Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.java.programmer > #37325

Re: Testing the functionality of sub classes

Show key headers only | View raw

On 8/20/2017 12:28 PM, Arne Vajhøj wrote:
> On 8/20/2017 12:13 PM, Cecil Westerhof wrote:
>> Arne Vajhøj <arne@vajhoej.dk> writes:
>>>> Nope, it shows that the H2 driver does follow the standards (and the
>>>> SQLite3 driver does not). The first ResultSet is closed as it should
>>>> be. You can do an isClosed on it. So it is not null, but displays a
>>>> null to show you should not use it anymore.
>>>
>>> The contract for toString is extremely vague.
>>>
>>> I do not see any indication than SQLite does not follow
>>> JDBC standard.
>>>
>>> Reusing result set object should be perfectly valid
>>> per JDBC standard.
>>
>> In the description of Statement (copied with spelling mistakes):
>>      All execution methods in the Statement interface implicitly close
>>      a statment's current ResultSet object if an open one exists.
> 
> It is exactly because of this that I think reuse is valid.

Maybe I am just babbling.

But let me try and show what I am thinking about.

The code is far from complete, but it should hopefully
illustrate what I am thinking about.

public class OpenCloseFun {
	public static interface Connection extends AutoCloseable {
		public Statement createStatement();
	}
	public static interface Statement extends AutoCloseable {
		public ResultSet executeQuery(String sql);
	}
	public static interface ResultSet extends AutoCloseable {
		public boolean next();
	}
	public static class MyConnection implements Connection {
		private MyRealConnection real;
		private MyConnection(MyRealConnection real) {
			this.real = real;
		}
		public static MyConnection create() {
			return new MyConnection(new MyRealConnection());
		}
		public Statement createStatement() {
			return new MyStatement(real.createStatement());
		}
		public void close() throws Exception {
			real.close();
		}
		public String toString() {
			return real.toString();
		}
	}
	public static class MyStatement implements Statement {
		private MyRealStatement real;
		public MyStatement(MyRealStatement real) {
			this.real = real;
		}
		public ResultSet executeQuery(String sql) {
			return new MyResultSet(real.executeQuery(sql));
		}
		public void close() throws Exception {
			real.close();
		}
		public String toString() {
			return real.toString();
		}
	}
	public static class MyResultSet implements ResultSet {
		private MyRealResultSet real;
		public MyResultSet(MyRealResultSet real) {
			this.real = real;
		}
		public boolean next() {
			return real.next();
		}
		public void close() throws Exception {
			real.close();
		}
		public String toString() {
			return real.toString();
		}
	}
	public static class MyRealConnection implements Connection {
		private MyRealStatement stmt = new MyRealStatement(); // only one 
concurrent active Statement per Connection
		public MyRealStatement createStatement() {
			stmt.init();
			return stmt;
		}
		public void close() throws Exception {
			stmt.close();
		}
	}
	public static class MyRealStatement implements Statement {
		private MyRealResultSet rs = new MyRealResultSet(); // only one 
concurrent active ResultSet per Statement
		public void init() {
		}
		public MyRealResultSet executeQuery(String sql) {
			rs.init(sql);
			return rs;
		}
		public void close() throws Exception {
			rs.close();
		}
	}
	public static class MyRealResultSet implements ResultSet {
		public void init(String sql) {
		}
		public boolean next() {
			return true;
		}
		public void close() throws Exception {
		}
	}
	public static void main(String[] args) throws Exception {
		try(Connection con = MyConnection.create()) {
			try(Statement stmt = con.createStatement();
			    ResultSet rs1 = stmt.executeQuery("something");
				ResultSet rs2 = stmt.executeQuery("something else")) {
				System.out.println(stmt);
				System.out.println(rs1);
				System.out.println(rs2);
			}
		}
	}
}

Arne

Back to comp.lang.java.programmer | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Testing the functionality of sub classes Cecil Westerhof <Cecil@decebal.nl> - 2017-08-19 19:40 +0200
  Re: Testing the functionality of sub classes Cecil Westerhof <Cecil@decebal.nl> - 2017-08-19 21:44 +0200
    Re: Testing the functionality of sub classes Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-08-19 16:47 -0400
      Re: Testing the functionality of sub classes Cecil Westerhof <Cecil@decebal.nl> - 2017-08-20 01:30 +0200
        Re: Testing the functionality of sub classes Andreas Leitgeb <avl@logic.at> - 2017-08-20 11:50 +0000
          Re: Testing the functionality of sub classes Cecil Westerhof <Cecil@decebal.nl> - 2017-08-20 14:49 +0200
            Re: Testing the functionality of sub classes Cecil Westerhof <Cecil@decebal.nl> - 2017-08-20 15:36 +0200
              Re: Testing the functionality of sub classes Arne Vajhøj <arne@vajhoej.dk> - 2017-08-20 09:46 -0400
                Re: Testing the functionality of sub classes Andreas Leitgeb <avl@logic.at> - 2017-08-20 14:33 +0000
                Re: Testing the functionality of sub classes Arne Vajhøj <arne@vajhoej.dk> - 2017-08-20 11:14 -0400
                Re: Testing the functionality of sub classes Cecil Westerhof <Cecil@decebal.nl> - 2017-08-20 16:35 +0200
                Re: Testing the functionality of sub classes Arne Vajhøj <arne@vajhoej.dk> - 2017-08-20 11:17 -0400
                Re: Testing the functionality of sub classes Cecil Westerhof <Cecil@decebal.nl> - 2017-08-20 18:13 +0200
                Re: Testing the functionality of sub classes Arne Vajhøj <arne@vajhoej.dk> - 2017-08-20 12:28 -0400
                Re: Testing the functionality of sub classes Arne Vajhøj <arne@vajhoej.dk> - 2017-08-20 13:06 -0400
                Re: Testing the functionality of sub classes Cecil Westerhof <Cecil@decebal.nl> - 2017-08-20 19:07 +0200
            Re: Testing the functionality of sub classes Arne Vajhøj <arne@vajhoej.dk> - 2017-08-20 11:21 -0400
              Re: Testing the functionality of sub classes Cecil Westerhof <Cecil@decebal.nl> - 2017-08-20 18:17 +0200
          Re: Testing the functionality of sub classes v_borchert@despammed.com (Volker Borchert) - 2017-08-21 19:53 +0000
    Re: Testing the functionality of sub classes v_borchert@despammed.com (Volker Borchert) - 2017-08-19 21:15 +0000
      Re: Testing the functionality of sub classes Cecil Westerhof <Cecil@decebal.nl> - 2017-08-20 01:36 +0200
    Re: Testing the functionality of sub classes Cecil Westerhof <Cecil@decebal.nl> - 2017-08-20 01:22 +0200

csiph-web