The best part of convention over configuration: when convention doesn't work you get to go on these fun easter egg hunts for where the configuration belongs. --------- Original Message --------- Subject: Re: Changing JDK version without specifying maven-compiler-plugin version From: "Stephen Connolly" <stephen.alan.conno...@gmail.com> Date: 11/27/13 2:25 pm To: "Maven Users List" <users@maven.apache.org>
ahh yes they got moved there... On 27 November 2013 20:52, Mirko Friedenhagen <mfriedenha...@gmail.com>wrote: > Hello, > > I thought the version is defined in > > https://git-wip-us.apache.org/repos/asf?p=maven.git;a=blob;f=maven-core/src/main/resources/META-INF/plexus/default-bindings.xml;h=09ecba441e61d4a997b01af0171815c558548537;hb=maven-3.0.4 > (replace hb with the version of your choice :-)). > Regards Mirko > -- > http://illegalstateexception.blogspot.com/ > https://github.com/mfriedenhagen/ (http://osrc.dfm.io/mfriedenhagen) > https://bitbucket.org/mfriedenhagen/ > > > On Wed, Nov 27, 2013 at 11:32 AM, Stephen Connolly > <stephen.alan.conno...@gmail.com> wrote: > > On 27 November 2013 10:18, Malte Skoruppa <skoru...@cs.uni-saarland.de > >wrote: > > > >> Hi all, > >> > >> thank you for your helpful answers. I grasped a lot about how Maven > >> internally works and learned some tricks (e.g., dependency:analyze). > This > >> is a great mailing list indeed. > >> > >> @Laird: that is quite interesting. From all the other posts I really > >> gained the impression that my original question was actually unsolvable > >> (e.g., Stephen explicitly stated the goals are "incompatible"). > >> > >> But this also led me to a new question. > >> > >> Always eager to learn, I tried - just to see what would happen - > >> specifying in my POM at the same time <maven.compiler.{source,target}> > in > >> the <properties> section, *as well as* specifying <{source,target}> in > the > >> <configuration> section of the maven-compiler-plugin. It turns out that > the > >> latter takes precedence over the former (i.e., when different Java > versions > >> are specified in these two places, the <configuration> of the > >> maven-compiler-plugin is used). > >> > >> Therefore, from my understanding up to this point, I suspected that > there > >> must be something in the "uber"-pom akin to this: > >> > >> > >> <plugin> > >> <groupId>org.apache.maven.plugins</groupId> > >> <artifactId>maven-compiler-plugin</artifactId> > >> <version>SOME_DEFAULT_VERSION</version> > >> <configuration> > >> <source>${maven.compiler.source}</source> > >> <target>${maven.compiler.target}</target> > >> </configuration> > >> </plugin> > >> > > > > actually what is the case is that these parameters have an annotation > like > > > > @Parameter(property="maven.compiler.source",defaultValue="1.5") > > private String source; > > > > So what happens is that if you don't specify a value in the > <configuration> > > section then Maven checks to see if the property is defined, if not then > it > > uses the default value > > > > Once you specify a value in the <configuration> section that is taken as > > gold. > > > > Hence why I said it was incompatible, as the property trick is just > that, a > > trick, and it will fall over under stress... none the less it is a handy > > trick to have... as long as you are aware that it is a trick. > > > > > >> > >> where the maven.compiler.{source,target} would be specified in the > >> <properties> section of the "uber"-pom. That would have explained both > why > >> Maven complains when I reconfigure the maven-compiler-plugin without > >> specifying the plugin version, as well as why redefining > >> maven.compiler.