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The Core Camel Java DSL based router
/**
* 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.camel.language.simple;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Stack;
import java.util.concurrent.atomic.AtomicBoolean;
import org.apache.camel.Expression;
import org.apache.camel.Predicate;
import org.apache.camel.builder.PredicateBuilder;
import org.apache.camel.language.simple.ast.BinaryExpression;
import org.apache.camel.language.simple.ast.DoubleQuoteEnd;
import org.apache.camel.language.simple.ast.DoubleQuoteStart;
import org.apache.camel.language.simple.ast.LiteralExpression;
import org.apache.camel.language.simple.ast.LiteralNode;
import org.apache.camel.language.simple.ast.LogicalExpression;
import org.apache.camel.language.simple.ast.NullExpression;
import org.apache.camel.language.simple.ast.SimpleFunctionEnd;
import org.apache.camel.language.simple.ast.SimpleFunctionStart;
import org.apache.camel.language.simple.ast.SimpleNode;
import org.apache.camel.language.simple.ast.SingleQuoteEnd;
import org.apache.camel.language.simple.ast.SingleQuoteStart;
import org.apache.camel.language.simple.ast.UnaryExpression;
import org.apache.camel.language.simple.types.BinaryOperatorType;
import org.apache.camel.language.simple.types.LogicalOperatorType;
import org.apache.camel.language.simple.types.SimpleIllegalSyntaxException;
import org.apache.camel.language.simple.types.SimpleParserException;
import org.apache.camel.language.simple.types.SimpleToken;
import org.apache.camel.language.simple.types.TokenType;
import org.apache.camel.util.ExpressionToPredicateAdapter;
/**
* A parser to parse simple language as a Camel {@link Predicate}
*/
public class SimplePredicateParser extends BaseSimpleParser {
@Deprecated
public SimplePredicateParser(String expression) {
super(expression, true);
}
public SimplePredicateParser(String expression, boolean allowEscape) {
super(expression, allowEscape);
}
public Predicate parsePredicate() {
clear();
try {
return doParsePredicate();
} catch (SimpleParserException e) {
// catch parser exception and turn that into a syntax exceptions
throw new SimpleIllegalSyntaxException(expression, e.getIndex(), e.getMessage(), e);
} catch (Exception e) {
// include exception in rethrown exception
throw new SimpleIllegalSyntaxException(expression, -1, e.getMessage(), e);
}
}
protected Predicate doParsePredicate() {
// parse using the following grammar
nextToken();
while (!token.getType().isEol()) {
// predicate supports quotes, functions, operators and whitespaces
//CHECKSTYLE:OFF
if (!singleQuotedLiteralWithFunctionsText()
&& !doubleQuotedLiteralWithFunctionsText()
&& !functionText()
&& !unaryOperator()
&& !binaryOperator()
&& !logicalOperator()
&& !isBooleanValue()
&& !token.getType().isWhitespace()
&& !token.getType().isEol()) {
// okay the symbol was not one of the above, so its not supported
// use the previous index as that is where the problem is
throw new SimpleParserException("Unexpected token " + token, previousIndex);
}
//CHECKSTYLE:ON
// take the next token
nextToken();
}
// now after parsing we need a bit of work to do, to make it easier to turn the tokens
// into and ast, and then from the ast, to Camel predicate(s).
// hence why there is a number of tasks going on below to accomplish this
// remove any ignorable white space tokens
removeIgnorableWhiteSpaceTokens();
// turn the tokens into the ast model
parseTokensAndCreateNodes();
// compact and stack blocks (eg function start/end, quotes start/end, etc.)
prepareBlocks();
// compact and stack unary expressions
prepareUnaryExpressions();
// compact and stack binary expressions
prepareBinaryExpressions();
// compact and stack logical expressions
prepareLogicalExpressions();
// create and return as a Camel predicate
List predicates = createPredicates();
if (predicates.isEmpty()) {
// return a false predicate as response as there was nothing to parse
return PredicateBuilder.constant(false);
} else if (predicates.size() == 1) {
return predicates.get(0);
} else {
return PredicateBuilder.and(predicates);
}
}
/**
* Parses the tokens and crates the AST nodes.
