Develop Reference

How to run only one (current) file and ignore others in intellij gradle project?

This must be a very simple task for many of you. Let me explain the scenario.
I recently started practicing questions on HackerRank. But, I found the platform not so friendly for debugging. No online platform is or can be because of its own limitations. HackerRank provides question and stub code for many of the problems on its problem page.
For example, let us consider, https://www.hackerrank.com/challenges/java-datatypes/problem
But, because of it's debugging limitations I can't make the best use of portal. Hence, I wrote a PHP script to scrape all the content from the website and generated problem statements in HTML/PDF formats and solutions in java format.
Here's the GitHub project for the same.
https://github.com/saint1729/hr-idea-integration
The main intention of this activity is to have an integration of the website with an IDE like Intellij IDEA. This is now complete.
I created a gradle project with existing sources. But, the project contains many java files (almost 500+ files and each file has it's own main method). My intention is to solve one problem at a time and see if it compiles and submit it using a REST API provided by HackerRank.
But, when I am trying to Right Click and Click on Solution.main() for every file, it tries to compile all files in the project and because there are some compilation issues with the project, I am unable to test my code for the current file. This is not productive for me.
Please let me know if it's possible to compile and run a single file in IDEA (without compiling the whole project). If the idea of creating a gradle project for this activity is not necessary, can somebody recommend me another efficient solution?
NOTE: Every scraped java file contains it's own main method. I know that a project can contain only 1 main method. But, I don't know a coherent solution to solve my problem.

If you want to continue using gradle, you create a module per solution.
Let's suppose you have 3 solutions. canyouaccess, duplicateword and java1darray.
So your repository looks like this:
java
canyouaccess
src/main/java
package
Solution.java
duplicateword
src/main/java
package
Solution.java
java1darray
src/main/java
package
Solution.java
build.gradle
settings.gradle
Each module can have its own main. Inside a settings.gradle file the modules can be defined or disabled by commenting it out.
Your build.gradle looks like this:
...
subprojects { project ->
apply plugin: "java"
sourceCompatibility = 11
}
...
For the settings.gradle looks like this:
include 'java:canyouaccees'
include 'java:dublicateword'
include 'java:java1darray'
Each module can be build separately, you could even group modules by creating a sub module structure.
And each module can have it's own debug configuration, where the module and the main is selected. If your set them as shared, they are stored in xml format under .idea/runConfigurations. So your script can create them as well.
Each module needs it's own gradle.build file, where the main class is declared.
jar {
manifest {
attributes('Main-Class': 'your.main.class.goes.here')
}
}
Something like this should do.

Optaplanner - The Website resource does not exist

I'm making a runnable jar for my project, and i keep getting this error when it starts generating the benchmark report:
Exception in thread "main" java.lang.IllegalStateException: The websiteResource (twitterbootstrap/css/bootstrap-responsive.css) does not exist.
at org.optaplanner.benchmark.impl.report.WebsiteResourceUtils.copyResource(WebsiteR esourceUtils.java:57)
at org.optaplanner.benchmark.impl.report.WebsiteResourceUtils.copyResourcesTo(WebsiteResourceUtils.java:33)
at org.optaplanner.benchmark.impl.report.BenchmarkReport.writeHtmlOverviewFile(BenchmarkReport.java:738)
at org.optaplanner.benchmark.impl.report.BenchmarkReport.writeReport(BenchmarkReport.java:287)
at org.optaplanner.benchmark.impl.DefaultPlannerBenchmark.benchmarkingEnded(DefaultPlannerBenchmark.java:315)
at org.optaplanner.benchmark.impl.DefaultPlannerBenchmark.benchmark(DefaultPlannerBenchmark.java:109)
Everything else works fine since i added "resources/" infront of the drools and the benchmarkConfig paths.
Since there are a few more resources just for the benchmark, i probably would need to do the same for them also.
How can i get access to the resources for the benchmarks?

Sounds like you're building from source with an IDE (Eclipse/IntelliJ/NetBeans/...) and your project isn't set up correctly to also copy *.css files as classpath resources (so it has a specific exclude for css somewhere).
With a modern IntelliJ IDEA version, opening the pom.xml file, this definitely doesn't happen. With a modern Eclipse/NetBeans version, I'd presume the same.

Can I force the order of dependencies in my classpath with Gradle?

