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package com.indeed.proctor.common;
import com.indeed.proctor.common.el.LibraryFunctionMapperBuilder;
import com.indeed.proctor.common.el.MulticontextReadOnlyVariableMapper;
import org.apache.commons.lang3.ClassUtils;
import org.apache.commons.lang3.StringUtils;
import org.apache.el.ExpressionFactoryImpl;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import javax.annotation.CheckForNull;
import javax.annotation.Nonnull;
import javax.el.ArrayELResolver;
import javax.el.BeanELResolver;
import javax.el.CompositeELResolver;
import javax.el.ELContext;
import javax.el.ELResolver;
import javax.el.ExpressionFactory;
import javax.el.FunctionMapper;
import javax.el.ListELResolver;
import javax.el.MapELResolver;
import javax.el.ValueExpression;
import javax.el.VariableMapper;
import java.util.Map;
/**
* A nice tidy packaging of javax.el stuff.
*
* @author ketan
* @author pwp
*/
public class RuleEvaluator {
private static final Logger LOGGER = LogManager.getLogger(RuleEvaluator.class);
static final FunctionMapper FUNCTION_MAPPER = defaultFunctionMapperBuilder().build();
static final ExpressionFactory EXPRESSION_FACTORY = new ExpressionFactoryImpl();
@Nonnull final ExpressionFactory expressionFactory;
@Nonnull final CompositeELResolver elResolver;
@Nonnull private final Map testConstants;
@Nonnull private final FunctionMapper functionMapper;
RuleEvaluator(
@Nonnull final ExpressionFactory expressionFactory,
@Nonnull final FunctionMapper functionMapper,
@Nonnull final Map testConstantsMap) {
this.expressionFactory = expressionFactory;
this.functionMapper = functionMapper;
elResolver = constructStandardElResolver();
testConstants =
ProctorUtils.convertToValueExpressionMap(expressionFactory, testConstantsMap);
}
public static RuleEvaluator createDefaultRuleEvaluator(
final Map testConstantsMap) {
return new RuleEvaluator(EXPRESSION_FACTORY, FUNCTION_MAPPER, testConstantsMap);
}
@Nonnull
private static CompositeELResolver constructStandardElResolver() {
final CompositeELResolver elResolver = new CompositeELResolver();
elResolver.add(new ArrayELResolver());
elResolver.add(new ListELResolver());
elResolver.add(new MapELResolver());
elResolver.add(new BeanELResolver()); // this must be last, because it throws Exception
return elResolver;
}
public static LibraryFunctionMapperBuilder defaultFunctionMapperBuilder() {
final LibraryFunctionMapperBuilder builder =
new LibraryFunctionMapperBuilder()
.add("indeed", ProctorRuleFunctions.class) // backwards compatibility
.add("fn", LegacyTaglibFunctions.class)
.add("proctor", ProctorRuleFunctions.class);
return builder;
}
@Nonnull
ELContext createElContext(@Nonnull final Map localContext) {
@SuppressWarnings("unchecked")
final VariableMapper variableMapper =
new MulticontextReadOnlyVariableMapper(testConstants, localContext);
return createELContext(variableMapper);
}
@Nonnull
ELContext createELContext(@Nonnull final VariableMapper variableMapper) {
return new ELContext() {
@Nonnull
@Override
public ELResolver getELResolver() {
return elResolver;
}
@Nonnull
@Override
public FunctionMapper getFunctionMapper() {
return functionMapper;
}
@Nonnull
@Override
public VariableMapper getVariableMapper() {
return variableMapper;
}
};
}
/**
* @deprecated Use evaluateBooleanRuleWithValueExpr(String, Map) instead, it's more efficient
*/
@Deprecated
public boolean evaluateBooleanRule(final String rule, @Nonnull final Map values)
throws IllegalArgumentException {
final Map localContext =
ProctorUtils.convertToValueExpressionMap(expressionFactory, values);
return evaluateBooleanRuleWithValueExpr(rule, localContext);
}
public boolean evaluateBooleanRuleWithValueExpr(
final String rule, @Nonnull final Map localContext)
throws IllegalArgumentException {
if (StringUtils.isBlank(rule)) {
return true;
}
if (!rule.startsWith("${") || !rule.endsWith("}")) {
LOGGER.error("Invalid rule '" + rule + "'"); // TODO: should this be an exception?
return false;
}
final ProctorUtils.ElExpressionClassification ec =
ProctorUtils.clasifyElExpression(rule, true);
if (ec == ProctorUtils.ElExpressionClassification.EMPTY
|| ec == ProctorUtils.ElExpressionClassification.CONSTANT_TRUE) {
return true; // always passes
}
if (ec == ProctorUtils.ElExpressionClassification.CONSTANT_FALSE) {
return false;
}
final ELContext elContext = createElContext(localContext);
final ValueExpression ve =
expressionFactory.createValueExpression(elContext, rule, boolean.class);
checkRuleIsBooleanType(rule, elContext, ve);
final Object result = ve.getValue(elContext);
if (result instanceof Boolean) {
return ((Boolean) result);
}
// this should never happen, evaluateRule throws ELException when it cannot coerce to
// Boolean
throw new IllegalArgumentException(
"Received non-boolean return value: "
+ (result == null ? "null" : result.getClass().getCanonicalName())
+ " from rule "
+ rule);
}
/** @throws IllegalArgumentException if type of expression is not boolean */
static void checkRuleIsBooleanType(
final String rule, final ELContext elContext, final ValueExpression ve) {
// apache-el is an expression language, not a rule language, and it is very lenient
// sadly that means it will just evaluate to false when users make certain mistakes, e.g. by
// coercing String value "xyz" to boolean false, instead of throwing an exception.
// To support users writing rules, be more strict here in requiring the type of the
// value to be expected before coercion
Class type = ve.getType(elContext);
if (ClassUtils.isPrimitiveWrapper(type)) {
type = ClassUtils.wrapperToPrimitive(type);
}
// allow null to be coerced for historic reasons
if ((type != null) && (type != boolean.class)) {
throw new IllegalArgumentException(
"Received non-boolean return value: " + type + " from rule " + rule);
}
}
/**
* @param expectedType class to coerce result to, use primitive instead of wrapper, e.g.
* boolean.class instead of Boolean.class.
* @return null or a Boolean value representing the expression evaluation result
* @throws RuntimeException: E.g. PropertyNotFound or other ELException when not of expectedType
* @deprecated Use evaluateBooleanRule() instead, it checks against more errors
*/
@CheckForNull
@Deprecated
public Object evaluateRule(
final String rule, final Map values, final Class expectedType) {
final ELContext elContext =
createElContext(
ProctorUtils.convertToValueExpressionMap(expressionFactory, values));
final ValueExpression ve =
expressionFactory.createValueExpression(elContext, rule, expectedType);
return ve.getValue(elContext);
}
}
