lua-resty-template
lua-resty-template is a compiling (1) (HTML) templating engine for Lua and OpenResty.
(1) with compilation we mean that templates are translated to Lua functions that you may call or string.dump
as a binary bytecode blobs to disk that can be later utilized with lua-resty-template or basic load and
loadfile standard Lua functions (see also Template Precompilation). Although,
generally you don't need to do that as lua-resty-template handles this behind the scenes.
Hello World with lua-resty-template
local template = require "resty.template" -- OR
local template = require "resty.template.safe" -- return nil, err on errors
-- Using template.new
local view = template.new "view.html"
view.message = "Hello, World!"
view:render()
-- Using template.render
template.render("view.html", { message = "Hello, World!" })
view.html
{{message}}
Output
Hello, World!
The same can be done with inline template string:
-- Using template string
template.render([[
{{message}}
]], { message = "Hello, World!" })
Contents
Template Syntax
You may use the following tags in templates:
{{expression}}, writes result of expression - html escaped
{*expression*}, writes result of expression
{% lua code %}, executes Lua code
{(template)}, includes template file, you may also supply context for include file {(file.html, { message = "Hello, World" } )} (NOTE: you cannot use comma (,) in file.html, in that case use {["file,with,comma"]} instead)
{[expression]}, includes expression file (the result of expression), you may also supply context for include file {["file.html", { message = "Hello, World" } ]}
{-block-}...{-block-}, wraps inside of a {-block-} to a value stored in a blocks table with a key block (in this case), see using blocks. Don't use predefined block names verbatim and raw.
{-verbatim-}...{-verbatim-} and {-raw-}...{-raw-} are predefined blocks whose inside is not processed by the lua-resty-template but the content is outputted as is.
{# comments #} everything between {# and #} is considered to be commented out (i.e. not outputted or executed)
From templates you may access everything in context table, and everything in template table.
In templates you can also access context and template by prefixing keys.
{{message}}
==
{{context.message}}
Short Escaping Syntax
If you don't want a particular template tag to be processed you may escape the starting tag with backslash \:
\{{message}}
This will output (instead of evaluating the message):
{{message}}
If you want to add backslash char just before template tag, you need to escape that as well:
\\{{message}}
This will output:
\[message-variables-content-here]
A Word About Complex Keys in Context Table
Say you have this kind of a context table:
local ctx = {["foo:bar"] = "foobar"}
And you want to render the ctx["foo:bar"]'s value foobar in your template. You have to specify it explicitly
by referencing the context in your template:
{# {*["foo:bar"]*} won't work, you need to use: #}
{*context["foo:bar"]*}
Or altogether:
template.render([[
{*context["foo:bar"]*}
]], {["foo:bar"] = "foobar"})
A Word About HTML Escaping
Only strings are escaped, functions are called without arguments (recursively) and results are returned as is,
other types are tostringified. nils and ngx.nulls are converted to empty strings "".
Escaped HTML characters:
& becomes &
< becomes <
> becomes >
" becomes "
' becomes '
/ becomes /
Example
Lua
local template = require "resty.template"
template.render("view.html", {
title = "Testing lua-resty-template",
message = "Hello, World!",
names = { "James", "Jack", "Anne" },
jquery = ''
})
view.html
{(header.html)}
{{message}}
{% for _, name in ipairs(names) do %}
{{name}}
{% end %}
{(footer.html)}
header.html
{{title}}
{*jquery*}
footer.html
Reserved Context Keys and Remarks
It is advised that you do not use these keys in your context tables:
___, holds the compiled template, if set you need to use {{context.___}}
context, holds the current context, if set you need to use {{context.context}}
echo, holds the echo helper function, if set you need to use {{context.echo}}
include, holds the include helper function, if set you need to use {{context.include}}
layout, holds the layout by which the view will be decorated, if set you need to use {{context.layout}}
blocks, holds the blocks, if set you need to use {{context.blocks}} (see: using blocks)
template, holds the template table, if set you need to use {{context.template}}
In addition to that with template.new you should not overwrite:
render, the function that renders a view, obviously ;-)
You should also not {(view.html)} recursively:
Lua
template.render "view.html"
view.html
{(view.html)}
You can load templates from "sub-directories" as well with {(syntax)}:
view.html
{(users/list.html)}
Also note that you can provide template either as a file path or as a string. If the file exists,
it will be used, otherwise the string is used. See also template.load.