A project runs on Google App Engine. The project has dependency that uses a class that can't be invoked on App Engine due to security constraints (it's not on the whitelist). My (very hacky) solution was to just copy a modified version of that class into my project (matching the original Class's name and package) that doesn't need the restricted class. This works on both dev and live, I assume because my source appears in the classpath before my external dependencies.
To make it a bit cleaner, I decided to put my modified version of that class into it's own project that can be packaged up in a jar and published for anyone else to use should they face this problem.
Here's my build.gradle:
// my jar that has 'fixed' version of Class.
compile files('path/to/my-hack-0.0.1.jar')
// dependency that includes class that won't run on appengine
compile 'org.elasticsearch:elasticsearch:1.4.4'
On my local dev server, this works fine, the code finds my hacked version of the class first at runtime. On live, for some unknown reason, the version in the elasticsearch dependency is loaded first.
I know having two versions of the same class in the classpath isn't ideal but I was hoping I could reliably force my version to be at the start of the classpath. Any ideas? Alternatively, is there a better way to solve this problem?

Not really sure if this is what people visiting this question were looking for, but this was what my problem and a solution that I reached at.
Jar A: contains class XYZ
Jar B: also contains class XYZ
My Project needs Jar B on the classpath before Jar A to be able to get compiled.
Problem is Gradle sorts the dependencies based on alphabetical order post resolving them which meant Jar B will be coming after Jar A in the generated classpath leading to error while compiling.
Solution:
Declare a custom configuration and patch the compileClasspath. This is how the relevant portion of build.gradle might look like.
configurations {
priority
sourceSets.main.compileClasspath = configurations.priority + sourceSets.main.compileClasspath
}
dependencies {
priority 'org.blah:JarB:2.3'
compile 'org.blah:JarA:2.4'
...
}

It's the app engine classloader I should have been investigating, not gradle...
App Engine allows you to customise the class loader JAR ordering with a little bit of xml in your appengine-web.xml. In my case:
<class-loader-config>
<priority-specifier filename="my-hack-0.0.1.jar"/>
</class-loader-config>
This places my-hack-0.0.1.jar as the first JAR file to be searched for classes, barring those in the directory war/WEB-INF/classes/.
...Thanks to a nudge in the right direction from #Danilo Tommasina :)
UPDATE 2020:
I just hit the same problem again and came across my own question... This time, live appengine was loading a different version of org.json than was being loaded in dev. Very frustrating and no amount of fiddling the build script would fix it. For future searchers, if you're getting this:
java.lang.NoSuchMethodError: org.json.JSONObject.keySet()Ljava/util/Set;
It's because it's loading an old org.json dependency from god-knows-where. I fixed it by adding this to my appengine-web.xml:
<class-loader-config>
<priority-specifier filename="json-20180130.jar"/>
</class-loader-config>
You'll also need a matching dependency in build.gradle if you don't already have one:
compile 'org.json:json:20180130'

According to gradle dependencies documentation, the order of dependencies defines the order in the classpath. So, we can simply put the libraries in the correct order in "dependencies".
But beware! here are two rules with higher priorities:
For a dynamic version, a 'higher' static version is preferred over a 'lower' version.
Modules declared by a module descriptor file (Ivy or POM file) are preferred over modules that have an artifact file only.

Grails 2.1.1 - How to develop a plugin with an AstTransformer?

I want to replace the auto injected log object, which is of type org.apache.commons.logging.Log with an object of type org.slf4j.Logger, so that I can use it properly with Logback.
Therefore I need to create a ...Transformer class (written in Java) - that's what I got from Graeme Rocher over at the "grails-user" mailing list. I'm also aware that I have to pack this ...Transformer class within a plugin and make it a *.jar archive which I can load within the lib/ folder of the plugin. But I guess I'm doing something wrong here as I have the class, along with a META-INF folder which contains the MANIFEST.MF file as well as another folder services which holds the following file org.codehaus.groovy.transform.ASTTransformation which holds just one String: the canonical name of the ...Transformer class.
Now, if I try to do a grails clean everything is fine, BUT if I try to run grails package-plugin the console comes up with a java.lang.ClassNotFoundException.
Clipping from Stacktrace:
| Packaging Grails application...
| Error Fatal error during compilation org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
Could not instantiate global transform class my.package.ast.LoggingTransformation specified at jar:file:/C:/Source/MyGrailsAST/lib/replace-logging-logback-ast.jar!/META-INF/services/org.codehaus.groovy.transform.ASTTransformation because of exception java.lang.ClassNotFoundException: my.package.ast.LoggingTransformation
1 error
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
Could not instantiate global transform class my.package.ast.LoggingTransformation specified at jar:file:/C:/Source/MyGrailsAST/lib/replace-logging-logback-ast.jar!/META-INF/services/org.codehaus.groovy.transform.ASTTransformation because of exception java.lang.ClassNotFoundException: my.package.ast.LoggingTransformation
Does anybody have some experience with Grails plugins which handle with AstTransformer and could give me some advice on this? Is there a good tutorial out there which I haven't seen so far?
Please let me know ;)

