Examples with XpathBackReference org.drools.core.rule.XpathBackReference used on opensource projects

Example 1 with XpathBackReference

use of org.drools.core.rule.XpathBackReference in project drools by kiegroup.

the class PatternBuilder method buildXPathDescr.

private Constraint buildXPathDescr(RuleBuildContext context, PatternDescr patternDescr, Pattern pattern, BaseDescr descr, MVELDumper.MVELDumperContext mvelCtx) {
    String expression = ((ExpressionDescr) descr).getExpression();
    XpathAnalysis xpathAnalysis = XpathAnalysis.analyze(expression);
    if (xpathAnalysis.hasError()) {
        registerDescrBuildError(context, patternDescr, "Invalid xpath expression '" + expression + "': " + xpathAnalysis.getError());
        return null;
    }
    XpathConstraint xpathConstraint = new XpathConstraint();
    ObjectType objectType = pattern.getObjectType();
    Class<?> patternClass = objectType.getClassType();
    List<Class<?>> backReferenceClasses = new ArrayList<Class<?>>();
    backReferenceClasses.add(patternClass);
    XpathBackReference backRef = new XpathBackReference(pattern, backReferenceClasses);
    pattern.setBackRefDeclarations(backRef);
    ObjectType originalType = pattern.getObjectType();
    ObjectType currentObjectType = originalType;
    mvelCtx.setInXpath(true);
    try {
        for (XpathAnalysis.XpathPart part : xpathAnalysis) {
            XpathConstraint.XpathChunk xpathChunk = xpathConstraint.addChunck(patternClass, part.getField(), part.getIndex(), part.isIterate(), part.isLazy());
            // make sure the Pattern is wired up to correct ClassObjectType and set as a target for rewiring
            context.getPkg().getClassFieldAccessorStore().wireObjectType(currentObjectType, xpathChunk);
            if (xpathChunk == null) {
                registerDescrBuildError(context, patternDescr, "Invalid xpath expression '" + expression + "': cannot access " + part.getField() + " on " + patternClass);
                pattern.setObjectType(originalType);
                return null;
            }
            if (part.getInlineCast() != null) {
                try {
                    patternClass = context.getDialect().getTypeResolver().resolveType(part.getInlineCast());
                } catch (ClassNotFoundException e) {
                    registerDescrBuildError(context, patternDescr, "Unknown class " + part.getInlineCast() + " in xpath expression '" + expression + "'");
                    return null;
                }
                part.addInlineCastConstraint(patternClass);
                currentObjectType = getObjectType(context, patternDescr, patternClass.getName());
                xpathChunk.setReturnedType(currentObjectType);
            } else {
                patternClass = xpathChunk.getReturnedClass();
                currentObjectType = getObjectType(context, patternDescr, patternClass.getName());
            }
            pattern.setObjectType(currentObjectType);
            backReferenceClasses.add(0, patternClass);
            backRef.reset();
            for (String constraint : part.getConstraints()) {
                ConstraintConnectiveDescr result = parseExpression(context, patternDescr, new ExprConstraintDescr(constraint), constraint);
                if (result == null) {
                    continue;
                }
                for (Constraint c : build(context, patternDescr, pattern, result, mvelCtx)) {
                    xpathChunk.addConstraint(c);
                }
            }
        }
    } finally {
        mvelCtx.setInXpath(false);
        pattern.setBackRefDeclarations(null);
        pattern.setObjectType(originalType);
    }
    xpathConstraint.setXpathStartDeclaration(patternDescr.getXpathStartDeclaration());
    if (descr instanceof BindingDescr) {
        xpathConstraint.setDeclaration(pattern.addDeclaration(((BindingDescr) descr).getVariable()));
    }
    return xpathConstraint;
}