org.z3950.zing.cql
Class CQLParser

java.lang.Object
  org.z3950.zing.cql.CQLParser

public class CQLParser
extends Object

Compiles CQL strings into parse trees of CQLNode subtypes.

See Also:

http://zing.z3950.org/cql/index.html

Field Summary

boolean	allowKeywordTerms
static int	V1POINT1
static int	V1POINT1SORT
static int	V1POINT2

Constructor Summary

CQLParser()
The new parser implements CQL 1.2

CQLParser(int compat)
The new parser implements a dialect of CQL specified by the compat argument: V1POINT1 - CQL version 1.1 V1POINT2 - CQL version 1.2 V1POINT1SORT - CQL version 1.1 but including sortby as specified for CQL 1.2.

CQLParser(int compat, boolean allowKeywordTerms)
Official CQL grammar allows registered keywords like 'and/or/not/sortby/prox' to be used unquoted in terms.

Method Summary

static void	main(String[] args) Simple test-harness for the CQLParser class.
CQLNode	parse(String cql) Compiles a CQL query.
boolean	registerCustomRelation(String relation) Registers custom relation in this parser.
boolean	unregisterCustomRelation(String relation) Unregisters previously registered custom relation in this instance of the parser.

Methods inherited from class java.lang.Object

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

Field Detail

V1POINT1

public static final int V1POINT1

See Also:

Constant Field Values

V1POINT2

public static final int V1POINT2

See Also:

Constant Field Values

V1POINT1SORT

public static final int V1POINT1SORT

See Also:

Constant Field Values

allowKeywordTerms

public final boolean allowKeywordTerms

Constructor Detail

CQLParser

public CQLParser(int compat)

The new parser implements a dialect of CQL specified by the compat argument:

• V1POINT1 - CQL version 1.1
• V1POINT2 - CQL version 1.2
• V1POINT1SORT - CQL version 1.1 but including sortby as specified for CQL 1.2.

CQLParser

public CQLParser(int compat,
                 boolean allowKeywordTerms)

Official CQL grammar allows registered keywords like 'and/or/not/sortby/prox' to be used unquoted in terms. This constructor allows to create an instance of a parser that prohibits this behavior while sacrificing compatibility.

Parameters:

compat - CQL version compatibility

allowKeywordTerms - when false registered keywords are disallowed in unquoted terms

CQLParser

public CQLParser()

The new parser implements CQL 1.2

Method Detail

registerCustomRelation

public boolean registerCustomRelation(String relation)

Registers custom relation in this parser. Note that when a custom relation is registered the parser is no longer strictly compliant with the chosen spec.

Parameters:

relation -

Returns:

true if custom relation has not been registered already

unregisterCustomRelation

public boolean unregisterCustomRelation(String relation)

Unregisters previously registered custom relation in this instance of the parser.

Parameters:

relation -

Returns:

true is relation has been previously registered

parse

public CQLNode parse(String cql)
              throws CQLParseException,
                     IOException

Compiles a CQL query.

The resulting parse tree may be further processed by hand (see the individual node-types' documentation for details on the data structure) or, more often, simply rendered out in the desired form using one of the back-ends. toCQL() returns a decompiled CQL query equivalent to the one that was compiled in the first place; toXCQL() returns an XML snippet representing the query; and toPQF() returns the query rendered in Index Data's Prefix Query Format.

Parameters:

cql - The query

Returns:

A CQLNode object which is the root of a parse tree representing the query.

Throws:

CQLParseException

IOException

main

public static void main(String[] args)

Simple test-harness for the CQLParser class.

Reads a CQL query either from its command-line argument, if there is one, or standard input otherwise. So these two invocations are equivalent:

  CQLParser 'au=(Kerninghan or Ritchie) and ti=Unix'
  echo au=(Kerninghan or Ritchie) and ti=Unix | CQLParser
 

The test-harness parses the supplied query and renders is as XCQL, so that both of the invocations above produce the following output:

        <triple>
          <boolean>
            <value>and</value>
          </boolean>
          <triple>
            <boolean>
              <value>or</value>
            </boolean>
            <searchClause>
              <index>au</index>
              <relation>
                <value>=</value>
              </relation>
              <term>Kerninghan</term>
            </searchClause>
            <searchClause>
              <index>au</index>
              <relation>
                <value>=</value>
              </relation>
              <term>Ritchie</term>
            </searchClause>
          </triple>
          <searchClause>
            <index>ti</index>
            <relation>
              <value>=</value>
            </relation>
            <term>Unix</term>
          </searchClause>
        </triple>
 

Parameters:

-1 - CQL version 1.1 (default version 1.2)

-d - Debug mode: extra output written to stderr.

-c - Causes the output to be written in CQL rather than XCQL - that is, a query equivalent to that which was input, is output. In effect, the test harness acts as a query canonicaliser.