org.weborganic.flint.query.PredicateSearchQuery.java Source code

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Here is the source code for org.weborganic.flint.query.PredicateSearchQuery.java

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/*
 * This file is part of the Flint library.
 *
 * For licensing information please see the file license.txt included in the release.
 * A copy of this licence can also be found at
 *   http://www.opensource.org/licenses/artistic-license-2.0.php
 */
package org.weborganic.flint.query;

import java.io.IOException;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.queryParser.ParseException;
import org.apache.lucene.queryParser.QueryParser;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.SortField;
import org.weborganic.flint.IndexManager;

import com.topologi.diffx.xml.XMLWriter;

/**
 * A search query to submit a predicate directly to the index.
 *
 * <p>This query uses the Lucene {@link QueryParser} to create a valid query instance from the
 * supplied predicate.
 *
 * @author Christophe Lauret (Weborganic)
 * @author Jean-Baptiste Reure (Weborganic)
 *
 * @version 2 August 2010
 */
public final class PredicateSearchQuery implements SearchQuery {

    /**
     * Bypasses all the other query parameters.
     */
    private final String _predicate;

    /**
     * The analyser used in this query.
     */
    private final Analyzer _analyser;

    /**
     * The sort order.
     */
    private final Sort _sort;

    /**
     * A flag to specify if wildcard ('*' or '?') is allowed as the first character of the predicate.
     */
    private boolean _allowLeadingWildcard = false;

    /**
     * Creates new predicate search query.
     *
     * @param predicate The predicate for this query.
     * @param sortField The field name to use to order the results.
     *
     * @throws IllegalArgumentException If the predicate is <code>null</code>.
     */
    public PredicateSearchQuery(String predicate, String sortField) throws IllegalArgumentException {
        this(predicate, sortField == null ? Sort.INDEXORDER : new Sort(new SortField(sortField, SortField.STRING)));
    }

    /**
     * Creates new predicate search query.
     *
     * @param predicate The predicate for this query.
     * @param analyzer  The analyzer to use for the query, should be the same as the one used to write the Index.
     * @param sortField The field name to use to order the results.
     *
     * @throws IllegalArgumentException If the predicate is <code>null</code>.
     */
    public PredicateSearchQuery(String predicate, Analyzer analyzer, String sortField)
            throws IllegalArgumentException {
        this(predicate, analyzer,
                sortField == null ? Sort.INDEXORDER : new Sort(new SortField(sortField, SortField.STRING)));
    }

    /**
     * Creates new predicate search query.
     *
     * @param predicate The predicate for this query.
     *
     * @throws IllegalArgumentException If the predicate is <code>null</code>.
     */
    public PredicateSearchQuery(String predicate) throws IllegalArgumentException {
        this(predicate, Sort.INDEXORDER);
    }

    /**
     * Creates new predicate search query.
     *
     * @param predicate The predicate for this query.
     * @param analyzer  The analyzer to use for the query, should be the same as the one used to write the Index.
     *
     * @throws IllegalArgumentException If the predicate is <code>null</code>.
     */
    public PredicateSearchQuery(String predicate, Analyzer analyzer) throws IllegalArgumentException {
        this(predicate, analyzer, Sort.INDEXORDER);
    }

    /**
     * Creates new predicate search query.
     *
     * @param predicate The predicate for this query.
     * @param sort      The sort order for the results.
     *
     * @throws IllegalArgumentException If the predicate is <code>null</code>.
     */
    public PredicateSearchQuery(String predicate, Sort sort) throws IllegalArgumentException {
        this(predicate, new StandardAnalyzer(IndexManager.LUCENE_VERSION), sort);
    }

    /**
     * Creates new predicate search query.
     *
     * @param predicate The predicate for this query.
     * @param analyzer  The analyzer to use for the query, should be the same as the one used to write the Index.
     * @param sort      The sort order for the results.
     *
     * @throws IllegalArgumentException If the predicate is <code>null</code>.
     */
    public PredicateSearchQuery(String predicate, Analyzer analyzer, Sort sort) throws IllegalArgumentException {
        if (predicate == null)
            throw new IllegalArgumentException("predicate is null");
        this._predicate = predicate;
        this._analyser = analyzer;
        this._sort = sort;
    }

    // getters and setters
    // --------------------------------------------------------------------------------------------

    /**
     * Whether or not a wildcard ('*' or '?') is allowed as the first character of the predicate.
     *
     * @param allowWildCardStart true if wildcard should be allowed, false otherwise
     */
    public void setAllowWildCardStart(boolean allowWildCardStart) {
        this._allowLeadingWildcard = allowWildCardStart;
    }

    /**
     * Returns <code>null</code>.
     *
     * @return <code>null</code>.
     */
    @Override
    public String getField() {
        return null;
    }

    /**
     * Returns the predicate to use for this search.
     *
     * @return The predicate for this search.
     */
    @Override
    public String getPredicate() {
        return this._predicate;
    }

    /**
     * Returns the Lucene query instance corresponding to this object.
     *
     * <p>
     * This method uses a query parser to parse the predicate.
     *
     * @return The Lucene query instance or <code>null</code> if the predicate was <code>null</code>.
     */
    @Override
    public Query toQuery() {
        if (this._predicate == null)
            return null;
        try {
            QueryParser parser = new QueryParser(IndexManager.LUCENE_VERSION, getField(), this._analyser);
            parser.setAllowLeadingWildcard(this._allowLeadingWildcard);
            return parser.parse(this._predicate);
        } catch (ParseException ex) {
            return null;
        }
    }

    /**
     * Returns <code>true</code> if the predicate has not been set.
     *
     * @return <code>true</code> if the predicate has not been set; <code>false</code> otherwise.
     */
    @Override
    public boolean isEmpty() {
        return this._predicate == null;
    }

    /**
     * Serialises the search query as XML.
     *
     * <pre>{@code
     *   <search-query>
     *     <predicate>[predicate]</predicate>
     *   <search-query>
     * }</pre>
     *
     * @param xml The XML writer.
     *
     * @throws IOException Should there be any I/O exception while writing the XML.
     */
    @Override
    public void toXML(XMLWriter xml) throws IOException {
        xml.openElement("search-query", true);
        xml.element("predicate", this._predicate);
        xml.closeElement();
    }

    /**
     * Returns the sort order.
     *
     * @return the sorting rules for the search results
     */
    @Override
    public Sort getSort() {
        return this._sort;
    }

}