{source,target} in the <properties> section of my own > pom is > >> a working solution for my original question. > >> > >> So I finally decided to take a look at this "uber"-pom :) > >> > >> I was suprised to find there is *no mention* of the > maven-compiler-plugin > >> *at all* in this super-pom, that is, > >> > >> $ export M2_HOME=/usr/share/maven > >> $ unzip -p $M2_HOME/lib/maven-model-builder-3.0.4.jar > >> org/apache/maven/model/pom-4.0.0.xml | grep compiler > >> $ > >> > >> ...the latter command produces no output (I'm using Maven 3.0.4, as can > be > >> seen from the path). > >> (Alternatively, one might search for "compiler" at > >> http://maven.apache.org/ref/3.0.4/maven-model-builder/super-pom.html, > but > >> I wanted to make sure that indeed the same uber-pom is used on my > machine). > >> > >> This is quite confusing. I firmly expected to see some kind of > >> configuration of the maven-compiler-plugin in the uber-pom. That is what > >> many of you led me to believe: > >> > >> Stephen: > >> > >> the "core" plugins all have a version specified in the über-pom that > >> is > >>> embedded within Maven. > >>> > >> > > Hmmm.. it seems I missed http://jira.codehaus.org/browse/MNG-4453 with > the > > transition to Maven 3.x... and as I lock plugin versions down anyways... > > > > > >> > >> Randal: > >> > >> As was pointed out, core components such as the compiler plugin have a > >>> stable default version via the 'uber-pom' as of a particular version of > >>> Maven > >>> > >> > >> Mark: > >> > >> generated POMs *do* specify the version of > >>> m-compiler-p, by *not* specifying it. There's a built-in set of > >>> defaults(1) buried inside Maven, which specify much of the > >>> not-otherwise-specified. > >>> > >> > >> So... where is this stable maven-compiler-plugin version specified, > >> precisely? > >> I did find some mentions of a stable maven-compiler-plugin version in > >> $M2_HOME/lib/maven-core-3.0.4.jar:META-INF/plexus/components.xml as well > >> as > $M2_HOME/lib/maven-core-3.0.4.jar:META-INF/plexus/artifact-handlers.xml, > >> but I'm not sure whether that's the actual place where the "default > >> version" of the maven-compiler-plugin is configured, and certainly none > of > >> them is the uber-pom. > >> > >> I'd just like to see it; I like to understand how stuff works ;-) > >> > >> Thanks, > >> > >> Malte > >> > >> > >> > >> On 11/26/2013 04:26 PM, Stephen Connolly wrote: > >> > >>> On 26 November 2013 14:59, Malte Skoruppa <skoru...@cs.uni-saarland.de > > > >>> wrote: > >>> > >>> > >>> Hi, > >>>> > >>>> I'm new to Maven and I'm currently going through the "Getting Started" > >>>> guide. > >>>> > >>>> While reading, the following question came to me. > >>>> As far as I understand, Maven defaults to compiling all Java source > files > >>>> with compatibility for JDK 1.3 (i.e., -source 1.3). > >>>> > >>>> Well actually with newer versions of the compiler plugin the default > has > >>> been upped to 1.5 > >>> > >>> > >>> The guide explains how to change that behaviour, by configuring the > >>>> maven-compiler-plugin in the pom.xml: > >>>> http://maven.apache.org/guides/getting-started/index. > >>>> html#How_do_I_use_plug-ins > >>>> > >>>> So far so good. However, if I do this, it appears that I also have to > >>>> specify the version of maven-compiler-plugin to be used (e.g., 2.5.1 > in > >>>> the > >>>> code snippet shown under the above link). > >>>> > >>>> Generally, I don't want to do that. On the one hand, I would like for > >>>> Maven to simply use the latest version of the maven-compiler-plugin > that > >>>> is > >>>> available (the default behaviour). > >>>> > >>> > >>> Not the default behaviour any more.... at least since 2.0.9 IIRC... the > >>> "core" plugins all have a version specified in the über-pom that is > >>> embedded within Maven. Thus if you do not specify a version, you get > the > >>> version specified in the über-pom... for non-core plugins you will > >>> get > the > >>> latest, but your build is now irreproducible. Best practice is to > specify > >>> the version for all plugins. > >>> > >>> > >>> On the other hand, I would like to use Java features above 1.3 (for > >>>> instance, generics). > >>>> > >>>> So my first attempt was to simply remove the > "<version>2.5.1</version>" > >>>> part from the pom.xml under the maven-compiler-plugin configuration. > >>>> While > >>>> this did in principle work, Maven was not happy at all and complained > >>>> with > >>>> this