implicit cast of bytea data to String (postgresql 9.2.10)

[Peter.C]

I'd like to get PreparedStatement.setString() to automatically save a Java String as UTF-8 bytes into a bytea field and ResultSet.getString() to automatically convert the bytea bytes as UTF-8 into a Java String.

I have the PreparedStatement.setString() assignment cast working:
create function bytea(text) returns bytea as
$$
select convert_to($1, 'UTF8');
$$
language sql strict;

create cast (text as bytea)
with function bytea(text)
as assignment;

create function bytea(character varying) returns bytea as
$$
select convert_to(CAST ($1 as text), 'UTF8');
$$
language sql strict;

create cast (character varying as bytea)
with function bytea(character varying)
as assignment;


I tried something similar with ResultSet.getString() but it does not work:
create function text(bytea) returns text as
$$
select convert_from($1, 'UTF8');
$$
language sql strict;

create cast (bytea as text)
with function text(bytea)
as assignment;

create function "varchar"(bytea) returns character varying as
$$
select cast(convert_from($1, 'UTF8') as character varying);
$$
language sql strict;

create cast (bytea as character varying)
with function "varchar"(bytea)
as assignment;

From JDBC I call ResultSet.getString(1) on a bytea field and I get something like:
\x736574537472696e672829

Using getBytes() and using Java to convert shows the data is good:
System.out.println("-------------------------From getString():");
System.out.println(rs.getString(1));

byte[] bytes = rs.getBytes(1);
String isStr = new String(bytes, Charset.forName("UTF-8"));
System.out.println("-------------------------From getBytes():");
System.out.println(isStr);

-------------------------From getString():
\x736574537472696e672829
-------------------------From getBytes():
setString()


Is there a way to get this to work?