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Jexl is an implementation of the JSTL Expression Language with extensions.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.jexl2;
import java.util.ArrayList;
import org.apache.commons.jexl2.parser.JexlNode;
import org.apache.commons.jexl2.parser.StringParser;
/**
* 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" mode
* but since these are RuntimeException, user-code should catch them where appropriate.
*
* @since 2.0
*/
public final class UnifiedJEXL {
/** The JEXL engine instance. */
private final JexlEngine jexl;
/** The expression cache. */
private final JexlEngine.SoftCache cache;
/** The default cache size. */
private static final int CACHE_SIZE = 256;
/**
* Creates a new instance of UnifiedJEXL with a default size cache.
* @param aJexl the JexlEngine to use.
*/
public UnifiedJEXL(JexlEngine aJexl) {
this(aJexl, CACHE_SIZE);
}
/**
* Creates a new instance of UnifiedJEXL creating a local cache.
* @param aJexl the JexlEngine to use.
* @param cacheSize the number of expressions in this cache
*/
public UnifiedJEXL(JexlEngine aJexl, int cacheSize) {
this.jexl = aJexl;
this.cache = aJexl.new SoftCache(cacheSize);
}
/**
* Types of expressions.
* Each instance carries a counter index per (composite sub-) expression type.
* @see ExpressionBuilder
*/
private static enum ExpressionType {
/** Constant expression, count index 0. */
CONSTANT(0),
/** Immediate expression, count index 1. */
IMMEDIATE(1),
/** Deferred expression, count index 2. */
DEFERRED(2),
/** Nested (which are deferred) expressions, count index 2. */
NESTED(2),
/** Composite expressions are not counted, index -1. */
COMPOSITE(-1);
/** The index in arrays of expression counters for composite expressions. */
private final int index;
/**
* Creates an ExpressionType.
* @param idx the index for this type in counters arrays.
*/
ExpressionType(int idx) {
this.index = idx;
}
}
/**
* A helper class to build expressions.
* Keeps count of sub-expressions by type.
*/
private static class ExpressionBuilder {
/** Per expression type counters. */
private final int[] counts;
/** The list of expressions. */
private final ArrayList expressions;
/**
* Creates a builder.
* @param size the initial expression array size
*/
ExpressionBuilder(int size) {
counts = new int[]{0, 0, 0};
expressions = new ArrayList(size <= 0 ? 3 : size);
}
/**
* Adds an expression to the list of expressions, maintain per-type counts.
* @param expr the expression to add
*/
void add(Expression expr) {
counts[expr.getType().index] += 1;
expressions.add(expr);
}
/**
* Builds an expression from a source, performs checks.
* @param el the unified el instance
* @param source the source expression
* @return an expression
*/
Expression build(UnifiedJEXL el, Expression source) {
int sum = 0;
for (int count : counts) {
sum += count;
}
if (expressions.size() != sum) {
StringBuilder error = new StringBuilder("parsing algorithm error, exprs: ");
error.append(expressions.size());
error.append(", constant:");
error.append(counts[ExpressionType.CONSTANT.index]);
error.append(", immediate:");
error.append(counts[ExpressionType.IMMEDIATE.index]);
error.append(", deferred:");
error.append(counts[ExpressionType.DEFERRED.index]);
throw new IllegalStateException(error.toString());
}
// if only one sub-expr, no need to create a composite
if (expressions.size() == 1) {
return expressions.get(0);
} else {
return el.new CompositeExpression(counts, expressions, source);
}
}
}
/**
* Gets the JexlEngine underlying the UnifiedJEXL.
* @return the JexlEngine
*/
public JexlEngine getEngine() {
return jexl;
}
/**
* The sole type of (runtime) exception the UnifiedJEXL can throw.
*/
public static class Exception extends RuntimeException {
/** Serial version UID. */
private static final long serialVersionUID = -8201402995815975726L;
/**
* Creates a UnifiedJEXL.Exception.
