My single build.gradle looks like this:

buildscript {
    ext {
        springBootVersion = '2.0.0.BUILD-SNAPSHOT'
    }
    repositories {
        mavenCentral()
        maven { url "https://repo.spring.io/snapshot" }
        maven { url "https://repo.spring.io/milestone" }
    }
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
    }
}

apply plugin: 'java'
apply plugin: 'org.springframework.boot'
compileJava {
    sourceCompatibility = 1.8
    targetCompatibility = 1.8
}
version = '0.0.1-SNAPSHOT'
sourceCompatibility = 1.8
targetCompatibility = 1.8

compileOptions {
    sourceCompatibility sourceCompatibility
    targetCompatibility targetCompatibility
}


repositories {
    mavenCentral()
    maven { url "https://repo.spring.io/snapshot" }
    maven { url "https://repo.spring.io/milestone" }
}


dependencies {
    compile('org.springframework.boot:spring-boot-starter-data-jpa')
    compile('org.springframework.boot:spring-boot-starter-jdbc')
    compile('org.springframework.boot:spring-boot-starter-security')
    compile('org.springframework.boot:spring-boot-starter-validation')
    compile('org.springframework.boot:spring-boot-starter-web')
    runtime('com.microsoft.sqlserver:mssql-jdbc')
    testCompile('org.springframework.boot:spring-boot-starter-test')
}

But gradle clean build produces:

FAILURE: Build failed with an exception.

* Where:                    
Build file 'D:\objectsharingsystem\build.gradle' line: 16

* What went wrong:          
A problem occurred evaluating root project 'object-sharing-system'.
> java.lang.UnsupportedClassVersionError: org/springframework/boot/gradle/plugin/SpringBootPlugin : Unsupported major.minor version 52.0

* Try:                      
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

Looks like I use java 8 everywhere.

java_home set to java 8