*
* After the initial parsing of the input (input -> tokens) then we
* parse again (tokens -> ast).
*
* In this parsing the balance of the blocks is checked, so that each block has a matching
* start and end token. For example a single quote block, or a function block etc.
*/
protected void parseTokensAndCreateNodes() {
// we loop the tokens and create a sequence of ast nodes
// we need to keep a bit of state for keeping track of single and double quotes
// which need to be balanced and have matching start/end pairs
SimpleNode lastSingle = null;
SimpleNode lastDouble = null;
SimpleNode lastFunction = null;
AtomicBoolean startSingle = new AtomicBoolean(false);
AtomicBoolean startDouble = new AtomicBoolean(false);
AtomicBoolean startFunction = new AtomicBoolean(false);
LiteralNode imageToken = null;
for (SimpleToken token : tokens) {
// break if eol
if (token.getType().isEol()) {
break;
}
// create a node from the token
SimpleNode node = createNode(token, startSingle, startDouble, startFunction);
if (node != null) {
// keep state of last single/double
if (node instanceof SingleQuoteStart) {
lastSingle = node;
} else if (node instanceof DoubleQuoteStart) {
lastDouble = node;
} else if (node instanceof SimpleFunctionStart) {
lastFunction = node;
}
// a new token was created so the current image token need to be added first
if (imageToken != null) {
nodes.add(imageToken);
imageToken = null;
}
// and then add the created node
nodes.add(node);
// continue to next
continue;
}
// if no token was created then its a character/whitespace/escaped symbol
// which we need to add together in the same image
if (imageToken == null) {
imageToken = new LiteralExpression(token);
}
imageToken.addText(token.getText());
}
// append any leftover image tokens (when we reached eol)
if (imageToken != null) {
nodes.add(imageToken);
}
// validate the single, double quote pairs and functions is in balance
if (startSingle.get()) {
int index = lastSingle != null ? lastSingle.getToken().getIndex() : 0;
throw new SimpleParserException("single quote has no ending quote", index);
}
if (startDouble.get()) {
int index = lastDouble != null ? lastDouble.getToken().getIndex() : 0;
throw new SimpleParserException("double quote has no ending quote", index);
}
if (startFunction.get()) {
// we have a start function, but no ending function
int index = lastFunction != null ? lastFunction.getToken().getIndex() : 0;
throw new SimpleParserException("function has no ending token", index);
}
}
/**
* Creates a node from the given token
*
* @param token the token
* @param startSingle state of single quoted blocks
* @param startDouble state of double quoted blocks
* @param startFunction state of function blocks
* @return the created node, or null to let a default node be created instead.
*/
private SimpleNode createNode(SimpleToken token, AtomicBoolean startSingle, AtomicBoolean startDouble,
AtomicBoolean startFunction) {
if (token.getType().isFunctionStart()) {
startFunction.set(true);
return new SimpleFunctionStart(token);
} else if (token.getType().isFunctionEnd()) {
startFunction.set(false);
return new SimpleFunctionEnd(token);
}
// if we are inside a function, then we do not support any other kind of tokens
// as we want all the tokens to be literal instead
if (startFunction.get()) {
return null;
}
// okay so far we also want to support quotes
if (token.getType().isSingleQuote()) {
SimpleNode answer;
boolean start = startSingle.get();
if (!start) {
answer = new SingleQuoteStart(token);
} else {
answer = new SingleQuoteEnd(token);
}
// flip state on start/end flag
startSingle.set(!start);
return answer;
} else if (token.getType().isDoubleQuote()) {
SimpleNode answer;
boolean start = startDouble.get();
if (!start) {
answer = new DoubleQuoteStart(token);
} else {
answer = new DoubleQuoteEnd(token);
}
// flip state on start/end flag
startDouble.set(!start);
return answer;
}
// if we are inside a quote, then we do not support any further kind of tokens
// as we want to only support embedded functions and all other kinds to be literal tokens
if (startSingle.get() || startDouble.get()) {
return null;
}
// okay we are not inside a function or quote, so we want to support operators
// and the special null value as well
if (token.getType().isUnary()) {
return new UnaryExpression(token);
} else if (token.getType().isBinary()) {
return new BinaryExpression(token);
} else if (token.getType().isLogical()) {
return new LogicalExpression(token);
} else if (token.getType().isNullValue()) {
return new NullExpression(token);
}
// by returning null, we will let the parser determine what to do
return null;
}
/**
* Removes any ignorable whitespace tokens.