* @param msg the exception message
* @param cause the exception cause
*/
public Exception(String msg, Throwable cause) {
super(msg, cause);
}
}
/**
* The abstract base class for all expressions, immediate '${...}' and deferred '#{...}'.
*/
public abstract class Expression {
/** The source of this expression (see {@link UnifiedJEXL.Expression#prepare}). */
protected final Expression source;
/**
* Creates an expression.
* @param src the source expression if any
*/
Expression(Expression src) {
this.source = src != null ? src : this;
}
/**
* Formats this expression, adding its source string representation in
* comments if available: 'expression /*= source *\/'' .
* @return the formatted expression string
*/
@Override
public String toString() {
StringBuilder strb = new StringBuilder();
if (source != this) {
strb.append(source.toString());
strb.append(" /*= ");
}
asString(strb);
if (source != this) {
strb.append(" */");
}
return strb.toString();
}
/**
* Generates this expression's string representation.
* @return the string representation
*/
public String asString() {
StringBuilder strb = new StringBuilder();
asString(strb);
return strb.toString();
}
/**
* Adds this expression's string representation to a StringBuilder.
* @param strb the builder to fill
*/
abstract void asString(StringBuilder strb);
/**
* When the expression is dependant upon immediate and deferred sub-expressions,
* evaluates the immediate sub-expressions with the context passed as parameter
* and returns this expression deferred form.
*
* In effect, this binds the result of the immediate sub-expressions evaluation in the
* context, allowing to differ evaluation of the remaining (deferred) expression within another context.
* This only has an effect to nested & composite expressions that contain differed & immediate sub-expressions.
*
*
* If the underlying JEXL engine is silent, errors will be logged through its logger as warning.
*
* @param context the context to use for immediate expression evaluations
* @return an expression or null if an error occurs and the {@link JexlEngine} is silent
* @throws UnifiedJEXL.Exception if an error occurs and the {@link JexlEngine} is not silent
*/
public abstract Expression prepare(JexlContext context);
/**
* Evaluates this expression.
*
* If the underlying JEXL engine is silent, errors will be logged through its logger as warning.
*
* @param context the variable context
* @return the result of this expression evaluation or null if an error occurs and the {@link JexlEngine} is
* silent
* @throws UnifiedJEXL.Exception if an error occurs and the {@link JexlEngine} is not silent
*/
public abstract Object evaluate(JexlContext context);
/**
* Checks whether this expression is immediate.
* @return true if immediate, false otherwise
*/
public boolean isImmediate() {
return true;
}
/**
* Checks whether this expression is deferred.
* @return true if deferred, false otherwise
*/
public final boolean isDeferred() {
return !isImmediate();
}
/**
* Retrieves this expression's source expression.
* If this expression was prepared, this allows to retrieve the
* original expression that lead to it.
* Other expressions return themselves.
* @return the source expression
*/
public final Expression getSource() {
return source;
}
/**
* Gets this expression type.
* @return its type
*/
abstract ExpressionType getType();
/**
* Prepares a sub-expression for interpretation.
* @param interpreter a JEXL interpreter
* @return a prepared expression
* @throws JexlException (only for nested & composite)
*/
abstract Expression prepare(Interpreter interpreter);
/**
* Intreprets a sub-expression.
* @param interpreter a JEXL interpreter
* @return the result of interpretation
* @throws JexlException (only for nested & composite)
*/
abstract Object evaluate(Interpreter interpreter);
}
/** A constant expression. */
private class ConstantExpression extends Expression {
/** The constant held by this expression. */
private final Object value;
/**
* Creates a constant expression.
*
* If the wrapped constant is a string, it is treated
* as a JEXL strings with respect to escaping.
