AbstractQueryClause.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.metamodel.query;

import java.util.ArrayList;
import java.util.List;

import org.apache.metamodel.util.BaseObject;

/**
 * Represents an abstract clause in a query. Clauses contains IQueryItems and
 * provide basic ways of adding, modifying and removing these.
 * 
 * @param <E>
 *            the type of query item this QueryClause handles
 * 
 * @see Query
 */
public abstract class AbstractQueryClause<E extends QueryItem> extends BaseObject implements QueryClause<E> {

    private static final long serialVersionUID = 3987346267433022231L;

    public static final String PREFIX_SELECT = "SELECT ";
    public static final String PREFIX_FROM = " FROM ";
    public static final String PREFIX_WHERE = " WHERE ";
    public static final String PREFIX_GROUP_BY = " GROUP BY ";
    public static final String PREFIX_HAVING = " HAVING ";
    public static final String PREFIX_ORDER_BY = " ORDER BY ";
    public static final String DELIM_COMMA = ", ";
    public static final String DELIM_AND = " AND ";

    private final Query _query;
    private final List<E> _items = new ArrayList<E>();
    private final String _prefix;
    private final String _delim;

    public AbstractQueryClause(Query query, String prefix, String delim) {
        _query = query;
        _prefix = prefix;
        _delim = delim;
    }

    @Override
    public QueryClause<E> setItems(E... items) {
        _items.clear();
        return addItems(items);
    }

    @Override
    public QueryClause<E> addItems(E... items) {
        for (E item : items) {
            addItem(item);
        }
        return this;
    }

    @Override
    public QueryClause<E> addItems(Iterable<E> items) {
        for (E item : items) {
            addItem(item);
        }
        return this;
    }

    public QueryClause<E> addItem(int index, E item) {
        if (item.getQuery() == null) {
            item.setQuery(_query);
        }
        _items.add(index, item);
        return this;
    };

    @Override
    public QueryClause<E> addItem(E item) {
        return addItem(getItemCount(), item);
    }

    @Override
    public int getItemCount() {
        return _items.size();
    }
    
    @Override
    public int indexOf(E item) {
        return _items.indexOf(item);
    }

    @Override
    public boolean isEmpty() {
        return getItemCount() == 0;
    }

    @Override
    public E getItem(int index) {
        return _items.get(index);
    }

    @Override
    public List<E> getItems() {
        return _items;
    }

    @Override
    public QueryClause<E> removeItem(int index) {
        _items.remove(index);
        return this;
    }

    @Override
    public QueryClause<E> removeItem(E item) {
        _items.remove(item);
        return this;
    }

    @Override
    public QueryClause<E> removeItems() {
        _items.clear();
        return this;
    }

    @Override
    public String toSql() {
        return toSql(false);
    }

    @Override
    public String toSql(boolean includeSchemaInColumnPaths) {
        if (_items.size() == 0) {
            return "";
        }
        final StringBuilder sb = new StringBuilder(_prefix);
        for (int i = 0; i < _items.size(); i++) {
            final E item = _items.get(i);
            if (i != 0) {
                sb.append(_delim);
            }
            final String sql = item.toSql(includeSchemaInColumnPaths);
            sb.append(sql);
        }
        return sb.toString();
    }

    @Override
    public String toString() {
        return toSql();
    }

    @Override
    protected void decorateIdentity(List<Object> identifiers) {
        identifiers.add(_items);
    }
}