*
* During the initial parsing (input -> tokens), then there may
* be excessive whitespace tokens, which can safely be removed,
* which makes the succeeding parsing easier.
*/
private void removeIgnorableWhiteSpaceTokens() {
// white space can be removed if its not part of a quoted text or within function(s)
boolean quote = false;
int functionCount = 0;
Iterator it = tokens.iterator();
while (it.hasNext()) {
SimpleToken token = it.next();
if (token.getType().isSingleQuote()) {
quote = !quote;
} else if (!quote) {
if (token.getType().isFunctionStart()) {
functionCount++;
} else if (token.getType().isFunctionEnd()) {
functionCount--;
} else if (token.getType().isWhitespace() && functionCount == 0) {
it.remove();
}
}
}
}
/**
* Prepares binary expressions.
*
* This process prepares the binary expressions in the AST. This is done
* by linking the binary operator with both the right and left hand side
* nodes, to have the AST graph updated and prepared properly.
*
* So when the AST node is later used to create the {@link Predicate}s
* to be used by Camel then the AST graph has a linked and prepared
* graph of nodes which represent the input expression.
*/
private void prepareBinaryExpressions() {
Stack stack = new Stack();
SimpleNode left = null;
for (int i = 0; i < nodes.size(); i++) {
if (left == null) {
left = i > 0 ? nodes.get(i - 1) : null;
}
SimpleNode token = nodes.get(i);
SimpleNode right = i < nodes.size() - 1 ? nodes.get(i + 1) : null;
if (token instanceof BinaryExpression) {
BinaryExpression binary = (BinaryExpression) token;
// remember the binary operator
String operator = binary.getOperator().toString();
if (left == null) {
throw new SimpleParserException("Binary operator " + operator + " has no left hand side token", token.getToken().getIndex());
}
if (!binary.acceptLeftNode(left)) {
throw new SimpleParserException("Binary operator " + operator + " does not support left hand side token " + left.getToken(), token.getToken().getIndex());
}
if (right == null) {
throw new SimpleParserException("Binary operator " + operator + " has no right hand side token", token.getToken().getIndex());
}
if (!binary.acceptRightNode(right)) {
throw new SimpleParserException("Binary operator " + operator + " does not support right hand side token " + right.getToken(), token.getToken().getIndex());
}
// pop previous as we need to replace it with this binary operator
stack.pop();
stack.push(token);
// advantage after the right hand side
i++;
// this token is now the left for the next loop
left = token;
} else {
// clear left
left = null;
stack.push(token);
}
}
nodes.clear();
nodes.addAll(stack);
}
/**
* Prepares logical expressions.
*
* This process prepares the logical expressions in the AST. This is done
* by linking the logical operator with both the right and left hand side
* nodes, to have the AST graph updated and prepared properly.
*
* So when the AST node is later used to create the {@link Predicate}s
* to be used by Camel then the AST graph has a linked and prepared
* graph of nodes which represent the input expression.
*/
private void prepareLogicalExpressions() {
Stack stack = new Stack();
SimpleNode left = null;
for (int i = 0; i < nodes.size(); i++) {
if (left == null) {
left = i > 0 ? nodes.get(i - 1) : null;
}
SimpleNode token = nodes.get(i);
SimpleNode right = i < nodes.size() - 1 ? nodes.get(i + 1) : null;
if (token instanceof LogicalExpression) {
LogicalExpression logical = (LogicalExpression) token;
// remember the logical operator
String operator = logical.getOperator().toString();
if (left == null) {
throw new SimpleParserException("Logical operator " + operator + " has no left hand side token", token.getToken().getIndex());
}
if (!logical.acceptLeftNode(left)) {
throw new SimpleParserException("Logical operator " + operator + " does not support left hand side token " + left.getToken(), token.getToken().getIndex());
}
if (right == null) {
throw new SimpleParserException("Logical operator " + operator + " has no right hand side token", token.getToken().getIndex());
}
if (!logical.acceptRightNode(right)) {
throw new SimpleParserException("Logical operator " + operator + " does not support right hand side token " + left.getToken(), token.getToken().getIndex());
}
// pop previous as we need to replace it with this binary operator
stack.pop();
stack.push(token);
// advantage after the right hand side
i++;
// this token is now the left for the next loop
left = token;
} else {
// clear left
left = null;
stack.push(token);
}
}
nodes.clear();
nodes.addAll(stack);
}
/**
* Creates the {@link Predicate}s from the AST nodes.
