > > > > variables > > >> > > > > > will evaluate to correct public getter method is > > required. > > >> > > > > > - ${inp.firstname} + “ “ + ${inp.lastname} > > >> > > > > > - Generate the full name as per given expression from > > >> > firstname > > >> > > > and > > >> > > > > > lastname field. > > >> > > > > > - long retVal=1; for (int i=0; ${inpF.value1}; i++) > > {retVal = > > >> > > > retVal * > > >> > > > > > ${inpF.value1}; } return retVal; > > >> > > > > > - This tells a complete method content to > > >> > ExpressionEvaluator. > > >> > > > The > > >> > > > > > library create an executable and compiled method using > > >> this > > >> > > > > > expression. > > >> > > > > > > > >> > > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > >> > > > > >> > > > >> > > > > > > > > >
