the whole project is based on spring cloud

build.gradle configuration of the parent project:

group "com.xxx.yyy"
version "0.1.0"

buildscript {
    ext {
        springBootVersion = "1.5.10.RELEASE"
    }
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
        classpath("se.transmode.gradle:gradle-docker:1.2")
    }
}

subprojects {
    apply plugin: "idea"
    apply plugin: "java"
    apply plugin: "docker"
    apply plugin: "org.springframework.boot"
    sourceCompatibility = 1.8
    targetCompatibility = 1.8
    
    sourceSets {
        main {
            java.srcDir "src"
        }
    }
    repositories {
        mavenCentral()
    }
    configurations {
        all*.exclude module: "spring-boot-starter-logging"
        all*.exclude module: "logback-classic"
    }
    dependencyManagement {
        imports {
            mavenBom "org.springframework.cloud:spring-cloud-dependencies:Edgware.SR3"
        }
    }
    dependencies {
        compile("org.springframework.boot:spring-boot-starter")
        compile("org.springframework.boot:spring-boot-starter-log4j2")
        compile("org.springframework.boot:spring-boot-starter-test")
        compile("com.fasterxml.jackson.dataformat:jackson-dataformat-yaml")
    }
}

the configuration of the subproject is relatively simple
subproject 1 :

group "com.xxx.yyy"
version "0.1.0"
archivesBaseName = "prj1"

dependencies {
    compile("org.springframework.boot:spring-boot-starter-web")
    // ...
}

subitem 2 :

group "com.xxx.yyy"
version "0.1.0"
archivesBaseName = "prj2"

dependencies {
    compile project(":prj1")
}

under the parent project directory, execute gradle build-x test command

> Task :prj2:compileJava
ConsumerHelper.java:5: : com.xxx.yyy.zzz

what is the cause of this?