*
* @return the created {@link Predicate}s, is never null.
*/
private List createPredicates() {
List answer = new ArrayList();
for (SimpleNode node : nodes) {
Expression exp = node.createExpression(expression);
if (exp != null) {
Predicate predicate = ExpressionToPredicateAdapter.toPredicate(exp);
answer.add(predicate);
}
}
return answer;
}
// --------------------------------------------------------------
// grammar
// --------------------------------------------------------------
// the predicate parser understands a lot more than the expression parser
// - boolean value = either true or false value (literal)
// - single quoted = block of nodes enclosed by single quotes
// - double quoted = block of nodes enclosed by double quotes
// - single quoted with functions = block of nodes enclosed by single quotes allowing embedded functions
// - double quoted with functions = block of nodes enclosed by double quotes allowing embedded functions
// - function = simple functions such as ${body} etc
// - numeric = numeric value
// - boolean = boolean value
// - null = null value
// - unary operator = operator attached to the left hand side node
// - binary operator = operator attached to both the left and right hand side nodes
// - logical operator = operator attached to both the left and right hand side nodes
protected boolean isBooleanValue() {
if (accept(TokenType.booleanValue)) {
return true;
}
return false;
}
protected boolean singleQuotedLiteralWithFunctionsText() {
if (accept(TokenType.singleQuote)) {
nextToken(TokenType.singleQuote, TokenType.eol, TokenType.functionStart, TokenType.functionEnd);
while (!token.getType().isSingleQuote() && !token.getType().isEol()) {
// we need to loop until we find the ending single quote, or the eol
nextToken(TokenType.singleQuote, TokenType.eol, TokenType.functionStart, TokenType.functionEnd);
}
expect(TokenType.singleQuote);
return true;
}
return false;
}
protected boolean singleQuotedLiteralText() {
if (accept(TokenType.singleQuote)) {
nextToken(TokenType.singleQuote, TokenType.eol);
while (!token.getType().isSingleQuote() && !token.getType().isEol()) {
// we need to loop until we find the ending single quote, or the eol
nextToken(TokenType.singleQuote, TokenType.eol);
}
expect(TokenType.singleQuote);
return true;
}
return false;
}
protected boolean doubleQuotedLiteralWithFunctionsText() {
if (accept(TokenType.doubleQuote)) {
nextToken(TokenType.doubleQuote, TokenType.eol, TokenType.functionStart, TokenType.functionEnd);
while (!token.getType().isDoubleQuote() && !token.getType().isEol()) {
// we need to loop until we find the ending double quote, or the eol
nextToken(TokenType.doubleQuote, TokenType.eol, TokenType.functionStart, TokenType.functionEnd);
}
expect(TokenType.doubleQuote);
return true;
}
return false;
}
protected boolean doubleQuotedLiteralText() {
if (accept(TokenType.doubleQuote)) {
nextToken(TokenType.doubleQuote, TokenType.eol);
while (!token.getType().isDoubleQuote() && !token.getType().isEol()) {
// we need to loop until we find the ending double quote, or the eol
nextToken(TokenType.doubleQuote, TokenType.eol);
}
expect(TokenType.doubleQuote);
return true;
}
return false;
}
protected boolean functionText() {
if (accept(TokenType.functionStart)) {
nextToken();
while (!token.getType().isFunctionEnd() && !token.getType().isEol()) {
if (token.getType().isFunctionStart()) {
// embedded function
functionText();
}
// we need to loop until we find the ending function quote, an embedded function, or the eol
nextToken();
}
// if its not an embedded function then we expect the end token
if (!token.getType().isFunctionStart()) {
expect(TokenType.functionEnd);
}
return true;
}
return false;
}
protected boolean unaryOperator() {
if (accept(TokenType.unaryOperator)) {
nextToken();
// there should be a whitespace after the operator
