Re: Annotations processing + type introspection + code generation

From:
Alex J <vstrength@gmail.com>
Newsgroups:
comp.lang.java.programmer
Date:
Mon, 12 Sep 2011 15:06:29 -0700 (PDT)
Message-ID:
<c681c248-39e6-4a04-a2b1-57ff5158f121@l10g2000yqe.googlegroups.com>
On Sep 12, 10:21 pm, Robert Klemme <shortcut...@googlemail.com> wrote:

On 12.09.2011 20:00, Alex J wrote:

On Sep 12, 8:56 pm, Robert Klemme<shortcut...@googlemail.com> wrote:

[snip]
Why do you want to generate code? I mean, you could process annotat=

ions

at runtime. Create appropriate classes for the handling and configu=

re

appropriate graphs of objects which do the work (or even use reflectio=

n).

I need to generate *source* code, the boilerplate code is complex
enough, unfortunately bytecode is not an option.

One of the reason why I need generated code is that the boilerplate
code is quite sofisticated, learning generated docs and debugging the
generated code most likely will be required.

There are other reasons, but I think that this one would be
sufficient.


Hm... If you need to generate a lot identical code there is something
wrong: that identical code could be better implemented directly and
used. So that leaves adapters and stuff Mark mentioned for generation.
  I am not convinced yet that it is a good idea to generate loads of
complex code.

Can you shed some more light on the nature of the application you are
going to implement?


Yes, that's a prototype of tool that helps to implement a part of code
for you.

You (as a user) define interface, the tool tries to guess what you
want based on the name patterns, references to domain objects, etc.

Say you have the following:

@Specification // tells tool "this interface is a subject to be
processed"
interface PersonDao {
 long savePerson(String name, int age);
 Person getPerson(long id);
 List<Long> getPersons();
}

interface Person {
  String getName();
  int getAge();
}

Then tool defines final class PersonDaoImpl and PersonImpl:

final class PersonDaoImpl implements PersonDao {
 private static final class PersonImpl extends JdbcDaoSupport
implements Person {
  private final String name;
  private final int age;

  PersonImpl(String name, int age) { this.name = name; this.age =
age; }

  @Override public String getName() { return name; }
  @Override public int getAge() { return age; }
 }

 @Override public long savePerson(String name, int age) {
   getJdbcTemplate().update("INSERT INTO person (name, age) VALUES
(?, ?)", name, age);
   return getJdbcTemplate.queryForInt("CALL identity()");
 }
 //.. etc.
}

This is not that simple as I gave above (as much more complex human-
friendly definitions might be involved), but this clearly describes
the idea.
I'm implementing this out of pure interest, as my hobby project :)

Kind regards

        robert

--
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