Examples of org.apache.commons.jexl2.UnifiedJEXL

org.apache.commons.jexl2.parser.JexlNode
An evaluator similar to the Unified EL evaluator used in JSP/JSF based on JEXL. It is intended to be used in configuration modules, XML based frameworks or JSP taglibs and facilitate the implementation of expression evaluation.
An expression can mix immediate, deferred and nested sub-expressions as well as string constants;
- The "immediate" syntax is of the form "...${jexl-expr}..."
- The "deferred" syntax is of the form "...#{jexl-expr}..."
- The "nested" syntax is of the form "...#{...${jexl-expr0}...}..."
- The "composite" syntax is of the form "...${jexl-expr0}... #{jexl-expr1}..."
Deferred & immediate expression carry different intentions:
- An immediate expression indicate that evaluation is intended to be performed close to the definition/parsing point.
- A deferred expression indicate that evaluation is intended to occur at a later stage.
For instance: "Hello ${name}, now is #{time}" is a composite "deferred" expression since one of its subexpressions is deferred. Furthermore, this (composite) expression intent is to perform two evaluations; one close to its definition and another one in a later phase.

The API reflects this feature in 2 methods, prepare and evaluate. The prepare method will evaluate the immediate subexpression and return an expression that contains only the deferred subexpressions (& constants), a prepared expression. Such a prepared expression is suitable for a later phase evaluation that may occur with a different JexlContext. Note that it is valid to call evaluate without prepare in which case the same JexlContext is used for the 2 evaluation phases.

In the most common use-case where deferred expressions are to be kept around as properties of objects, one should parse & prepare an expression before storing it and evaluate it each time the property storing it is accessed.

Note that nested expression use the JEXL syntax as in: "#{${bar}+'.charAt(2)'}" The most common mistake leading to an invalid expression being the following: "#{${bar}charAt(2)}"

Also note that methods that parse evaluate expressions may throw unchecked ecxeptions; The {@link UnifiedJEXL.Exception} are thrown when the engine instance is in "non-silent" modebut since these are RuntimeException, user-code should catch them where appropriate.
@since 2.0

         */
        Object left = node.jjtGetChild(0).jjtAccept(this, data);
        for(int c = 2, size = node.jjtGetNumChildren(); c < size; c += 2) {
            Object right = node.jjtGetChild(c).jjtAccept(this, data);
            try {
                JexlNode op = node.jjtGetChild(c - 1);
                if (op instanceof ASTAdditiveOperator) {
                    String which = ((ASTAdditiveOperator) op).image;
                    if ("+".equals(which)) {
                        left = arithmetic.add(left, right);
                        continue;
                    }
                    if ("-".equals(which)) {
                        left = arithmetic.subtract(left, right);
                        continue;
                    }
                    throw new UnsupportedOperationException("unknown operator " + which);
                }
                throw new IllegalArgumentException("unknown operator " + op);
            } catch (RuntimeException xrt) {
                JexlNode xnode = findNullOperand(xrt, node, left, right);
                throw new JexlException(xnode, "+/- error", xrt);
            }
        }
        return left;
    }

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        Object object = node.jjtGetChild(0).jjtAccept(this, data);
        // can have multiple nodes - either an expression, integer literal or
        // reference
        int numChildren = node.jjtGetNumChildren();
        for (int i = 1; i < numChildren; i++) {
            JexlNode nindex = node.jjtGetChild(i);
            if (nindex instanceof JexlNode.Literal<?>) {
                object = nindex.jjtAccept(this, object);
            } else {
                Object index = nindex.jjtAccept(this, null);
                object = getAttribute(object, index, nindex);
            }
        }


        return object;

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    }
    
    /** {@inheritDoc} */
    public Object visit(ASTAssignment node, Object data) {
        // left contains the reference to assign to
        JexlNode left = node.jjtGetChild(0);
        if (!(left instanceof ASTReference)) {
            throw new JexlException(left, "illegal assignment form");
        }
        // right is the value expression to assign
        Object right = node.jjtGetChild(1).jjtAccept(this, data);


        // determine initial object & property:
        JexlNode objectNode = null;
        Object object = null;
        JexlNode propertyNode = null;
        Object property = null;
        boolean isVariable = true;
        int v = 0;
        StringBuilder variableName = null;
        // 1: follow children till penultimate

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            return arithmetic.divide(left, right);
        } catch (RuntimeException xrt) {
            if (!strict && xrt instanceof ArithmeticException) {
                return new Double(0.0);
            }
            JexlNode xnode = findNullOperand(xrt, node, left, right);
            throw new JexlException(xnode, "divide error", xrt);
        }
    }

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        /* second objectNode is the variable to iterate */
        Object iterableValue = node.jjtGetChild(1).jjtAccept(this, data);
        // make sure there is a value to iterate on and a statement to execute
        if (iterableValue != null && node.jjtGetNumChildren() >= 3) {
            /* third objectNode is the statement to execute */
            JexlNode statement = node.jjtGetChild(2);
            // get an iterator for the collection/array etc via the
            // introspector.
            Iterator<?> itemsIterator = getUberspect().getIterator(iterableValue, node);
            if (itemsIterator != null) {
                while (itemsIterator.hasNext()) {
                    // set loopVariable to value of iterator
                    Object value = itemsIterator.next();
                    context.set(loopVariable.image, value);
                    // execute statement
                    result = statement.jjtAccept(this, data);
                }
            }
        }
        return result;
    }

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    /** {@inheritDoc} */
    public Object visit(ASTJexlScript node, Object data) {
        int numChildren = node.jjtGetNumChildren();
        Object result = null;
        for (int i = 0; i < numChildren; i++) {
            JexlNode child = node.jjtGetChild(i);
            result = child.jjtAccept(this, data);
        }
        return result;
    }

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            return arithmetic.mod(left, right);
        } catch (RuntimeException xrt) {
            if (!strict && xrt instanceof ArithmeticException) {
                return new Double(0.0);
            }
            JexlNode xnode = findNullOperand(xrt, node, left, right);
            throw new JexlException(xnode, "% error", xrt);
        }
    }

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        Object left = node.jjtGetChild(0).jjtAccept(this, data);
        Object right = node.jjtGetChild(1).jjtAccept(this, data);
        try {
            return arithmetic.multiply(left, right);
        } catch (RuntimeException xrt) {
            JexlNode xnode = findNullOperand(xrt, node, left, right);
            throw new JexlException(xnode, "* error", xrt);
        }
    }

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        Object left = node.jjtGetChild(0).jjtAccept(this, data);
        Object right = node.jjtGetChild(1).jjtAccept(this, data);
        try {
            return arithmetic.equals(left, right) ? Boolean.FALSE : Boolean.TRUE;
        } catch (RuntimeException xrt) {
            JexlNode xnode = findNullOperand(xrt, node, left, right);
            throw new JexlException(xnode, "!= error", xrt);
        }
    }

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        Object result = null;
        StringBuilder variableName = null;
        boolean isVariable = true;
        int v = 0;
        for (int c = 0; c < numChildren; c++) {
            JexlNode theNode = node.jjtGetChild(c);
            // integer literals may be part of an antish var name only if no bean was found so far
            if (result == null && theNode instanceof ASTIntegerLiteral) {
                isVariable &= v > 0;
            } else {
                isVariable &= (theNode instanceof ASTIdentifier);
                result = theNode.jjtAccept(this, result);
            }
            // if we get null back a result, check for an ant variable
            if (result == null && isVariable) {
                if (v == 0) {
                    variableName = new StringBuilder(node.jjtGetChild(0).image);

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