ansible reading variable from json file

i am new to ansible world. trying to providing all variable from json file, but its not accepting. it shows and error variable undefined

below is my json file

{  
   "Tomcat":{  
       "SHPN":"8905",
       "HTPN":"8980",
       "SSPN":"8943",
       "AJPN":"8909",
       "Server":"test.example.com",
       "JENKINS_HOME":"/apps/tech/jenkins/jenkins-configuration",
       "PName":"Tomcat-Installation",
       "IName":"ansible_test",
       "IUID":"jbosscfg",
       "IGID":"staff",
       "IDEPT":"tech",
       "IRECPT":"test@example.com"
   }
}

below is my playbook

--- 
- 
  gather_facts: false
  hosts: "{{Server}}"
  tasks: 
    - 
      ignore_errors: true
      name: "find no of Tomcat Instance available on the Server"
      copy: 
        src: "{{ JENKINS_HOME }}/workspace/{{ PName }}/instance/"
        dest: /apps/tech/{{IName}}
        group: "{{IGID}}"
        owner: "{{IUID}}"
        mode: 0755 
    - 
      replace: "dest='/apps/tech/{{IName}}/scripts/set_env.sh' regexp='<DEPARTMENT NAME>' replace='{{IDEPT}}'"
    - 
      replace: "dest='/apps/tech/{{IName}}/scripts/set_env.sh' regexp='<RECIPIENT>' replace='{{IRECPT}}'"
    - 
      replace: "dest='/apps/tech/{{IName}}/scripts/set_env.sh' regexp='<TOMCAT INSTANCE NAME>' replace='{{IName}}'"
    - 
      replace: "dest='/apps/tech/{{IName}}/scripts/set_env.sh' regexp='<USER ID>' replace='{{IUID}}'"
    - 
      name: "Ansible Template Example"
      template: 
        src: tomcat_server.j2
        dest: /apps/tech/{{IName}}/conf/server.xml
        mode: 0777

i am below while executing the ansible playbook - error says variable undefined

test.example.com:~/final:$ ansible-playbook configure-tomcat-instance.yml --extra-vars "@test.json"
ERROR! the field 'hosts' has an invalid value, which appears to include a variable that is undefined. The error was: 'Server' is undefined

The error appears to have been in '/home/jbosscfg/final/configure-tomcat-instance.yml': line 3, column 3, but may
be elsewhere in the file depending on the exact syntax problem.

The offending line appears to be:

-
  gather_facts: false
  ^ here