Migrate to Gradle wrapper build

[wcmatthysen]

Migrated this issue from upstream originally logged by @pdavidc: NASAWorldWind#60

Migrate World Wind Java to a Gradle wrapper based build system. Gradle builds integrate fully with the IntelliJ IDE internal build system, eliminating the duplicity of separate IDE build and ANT build process.

[AndrewTasso]

This would be a very large undertaking and would likely require some lines drawn in the sand in regards to certain features of WW that might not easily be carried forward (such as WebStart). That said, I'm going to take a peek at the repo and see what can be done. I'm short on personal time nowadays. So, at the very least, I'd like to provide some guidance.

[wcmatthysen]

Great, thanks. Any help with regards to this would be very much appreciated. I think if we can at least just build the worldwind.jar and worldwindx.jar files then that would be a great start. Also, if we can let Gradle fetch the JOGL and Gluegen jars as external dependencies then that would be great too. We can leave the WebStart stuff for later (I think).

I think the main issue that we need to discuss is whether we are going to change the structure of the source folders to fit in with the recommended way of doing things (i.e. a src/main/java folder). That is probably going to be a bit of a disruptive change. I have managed to do it in my own fork of WorldWind back in the day (when I built it with Maven) but the problem is that it will make merging any upstream code-changes a difficult task.

[AndrewTasso]

@wcmatthysen In all honesty, I would treat those as two changes/issue. I highly recommend the maven standard directory layout for project organization (which Gradle uses as a default). But Gradle can be configured to utilize the current source/project paths. So, it's entirely up to those in charge which they'd like to come first.

[wcmatthysen]

Yeah, I agree. It is probably best if the restructuring is a separate issue. One of the things that I'm not sure about is whether there will still be development done upstream or whether all development will cease on the 3rd of May. If development starts again and we go through with the restructure, then merging patches from upstream will be a pain. So, this issue should probably just be focused on getting Gradle to build a WorldWind jar given the current directory structure.

[PJHogan]

Right now, I have my money on NASA continuing development. Their Keystone Cops behavior on this one had to sober up a bit when another Federal agency said they would hire the NASA dev team if NASA was walking away from the project. This crew is the some of the best geospatial talent on the planet! Maybe NASA is starting to smell the coffee. . .

[wcmatthysen]

@AndrewTasso, I added an initial gradle build configuration in this pull request: #30.

It just compiles the worldwind and worldwindx jars. The tests can also be run, as well as building the javadoc. There are still a lot of tasks that need to be added such as the webstart stuff, as well as building the MilStd2525 jar among others. But, I think this is a good starting point for us to get this going. So basically the commands are:

gradle clean build -- To clean, compile and run the tests.
gradle test -- To just run the tests.
gradle javadoc -- To generate the javadocs.

Then, I just wanted to hear your opinion on adding the gradle wrapper. I see that it is a bit of a contentious issue online whether or not to commit the wrapper to version-control. I personally feel that we should not commit the gradle wrapper to version control. Instead we should specify somewhere in our readme that the user should run a command like:

gradle wrapper --gradle-version 5.4

to get the gradle-wrapper that can then be used to build the project.

[wcmatthysen]

As a reference, here is the contents of the build.gradle file:

apply plugin: 'java'

group = 'gov.nasa'
version = '2.2.0'

sourceCompatibility = '1.8'
targetCompatibility = '1.8'

repositories {
    mavenLocal()
    mavenCentral()
    jcenter()
}

dependencies {
    def joglVersion = '2.3.2'
    implementation "org.jogamp.jogl:jogl-all-main:$joglVersion"
    implementation "org.jogamp.gluegen:gluegen-rt-main:$joglVersion"

    implementation files('gdal.jar')

    implementation 'org.codehaus.jackson:jackson-core-asl:1.9.13'

    testImplementation 'junit:junit:4.5'
}

sourceSets {
    main {
        java {
            srcDirs = ['src']
        }
    }
    test {
        java {
            srcDirs = ['test']
        }
    }
}

// Compile worldwind jar.
jar {
    dependsOn classes
    version = null
    from sourceSets.main.output
    exclude 'gov/nasa/worldwindx/**'
    from(sourceSets.main.allSource) {
        include 'gov/nasa/worldwind/util/**/*.properties'
        include 'config/**'
        include 'images/**'
    }
}
// Copy worldwind jar to project-directory.
jar.doLast {
    copy {
        from "$buildDir/libs/${jar.archiveName}"
        into "${project.projectDir}"
    }
}

// Compile worldwindx jar.
task extensionsJar(type: Jar) {
    archiveBaseName = 'worldwindx'
    version = null
    from sourceSets.main.output
    include 'gov/nasa/worldwindx/**/*.class'
    from(sourceSets.main.allSource) {
        include 'gov/nasa/worldwindx/applications/sar/*.html'
        include 'gov/nasa/worldwindx/applications/sar/config/**'
        include 'gov/nasa/worldwindx/applications/sar/data/**'
        include 'gov/nasa/worldwindx/applications/sar/images/**'
        include 'gov/nasa/worldwindx/applications/worldwindow/config/**'
        include 'gov/nasa/worldwindx/applications/worldwindow/images/**'
        include 'gov/nasa/worldwindx/examples/data/**'
        include 'gov/nasa/worldwindx/examples/images/**'
    }
}
// Copy worldwindx jar to project-directory.
extensionsJar.doLast {
    copy {
        from "$buildDir/libs/${extensionsJar.archiveName}"
        into "${project.projectDir}"
    }
}

artifacts {
    archives extensionsJar
}

test {
    dependsOn jar
    classpath += project.files("$buildDir/libs/${jar.archiveName}", configurations.runtime)
}

javadoc {
    options {
        overview = "${project.projectDir}/src/overview.html"
        windowTitle = 'WorldWindJava API'
        title = 'NASA WorldWind Java-Community Edition'
        header = 'NASA WorldWind-CE'
        splitIndex = true
        noDeprecated = true
        version = false
        author = false
        use = true
    }
    exclude 'com/**'
    exclude 'gov/nasa/worldwind/formats/**'
}

[wcmatthysen]

You'll see I'm building against a local gdal jar:

implementation files('gdal.jar')

The reason for this is that the WorldWind gdal jar has a custom class or two that is not included in the distributed jars on maven-central. We still need to figure out how we are going to solve this (see #17).