annotation-parser

A library for parsing custom annotations in any data structures.

JDK Version

JDK 21

Maven Dependency

<dependency>
    <groupId>io.allurx</groupId>
    <artifactId>annotation-parser</artifactId>
    <version>${latest version}</version>
</dependency>

Example

Custom Annotation

@Target(ElementType.TYPE_USE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Parse(handler = EraseStringAnnotationHandler.class, annotation = EraseString.class)
public @interface EraseString {
}

Writing an Annotation Handler

public class EraseStringAnnotationHandler implements AnnotationHandler<String, EraseString, String> {

    @Override
    public String handle(String target, EraseString annotation) {
        return "******";
    }
}

Parsing with AnnotationParser

You can parse the annotation in any data structure using the AnnotationParser. Here are some examples:

void parse() {

    // String
    var v1 = AnnotationParser.parse("123456", new AnnotatedTypeToken<@EraseString String>() {
    });
    assertEquals("******", v1);

    // Collection
    var v2 = AnnotationParser.parse(Stream.of("123456").collect(Collectors.toList()), new AnnotatedTypeToken<List<@EraseString String>>() {
    });
    v2.forEach(s -> assertEquals("******", s));

    // Array
    var v3 = AnnotationParser.parse(new String[]{"123456"}, new AnnotatedTypeToken<@EraseString String[]>() {
    });
    Arrays.stream(v3).forEach(s -> assertEquals("******", s));

    // Map
    var v4 = AnnotationParser.parse(Stream.of("allurx").collect(Collectors.toMap(s -> s, s -> "123456")), new AnnotatedTypeToken<Map<@EraseString String, @EraseString String>>() {
    });
    v4.forEach((s1, s2) -> {
        assertEquals("******", s1);
        assertEquals("******", s2);
    });

    // Object
    record Person(@EraseString String password) {
    }
    var v5 = AnnotationParser.parse(new Person("123456"), new AnnotatedTypeToken<@Cascade Person>() {
    });
    assertEquals("******", v5.password);
}

Principles

The annotation-parser library is built on the AnnotatedType type system introduced in JDK 1.8 and utilizes the Chain of Responsibility design pattern to parse custom annotations in arbitrary data structures. A thorough understanding of Java's Type and AnnotatedType systems is essential for grasping the underlying implementation principles. For deeper insights, consider reading the following articles:

• Java Type
• Java AnnotatedType
• Java AnnotatedElement

License

This project is licensed under the Apache License 2.0.