This document discusses the disadvantages of using Java annotations and provides alternatives to annotations for various use cases. It argues that annotations hurt maintainability by embedding logic into code comments rather than classes. It then provides examples of how to implement caching, dependency injection, XML marshalling, HTTP endpoints, and other features without using annotations by moving the logic and configuration into dedicated classes and objects.

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Yegor Bugayenko
Java Annotations Are
a Bad Idea

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14K+
1.2K+
250+ Why Me?

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takes.org
eolang.org
“Elegant Objects”

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cactoos.org

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Object

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Object
Smth

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Maintainability suffers.

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Object

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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

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w/o annotation
No Singletons!

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Object

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