org.apache.ambari.server.api.predicate

Class QueryParser

java.lang.Object

org.apache.ambari.server.api.predicate.QueryParser

public class QueryParser
extends Object

Parser which produces a predicate instance from an array of tokens, which is generated by the lexer.

Constructor Summary

Constructors

Constructor and Description
QueryParser() Constructor.

Method Summary

Modifier and Type	Method and Description
Predicate	parse(Token[] tokens) Generate a Predicate instance from an array of tokens.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

QueryParser

public QueryParser()

Constructor. Register token handlers.

Method Detail

parse

public Predicate parse(Token[] tokens)
                throws InvalidQueryException

Generate a Predicate instance from an array of tokens. Each input token contains a type and a value. 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. The predicate is built by traversing the expression tree in-order with each node expressing itself as a predicate.

Parameters:

tokens - an array of tokens which represent the query, each token contains type and value information

Returns:

a new predicate instance based on the supplied tokens

Throws:

InvalidQueryException - if unable to parse the tokens and produce a predicate