@Override
public int _handleToken(ParseContext ctx) throws InvalidQueryException {
Token token = ctx.getTokens()[ctx.getCurrentTokensIndex()];
ctx.getPrecedingExpression().setLeftOperand(token.getValue());
return 1;
}
/**
* Generate a Predicate instance from an array of tokens. Each input token contains a type and a
* value.
*
* <p>Based on the token type and location, the tokens are first translated into a list of
* expressions, both relational and logical. These expressions are then merged into a tree of
* expressions with a single root following operator precedence and explicit grouping rules.
* Depending on the query, this merging of expressions into a tree of expressions may occur in
* several passes, one pass per level of precedence starting at the highest level of precedence.
*
* <p>The predicate is built by traversing the expression tree in-order with each node expressing
* itself as a predicate.
*
* @param tokens an array of tokens which represent the query, each token contains type and value
* information
* @return a new predicate instance based on the supplied tokens
* @throws InvalidQueryException if unable to parse the tokens and produce a predicate
*/
public Predicate parse(Token[] tokens) throws InvalidQueryException {
ParseContext ctx = parseExpressions(tokens);
List<Expression> listExpressions = ctx.getExpressions();
List<Expression> listMergedExpressions =
mergeExpressions(listExpressions, ctx.getMaxPrecedence());
return listMergedExpressions.isEmpty() ? null : listMergedExpressions.get(0).toPredicate();
}
@Override
public int _handleToken(ParseContext ctx) throws InvalidQueryException {
Token token = ctx.getTokens()[ctx.getCurrentTokensIndex()];
RelationalOperator relationalOp = RelationalOperatorFactory.createOperator(token.getValue());
// todo: use factory to create expression
ctx.addExpression(new RelationalExpression(relationalOp));
return 1;
}
@Override
public int _handleToken(ParseContext ctx) throws InvalidQueryException {
Token token = ctx.getTokens()[ctx.getCurrentTokensIndex()];
LogicalOperator logicalOp =
LogicalOperatorFactory.createOperator(token.getValue(), ctx.getPrecedenceLevel());
ctx.updateMaxPrecedence(logicalOp.getPrecedence());
ctx.addExpression(LogicalExpressionFactory.createLogicalExpression(logicalOp));
return 1;
}
/**
* Create parse context from an array of tokens. The parse context contains a list of expressions
* and other information about the expressions an parsed tokens.
*
* @param tokens an array of tokens which represent the query, each token contains type and value
* information
* @return a parse context which contains a list of expressions
* @throws InvalidQueryException if unable to properly parse the tokens into a parse context
*/
private ParseContext parseExpressions(Token[] tokens) throws InvalidQueryException {
ParseContext ctx = new ParseContext(tokens);
while (ctx.getCurrentTokensIndex() < tokens.length) {
TOKEN_HANDLERS.get(tokens[ctx.getCurrentTokensIndex()].getType()).handleToken(ctx);
}
if (ctx.getPrecedenceLevel() != 0) {
throw new InvalidQueryException("Invalid query string: mismatched parentheses.");
}
return ctx;
}
@Override
public int _handleToken(ParseContext ctx) throws InvalidQueryException {
Token[] tokens = ctx.getTokens();
int idx = ctx.getCurrentTokensIndex();
Token token = tokens[idx];
RelationalOperator relationalOp = RelationalOperatorFactory.createOperator(token.getValue());
ctx.addExpression(new RelationalExpression(relationalOp));
ctx.setCurrentTokensIndex(++idx);
TokenHandler propertyHandler = new PropertyOperandTokenHandler();
propertyHandler.handleToken(ctx);
// handle right operand if applicable to operator
idx = ctx.getCurrentTokensIndex();
if (ctx.getCurrentTokensIndex() < tokens.length
&& tokens[idx].getType().equals(Token.TYPE.VALUE_OPERAND)) {
TokenHandler valueHandler = new ValueOperandTokenHandler();
valueHandler.handleToken(ctx);
}
// skip closing bracket
idx = ctx.getCurrentTokensIndex();
if (idx >= tokens.length || tokens[idx].getType() != Token.TYPE.BRACKET_CLOSE) {
throw new InvalidQueryException("Missing closing bracket for in expression.");
}
return 1;
}
/**
* Process a token. Handles common token processing functionality then delegates to the
* individual concrete handlers.
*
* @param ctx the current parse context
* @throws InvalidQueryException if unable to process the token
*/
public void handleToken(ParseContext ctx) throws InvalidQueryException {
Token token = ctx.getTokens()[ctx.getCurrentTokensIndex()];
if (!validate(ctx.getPreviousTokenType())) {
throw new InvalidQueryException(
"Unexpected token encountered in query string. Last Token Type="
+ ctx.getPreviousTokenType()
+ ", Current Token[type="
+ token.getType()
+ ", value='"
+ token.getValue()
+ "']");
}
ctx.setTokenType(token.getType());
int idxIncrement = _handleToken(ctx);
ctx.setCurrentTokensIndex(ctx.getCurrentTokensIndex() + idxIncrement);
}
@Override
public int _handleToken(ParseContext ctx) throws InvalidQueryException {
ctx.decPrecedenceLevel(Operator.MAX_OP_PRECEDENCE);
return 1;
}
@Override
public int _handleToken(ParseContext ctx) {
ctx.incPrecedenceLevel(Operator.MAX_OP_PRECEDENCE);
return 1;
}