*
* @param val the constant value
* @param source the source expression if any
*/
ConstantExpression(Object val, Expression source) {
super(source);
if (val == null) {
throw new NullPointerException("constant can not be null");
}
if (val instanceof String) {
val = StringParser.buildString((String) val, false);
}
this.value = val;
}
/** {@inheritDoc} */
@Override
public String asString() {
StringBuilder strb = new StringBuilder();
strb.append('"');
asString(strb);
strb.append('"');
return strb.toString();
}
/** {@inheritDoc} */
@Override
ExpressionType getType() {
return ExpressionType.CONSTANT;
}
/** {@inheritDoc} */
@Override
void asString(StringBuilder strb) {
String str = value.toString();
if (value instanceof String || value instanceof CharSequence) {
for (int i = 0, size = str.length(); i < size; ++i) {
char c = str.charAt(i);
if (c == '"' || c == '\\') {
strb.append('\\');
}
strb.append(c);
}
} else {
strb.append(str);
}
}
/** {@inheritDoc} */
@Override
public Expression prepare(JexlContext context) {
return this;
}
/** {@inheritDoc} */
@Override
Expression prepare(Interpreter interpreter) {
return this;
}
/** {@inheritDoc} */
@Override
public Object evaluate(JexlContext context) {
return value;
}
/** {@inheritDoc} */
@Override
Object evaluate(Interpreter interpreter) {
return value;
}
}
/** The base for Jexl based expressions. */
private abstract class JexlBasedExpression extends Expression {
/** The JEXL string for this expression. */
protected final CharSequence expr;
/** The JEXL node for this expression. */
protected final JexlNode node;
/**
* Creates a JEXL interpretable expression.
* @param theExpr the expression as a string
* @param theNode the expression as an AST
* @param theSource the source expression if any
*/
protected JexlBasedExpression(CharSequence theExpr, JexlNode theNode, Expression theSource) {
super(theSource);
this.expr = theExpr;
this.node = theNode;
}
/** {@inheritDoc} */
@Override
public String toString() {
StringBuilder strb = new StringBuilder(expr.length() + 3);
if (source != this) {
strb.append(source.toString());
strb.append(" /*= ");
}
strb.append(isImmediate() ? '$' : '#');
strb.append("{");
strb.append(expr);
strb.append("}");
if (source != this) {
strb.append(" */");
}
return strb.toString();
}
/** {@inheritDoc} */
@Override
public void asString(StringBuilder strb) {
strb.append(isImmediate() ? '$' : '#');
strb.append("{");
strb.append(expr);
strb.append("}");
}
/** {@inheritDoc} */
@Override
public Expression prepare(JexlContext context) {
return this;
}
/** {@inheritDoc} */
@Override
Expression prepare(Interpreter interpreter) {
return this;
}
/** {@inheritDoc} */
@Override
public Object evaluate(JexlContext context) {
return UnifiedJEXL.this.evaluate(context, this);
}
/** {@inheritDoc} */
@Override
Object evaluate(Interpreter interpreter) {
return interpreter.interpret(node);
}
}
/** An immediate expression: ${jexl}. */
private class ImmediateExpression extends JexlBasedExpression {
/**
* Creates an immediate expression.
* @param expr the expression as a string
* @param node the expression as an AST
* @param source the source expression if any
*/
ImmediateExpression(CharSequence expr, JexlNode node, Expression source) {
super(expr, node, source);
}
/** {@inheritDoc} */
@Override
ExpressionType getType() {
return ExpressionType.IMMEDIATE;
}
/** {@inheritDoc} */
@Override
public boolean isImmediate() {
return true;
}
}
/** An immediate expression: ${jexl}. */
private class DeferredExpression extends JexlBasedExpression {
/**
* Creates a deferred expression.
* @param expr the expression as a string
* @param node the expression as an AST
* @param source the source expression if any
*/
DeferredExpression(CharSequence expr, JexlNode node, Expression source) {
super(expr, node, source);
}
/** {@inheritDoc} */
@Override
ExpressionType getType() {
return ExpressionType.DEFERRED;
}
/** {@inheritDoc} */
@Override
public boolean isImmediate() {
return false;
}
}
/**
* A deferred expression that nests an immediate expression.
* #{...${jexl}...}
* Note that the deferred syntax is JEXL's, not UnifiedJEXL.
*/
private class NestedExpression extends DeferredExpression {
/**
* Creates a nested expression.
