When a new ObjectName is constructed form a string where one key is "", then the value of this key does not appear in the ObjectName's canonical name:

For example:

try {
  System.out.println(
    (new javax.management.ObjectName(
      "spacedomain:%$#@!=&^{}[],2=2,\"\"=;,*")).getCanonicalName());
}
catch (Exception e) {}

produces the following output:
space domain:%$#@!=&^{}[],2=2,=;