def startBuildTime,endBuildTime
this.afterEvaluate { Project project ->
    println "xxxxxx"
    def preBuildTask = project.tasks.getByName('compileJava')
    preBuildTask.doFirst {
        startBuildTime = System.currentTimeMillis()
        println("ccccccccccccccc")
        println 'ths start time is:'+startBuildTime
    }
    def buildTask = project.tasks.getByName('build')
    buildTask.doLast {
        endBuildTime = System.currentTimeMillis()
        println "eeeeeeee"
//        println "the build time is:${endBuildTime - startBuildTime}"
    }
    println "zzzzzz"
}

为什么我这个例子，doFirst不执行？

输出结果：

D:\source\demo\gradleTest4>gradle build

xxxxxx                                     

zzzzzz

:compileJava UP-TO-DATE     

:processResources UP-TO-DATE

:classes UP-TO-DATE

:jar UP-TO-DATE      

:assemble UP-TO-DATE

:compileTestJava UP-TO-DATE

:processTestResources UP-TO-DATE

:testClasses UP-TO-DATE

:test UP-TO-DATE

:check UP-TO-DATE

:build

eeeeeeee

BUILD SUCCESSFUL