how do I use java concurrency while running select querys

Question

I have three queries to run all are like "select * from table" they are taking so much time. I want to run all query in parallel using java concurrency, how I achieve this.

Answer 1

You can wrap your db calls in a Callable like this:

public class SqlTask implements Callable<ResultSet> {

    private String sql;

    public SqlTask(final String sql) {
        this.sql = sql;
    }

    @Override
    public ResultSet call() throws Exception {
        Connection connection = ...; // get connection
        Statement stmt = connection.createStatement();
        return stmt.executeQuery(this.sql);
    }
}

and then execute them in parralel using an ExecutorService, for example:

    final ExecutorService executor = Executors.newCachedThreadPool();
    final Future<ResultSet> futureResult1 = executor.submit (new SqlTask("SELECT * FROM table1"));
    final Future<ResultSet> futureResult2 = executor.submit(new SqlTask("SELECT * FROM table2"));
    final Future<ResultSet> futureResult3 = executor.submit(new SqlTask("SELECT * FROM table3"));
    final ResultSet result1 = futureResult1.get();
    final ResultSet result2 = futureResult2.get();
    final ResultSet result3 = futureResult3.get();