SearchTerm.java

/**
 * Copyright 1999-2009 The Pegadi Team
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.pegadi.sqlsearch;

import java.util.*;

import static org.apache.commons.lang.StringUtils.isNotBlank;

/**
 * This is an abstract class representing a search-term.
 * Search criteria are represented as a tree of seach-terms, forming a
 * parse-tree used to generate the SQL query that returns the matching
 * Articles.
 * <p/>
 * SearchTerms are represented by this class. This is an abstract class:
 * subclasses implement specific math methods.
 *
 * @author Eirik Bjorsnos <bjorsnos@underdusken.no>
 * @version $Revision$, $Date$
 */
public abstract class SearchTerm implements java.io.Serializable {

    private boolean selectDistinct = false;

    private String orderBy;

    /**
     * Generates the WHERE part of the SQL query (without including the string
     * "WHERE").
     *
     * @return the WHERE clause
     */
    public abstract String whereClause();

    /**
     * Returns the names of the tables involved in this search.
     *
     * @return A String[] containing the involved tables. The array may contain
     *         multiple instances of each table name.
     */
    public abstract List<String> getTables();

    /**
     * Returns the names of tables that should be ignored
     */
    public List<String> getIgnoreTables() {
        return Collections.emptyList();
    }


    /**
     * Returns the SQL query for this SearchTerm
     *
     * @param selectString the part following SELECT (what to select)
     * @return the SQL query
     */
    public String getQuery(String selectString) {

        StringBuilder query = new StringBuilder();
        query.append("SELECT ");
        if (selectDistinct) {
            query.append("distinct ");
        }
        query.append(selectString);
        query.append(" FROM ");

        Set<String> tables = new LinkedHashSet<String>(getTables());
        Collection<String> ignoreTables = getIgnoreTables();

        tables.removeAll(ignoreTables);

        for (Iterator<String> iterator = tables.iterator(); iterator.hasNext(); ) {
            String table = iterator.next();
            query.append(table);
            if(iterator.hasNext()){
                query.append(", ");
            }
        }

        query.append(" WHERE ");
        query.append(whereClause());

        if(isNotBlank(orderBy)){
            query.append(" ORDER BY ");
            query.append(orderBy);
        }

        return query.toString();

    }

    public void setSelectDistinct(boolean selectDistinct) {
        this.selectDistinct = selectDistinct;
    }

    public String getOrderBy() {
        return orderBy;
    }

    public void setOrderBy(String orderBy) {
        this.orderBy = orderBy;
    }
}