CLASSINDEX - SZYBKA ALTERNATYWA DLA SKANOWANIA KLAS W Javie częstym problemem jest potrzeba znalezienia klas oznaczonych daną adnotacją. Choć oficjalnie Java nie wspiera takiej funkcjonalności, de facto standardowym rozwiązaniem tego problemu jest skanowanie klas. W tej prezentacji chciałbym przedstawić dużo szybszą alternatywę - autorski projekt oparty na mechanizmach procesowania adnotacji.

1. ClassIndexClassIndex
A quicker alternative to classpath scanningA quicker alternative to classpath scanning
Sławek PiotrowskiSławek Piotrowski

2. 3
Evo InflectorEvo Inflector

3. 4
Evo InflectorEvo Inflector

4. 5
ClassindexClassindex

5. 6
Annotation basicsAnnotation basics
@Plugin(description = ''…'')@Plugin(description = ''…'')
class AuthPlugin {class AuthPlugin {
}}
Plugin pluginAnnotation = AuthPlugin.classPlugin pluginAnnotation = AuthPlugin.class
.getAnnotation(Plugin.class);.getAnnotation(Plugin.class);

6. 7
• @Bean, @Entity,@Bean, @Entity,
@Configuration,@Configuration,
@XmlRootElement, @Indexed,@XmlRootElement, @Indexed,
@Documented, @WebServlet,@Documented, @WebServlet,
@WebFilter, ...@WebFilter, ...

7. 8
List of classesList of classes
@Plugin@Plugin
class AuthPlugin {class AuthPlugin {
}}
How to get a list of plugins?How to get a list of plugins?

8. 9
List of classesList of classes
@Plugin@Plugin
class AuthPlugin {class AuthPlugin {
}}
How to get a list of plugins?How to get a list of plugins?
There is no API in Java for that!There is no API in Java for that!

9. 10
Why?Why?
class ClassLoader {class ClassLoader {
......
protected Class<?> findClass(String name)protected Class<?> findClass(String name)
throws ClassNotFoundExceptionthrows ClassNotFoundException
......

10. 11
Ugly hackUgly hack
((UrlClassLoader) classloader).getURLs();((UrlClassLoader) classloader).getURLs();
Returns the list of URLs to scanReturns the list of URLs to scan
==> Classpath Scanning==> Classpath Scanning

11. 12
Ugly hackUgly hack
((UrlClassLoader) classloader).getURLs();((UrlClassLoader) classloader).getURLs();
Returns the list of URLs to scanReturns the list of URLs to scan
==> Classpath Scanning==> Classpath Scanning
Scannotation, Reflections, Corn CPS,Scannotation, Reflections, Corn CPS,
Spring, JavaEESpring, JavaEE

12. 13
ReflectionsReflections
new Reflections()new Reflections()
.getTypesAnnotatedWith(Important.class).getTypesAnnotatedWith(Important.class)

13. 14
Classpath ScanningClasspath Scanning
How long it takes?How long it takes?

14. 15
ClassIndexClassIndex
Annotation Processor
Index files Index API

15. 16
Annotation ProcessorAnnotation Processor
Compiler plugin which can:Compiler plugin which can:
analyse syntax tree of the source filesanalyse syntax tree of the source files
analyse resource filesanalyse resource files
generate new source code filesgenerate new source code files
generate new resource filesgenerate new resource files
generate error messagesgenerate error messages
generate completionsgenerate completions

16. 17
Screenshot demoScreenshot demo

17. 18
Annotation ProcessorAnnotation Processor
Automatic discovery (Automatic discovery (ServiceLoaderServiceLoader))
<dependency><dependency>
<groupId>org.atteo.classindex</groupId><groupId>org.atteo.classindex</groupId>
<artifactId>classindex</artifactId><artifactId>classindex</artifactId>
<version>3.4</version><version>3.4</version>
</dependency></dependency>
Except in Eclipse...Except in Eclipse... linklink

18. 19
ClassIndex usageClassIndex usage
@IndexAnnotated@IndexAnnotated
public @interface Plugin {public @interface Plugin {
}}

19. 20
ClassIndex usageClassIndex usage
@IndexAnnotated@IndexAnnotated
public @interface Important {public @interface Important {
}}
Iterable<Class<?>> annotated =Iterable<Class<?>> annotated =
ClassIndex.getAnnotated(Plugin.class)ClassIndex.getAnnotated(Plugin.class)

20. 21
ClassIndex usageClassIndex usage
@IndexSubclasses@IndexSubclasses
public interface Service {public interface Service {
}}
Iterable<Class<?>> subclasses =Iterable<Class<?>> subclasses =
ClassIndex.getSubclasses(Service.class)ClassIndex.getSubclasses(Service.class)

21. 22
ClassIndex usageClassIndex usage
In package-info.java:In package-info.java:
@IndexSubclasses@IndexSubclasses
package org.atteo.test;package org.atteo.test;
Iterable<Class<?>> packageClasses =Iterable<Class<?>> packageClasses =
ClassIndex.getPackageClasses(''org.atteo.test'')ClassIndex.getPackageClasses(''org.atteo.test'')

22. 23
ClassIndexClassIndex
Annotation Processor
Index files Java API

23. 24
Javadoc StorageJavadoc Storage
@IndexAnnotated(storeJavadoc = true)@IndexAnnotated(storeJavadoc = true)
public @interface Plugin {}public @interface Plugin {}
/** Authorization plugin. *//** Authorization plugin. */
@Plugin@Plugin
public class AuthPlugin {public class AuthPlugin {
}}
assertEquals("Authorization plugin"assertEquals("Authorization plugin"
ClassIndex.getClassSummary(Plugin.class));ClassIndex.getClassSummary(Plugin.class));

24. 25
Alternatives?Alternatives?
●
ServiceLoaderServiceLoader
●
Google AutoGoogle Auto
●
Reflections with Maven pluginReflections with Maven plugin
●
Dependency injection frameworksDependency injection frameworks

25. 26
What's moreWhat's more
Android compatibilityAndroid compatibility
• Maven transformer for shader jarsMaven transformer for shader jars
●
Project Jigsaw will have @IndexedProject Jigsaw will have @Indexed
Efficient annotation detection — It must be possible to identify all of the class filesEfficient annotation detection — It must be possible to identify all of the class files
in a module… [in a module… [linklink]]
●
Incremental compilationIncremental compilation
●
MoonshineMoonshine

26. 27
ClassFilterClassFilter
ClassFilter.only()ClassFilter.only()
.topLevel().topLevel()
.withModifiers(Modifier.PUBLIC).withModifiers(Modifier.PUBLIC)
.from(ClassIndex.getAnnotated(Important.class));.from(ClassIndex.getAnnotated(Important.class));
More filters:More filters: linklink

27. 28
LinksLinks
●
https://github.com/atteo/classindexhttps://github.com/atteo/classindex
●
https://github.com/google/auto/tree/master/servicehttps://github.com/google/auto/tree/master/service
●
https://github.com/atteo/moonshinehttps://github.com/atteo/moonshine
●
https://github.com/atteo/classindex-benchmarkhttps://github.com/atteo/classindex-benchmark