I have several java projects on the same machine which really need to be built with different java compilers, one with java 1.6 and one with java 1.7. (No, it's not sufficient to build them with the higher version of java and specify source and target for the project that requires the lower version-- the differences between them produce test failures).
My colleagues do not have this problem -- they have only one project that requires 1.6. I would like to put in some configuration that enables me to override the java compiler without requiring them to add environment variables. I'm imagining something like this:
<javac executable='${java.executable.path}' srcdir='${src.dir}' destdir='${dest.dir.classes}' source='1.6' target='1.6' fork='true' />
where ${java.executable.path} is defined earlier in the file as:
<condition property="java.executable.path" value="${env.PROJ_JAVA_HOME}" else="${DEFAULT_JAVAC}">
<isset property="env.PROJ_JAVA_HOME" />
</condition>
except... there is no ${DEFAULT_JAVAC} that I can find. Is there a better way to do this that I'm missing? Or is ant just not built for things like this?
you could default to whatever javac is on the path.
its possible to set an ant property by executing a shell script, so you'll need to execute something like which javac
Related
I'm attempting to optimize our build procedure for our applications we have here. I'd like to skip the compilation of our backend .dll file should the file timestamp not have change using Netbeans Ant scripts.
I've been using Incremental and fast build using Ant and Advanced Free-form project configuration as a reference point but it seems to require 2 build targets to create the .timestamp comparison in the first link.
Is there a way to circumvent the need for 2 targets and check the timestamp of the .dll file instead? or do I simply need to add another tag inside of my call to make the comparison, or is what I'm trying to do not feasible?
Any help would be greatly appreciated or if better methods of doing this are known I am open to listening to it.
We use Netbeans to compile our projects, and uses Ant by default. I've included a snippit of my build.xml Ant script so far.
Thanks in advance!
<target name="init-skip-dll" description="initializes the skip property for the Ada dll">
<uptodate srcfile="create-ada-dll.timestamp" targetfile="ada-dll.timestamp" property="ada-dll.skip" value="true" />
</target>
<target name="-build-dll" description="builds the Ada dll if needed" depends="init-skip-dll">
<exec executable="gprbuild.exe">
<arg value="-P"/>
<arg file="..\DLL\ifccs_dll.gpr"/>
</exec>
<touch file="create-ada-dll.timestamp"/>
</target>
I don’t use Ant, but the same problem exists with Make; the Ada dependency rules are complex, and best handled by unconditionally letting gprbuild do whatever it needs to to bring the DLL up-to-date. Gprbuild will do nothing besides checking dependencies if the DLL is actually up-to-date.
In Make, this involves a phony target: e.g. for a real target testbed,
testbed: force
gprbuild -p -P testbed
.PHONY: force
or for an already-phony target
all:
gprbuild -p -P build_runtime.gpr
.PHONY: all
By the way, note the -p, which says to create needed directories, e.g. an object directory.
In a project's build.xml there is a properity
<property name="ant.build.javac.source" value="1.7"/>
it is not used in other places in the build.xml, but if i modify it's value to 1.6, i will
get an error.
what does this properity mean?
i am in China, Google has been blocked here.....
http://ant.apache.org/manual/javacprops.html
They define values for the javac (and javadoc) task since there are no default values.
This can cause problems in some circumstances, so magic properties were defined.
If you're trying to compile 1.7 source using a 1.6 compiler you'll have issues if you're using 1.7 constructs/etc.
The value determines what version of the JDK is used to build the project. You probably get an error on 1.6 because it's not installed/doesn't support something you use in your project.
http://ant.apache.org/manual/javacprops.html
I receive the following warning:
[javac] build.xml:9: warning: 'includeantruntime' was not set,
defaulting to build.sysclasspath=last; set to false for repeatable builds
What does this mean?
Ant Runtime
Simply set includeantruntime="false":
<javac includeantruntime="false" ...>...</javac>
If you have to use the javac-task multiple times you might want to consider using PreSetDef to define your own javac-task that always sets includeantruntime="false".
Additional Details
From http://www.coderanch.com/t/503097/tools/warning-includeantruntime-was-not-set:
That's caused by a misfeature
introduced in Ant 1.8. Just add an
attribute of that name to the javac
task, set it to false, and forget it
ever happened.
From http://ant.apache.org/manual/Tasks/javac.html:
Whether to include the Ant run-time
libraries in the classpath; defaults
to yes, unless build.sysclasspath is
set. It is usually best to set this to
false so the script's behavior is not
sensitive to the environment in which
it is run.
