refactor DALParser

import io.shardingjdbc.core.parsing.lexer.LexerEngine;

import io.shardingjdbc.core.parsing.parser.clause.TableReferencesClauseParser;

import io.shardingjdbc.core.parsing.parser.dialect.mysql.statement.DescribeStatement;

import io.shardingjdbc.core.parsing.parser.sql.SQLParser;

import io.shardingjdbc.core.parsing.parser.sql.dal.describe.AbstractDescribeParser;

import io.shardingjdbc.core.rule.ShardingRule;

/**

 *

 * @author zhangliang

 */

public final class MySQLDescribeParser implements SQLParser {

public final class MySQLDescribeParser extends AbstractDescribeParser {

    private final LexerEngine lexerEngine;

import io.shardingjdbc.core.parsing.parser.dialect.mysql.statement.ShowDatabasesStatement;

import io.shardingjdbc.core.parsing.parser.dialect.mysql.statement.ShowOtherStatement;

import io.shardingjdbc.core.parsing.parser.dialect.mysql.statement.ShowTablesStatement;

import io.shardingjdbc.core.parsing.parser.sql.SQLParser;

import io.shardingjdbc.core.parsing.parser.sql.dal.DALStatement;

import io.shardingjdbc.core.parsing.parser.sql.dal.show.AbstractShowParser;

import io.shardingjdbc.core.parsing.parser.token.SchemaToken;

import io.shardingjdbc.core.rule.ShardingRule;

import lombok.RequiredArgsConstructor;

 * @author zhangliang

 */

@RequiredArgsConstructor

public final class MySQLShowParser implements SQLParser {

public final class MySQLShowParser extends AbstractShowParser {

    private final LexerEngine lexerEngine;

package io.shardingjdbc.core.parsing.parser.dialect.mysql.sql;

import io.shardingjdbc.core.parsing.parser.dialect.mysql.statement.UseStatement;

import io.shardingjdbc.core.parsing.parser.sql.SQLParser;

import io.shardingjdbc.core.parsing.parser.sql.dal.DALStatement;

import io.shardingjdbc.core.parsing.parser.sql.dal.use.AbstractUseParser;

/**

 * Use parser for MySQL.

 *

 * @author zhangliang

 */

public final class MySQLUseParser implements SQLParser {

public final class MySQLUseParser extends AbstractUseParser {

    @Override

    public DALStatement parse() {

    public UseStatement parse() {

        return new UseStatement();

    }

}

import io.shardingjdbc.core.parsing.lexer.token.DefaultKeyword;

import io.shardingjdbc.core.parsing.lexer.token.Keyword;

import io.shardingjdbc.core.parsing.lexer.token.TokenType;

import io.shardingjdbc.core.parsing.parser.dialect.mysql.sql.MySQLDescribeParser;

import io.shardingjdbc.core.parsing.parser.dialect.mysql.sql.MySQLShowParser;

import io.shardingjdbc.core.parsing.parser.dialect.mysql.sql.MySQLUseParser;

import io.shardingjdbc.core.parsing.parser.exception.SQLParsingUnsupportedException;

import io.shardingjdbc.core.parsing.parser.sql.dal.describe.DescribeParserFactory;

import io.shardingjdbc.core.parsing.parser.sql.dal.show.ShowParserFactory;

import io.shardingjdbc.core.parsing.parser.sql.dal.use.UseParserFactory;

import io.shardingjdbc.core.parsing.parser.sql.ddl.alter.AlterParserFactory;

import io.shardingjdbc.core.parsing.parser.sql.ddl.create.CreateParserFactory;

import io.shardingjdbc.core.parsing.parser.sql.ddl.drop.DropParserFactory;

            return getTCLParser(dbType, shardingRule, lexerEngine);

        }

        if (isDAL(tokenType)) {

            return getDALParser((Keyword) tokenType, shardingRule, lexerEngine);

            return getDALParser(dbType, (Keyword) tokenType, shardingRule, lexerEngine);

        }

        throw new SQLParsingUnsupportedException(tokenType);

    }

        return TCLParserFactory.newInstance(dbType, shardingRule, lexerEngine);

    }

    private static SQLParser getDALParser(final Keyword tokenType, final ShardingRule shardingRule, final LexerEngine lexerEngine) {

    private static SQLParser getDALParser(final DatabaseType dbType, final Keyword tokenType, final ShardingRule shardingRule, final LexerEngine lexerEngine) {

        if (DefaultKeyword.USE == tokenType) {

            return new MySQLUseParser();

            return UseParserFactory.newInstance(dbType, shardingRule, lexerEngine);

        }

        if (DefaultKeyword.DESC == tokenType || MySQLKeyword.DESCRIBE == tokenType) {

            return new MySQLDescribeParser(shardingRule, lexerEngine);

            return DescribeParserFactory.newInstance(dbType, shardingRule, lexerEngine);

        }

        if (MySQLKeyword.SHOW == tokenType) {

            return new MySQLShowParser(shardingRule, lexerEngine);

            return ShowParserFactory.newInstance(dbType, shardingRule, lexerEngine);

        }

        throw new SQLParsingUnsupportedException(tokenType);

    }

package io.shardingjdbc.core.parsing.parser.sql.dal;

import io.shardingjdbc.core.parsing.parser.sql.SQLParser;

/**

 * Database administrator parser.

 *

 * @author zhangliang

 */

public abstract class AbstractDALParser implements SQLParser {

}