编写Java代码，使用druid实现sql解析，sql为select语句，解析出select字段的依赖的表明.字段名

以下是使用druid实现sql解析，解析出select字段的依赖的表名和字段名的Java代码：

import com.alibaba.druid.sql.ast.SQLExpr;
import com.alibaba.druid.sql.ast.SQLStatement;
import com.alibaba.druid.sql.ast.expr.*;
import com.alibaba.druid.sql.ast.statement.*;
import com.alibaba.druid.sql.dialect.mysql.parser.MySqlStatementParser;
import com.alibaba.druid.sql.parser.ParserException;

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

public class SqlParser {
    public static void main(String[] args) {
        String sql = "SELECT a.id, a.name, b.age FROM table_a a LEFT JOIN table_b b ON a.id = b.id WHERE a.gender = 'M'";
        List<String> tableFields = parseSql(sql);
        for (String tableField : tableFields) {
            System.out.println(tableField);
        }
    }

    public static List<String> parseSql(String sql) {
        List<String> tableFields = new ArrayList<>();
        try {
            SQLStatement stmt = new MySqlStatementParser(sql).parseStatement();
            if (stmt instanceof SQLSelectStatement) {
                SQLSelectStatement selectStmt = (SQLSelectStatement) stmt;
                SQLSelect select = selectStmt.getSelect();

                List<SQLSelectItem> selectItems = select.getSelectList();
                for (SQLSelectItem selectItem : selectItems) {
                    SQLExpr expr = selectItem.getExpr();
                    String tableField = parseExpr(expr);
                    if (tableField != null) {
                        tableFields.add(tableField);
                    }
                }
            }
        } catch (ParserException e) {
            e.printStackTrace();
        }
        return tableFields;
    }

    private static String parseExpr(SQLExpr expr) {
        if (expr instanceof SQLPropertyExpr) {
            SQLPropertyExpr propertyExpr = (SQLPropertyExpr) expr;
            String owner = propertyExpr.getOwner().toString();
            String column = propertyExpr.getName();

            return owner + "." + column;
        } else if (expr instanceof SQLIdentifierExpr) {
            SQLIdentifierExpr identifierExpr = (SQLIdentifierExpr) expr;
            String column = identifierExpr.getName();

            return column;
        } else if (expr instanceof SQLAllColumnExpr) {
            return "*";
        } else {
            return null;
        }
    }
}

以上代码实现了将输入的SQL语句解析出所有select字段依赖的表名和字段名，并以"表名.字段名"的形式存储在一个List<String>中返回。例如，对于输入的SQL语句"SELECT a.id, a.name, b.age FROM table_a a LEFT JOIN table_b b ON a.id = b.id WHERE a.gender = 'M'"，解析出的select字段依赖的表名和字段名为：

- table_a.id
- table_a.name
- table_b.age

注意，该代码仅支持解析MySQL语法的SQL语句，其他数据库的SQL语句需要根据具体语法进行相应修改。