io.rapidpro.expressions.evaluator

Class Evaluator

java.lang.Object

io.rapidpro.expressions.evaluator.Evaluator

public class Evaluator
extends Object

The template and expression evaluator

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Evaluator.EvaluationStrategy

Field Summary

Fields

Modifier and Type	Field and Description
protected static org.slf4j.Logger	logger

Constructor Summary

Constructors

Constructor and Description
Evaluator(char expressionPrefix, Set<String> allowedTopLevels, List<Class<?>> functionLibraries) Creates a new evaluator

Method Summary

Modifier and Type	Method and Description
Object	evaluateExpression(String expression, EvaluationContext context) Evaluates a single expression, e.g.
Object	evaluateExpression(String expression, EvaluationContext context, Evaluator.EvaluationStrategy strategy) Evaluates a single expression, e.g.
EvaluatedTemplate	evaluateTemplate(String template, EvaluationContext context) Evaluates a template string, e.g.
EvaluatedTemplate	evaluateTemplate(String template, EvaluationContext context, boolean urlEncode) Evaluates a template string, e.g.
EvaluatedTemplate	evaluateTemplate(String template, EvaluationContext context, boolean urlEncode, Evaluator.EvaluationStrategy strategy) Evaluates a template string, e.g.
protected String	resolveAvailable(org.antlr.v4.runtime.CommonTokenStream tokens, EvaluationContext context) Checks the token stream for context references and if there are missing references - substitutes available references and returns a partially evaluated expression.
protected String	resolveExpressionBlock(String expression, EvaluationContext context, boolean urlEncode, Evaluator.EvaluationStrategy strategy, List<String> errors) Resolves an expression block found in the template, e.g. @(...).

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

logger

protected static org.slf4j.Logger logger

Constructor Detail

Evaluator

public Evaluator(char expressionPrefix,
                 Set<String> allowedTopLevels,
                 List<Class<?>> functionLibraries)

Creates a new evaluator

Parameters:

expressionPrefix - the prefix for expressions, e.g. @

allowedTopLevels - top-level context items allowed outside of parentheses, e.g. contact, flow

functionLibraries - the function libraries to include

Method Detail

evaluateTemplate

public EvaluatedTemplate evaluateTemplate(String template,
                                          EvaluationContext context)

Evaluates a template string, e.g. "Hello @contact.name you have @(contact.reports * 2) reports"

Parameters:

template - the template string

context - the evaluation context

Returns:

a tuple of the evaluated template and a list of evaluation errors

evaluateTemplate

public EvaluatedTemplate evaluateTemplate(String template,
                                          EvaluationContext context,
                                          boolean urlEncode)

Evaluates a template string, e.g. "Hello @contact.name you have @(contact.reports * 2) reports"

Parameters:

template - the template string

context - the evaluation context

urlEncode - whether or not values should be URL encoded

Returns:

a tuple of the evaluated template and a list of evaluation errors

evaluateTemplate

public EvaluatedTemplate evaluateTemplate(String template,
                                          EvaluationContext context,
                                          boolean urlEncode,
                                          Evaluator.EvaluationStrategy strategy)

Evaluates a template string, e.g. "Hello @contact.name you have @(contact.reports * 2) reports"

Parameters:

template - the template string

context - the evaluation context

urlEncode - whether or not values should be URL encoded

strategy - the evaluation strategy

Returns:

a tuple of the evaluated template and a list of evaluation errors

resolveExpressionBlock

protected String resolveExpressionBlock(String expression,
                                        EvaluationContext context,
                                        boolean urlEncode,
                                        Evaluator.EvaluationStrategy strategy,
                                        List<String> errors)

Resolves an expression block found in the template, e.g. @(...). If an evaluation error occurs, expression is returned as is.

evaluateExpression

public Object evaluateExpression(String expression,
                                 EvaluationContext context)
                          throws EvaluationError

Evaluates a single expression, e.g. "contact.reports * 2"

Parameters:

expression - the expression string

context - the evaluation context

Returns:

the evaluated expression value

Throws:

EvaluationError - if an error occurs during evaluation

evaluateExpression

public Object evaluateExpression(String expression,
                                 EvaluationContext context,
                                 Evaluator.EvaluationStrategy strategy)
                          throws EvaluationError

Evaluates a single expression, e.g. "contact.reports * 2"

Parameters:

expression - the expression string

context - the evaluation context

strategy - the evaluation strategy

Returns:

the evaluated expression value

Throws:

EvaluationError - if an error occurs during evaluation

resolveAvailable

protected String resolveAvailable(org.antlr.v4.runtime.CommonTokenStream tokens,
                                  EvaluationContext context)

Checks the token stream for context references and if there are missing references - substitutes available references and returns a partially evaluated expression.

Parameters:

tokens - the token stream (all tokens fetched)

context - the evaluation context

Returns:

the partially evaluated expression or null if expression can be fully evaluated