Question

I am trying to create a framework in Java which would support chained/pipelined queries wherein the Output of one query would be transformed to be used as input of another queries. Something like PyCascading These queries will be made at runtime. I looked upon some frameworks and came upon Apache Camel
& Spring Integration as they provide concept of Chaining and routing(Enterprise Integration Patterns). I found Apache Camel better than Spring Integration(IMHO).

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Should I go for Apache Camel for my framework or is there a better way I can achieve this?

My Query Syntax would be

Query query1 = "select customer.id from customer where customer.name = 'ABC'";
Query query2 = "select account.id from account where account.custid in {$1}";
// $1 will be the input of second query
from(query1).inputto(query2).printOutput();

Answer 1

This is possible using camel-jdbc and a few basic Camel features (like simple) to allow you to inline the result parsing…

The [CAMEL-JDBC] result is returned in the OUT body as an ArrayList[HashMap[String,Object]]
The List object contains the list of rows and the Map
objects contain each row with the String key as the column name.

This result can then be used to dynamically construct subsequent queries…

from("direct:start")
  .setBody(constant("select customer.id as ID from customer where customer.name = 'ABC'"))
  .to("jdbc:myDataSource")

  //now, use simple/ognl to extract the first result and the 'ID' from the Map in the body
  .setBody(simple("select account.id from account where account.custid in ${body[0][ID]}"))
  .to("jdbc:myDataSource")

  .log("ACCOUNT IDS = ${body}");