Parsing table and column names from SQL/HQL Java

Question

I am looking for an open source API in Java to parse an SQL / HQL query so that it gives me the column names and the table names used in it. I tried using JSQLParser which gives me the table names used in the query. But I don't see a support for getting the column names used in the query. Is there any other API which can help me with this? I am aware of General SQL parser but it seems to be a paid one.

Here is the code snippet using JSQLParser which gives me the table names in the query:

Statement statement;
    try
    {
        statement = CCJSqlParserUtil.parse( " SELECT * FROM  ( ( SELECT TBL.ID AS rRowId, TBL.NAME AS name, TBL.DESCRIPTION as description, TBL.TYPE AS type, TBL1.SHORT_NAME AS shortName  FROM ROLE_TBL TBL WHERE ( TBL.TYPE = 'CORE' OR  TBL1.SHORT_NAME = 'TNG' AND  TBL.IS_DELETED <> 1  ) ) MINUS ( SELECT TBL.ID AS rRowId, TBL.NAME AS name, TBL.DESCRIPTION as description, TBL.TYPE AS type, TBL3.SHORT_NAME AS shortName,TBL3.NAME AS tenantName FROM ROLE_TBL TBL INNER JOIN TYPE_ROLE_TBL TBL1 ON TBL.ID=TBL1.ROLE_FK LEFT OUTER JOIN TNT_TBL TBL3 ON TBL3.ID = TBL.TENANT_FK LEFT OUTER JOIN USER_TBL TBL4 ON TBL4.ID = TBL1.USER_FK WHERE ( TBL4.ID =771100 AND  TBL.IS_DELETED <> 1  ) ) ) ORDER BY name ASC" );
        Select selectStatement = (Select) statement;
        TablesNamesFinder tablesNamesFinder = new TablesNamesFinder();
        List<String> tableList = tablesNamesFinder.getTableList( selectStatement );
        System.out.println( tableList.size() );
        for( String s : tableList )
            System.out.println( s );
    }
    catch( JSQLParserException e )
    {
        e.printStackTrace();
    }

Thanks in advance for any help in this regard.

Answer 1

There are multiple ways to achieve this using JSqlParser (https://github.com/JSQLParser/JSqlParser):

1. You could pimp TableNamesFinder to traverse all columns as well. As you could see at the result list, TableNamesFinder does not traverse all occurences of Columns, because it is not necessary for it. So one has to complete the traversal implementation here as well, which I did not.

2. You could use JSqlParser AST - Node feature to get all Columns. For specific productions JSqlParser produces nodes for a parse tree. Column is one of them.

To complete the implementation one has to collect all columns and make this list distinct (case, table, etc.)

String sql = "SELECT * FROM  ( ( SELECT TBL.ID AS rRowId, TBL.NAME AS name, TBL.DESCRIPTION as description, TBL.TYPE AS type, TBL1.SHORT_NAME AS shortName  FROM ROLE_TBL TBL WHERE ( TBL.TYPE = 'CORE' OR  TBL1.SHORT_NAME = 'TNG' AND  TBL.IS_DELETED <> 1  ) ) MINUS ( SELECT TBL.ID AS rRowId, TBL.NAME AS name, TBL.DESCRIPTION as description, TBL.TYPE AS type, TBL3.SHORT_NAME AS shortName,TBL3.NAME AS tenantName FROM ROLE_TBL TBL INNER JOIN TYPE_ROLE_TBL TBL1 ON TBL.ID=TBL1.ROLE_FK LEFT OUTER JOIN TNT_TBL TBL3 ON TBL3.ID = TBL.TENANT_FK LEFT OUTER JOIN USER_TBL TBL4 ON TBL4.ID = TBL1.USER_FK WHERE ( TBL4.ID =771100 AND  TBL.IS_DELETED <> 1  ) ) ) ORDER BY name ASC";

    System.out.println("using TableNamesFinder to get column names");
    Statement statement = CCJSqlParserUtil.parse(sql);
    Select selectStatement = (Select) statement;
    TablesNamesFinder tablesNamesFinder = new TablesNamesFinder() {
        @Override
        public void visit(Column tableColumn) {
            System.out.println(tableColumn);
        }
    };
    tablesNamesFinder.getTableList(selectStatement);

    System.out.println("-------------------------------------------");
    System.out.println("using ast nodes to get column names");
    SimpleNode node = (SimpleNode) CCJSqlParserUtil.parseAST(sql);

    node.jjtAccept(new CCJSqlParserDefaultVisitor() {
        @Override
        public Object visit(SimpleNode node, Object data) {
            if (node.getId() == CCJSqlParserTreeConstants.JJTCOLUMN) {
                System.out.println(node.jjtGetValue());
                return super.visit(node, data);
            } else {
                return super.visit(node, data);
            }
        }
    }, null);

One has to have in mind, that JSqlParser is only a parser. Therefore it is not possible to get the columns table name without having it specified like in (table.column). To get this right the database schema must be available. This becomes clear if you look at:

select a from table1, table2

which is a valid SQL.