message: > >>>> > >>>> [WARNING] Some problems were encountered while building the effective > >>>> model for com.mycompany.app:my-app:jar:1.0-SNAPSHOT > >>>> [WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins: > >>>> maven-compiler-plugin > >>>> is missing. @ line 19, column 15 > >>>> [WARNING] > >>>> [WARNING] It is highly recommended to fix these problems because they > >>>> threaten the stability of your build. > >>>> [WARNING] > >>>> [WARNING] For this reason, future Maven versions might no longer > support > >>>> building such malformed projects. > >>>> > >>>> So my question boils down to this: is there some way for me to achieve > >>>> the > >>>> > >>>> following three things at the same time: > >>>> (1) have Maven compile my source files with -source 1.4 (or anything > >>>> higher than 1.3) > >>>> (2) *not* specify the maven-compiler-plugin version to use; instead, > have > >>>> Maven dynamically use the latest one available; > >>>> (3) *not* have Maven bitch about my project being "malformed" ;-) > >>>> > >>>> I would imagine that this is not such a rare scenario: > >>>> (1) I do want to use Java features higher than those available in Java > >>>> 1.3; > >>>> > >>>> Then set source and target to 1.3... and hope you never upgrade to > Java > >>> 8 > >>> > >>> > >>> (2) I do *not* want having to monitor the maven-compiler-plugin by > myself > >>>> all the time in order to check for updates and keep my pom.xml > referring > >>>> to > >>>> the currently latest version; > >>>> > >>>> Incompatible goal. If you have a version of the compiler plugin that > is > >>> working. Leave it as is. If it isn't broken, don't fix it. If you > decide > >>> that it is broken (e.g. you think the version you have is not compiling > >>> fast enough) then try upgrading... this way you have control over your > >>> build > >>> > >>> > >>> (3) yet I do *not* want Maven complaining about my project.xml being > >>>> malformed either. > >>>> > >>>> Specify the version, or live with Maven complaining. > >>> > >>> The Maven way is to make doing "the right thing" easy... doing the > "not so > >>> right thing" should encounter some friction... but unless we have good > >>> reason we should not prevent you from shooting your foot off... we can > >>> make > >>> it difficult to aim the gun at your foot though! > >>> > >>> So what's the "clean" way to do this? :-) > >>>> > >>>> For clarity, I have written down the steps to reproduce my problem in > the > >>>> Appendix, below. > >>>> > >>>> Thanks, > >>>> > >>>> Malte > >>>> > >>>> > >>>> > >>>> > >>>> > >>>> APPENDIX: Steps to reproduce: > >>>> > >>>> 1. Generate a simple Maven project using the very command stated on > >>>> http://maven.apache.org/guides/getting-started/index. > >>>> html#How_do_I_make_my_first_Maven_project : > >>>> > >>>> mvn archetype:generate \ > >>>> -DarchetypeGroupId=org.apache.maven.archetypes \ > >>>> -DgroupId=com.mycompany.app \ > >>>> -DartifactId=my-app > >>>> > >>>> 2. Replace the generated src/main/java/com/mycompany/app/App.java > with > >>>> something that uses generics (not available in Java 1.3), e.g.: > >>>> > >>>> package com.mycompany.app; > >>>> import java.util.*; > >>>> > >>>> /** > >>>> * Hello world! > >>>> * > >>>> */ > >>>> public class App { > >>>> > >>>> public static void main( String[] args) { > >>>> > >>>> List<String> myList = new ArrayList<String>(); > >>>> myList.add( "Hello"); > >>>> myList.add( "world"); > >>>> > >>>> for( Iterator<String> i = myList.iterator(); i.hasNext();) > >>>> System.out.println( i.next()); > >>>> } > >>>> } > >>>> > >>>> 3. Try to compile using the command 'mvn compile'. Maven fails: > >>>> > >>>> $ mvn compile > >>>> [INFO] Scanning for projects... > >>>> ... > >>>> [INFO] ------------------------------------------------------------ > >>>> ------------ > >>>> [INFO] BUILD FAILURE > >>>> [INFO] ------------------------------------------------------------ > >>>> ------------ > >>>> [INFO] Total time: 0.995s > >>>> [INFO] Finished at: Tue Nov 26 15:26:00 CET 2013 > >>>> [INFO] Final Memory: 