* @param expr the expression as a string
* @param node the expression as an AST
* @param source the source expression if any
*/
NestedExpression(CharSequence expr, JexlNode node, Expression source) {
super(expr, node, source);
if (this.source != this) {
throw new IllegalArgumentException("Nested expression can not have a source");
}
}
/** {@inheritDoc} */
@Override
ExpressionType getType() {
return ExpressionType.NESTED;
}
/** {@inheritDoc} */
@Override
public String toString() {
return expr.toString();
}
/** {@inheritDoc} */
@Override
public Expression prepare(JexlContext context) {
return UnifiedJEXL.this.prepare(context, this);
}
/** {@inheritDoc} */
@Override
public Expression prepare(Interpreter interpreter) {
String value = interpreter.interpret(node).toString();
JexlNode dnode = toNode(value, jexl.isDebug()? node.getInfo() : null);
return new DeferredExpression(value, dnode, this);
}
/** {@inheritDoc} */
@Override
public Object evaluate(Interpreter interpreter) {
return prepare(interpreter).evaluate(interpreter);
}
}
/** A composite expression: "... ${...} ... #{...} ...". */
private class CompositeExpression extends Expression {
/** Bit encoded (deferred count > 0) bit 1, (immediate count > 0) bit 0. */
private final int meta;
/** The list of sub-expression resulting from parsing. */
private final Expression[] exprs;
/**
* Creates a composite expression.
* @param counters counters of expression per type
* @param list the sub-expressions
* @param src the source for this expresion if any
*/
CompositeExpression(int[] counters, ArrayList list, Expression src) {
super(src);
this.exprs = list.toArray(new Expression[list.size()]);
this.meta = (counters[ExpressionType.DEFERRED.index] > 0 ? 2 : 0)
| (counters[ExpressionType.IMMEDIATE.index] > 0 ? 1 : 0);
}
/** {@inheritDoc} */
@Override
ExpressionType getType() {
return ExpressionType.COMPOSITE;
}
/** {@inheritDoc} */
@Override
public boolean isImmediate() {
// immediate if no deferred
return (meta & 2) == 0;
}
/** {@inheritDoc} */
@Override
void asString(StringBuilder strb) {
for (Expression e : exprs) {
e.asString(strb);
}
}
/** {@inheritDoc} */
@Override
public Expression prepare(JexlContext context) {
return UnifiedJEXL.this.prepare(context, this);
}
/** {@inheritDoc} */
@Override
Expression prepare(Interpreter interpreter) {
// if this composite is not its own source, it is already prepared
if (source != this) {
return this;
}
// we need to eval immediate expressions if there are some deferred/nested
// ie both immediate & deferred counts > 0, bits 1 & 0 set, (1 << 1) & 1 == 3
final boolean evalImmediate = meta == 3;
final int size = exprs.length;
final ExpressionBuilder builder = new ExpressionBuilder(size);
// tracking whether prepare will return a different expression
boolean eq = true;
for (int e = 0; e < size; ++e) {
Expression expr = exprs[e];
Expression prepared = expr.prepare(interpreter);
if (evalImmediate && prepared instanceof ImmediateExpression) {
// evaluate immediate as constant
Object value = prepared.evaluate(interpreter);
prepared = value == null ? null : new ConstantExpression(value, prepared);
}
// add it if not null
if (prepared != null) {
builder.add(prepared);
}
// keep track of expression equivalence
eq &= expr == prepared;
}
Expression ready = eq ? this : builder.build(UnifiedJEXL.this, this);
return ready;
}
/** {@inheritDoc} */
@Override
public Object evaluate(JexlContext context) {
return UnifiedJEXL.this.evaluate(context, this);
}
/** {@inheritDoc} */
@Override
Object evaluate(Interpreter interpreter) {
final int size = exprs.length;
Object value = null;
// common case: evaluate all expressions & concatenate them as a string
StringBuilder strb = new StringBuilder();
for (int e = 0; e < size; ++e) {
value = exprs[e].evaluate(interpreter);
if (value != null) {
strb.append(value.toString());
}
}
value = strb.toString();
return value;
}
}
/** Creates a a {@link UnifiedJEXL.Expression} from an expression string.
