How to define and call custom methods in build.gra

问题:

As part of my project, I need to read files from a directory and do some operations all these in build script. For each file, the operation is the same(reading some sql queries and execute it). I think its a repetitive task and better to write inside a method. Since I'm new to gradle, I dont know how it should be. Please help.

回答1:

One approach given below:

ext.myMethod = { param1, param2 ->
    // Method body here
}

Note that this gets created for the project scope, ie. globally available for the project, which can be invoked as follows anywhere in the build script using myMethod(p1, p2) which is equivalent to project.myMethod(p1, p2)

The method can be defined under different scopes as well, such as within tasks:

task myTask {
    ext.myMethod = { param1, param2 ->
        // Method body here
    }

    doLast {
        myMethod(p1, p2) // This will resolve 'myMethod' defined in task
    }
}

回答2:

If you have defined any methods in any other file *.gradle - ext.method() makes it accessible project wide. For example here is a

versioning.gradle

// ext makes method callable project wide
ext.getVersionName = { ->
    try {
        def branchout = new ByteArrayOutputStream()
        exec {
            commandLine 'git', 'rev-parse', '--abbrev-ref', 'HEAD'
            standardOutput = branchout
        }
        def branch = branchout.toString().trim()

        if (branch.equals("master")) {
            def stdout = new ByteArrayOutputStream()
            exec {
                commandLine 'git', 'describe', '--tags'
                standardOutput = stdout
            }
            return stdout.toString().trim()
        } else {
            return branch;
        }
    }
    catch (ignored) {
        return null;
    }
}

build.gradle

task showVersion << {
    // Use inherited method
    println 'VersionName: ' + getVersionName()
}

Without ext.method() format , the method will only be available within the *.gradle file it is declared. This is the same with properties.

回答3:

You can define methods in the following way:

// Define an extra property
ext.srcDirName = 'src/java'

// Define a method
def getSrcDir(project) {
    return project.file(srcDirName)
}

You can find more details in gradle documentation Chapter 62. Organizing Build Logic

回答4:

An example with a root object containing methods.

hg.gradle file:

ext.hg = [

    cloneOrPull: { source, dest, branch ->
        if (!dest.isDirectory())
            hg.clone(source, dest, branch)
        else
            hg.pull(dest)
        hg.update(dest, branch)
    },

    clone: { source, dest, branch ->
        dest.mkdirs()
        exec {
            commandLine 'hg', 'clone', '--noupdate', source, dest.absolutePath
        }
    },

    pull: { dest ->
        exec {
            workingDir dest.absolutePath
            commandLine 'hg', 'pull'
        }
    },

]

build.gradle file

apply from: 'hg.gradle'

hg.clone('path/to/repo')