As #Daniel Kutik mentioned, presetdef is a good option. Especially if one is working on a project with many build.xml files which one cannot, or prefers not to, edit (e.g., those from third-parties.)
To use presetdef, add these lines in your top-level build.xml file:
<presetdef name="javac">
<javac includeantruntime="false" />
</presetdef>
Now all subsequent javac tasks will essentially inherit includeantruntime="false". If your projects do actually need ant runtime libraries, you can either add them explicitly to your build files OR set includeantruntime="true". The latter will also get rid of warnings.
Subsequent javac tasks can still explicitly change this if desired, for example:
<javac destdir="out" includeantruntime="true">
<src path="foo.java" />
<src path="bar.java" />
</javac>
I'd recommend against using ANT_OPTS. It works, but it defeats the purpose of the warning. The warning tells one that one's build might behave differently on another system. Using ANT_OPTS makes this even more likely because now every system needs to use ANT_OPTS in the same way. Also, ANT_OPTS will apply globally, suppressing warnings willy-nilly in all your projects
Chet Hosey wrote a nice explanation here:
Historically, Ant always included its own runtime in the classpath made available to the javac task. So any libraries included with Ant, and any libraries available to ant, are automatically in your build's classpath whether you like it or not.
It was decided that this probably wasn't what most people wanted. So now there's an option for it.
If you choose "true" (for includeantruntime), then at least you know that your build classpath will include the Ant runtime. If you choose "false" then you are accepting the fact that the build behavior will change between older versions and 1.8+.
As annoyed as you are to see this warning, you'd be even less happy if your builds broke entirely. Keeping this default behavior allows unmodified build files to work consistently between versions of Ant.
The answer from Daniel works just perfect. Here is a sample snippet that I added to my build.xml:
<target name="compile">
<mkdir dir="${classes.dir}"/>
<javac srcdir="${src.dir}" destdir="${classes.dir}" includeantruntime="false">
<!-- ^^^^^^^^^^^^^^^^^^^^^^^^^ -->
<classpath>
<path id="application" location="${jar.dir}/${ant.project.name}.jar"/>
<path id="junit" location="${lib.dir}/junit-4.9b2.jar"/>
</classpath>
</javac>
</target>
If you like me work from commandline the quick answer is executing
export ANT_OPTS=-Dbuild.sysclasspath=ignore
And then run your ant script again.
Use <property name="build.sysclasspath" value="last"/> in your build.xml file
For more details search includeAntRuntime in Ant javac
Other possible values could be found here
i faced this same, i check in in program and feature. there was an update has install for jdk1.8 which is not compatible with my old setting(jdk1.6.0) for ant in eclipse.
I install that update.
right now, my ant project is build success.
Try it, hope this will be helpful.
Recently I started to use Eclipse's java compiler, because it is significantly faster than standard javac. I was told that it's faster because it performs incremental compiling. But I'm still a bit unsure about this since I can't find any authoritative documentation about both - eclispse's and sun's - compilers "incremental feature". Is it true that Sun's compiler always compiles every source file and Eclipse's compiler compile only changed files and those that are affected by such a change?
Edit: I'm not using Eclipse autobuild feature but instead I'm setting
-Dbuild.compiler=org.eclipse.jdt.core.JDTCompilerAdapter
for my ant builds.
Is it true that Sun's compiler always compiles every source file and Eclipse's compiler compile only changed files and those that are affected by such a change?
I believe that you are correct on both counts.
You can of course force Eclipse to recompile everything.
But the other part of the equation is that Java build tools like Ant and Maven are capable of only compiling classes that have changed, and their tree of dependent classes.
EDIT
In Ant, incremental compilation can be done in two ways:
By default the <javac> task compares the timestamps of .java and corresponding .class files, and only tells the Java compiler to recompile source (.java) files that are newer than their corresponding target (.class) files, or that don't have a target file at all.
The <depend> task also takes into account dependencies between classes, which it determines by reading and analysing the dependency information embedded in the .class files. Having determined which .class files are out of date, the <depend> task deletes them so a following <javac> task will recompile them. However, this is not entirely fool-proof. For example, extensive changes to the source code can lead to the <depend> task may be analysing stale dependencies. Also certain kinds of dependency (e.g. on static constants) are not apparent in the .class file format.
To understand why Ant <depend> is not fool-proof, read the "Limitations" section of the documentation.
Javac only compiles source files that are either named on the command line or are dependencies and are out of date. Eclipse may have a finer-grained way of deciding what that means.
Eclipse certainly does this. Also it does it at save time if you have that option turned on (and it is by default). It looks like sun also doesn't do this (it is very easy to test, just make a small project where A is the main class that uses class B, but B doesn't use class A. Then change A and compile the project again, see if the timestamp for b.class has changed.
