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Java Forum / General / May 2006What is a Java Annotation?
Probably a very stupid newbee question, but what is meant with annotation? See: http://blogs.sun.com/roller/page/dannycoward?entry=the_10_things_you_need 7 Pluggable Annotation ... Bablefish translate it into Dutch, my native language as annotatie. <Dutch>Ja daar schiet ik wat mee op zeg!</Dutch> > Probably a very stupid newbee question, but what is meant with > annotation? [quoted text clipped - 7 lines] > Bablefish translate it into Dutch, my native language as annotatie. > <Dutch>Ja daar schiet ik wat mee op zeg!</Dutch> http://java.sun.com/j2se/1.5.0/docs/guide/language/annotations.html robert > Probably a very stupid newbee question, but what is meant with > annotation A generic mechanism to add meta data to the source code. Tools, like the compiler, but also additional tools, can then do some magic tricks if they find an annotation in the code. Depending on the type of annotation, the meta data is removed when compiling, or is compiled into the class file. If you do the later, you can check the meta data during runtime, an do even more magic tricks while the program runs. /Thomas  SignatureThe comp.lang.java.gui FAQ: ftp://ftp.cs.uu.nl/pub/NEWS.ANSWERS/computer-lang/java/gui/faq http://www.uni-giessen.de/faq/archiv/computer-lang.java.gui.faq/ > Depending on the type of annotation, the meta data is removed when > compiling, or is compiled into the class file. Nitpick: the metadata is always added to the classfile (or it wouldn't be a lot of use ;-) The distinction is between whether the /JVM/ discards the metadata as it loads the class, or retains it for runtime use by the application. -- chris >> Depending on the type of annotation, the meta data is removed when >> compiling, or is compiled into the class file. > > Nitpick: the metadata is always added to the classfile (or it wouldn't be a lot > of use ;-) The distinction is between whether the /JVM/ discards the metadata > as it loads the class, or retains it for runtime use by the application. Nit-nitpick: Annotations are not necessarily added to the class file. There are 3 RetentionPolicy values defined that specify how long annotations are to be retained: SOURCE, CLASS, RUNTIME. The SOURCE value is used for things that are only significant to the compiler. For example, the Override and SuppressWarnings annotations are source only annotations. With the annotation processing API coming in JSE 6 (JSR 269) there will probably be many more uses for source only annotations. SignatureDale King > Annotations are not necessarily added to the class file. There are 3 > RetentionPolicy values defined that specify how long annotations are to > be retained: SOURCE, CLASS, RUNTIME. I'd completely forgotten about SOURCE. Thanks for the correction. -- chris >> Annotations are not necessarily added to the class file. There are 3 >> RetentionPolicy values defined that specify how long annotations are to >> be retained: SOURCE, CLASS, RUNTIME. > > I'd completely forgotten about SOURCE. Thanks for the correction. Presumably if Java were being designed from scratch today Javadoc would be SOURCE. > Presumably if Java were being designed from scratch today Javadoc would be > SOURCE. Quite possibly. An even more interesting possibility (IMO) would be to give it CLASS status. Classfile format is a high-level programming language anyway, so why not ship the API documentation along with the "code" ? -- chris >> Presumably if Java were being designed from scratch today Javadoc would >> be [quoted text clipped - 7 lines] > ship > the API documentation along with the "code" ? In some cases, security via obfuscation. [me:] > > Classfile format is a high-level programming language anyway, so why not > > ship > > the API documentation along with the "code" ? > > In some cases, security via obfuscation. Well, there's nothing to say that the info couldn't be stripped out, or never added in the first place (cf. debugging info). But it was just an idle thought ;-) -- chris And I thank you for all the answers :-) You're all very kinf Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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