Request json file:
{
"ab" : "cd" ,
"ef" : "gh"
}

Response json file
{
"ij" : "kl" ,
"mn" : "op"
}

build.gradle :
------------------- Start build.gradle ---------------------------
jsonSchema2Pojo {
    source = files("${sourceSets.main.output.resourcesDir}/json")
    targetDirectory = file("${project.buildDir}/src/main/java")
    targetPackage = 'com.json'
    sourceType = 'json'
    removeOldOutput = true
}


task fixSuperClass {
    doLast {
        String contents = new File("${project.buildDir}/src/main/java/json/Request.java").getText( 'UTF-8' )
        contents = contents.replaceAll( 'Request \{', 'Request extends BaseRequest {' )
        new File("${project.buildDir}/src/main/java/json/Request.java").write( contents, 'UTF-8' )

        String contents3 = new File("${project.buildDir}/src/main/java/json/Response.java").getText( 'UTF-8' )
        contents3 = contents3.replaceAll( 'Response \{', 'Response extends BaseResponse {' )
        new File("${project.buildDir}/src/main/java/json/Response.java").write( contents3, 'UTF-8' )

    }
}

fixSuperClass.dependsOn generateJsonSchema2Pojo
compileJava.dependsOn fixSuperClass