expect(TokenType.whiteSpace);
return true;
}
return false;
}
protected boolean binaryOperator() {
if (accept(TokenType.binaryOperator)) {
// remember the binary operator
BinaryOperatorType operatorType = BinaryOperatorType.asOperator(token.getText());
nextToken();
// there should be at least one whitespace after the operator
expectAndAcceptMore(TokenType.whiteSpace);
// okay a binary operator may not support all kind if preceding parameters, so we need to limit this
BinaryOperatorType.ParameterType[] types = BinaryOperatorType.supportedParameterTypes(operatorType);
// based on the parameter types the binary operator support, we need to set this state into
// the following booleans so we know how to proceed in the grammar
boolean literalWithFunctionsSupported = false;
boolean literalSupported = false;
boolean functionSupported = false;
boolean numericSupported = false;
boolean booleanSupported = false;
boolean nullSupported = false;
if (types == null || types.length == 0) {
literalWithFunctionsSupported = true;
// favor literal with functions over literals without functions
literalSupported = false;
functionSupported = true;
numericSupported = true;
booleanSupported = true;
nullSupported = true;
} else {
for (BinaryOperatorType.ParameterType parameterType : types) {
literalSupported |= parameterType.isLiteralSupported();
literalWithFunctionsSupported |= parameterType.isLiteralWithFunctionSupport();
functionSupported |= parameterType.isFunctionSupport();
nullSupported |= parameterType.isNumericValueSupported();
booleanSupported |= parameterType.isBooleanValueSupported();
nullSupported |= parameterType.isNullValueSupported();
}
}
// then we proceed in the grammar according to the parameter types supported by the given binary operator
//CHECKSTYLE:OFF
if ((literalWithFunctionsSupported && singleQuotedLiteralWithFunctionsText())
|| (literalWithFunctionsSupported && doubleQuotedLiteralWithFunctionsText())
|| (literalSupported && singleQuotedLiteralText())
|| (literalSupported && doubleQuotedLiteralText())
|| (functionSupported && functionText())
|| (numericSupported && numericValue())
|| (booleanSupported && booleanValue())
|| (nullSupported && nullValue())) {
// then after the right hand side value, there should be a whitespace if there is more tokens
nextToken();
if (!token.getType().isEol()) {
expect(TokenType.whiteSpace);
}
} else {
throw new SimpleParserException("Binary operator " + operatorType + " does not support token " + token, token.getIndex());
}
//CHECKSTYLE:ON
return true;
}
return false;
}
protected boolean logicalOperator() {
if (accept(TokenType.logicalOperator)) {
// remember the logical operator
LogicalOperatorType operatorType = LogicalOperatorType.asOperator(token.getText());
nextToken();
// there should be at least one whitespace after the operator
expectAndAcceptMore(TokenType.whiteSpace);
// then we expect either some quoted text, another function, or a numeric, boolean or null value
if (singleQuotedLiteralWithFunctionsText()
|| doubleQuotedLiteralWithFunctionsText()
|| functionText()
|| numericValue()
|| booleanValue()
|| nullValue()) {
// then after the right hand side value, there should be a whitespace if there is more tokens
nextToken();
if (!token.getType().isEol()) {
expect(TokenType.whiteSpace);
}
} else {
throw new SimpleParserException("Logical operator " + operatorType + " does not support token " + token, token.getIndex());
}
return true;
}
return false;
}
protected boolean numericValue() {
return accept(TokenType.numericValue);
// no other tokens to check so do not use nextToken
}
protected boolean booleanValue() {
return accept(TokenType.booleanValue);
// no other tokens to check so do not use nextToken
}
protected boolean nullValue() {
return accept(TokenType.nullValue);
// no other tokens to check so do not use nextToken
}
}