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
|
Jsonnet to Java
---------------
This little code example shows how a Jsonnet config using object-oriented features can be
transliterated (in a structure-preserving manner) to use the object-oriented features of Java. Not
all Jsonnet programs can be converted to Java because Jsonnet has mixins and virtual inner classes.
Execution order is also different, as Jsonnet is lazy and Java is eager. Likewise, Java programs
cannot all be converted to Jsonnet because they have mutable state and I/O.
However said all this, there is a significant overlap between the two languages. This example fits
within that overlap.
Execute Jsonnet code
--------------------
```
jsonnet sub-template.jsonnet
```
Execute Java code
-----------------
We pipe into jsonnet - to pretty-print the output JSON.
```
javac *.java && java Test | jsonnet -
```
Structure of Java code
----------------------
The translation is as as follows:
* Everything is typed as Object, as Jsonnet is dynamically typed. Everything is public, as is implicit in Jsonnet.
* Jsonnet arrays are Object[], and primitives are Boolean / Double / String.
* Jsonnet objects are singleton instances of named Java classes that extend JsonnetObject.
* Jsonnet fields become Java methods with no parameters (fields are virtual in Jsonnet).
* Jsonnet hidden field status is represented with a method nonHiddenFields which returns a set of
field names. Other fields are considered hidden.
* There are 2 liberties taken -- output strings are not escaped properly, and the JSON is printed on
a single line instead of pretty-printed with indenting.
The Java code has a number of auxiliary framework functions to provide Jsonnet functionality that is
implicit in the Jsonnet language.
* The Test class chooses an object and manifests it to stdout.
* The JsonnetValue class implements manifestation, as a visitor over possible JSON values that
builds JSON strings. For objects, it iterates over the non-hidden fields and manifests each value
by reflectively calling that function.
Reference JSON
--------------
For reference, the JSON that should be output is given in sub-template.json
|