* Uses & fills up the expression cache if any.
*
* If the underlying JEXL engine is silent, errors will be logged through its logger as warnings.
*
* @param expression the UnifiedJEXL string expression
* @return the UnifiedJEXL object expression, null if silent and an error occured
* @throws UnifiedJEXL.Exception if an error occurs and the {@link JexlEngine} is not silent
*/
public Expression parse(String expression) {
Exception xuel = null;
Expression stmt = null;
try {
if (cache == null) {
stmt = parseExpression(expression);
} else {
synchronized (cache) {
stmt = cache.get(expression);
if (stmt == null) {
stmt = parseExpression(expression);
cache.put(expression, stmt);
}
}
}
} catch (JexlException xjexl) {
xuel = new Exception("failed to parse '" + expression + "'", xjexl);
} catch (Exception xany) {
xuel = xany;
} finally {
if (xuel != null) {
if (jexl.isSilent()) {
jexl.logger.warn(xuel.getMessage(), xuel.getCause());
return null;
}
throw xuel;
}
}
return stmt;
}
/**
* Prepares an expression (nested & composites), handles exception reporting.
*
* @param context the JEXL context to use
* @param expr the expression to prepare
* @return a prepared expression
* @throws UnifiedJEXL.Exception if an error occurs and the {@link JexlEngine} is not silent
*/
Expression prepare(JexlContext context, Expression expr) {
try {
Interpreter interpreter = jexl.createInterpreter(context);
interpreter.setSilent(false);
return expr.prepare(interpreter);
} catch (JexlException xjexl) {
Exception xuel = createException("prepare", expr, xjexl);
if (jexl.isSilent()) {
jexl.logger.warn(xuel.getMessage(), xuel.getCause());
return null;
}
throw xuel;
}
}
/**
* Evaluates an expression (nested & composites), handles exception reporting.
*
* @param context the JEXL context to use
* @param expr the expression to prepare
* @return the result of the evaluation
* @throws UnifiedJEXL.Exception if an error occurs and the {@link JexlEngine} is not silent
*/
Object evaluate(JexlContext context, Expression expr) {
try {
Interpreter interpreter = jexl.createInterpreter(context);
interpreter.setSilent(false);
return expr.evaluate(interpreter);
} catch (JexlException xjexl) {
Exception xuel = createException("evaluate", expr, xjexl);
if (jexl.isSilent()) {
jexl.logger.warn(xuel.getMessage(), xuel.getCause());
return null;
}
throw xuel;
}
}
/**
* Use the JEXL parser to create the AST for an expression.
* @param expression the expression to parse
* @return the AST
* @throws JexlException if an error occur during parsing
*/
private JexlNode toNode(CharSequence expression) {
return jexl.parse(expression, null);
}
/**
* Use the JEXL parser to create the AST for an expression.
* @param expression the expression to parse
* @param info debug information
* @return the AST
* @throws JexlException if an error occur during parsing
*/
private JexlNode toNode(CharSequence expression, JexlInfo info) {
return jexl.parse(expression, info);
}
/**
* Creates a UnifiedJEXL.Exception from a JexlException.
* @param action parse, prepare, evaluate
* @param expr the expression
* @param xany the exception
* @return an exception containing an explicit error message
*/
private Exception createException(String action, Expression expr, java.lang.Exception xany) {
StringBuilder strb = new StringBuilder("failed to ");
strb.append(action);
strb.append(" '");
strb.append(expr.toString());
strb.append("'");
Throwable cause = xany.getCause();
if (cause != null) {
String causeMsg = cause.getMessage();
if (causeMsg != null) {
strb.append(", ");
strb.append(causeMsg);
}
}
return new Exception(strb.toString(), xany);
}
/** The different parsing states. */
private static enum ParseState {
/** Parsing a constant. */
CONST,
/** Parsing after $ .*/
IMMEDIATE0,
/** Parsing after # .*/
DEFERRED0,
/** Parsing after ${ .*/
IMMEDIATE1,
/** Parsing after #{ .*/
DEFERRED1,
/** Parsing after \ .*/
ESCAPE
}
/**
* Parses a unified expression.
