Jsonnet是Google推出的一门为应用程序和工具开发人员提供的、基于Json的数据模板语言
安装
brew install jsonnet
$ go install github.com/google/go-jsonnet/cmd/jsonnet@latest
使用场景
jsonnet 主要是用做 Kubernetes、Prometheus、Grafana 等的配置管理
help
$ jsonnet --help
Jsonnet commandline interpreter (Go implementation) v0.19.1
jsonnet {<option>} <filename>
Available options:
-h / --help This message
-e / --exec Treat filename as code
-J / --jpath <dir> Specify an additional library search dir
(right-most wins)
-o / --output-file <file> Write to the output file rather than stdout
-m / --multi <dir> Write multiple files to the directory, list files
on stdout
-c / --create-output-dirs Automatically creates all parent directories for
files
-y / --yaml-stream Write output as a YAML stream of JSON documents
-S / --string Expect a string, manifest as plain text
-s / --max-stack <n> Number of allowed stack frames
-t / --max-trace <n> Max length of stack trace before cropping
--version Print version
Available options for specifying values of 'external' variables:
Provide the value as a string:
-V / --ext-str <var>[=<val>] If <val> is omitted, get from environment
var <var>
--ext-str-file <var>=<file> Read the string from the file
Provide a value as Jsonnet code:
--ext-code <var>[=<code>] If <code> is omitted, get from environment
var <var>
--ext-code-file <var>=<file> Read the code from the file
Available options for specifying values of 'top-level arguments':
Provide the value as a string:
-A / --tla-str <var>[=<val>] If <val> is omitted, get from environment
var <var>
--tla-str-file <var>=<file> Read the string from the file
Provide a value as Jsonnet code:
--tla-code <var>[=<code>] If <code> is omitted, get from environment
var <var>
--tla-code-file <var>=<file> Read the code from the file
Environment variables:
JSONNET_PATH is a colon (semicolon on Windows) separated list of directories
added in reverse order before the paths specified by --jpath (i.e. left-most
wins). E.g. these are equivalent:
JSONNET_PATH=a:b jsonnet -J c -J d
JSONNET_PATH=d:c:a:b jsonnet
jsonnet -J b -J a -J c -J d
In all cases:
<filename> can be - (stdin)
Multichar options are expanded e.g. -abc becomes -a -b -c.
The -- option suppresses option processing for subsequent arguments.
Note that since filenames and jsonnet programs can begin with -, it is
advised to use -- if the argument is unknown, e.g. jsonnet -- "$FILENAME".
语法
注释
// 单行注释
/* 多行
注释 */
简单运算
$ jsonnet -e '{key: 1+2}'
{
"key": 3
}
self 引用
$ cat << EOF >> t1.jsonnet
{
person1: {
name: "Alice",
welcome: "Hello " + self.name + "!",
},
person2: self.person1 { name: "Bob" },
}
EOF
$ jsonnet t1.jsonnet
{
"person1": {
"name": "Alice",
"welcome": "Hello Alice!"
},
"person2": {
"name": "Bob",
"welcome": "Hello Bob!"
}
}
复杂运算
支持四则运算、条件语句、字符串拼接、字符串格式化、数据拼接、数据切片、python风格的lambda表达式
$ cat > t2.jsonnet << EOF
{
array: [1, 2] + [3],
math: (4 + 5) / 3 * 2,
format: 'Hello, I am %s' % 'alei',
concat: 'Hello, ' + 'I am alei',
slice: [1,2,3,4][1:3],
'list comprehension': [x * x for x in [1,2,3,4]],
condition:
if 2 > 1 then
'true'
else
'false',
}
EOF
$ jsonnet t2.jsonnet
{
"array": [
1,
2,
3
],
"concat": "Hello, I am alei",
"condition": "true",
"format": "Hello, I am alei",
"list comprehension": [
1,
4,
9,
16
],
"math": 6,
"slice": [
2,
3
]
}
变量与引用
local 关键字定义内部变量，通过变量名直接引用$ 指向根对象
$ cat > t3.jsonnet <<EOF
{
local name = 'aylei',
language:: 'jsonnet',
message: {
target: $.language,
author: name,
by: self.author,
}
}
EOF
$ jsonnet t3.jsonnet
{
"message": {
"author": "aylei",
"by": "aylei",
"target": "jsonnet"
}
}
函数
- local 也可以定义函数，引用方式与变量相同，语法与 Python 类似
$ cat > t4.jsonnet << EOF
{
local hello(name) = 'hello %s' % name,
sum(x, y):: x + y,
newObj(name='alei', age=23, gender='male'):: {
name: name,
age: age,
gender: gender,
},
call_sum: $.sum(1, 2),
call_hello: hello('world'),
me: $.newObj(age=24),
}
EOF
$ jsonnet test.jsonnet
{
"call_hello": "hello world",
"call_sum": 3,
"me": {
"age": 24,
"gender": "male",
"name": "alei"
}
}
面向对象
$ cat > t5.jsonnet << EOF
local base = {
f: 2,
g: self.f + 100,
};
base + {
f: 5,
old_f: super.f,
old_g: super.g,
}
EOF
$ jsonnet t5.jsonnet
{
"f": 5,
"g": 105,
"old_f": 2,
"old_g": 105
}
扩展