Gradle project, sub projects executed repeatedly - gradle

Question

I have a project with sub projects. The layout:
rootproj
--subproj1
----mybuild.number
--subproj2
--build.gradle
--gradle.properties
--settings.gradle
mybuild.number
#Build Number for ANT. Do not edit!
#Wed Nov 210 2121:210:2121 PST 2102121
build.number=1
settings.gradle
include ('subproj1', 'subproj2')
build.gradle
allprojects {
repositories {
mavenLocal()
maven {url "http://repo1.maven.org/maven2"}
}
}
subprojects {
project (':subproj1') {
def oldN = new File("D:/rootproj/subproj1/mybuild.number").text.split("=")[1]
def newN = (oldN.toInteger() + 1).toString()
ant.replace(
file: "mybuild.number",
token: "${oldN}",
value: "${newN}"
)
println "From subproj1 : ${newN}"
task hello(overwrite: true){
doLast{
println "hello from subproject 1"
}
}
}
project (':subproj2'){
println "the build Dir: $buildDir"
task hello(overwrite: true){
doLast{
println "hello from subproject 2"
}
}
}
}
when I run
gradle -q subproj1:hello
or
gradle -q subproj2:hello
or
gradle
from the rootproj, I always get e.g.
....
From subproj1 : 24
the build Dir: D:\rootproj\subproj2\build
From subproj1 : 25
the build Dir: D:\rootproj\subproj2\build
1. Why the two sub projects always get executed twice, therefore the build number is incremented twice, instead of once?
2. why all sub projects get executed even though I explicitly specified the project:task in the command line?
I have searched the Internet, could not find useful information.
Thanks for your help in advance.
EDIT:
Change build.gradle as #JB Nizet suggested:
move the ant.replace to task incr
comment out subprojects
It works exactly as I expected.
allprojects {
repositories {
mavenLocal()
maven {url "http://repo1.maven.org/maven2"}
}
}
//subprojects {
def oldN = new File("E:/hqin/build/gradle/rootproj/subproj1/mybuild.number").text.split("=")[1]
def newN = (oldN.toInteger() + 1).toString()
project (':subproj1') {
task incr {
doLast{
ant.replace(
file: "mybuild.number",
token: "${oldN}",
value: "${newN}"
)
}
println "From subproj1 : ${newN}"
}
task hello(overwrite: true, dependsOn: 'incr'){
doLast{
println "hello from subproject 1"
}
}
}
project (':subproj2'){
task hello(overwrite: true){
doLast{
println "the build Dir: $buildDir"
println "hello from subproject 2"
}
}
}
//}

Answer 1

Regarding the second point: because your code is run as part of the project configuration, which is always run, whatever the task being executed. If you want code being executed when a task is executed, then it should be inside the doLast closure of a task definition:
task someTask {
doLast {
...
}
}
Regarding the first point: the closure passed to subprojects is executed for every subproject. So, it's called once for the subproject 1, and configures subproject 1 and subproject 2, then it's called again for subproject 2, and reconfigures subproject 1 and subproject 2 again. You shouldn't have subprojects at all.