* @param expr the string expression
* @return the expression instance
* @throws JexlException if an error occur during parsing
*/
private Expression parseExpression(String expr) {
final int size = expr.length();
ExpressionBuilder builder = new ExpressionBuilder(0);
StringBuilder strb = new StringBuilder(size);
ParseState state = ParseState.CONST;
int inner = 0;
boolean nested = false;
int inested = -1;
for (int i = 0; i < size; ++i) {
char c = expr.charAt(i);
switch (state) {
default: // in case we ever add new expression type
throw new UnsupportedOperationException("unexpected expression type");
case CONST:
if (c == '$') {
state = ParseState.IMMEDIATE0;
} else if (c == '#') {
inested = i;
state = ParseState.DEFERRED0;
} else if (c == '\\') {
state = ParseState.ESCAPE;
} else {
// do buildup expr
strb.append(c);
}
break;
case IMMEDIATE0: // $
if (c == '{') {
state = ParseState.IMMEDIATE1;
// if chars in buffer, create constant
if (strb.length() > 0) {
Expression cexpr = new ConstantExpression(strb.toString(), null);
builder.add(cexpr);
strb.delete(0, Integer.MAX_VALUE);
}
} else {
// revert to CONST
strb.append('$');
strb.append(c);
state = ParseState.CONST;
}
break;
case DEFERRED0: // #
if (c == '{') {
state = ParseState.DEFERRED1;
// if chars in buffer, create constant
if (strb.length() > 0) {
Expression cexpr = new ConstantExpression(strb.toString(), null);
builder.add(cexpr);
strb.delete(0, Integer.MAX_VALUE);
}
} else {
// revert to CONST
strb.append('#');
strb.append(c);
state = ParseState.CONST;
}
break;
case IMMEDIATE1: // ${...
if (c == '}') {
// materialize the immediate expr
Expression iexpr = new ImmediateExpression(strb.toString(), toNode(strb), null);
builder.add(iexpr);
strb.delete(0, Integer.MAX_VALUE);
state = ParseState.CONST;
} else {
// do buildup expr
strb.append(c);
}
break;
case DEFERRED1: // #{...
// skip inner strings (for '}')
if (c == '"' || c == '\'') {
strb.append(c);
i = StringParser.readString(strb, expr, i + 1, c);
continue;
}
// nested immediate in deferred; need to balance count of '{' & '}'
if (c == '{') {
if (expr.charAt(i - 1) == '$') {
inner += 1;
strb.deleteCharAt(strb.length() - 1);
nested = true;
}
continue;
}
// closing '}'
if (c == '}') {
// balance nested immediate
if (inner > 0) {
inner -= 1;
} else {
// materialize the nested/deferred expr
Expression dexpr = null;
if (nested) {
dexpr = new NestedExpression(expr.substring(inested, i + 1), toNode(strb), null);
} else {
dexpr = new DeferredExpression(strb.toString(), toNode(strb), null);
}
builder.add(dexpr);
strb.delete(0, Integer.MAX_VALUE);
nested = false;
state = ParseState.CONST;
}
} else {
// do buildup expr
strb.append(c);
}
break;
case ESCAPE:
if (c == '#') {
strb.append('#');
} else if (c == '$') {
strb.append('$');
} else {
strb.append('\\');
strb.append(c);
}
state = ParseState.CONST;
}
}
// we should be in that state
if (state != ParseState.CONST) {
throw new Exception("malformed expression: " + expr, null);
}
// if any chars were buffered, add them as a constant
if (strb.length() > 0) {
Expression cexpr = new ConstantExpression(strb.toString(), null);
builder.add(cexpr);
}
return builder.build(this, null);
}
}