6M/117M > >>>> [INFO] ------------------------------------------------------------ > >>>> ------------ > >>>> [ERROR] Failed to execute goal org.apache.maven.plugins: > >>>> maven-compiler-plugin:2.0.2:compile (default-compile) on project > my-app: > >>>> Compilation failure > >>>> [ERROR] /home/malte/dev/java/testMaven/my-app/src/main/ > >>>> java/com/mycompany/app/App.java:[13,5] error: generics are not > supported > >>>> in -source 1.3 > >>>> ... > >>>> > >>>> 4. Ok, so let's add the following to our pom.xml. This is > copied&pasted > >>>> from http://maven.apache.org/guides/getting-started/index. > >>>> html#How_do_I_use_plug-ins : > >>>> > >>>> <build> > >>>> <plugins> > >>>> <plugin> > >>>> <groupId>org.apache.maven.plugins</groupId> > >>>> <artifactId>maven-compiler-plugin</artifactId> > >>>> <version>2.5.1</version> > >>>> <configuration> > >>>> <source>1.5</source> > >>>> <target>1.5</target> > >>>> </configuration> > >>>> </plugin> > >>>> </plugins> > >>>> </build> > >>>> > >>>> Running 'mvn compile' again, everything works fine now. > >>>> > >>>> 5. Yet, I would like to avoid having to specify the version of > >>>> maven-compiler-plugin to be used. I simply want Maven to use the > latest > >>>> one > >>>> available. So, let's remove the line > >>>> > >>>> <version>2.5.1</version> > >>>> > >>>> from the pom.xml again. > >>>> > >>>> Running 'mvn compile' again, this works too, but Maven complains: > >>>> > >>>> $ mvn compile > >>>> [INFO] Scanning for projects... > >>>> [WARNING] > >>>> [WARNING] Some problems were encountered while building the effective > >>>> model for com.mycompany.app:my-app:jar:1.0-SNAPSHOT > >>>> [WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins: > >>>> maven-compiler-plugin > >>>> is missing. @ line 19, column 15 > >>>> [WARNING] > >>>> [WARNING] It is highly recommended to fix these problems because they > >>>> threaten the stability of your build. > >>>> [WARNING] > >>>> [WARNING] For this reason, future Maven versions might no longer > support > >>>> building such malformed projects. > >>>> [WARNING] > >>>> ... > >>>> [INFO] ------------------------------------------------------------ > >>>> ------------ > >>>> [INFO] BUILD SUCCESS > >>>> [INFO] ------------------------------------------------------------ > >>>> ------------ > >>>> [INFO] Total time: 0.877s > >>>> [INFO] Finished at: Tue Nov 26 15:37:17 CET 2013 > >>>> [INFO] Final Memory: 5M/117M > >>>> [INFO] ------------------------------------------------------------ > >>>> ------------ > >>>> > >>>> > >>>> > >>>> --------------------------------------------------------------------- > >>>> To unsubscribe, e-mail: users-unsubscr...@maven.apache.org > >>>> For additional commands, e-mail: users-h...@maven.apache.org > >>>> > >>>> > >>>> > >> > >> > >> On 11/27/2013 01:47 AM, Laird Nelson wrote: > >> > >>> On Tuesday, November 26, 2013, Malte Skoruppa wrote: > >>> > >>>> is there some way for me to achieve the following three things at the > >>>> same > >>>> time: > >>>> (1) have Maven compile my source files with -source 1.4 (or anything > >>>> higher than 1.3) > >>>> (2) *not* specify the maven-compiler-plugin version to use; instead, > have > >>>> Maven dynamically use the latest one available; > >>>> (3) *not* have Maven bitch about my project being "malformed" ;-) > >>>> > >>> > >>> Yes. In your pom.xml's <properties> section add this: > >>> > >>> <maven.compiler.source>1.6</maven.compiler.source> > >>> <maven.compiler.target>1.6</maven.compiler.target> > >>> > >>> No other configuration or verbiage needed. > >>> > >>> All of the other posters' words are good. But no one answered your > >>> question. > >>> > >>> Best, > >>> Laird > >>> > >>> > >>> > >> > >> --------------------------------------------------------------------- > >> To unsubscribe, e-mail: users-unsubscr...@maven.apache.org > >> For additional commands, e-mail: users-h...@maven.apache.org > >> > >> > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@maven.apache.org > For additional commands, e-mail: users-h...@maven.apache.org > >
