1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
|
open Printf
let param_template =
(* Sample item used to populate the template config file *)
{
Config_v.name = "foo";
key = "0123456789abcdef"
}
let config_template =
(*
Records can be conveniently created using functions generated by
"atdgen -v".
Here we use Config_v.create_config to create a record of type
Config_t.config. The big advantage over creating the record
directly using the record notation {...} is that we don't have to
specify default values (such as timeout in this example).
*)
Config_v.create_config ~title:"" ~credentials: [param_template] ()
let make_json_template () =
(* Thanks to the -j-defaults flag passed to atdgen, even default
fields will be printed out *)
let compact_json = Config_j.string_of_config config_template in
Yojson.Safe.prettify compact_json
let print_template () =
print_endline (make_json_template ())
let print_format () =
print_string Config_atd.contents
let validate fname =
let x =
try
(* Read config data structure from JSON file *)
let x = Atdgen_runtime.Util.Json.from_file Config_j.read_config fname in
(* Call the validators specified by <ocaml valid=...> *)
match Config_v.validate_config [] x with
| Some _ -> failwith "Some fields are invalid"
| None -> x
with e ->
(* Print decent error message and exit *)
let msg =
match e with
Failure s
| Yojson.Json_error s -> s
| e -> Printexc.to_string e
in
eprintf "Error: %s\n%!" msg;
exit 1
in
(* Convert config to compact JSON and pretty-print it.
~std:true means that the output will not use extended syntax for
variants and tuples but only standard JSON. *)
let json = Yojson.Safe.prettify ~std:true (Config_j.string_of_config x) in
print_endline json
type action = Template | Format | Validate of string
let main () =
let action = ref Template in
let options = [
"-template", Arg.Unit (fun () -> action := Template),
"
prints a sample configuration file";
"-format", Arg.Unit (fun () -> action := Format),
"
prints the format specification of the config files (atd format)";
"-validate", Arg.String (fun s -> action := Validate s),
"<CONFIG FILE>
reads a config file, validates it, adds default values
and prints the config nicely to stdout";
]
in
let usage_msg = sprintf "\
Usage: %s [-template|-format|-validate ...]
Demonstration of how to manage JSON configuration files with atdgen.
"
Sys.argv.(0)
in
let anon_fun s = eprintf "Invalid command parameter %S\n%!" s; exit 1 in
Arg.parse options anon_fun usage_msg;
match !action with
Template -> print_template ()
| Format -> print_format ()
| Validate s -> validate s
let () = main ()
|