so, after some research, browsing and finally asking at the Grails Mailing List (see the mailing list archives at: http://grails.1312388.n4.nabble.com/Grails-user-f1312389.html I found a solution.
my goal was to create a Globals ASTTransformation, to inject a org.slf4j.Logger object instead of the usual org.apache.commons.logging.Log object into every Artefact class without annotation.
so, here are the steps:
I created Java class similar to https://github.com/grails/grails-core/blob/master/grails-logging/src/main/groovy/org/codehaus/groovy/grails/compiler/logging/LoggingTransformer.java but with my own implementation of the org.slf4j.Logger object. It is crucial that you place the Java.class under the following package: org.codehaus.groovy.grails.compiler as
Grails scans for classes that are annotated with #AstTransformer in this package. (Graeme Rocher)
and pack it into a JAR along with its MANIFEST.MF file within the META-INF/ folder. A META-INF/services directory with all its stuff is not needed as Graeme Rocher stated:
You do not need the META-INF/services stuff and I would remove it as it is probably complicating matters.
So, I guess this statement was more related to my specific problem as I only have one #AstTransformer class within my plugin, but that's just a guess. And I haven't searched for further informations on this topic. Maybe some other developer here who needs this could do some research and share his solution within this thread...
The JAR should be imported to the plugin and placed under the lib/ directory. After this you should be able to do grails clean, grails compile and grails package-plugin.
If you want to replace the log implementation, as I did, you should exclude the grails-logging and grails-plugin-log4j JARs from your designated project's classpath. This is done in the BuildConfig.groovy file:
inherits("global") {
excludes "grails-plugin-log4j", "grails-logging"
}
Now install your plugin grails install-plugin \path\to\plugin.zip and everthing should work as expected.
Hope this helps...

Debugging java file compiling (using gwt)

I was asked in a precedent question to be more precise about my compilation error message. Here's the fact : I know nothing about GWT and Java. Following the docs, I tried to compile Java files from a web project that had been precedently developed using GWT. So, to test and understand how all this work, I took the java folder (that had been precedently compiled with an appropriate tool)
into src folder of a web app project in my ide Eclipse
When running the compiler using the command GWT Compile, I had this message error :
Compiling module java.org.primagora
Validating newly compiled units
Ignored 5 units with compilation errors in first pass.
Compile with -strict or with -logLevel set to TRACE or DEBUG to see all errors.
Finding entry point classes
[ERROR] Unable to find type 'org.client.primagoraEntryPoint'
[ERROR] Hint: Check that the type name 'org.client.primagoraEntryPoint' is really what you meant
[ERROR] Hint: Check that your classpath includes all required source roots
When I look at the error on the file, for example java.org.client.primagoraEntryPoint, I find an error when it is declared "package org.client" at the very beginning of the file. There seem to be an error path. I thought the java folder I took would be correctly implemented in Eclipse.
Is that clearly a file path problem ? How should I debugg it ? (I reallly know nothing about gwt, java , eclipse)
Best,
Newben

Where is your GWT module file (i.e. a file that ends in .gwt.xml), and what are its contents? The package you list for your entrypoint is org.client, and the full name is org.client.primagoraEntryPoint, suggesting that there is a file in org/client/primagoraEntryPoint.java. By default, module files include the client package relative to them as source, so if the file is in the wrong location, this won't work correctly.
Based on this, your module file should be in the org package:
src/
org/
SampleModule.gwt.xml
client/
primagoraEntryPoint.java
From the very beginning of your error, you list java.org.primagora as the module:
Compiling module java.org.primagora
This suggests the following structure:
src/
org/
client/
primagoraEntryPoint.java
java/
org/
primagora.gwt.xml
This doesn't make sense, since GWT is now looking for a java.org.client package instead of a org.client package. Try using the package setup mentioned earlier here.
A better option might be to pick an existing working project, like what the GWT plugin for Eclipse will create, or one of the samples in the GWT download.