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An implementation of the Criteria API for Mongo DB.
There is a newer version: 1.0.5
/*
 * Copyright (C) 2011 by Apaq
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see .
 */
package dk.apaq.framework.criteria.mongo;


import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import dk.apaq.framework.criteria.Limit;
import dk.apaq.framework.criteria.Rule;
import dk.apaq.framework.criteria.Sorter;
import dk.apaq.framework.criteria.Sorter.SorterEntry;
import dk.apaq.framework.criteria.mongo.interpreter.CompareRuleInterpreter;
import dk.apaq.framework.criteria.mongo.interpreter.Interpreter;
import dk.apaq.framework.criteria.rules.AndRule;
import dk.apaq.framework.criteria.rules.CompareRule;
import dk.apaq.framework.criteria.rules.NotRule;
import dk.apaq.framework.criteria.rules.OrRule;
import org.springframework.data.mongodb.core.query.Criteria;
import org.springframework.data.mongodb.core.query.Order;
import org.springframework.data.mongodb.core.query.Query;

/**
 *  Translates Rule, Sorters and Limits to JPA Query.
 */
public class CriteriaForMongoDb {

    private static final Map, Interpreter> interpreterMap = new HashMap, Interpreter>();

    static {
        interpreterMap.put(CompareRule.class, new CompareRuleInterpreter());
    }
    
    public static Query translate(Class entityClass, dk.apaq.framework.criteria.Criteria criteria) {
        return translate(null, entityClass, criteria);
    }
    
    public static Query translate(String[] fields, Class entityClass, dk.apaq.framework.criteria.Criteria criteria) {
        Rule rule = criteria == null ? null : criteria.getRule();
        Limit limit = criteria == null ? null : criteria.getLimit();
        Sorter sorter = criteria == null ? null : criteria.getSorter();
        Query q = new Query();
    
        // Handle fields
        if(fields != null) {
            for(String field : fields) {
                q.fields().include(field);
            }
        }
                
        //Handle filter
        Criteria c = new Criteria();
        buildCriteria(c, rule);
        q.addCriteria(c);
        
        //Handle sorting
        if(sorter != null && ! sorter.getSorterEntries().isEmpty()) {
            if(sorter.getSorterEntries().size()>1) {
                throw new IllegalArgumentException("One a single sorter element is supported by this translator.");
            }
            
            SorterEntry entry = sorter.getSorterEntries().get(0);
            q.sort().on(entry.getPropertyId(), entry.getDirection() == Sorter.Direction.Ascending ? Order.ASCENDING : Order.DESCENDING);
        }
        
        //Handle limits
        if(limit != null) {
            q.skip(limit.getOffset());
            q.limit(limit.getCount());
        }
        
        return q;

    }
    
    private static boolean buildCriteria(Criteria clause, Rule filter) {

        if (filter == null) {
            return false;
        }

        //First try an interpreter
        Interpreter interpreter = interpreterMap.get(filter.getClass());
        if (interpreter != null) {
            return interpreter.interpret(clause, filter);
        }


        //..else try our special handlers for filtercontainers.
        if (filter instanceof AndRule) {
            AndRule af = (AndRule) filter;
            List criterias = new ArrayList();
            boolean hasAddedRule = false;
            
            for (Rule currentRule : af.getRules()) {
                Criteria c = new Criteria();
                boolean statementAppended = buildCriteria(c, currentRule);

                if (statementAppended) {
                    criterias.add(c);
                    hasAddedRule = true;
                }
            }

            clause.andOperator(criterias.toArray(new Criteria[0]));
            return hasAddedRule;
        }

        if (filter instanceof OrRule) {
            OrRule of = (OrRule) filter;
            List criterias = new ArrayList();
            boolean hasAddedRule = false;

            for (Rule currentRule : of.getRules()) {
                Criteria c = new Criteria();
                boolean statementAppended = buildCriteria(c, currentRule);

                if (statementAppended) {
                    criterias.add(c);
                    hasAddedRule = true;
                }
            }

            clause.orOperator(criterias.toArray(new Criteria[0]));
            return hasAddedRule;
        }

        if (filter instanceof NotRule) {
            NotRule af = (NotRule) filter;

            clause.not();
            return buildCriteria(clause, af.getRuleElement());
        }

        return false;
    }
}