This is the way many compilers work (also gcc for instance). You can use tools like ant and make to compile only the part the project that has changed. Also note that these tools aren't perfect, sometimes eclipse just loses track of the changes and you'll need to do a full rebuild.
Restating what I've heard here and phrasing it for lazy folks like me:
You can achieve incremental builds with the javac task in ant, but you should use the depend task to clear out .class files for your modified .java AND you must not leave the includes statement unspecified in the javac task. (Specifying just src path in the javac task and leaving includes unspecified causes javac recompile all sources it finds.)
Here are my depends and javac tasks. With the standard Oracle java compiler, only .java files I modify are compiled. Hope this helps!
<depend srcdir="JavaSource" destdir="${target.classes}" cache="${dependencies.dir}" closure="yes">
<classpath refid="compiler.classpath" />
<include name="**/*.java"/>
</depend>
<javac destdir="${target.classes}" debug="true" debuglevel="${debug.features}" optimize="${optimize.flag}" fork="yes" deprecation="no" source="1.6" target="1.6" encoding="UTF-8" includeantruntime="no">
<classpath refid="compiler.classpath"/>
<src path="JavaSource"/>
<include name="**/*.java" /> <!-- This enables the incremental build -->
</javac>
As an experiment we want to build our products using the Eclipse java compiler (ecj-3.5.jar downloaded from eclipse.org) on the runtime version of Java 6 instead of the JDK, and as I understand it, it is a matter of adding this jar to the ant classpath, and setting the build.compiler property to point to the adapter.
By including
<property name="build.compiler" value="org.eclipse.jdt.core.JDTCompilerAdapter" />
in my build.xml and invoking ant with a JRE, I get the expected error that the adapter cannot be found, and by adding ecj-3.5.jar to the classpath in the Eclipse panel I can compile my code as expected. I believe the same functionality to be available with "-lib foo.jar" from the command line with modern ants.
Now, I want to specify from within build.xml that I want ecj-3.5.jar on my classpath satisfying the same as above. We can already do this with ant tasks, so I believe it is possible.
So the question is: How can I add to the classpath used by javac to locate the compiler only from within build.xml?
It appears that the upcoming ant4eclipse 1.0 includes the Eclipse compiler (which is what I wanted to use this for), so by upgrading to that (from 0.5) should solve the problem we have.
2010-09-24: Ant4Eclipse is still at M4 without indication of when the release will happen.
2011-12-01: We have now migrated from ant to maven. The build.xml scripts hit the complexity wall and a fresh approach was needed. Anyone needing to choose what to do - do not go the ant4eclipse path except for trivial projects.
2012-11-30: A year later, the maven experience is still mostly good. There is a lot of quirks and changes in mindset but most make sense in the context. Maven can specify the compiler level on individual projects easily. We are looking into using ecj instead of javac (for several reasons) but for most purposes javac works nicely.
One way is to specify a reference to a componentdef when using javac.
<componentdef name="ecj"
classname="org.eclipse.jdt.core.JDTCompilerAdapter"
classpath="ecj-3.7.1.jar" />
<javac ....>
<ecj/>
</javac>
Another option is to set build.compiler as you have or the compiler attribute for javac and then specify a compilerclasspath for javac. This is a normal path like structure to hold the classpath for loading your compiler adapter.
<javac compiler="org.eclipse.jdt.core.JDTCompilerAdapter" ....>
<compilerclasspath>
...
</compilerclasspath>
</javac>
See the javac task documentation in the Ant manual for more details. Note that both these both solutions only work from Ant 1.8 onwards.
Reading Running Ant via Java. I think you can write a simple wrapper that will properly set a classpath and add your jar file to the resulting class path.
Here I'm just cutting and pasting the sample from the above link with addition of the library that you are interested in to the classpath:
<java
classname="org.apache.tools.ant.launch.Launcher"
fork="true"
failonerror="true"
dir="${sub.builddir}"
timeout="4000000"
taskname="startAnt"
>
<classpath>
<pathelement location="${ant.home}/lib/ant-launcher.jar"/>
<pathelement location="/path/to/ecj-3.5.jar"/>
</classpath>
<arg value="-buildfile"/>
<arg file="${sub.buildfile}"/>
<arg value="-Dthis=this"/>
<arg value="-Dthat=that"/>
<arg value="-Dbasedir=${sub.builddir}"/>
<arg value="-Dthe.other=the.other"/>
<arg value="${sub.target}"/>
</java>
I think you can even reuse the same build file, just give a different target as an entry point.