Java Annotations Are a Bad Idea

/24@yegor256 1
Yegor Bugayenko
Java Annotations Are 
a Bad Idea

/34@yegor256 2
14K+
1.2K+
250+ Why Me?

/42@yegor256 3
takes.org
eolang.org
“Elegant Objects”

/42@yegor256 7
Maintainability suﬀers.

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class Storage {
void save(@NotNull Book book) {
//
}
}
storage.save(book);
w/annotation

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class Storage {
void save(Book book) {
//
}
}
storage.save(new NotNullBook(book));
w/o annotation

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class Storage {
@RetryOnFailure
boolean save(Book book) {
//
}
}
boolean done = storage.save(book);
w/annotation
jcabi.com

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class Storage {
void save(Book book) {
//
}
}
boolean done = new RetryFunc<>(
book -> storage.save(book)
);
w/o annotation
cactoos.org

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class Storage {
@Cacheable(forever = true)
Book find(int id) {
//
}
}
Book book = storage.find(123);
storage.find(123);
w/annotation
jcabi.com

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class Storage {
private final Func<Integer, Book> cache = new StickyFunc<>(
id -> this.findById(id)
);
Book find(int id) {
return this.cache.apply(id);
}
Book findById(int id) {
// ..
}
}
Book book = storage.find(123);
storage.find(123);
cactoos.org
w/o annotation

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class Book {
@XmlElement
void getName() {
//
}
}
String xml = marshaller.marshal(book);
w/annotation

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class Book {
private ﬁnal String name;
String asXML() {
return new Xembler(
new Directives()
.add(“book”)
.add(“name”)
.set(this.name)
).xmlQuietly();
}
}
String xml = book.asXML();
w/o annotation
xembly.org

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class BookResource {
@GET
String index() {
return “Hello, world!”;
}
}
// ???
w/annotation

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class BookFront implements Take {
Response act(Request req) {
return new RsText(“Hello, world!”);
}
}
new FtCli(new BookFront()).exec();
w/o annotation
takes.org

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class Book {
@Inject
private ﬁnal Storage storage;
String name() {
return this.storage.sql(
“SELECT name FROM book WHERE id=123”
);
}
}
Book book = container.get(Book.class);
String name = book.name();
w/annotation

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class Book {
private ﬁnal Storage storage;
Book(Storage s) {
this.storage = s;
}
String name() {
return this.storage.sql(
“SELECT name FROM book WHERE id=123”
);
}
}
Book book = new Book(new Storage());
String name = book.name();
w/o annotation

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@Singleton
class Storage {
String fetch(String sql) {
// ..
}
}
Storage storage = container.get(Storage.class);
container.get(Storage.class);
w/annotation

/24@yegor256 22
w/o annotation
No Singletons!

Java Annotations Are a Bad Idea

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Java Annotations Are a Bad Idea