根据写定的查询SQL获取其中的所有表名

记录一下根据查询SQL获取其中所有表名的方法

 

因为使用的是比较暴力的拆解方式，所以不能保证效率问题，仅用来解决部分业务逻辑问题

也因为是比较暴力的拆解，所以理论上哪种数据库的SQL都没有什么影响的，只要SQL是可执行的，都可以满足

 

直接贴代码

import org.apache.commons.lang.StringUtils;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

/**
 * 从写定的SQL中解析表名
 *
 * @author chenjunxu
 * @date 2018/12/27
 */
public class SQLMain {

	private static final String FROM_LOWER = "from";
	private static final String FROM_UPPER = "FROM";
	private static final String[] SPLIT_KEY = {"select", "SELECT", " where ", " WHERE "};
	private static final String[] JOIN_KEY = {",", " join ", " JOIN "};

	public static void main(String[] args) {
//		String sql = "select a, b, c from user u,org o where u.id = o.uid and u.id in (select id from user_org uo)";
//		String sql = "select * FROM     u   order    by  b";
//		String sql = "select count(a) from `user`  u  ,   org  o  where u.a = o.b group by d";
		String sql = "select a, b, c from user u,org o where u.id = o.uid and u.id in (select id from user_org uo LEFT JOIN table_o to " +
				"where uo.id not exist (select id from org_user  ))";
//		String sql = "select a, b, c from user u INNER   JOIN  org o on u.id = o.id where user.a = 'aaa'";
		sql = formatSQL(sql);
		List list = new ArrayList<>();
		if (getSplitKey(sql) != null) {
			splitSQL(sql, list);
		}
		Set tables = new HashSet<>();
		for (String s : list) {
			getTables(s, tables);
		}
		for (String table : tables) {
			System.out.println(table);
		}
	}

	private static void getTables(String str, Set tables) {
		if (str.contains(FROM_LOWER)) {
			str = str.substring(str.indexOf(FROM_LOWER) + 5, str.length());
		} else if (str.contains(FROM_UPPER)) {
			str = str.substring(str.indexOf(FROM_UPPER) + 5, str.length());
		} else {
			return;
		}
		for (String key : JOIN_KEY) {
			for (String s : str.split(key)) {
				tables.add(s.split(" ")[0]);
			}
		}
	}

	private static void splitSQL(String sql, List temp) {
		// 根据from关键字切割SQL
		sql = sql.contains("from") ? sql.substring(sql.indexOf("from"), sql.length()) : sql.substring(sql.indexOf("FROM"), sql.length());
		// 是否需要二次切割
		if (getSplitKey(sql) != null) {
			for (String s : sql.split(getSplitKey(sql))) {
				if (getSplitKey(s) != null) {
					splitSQL(s, temp);
				} else {
					temp.add(s);
				}
			}
		} else {
			temp.add(sql);
		}
	}

	private static String getSplitKey(String str) {
		if (StringUtils.isNotBlank(str)) {
			for (String split : SPLIT_KEY) {
				if (str.contains(split)) {
					return split;
				}
			}
		}
		return null;
	}

	private static String formatSQL(String sql) {
		sql = sql.replaceAll("\\s+", " ");
		sql = sql.replaceAll("\\s+,\\s+", ",");
		return sql;
	}

}