Java调度与SQL调度

Question

Here is my requirement:

a date is inserted in to a db table with each record. Two weeks before that particulate date, a separate record should be entered to a different table.

My initial solution was to put up a SQL schedule job, but my client insisted on it being handled through java.

• What is the best approach for this?
• What are the pros and cons of using SQL schedule job and Java scheduling for this task?

Answer 1

Ask yourself the question: to what domain does this piece of work belong? If it's required for data integrity, then it's obviously the DBMS' problem and would probably best be handled there. If it's part of the business domain rather than the data, or might require information or processing that's not available or natural to the DBMS, it's probably best made external.

I'd say, use the best tool for the job. Having stuff handled by the database using whatever features it offers is often nice. For example, a log table that keeps "snapshots" of status updates of records in another table is something I typically like to have a trigger for, taking that responsibility out of my app's hands.

But that's something that's available in practically any DBMS. There's the possibility that other databases won't offer the job scheduling capacities you require. If it's conceivable that some day you'll be switching to a different DBMS, you'll then be forced to do it in Java anyway. That's the advantage of the Java approach: you've got the functionality independently of the database. If you're using pure JDBC with standard SQL queries, you've got a fully portable solution.

Both approaches seem valid. Consider what induces the least work and worries. If it's done in Java you'll need to make sure that process is running or scheduled. That's some external dependency. If it's in the database, you'll be sure the job is done as long as the DB is up.

Answer 2

Well, first off, if you want to do it in Java, you can use the Timer for a simple basic repetitive job, or Quartz for more advanced stuff.

Personally I also think that it would be better to have the same entity (application) deal with all related database actions. In other words, if your Java app is reading/writing to/from the db, it should be consistent and also deal with scheduled reading/writings. And as a plus, this way you can synchronize your actions easier, like, if you want to make sure that a scheduled job is running, has started, has finished, you can do that a lot easier if all is done in Java as compared with having a different process (like the SQL Scheduler) doing it.