[Question] how can I write a annotation processor ?

[finite mural]

hey guys, for some reason, I need to define a annotation with the retention of source, and you can check the source code I have uploaded, these file is in the annotation-processor module

in another module, I use the Builder annotation in this way

@Builder
public class Article {
    public int id;

    @Nonnull
    public String title;

    @Nonnull
    public String markdownContent;

    @Nonnull
    public String htmlContent;

    @Nonnull
    public String summary;

    @Nonnull
    public java.sql.Timestamp publishDate;

    @Nonnull
    public java.sql.Timestamp editTime;

    private Article() {
        this.id = -1;
        this.title = null;
        this.markdownContent = null;
        this.htmlContent = null;
        this.summary = null;
        this.publishDate = null;
        this.editTime = null;
    }
}

when build this module,the error occurs

4 actionable tasks: 3 executed, 1 up-to-date
错误: [IOException] generate code failed: `Attempt to recreate a file for type com.steiner.source_retention.model.Article`
1 个错误

so this is the error, I don't know how to fix it, and I don't know how can I process the generate content(file content) ,
how does the @Builder in lombok process, may I ask ?

[knotty yew]

<@&987246399047479336> please have a look, thanks.

[cedar venture]

So okay

i think a very common misconception that lombok proliferates is the idea that an annotation processor can edit code

it cannot

lombok is breaking the rules of annotation processors when it does so

All you can do is generate new files

You can't change existing ones

Now there isn't going to be a way to generate a new source file that does what you want - you can have an unnested ArticleBuilder, but not an Article.Builder

You could use the class file api to make a new class file and that could work though

[fiery saffron]

For reference: https://www.reddit.com/r/java/comments/1dzw92m/comment/lck7qj6/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

[finite mural]

@cedar venture ok I got it
but how can I get the Builder instance from Article ?
what can I do is to insert a static method called builder , which return the Builder instance (using javapoet, that means change the existing file, it will failed anyway)

[cedar venture]

so there is one thing you can abuse to do this

static methods are "inherited" and classes you extend from are technically new files

https://github.com/bowbahdoe/magic-bean

I do that here

where if you have

@MagicBean(allArgsStaticFactory = true)
public final class Person extends PersonOps {
    String name;
    int age;
}

it will generate

sealed abstract class PersonOps extends java.lang.Object permits Person {

    private Person self() {
        return (switch (this) { case Person __ -> __; });
    }

    /**
     * Creates an instance of Person.
     */
    public static Person of(
        java.lang.String name,
        int age
    ) {
        var o$ = new Person();
        o$.setName(name);
        o$.setAge(age);
        return o$;
    }

    /**
     * Get the current value for name.
     */
    public java.lang.String getName() {
        return self().name;
    }

    /**
     * Set the current value for name.
     */
    public void setName(java.lang.String name) {
        self().name = name;
    }

    /**
     * Get the current value for age.
     */
    public int getAge() {
        return self().age;
    }

    /**
     * Set the current value for age.
     */
    public void setAge(int age) {
        self().age = age;
    }

}

and that of static method is inherited

so it pops up when you use the class