Installation
Just place template.lua and
template directory somewhere in
your package.path, under resty directory. If you are using OpenResty, the default location would
be /usr/local/openresty/lualib/resty.
Using OpenResty Package Manager (opm)
$ opm get bungle/lua-resty-template
Using LuaRocks
$ luarocks install lua-resty-template
LuaRocks repository for lua-resty-template is located at https://luarocks.org/modules/bungle/lua-resty-template.
Nginx / OpenResty Configuration
When lua-resty-template is used in context of Nginx / OpenResty there are a few configuration directives
that you need to be aware:
template_root (set $template_root /var/www/site/templates)
template_location (set $template_location /templates)
If none of these are set in Nginx configuration, ngx.var.document_root (aka root-directive) value is used.
If template_location is set, it will be used first, and if the location returns anything but 200 as
a status code, we do fallback to either template_root (if defined) or document_root.
With lua-resty-template 2.0 it is possible to override $template_root and $template_location with
Lua code:
local template = require "resty.template".new({
root = "/templates",
location = "/templates"
})
Using document_root
This one tries to load file content with Lua code from html directory (relative to Nginx prefix).
http {
server {
location /{
root html;
content_by_lua '
local template = require "resty.template"
template.render("view.html", { message = "Hello, World!" })
';
}
}
}
Using template_root
This one tries to load file content with Lua code from /usr/local/openresty/nginx/html/templates directory.
http {
server {
set $template_root /usr/local/openresty/nginx/html/templates;
location /{
root html;
content_by_lua '
local template = require "resty.template"
template.render("view.html", { message = "Hello, World!" })
';
}
}
}
Using template_location
This one tries to load content with ngx.location.capture from /templates location (in this case this is
served with ngx_static module).
http {
server {
set $template_location /templates;
location /{
root html;
content_by_lua '
local template = require "resty.template"
template.render("view.html", { message = "Hello, World!" })
';
}
location /templates{
internal;
alias html/templates/;
}
}
}
Lua API
template.root
You can setup template root by setting this variable which will be looked for template files:
local template = require "resty.template".new({
root = "/templates"
})
template.render_file("test.html")
This property overrides the one set in Nginx configuration (set $template_root /my-templates;)
template.location
This is what you can use with OpenResty as that will use ngx.location.capture to fetch templates
files in non-blocking fashion.
local template = require "resty.template".new({
location = "/templates"
})
template.render_file("test.html")
This property overrides the one set in Nginx configuration (set $template_location /my-templates;)
table template.new(view, layout)
Creates a new template instance that is used as a (default) context when rendered. A table that gets created has
only one method render, but the table also has metatable with __tostring defined. See the example below. Both
view and layout arguments can either be strings or file paths, but layout can also be a table created previously
with template.new.
With 2.0 the new can also be used without arguments, which creates a new template instance:
local template = require "resty.template".new()
You can also pass a table that is then modified to be a template:
local config = {
root = "/templates"
}
local template = require "resty.template".new(config)
This is handy as the template created by new does not share the cache with the global template returned
by require "resty.template" (this was reported with issue #25).
You can also pass a boolean true or false as a view parameter which means that either safe or un-safe
version of template is returned:
local unsafe = require "resty.template"
local safe = unsafe.new(true)
There is also a default safe implementation available:
local safe = require "resty.template.safe"
-- you can create instance of safe too:
local safe_instance = safe.new()
safe version uses return nil, err Lua error handling pattern and unsafe just throws the errors, which you
can catch with pcall, xpcall or coroutine.wrap.
Here are examples of using new with arguments:
local view = template.new"template.html" -- or
local view = template.new("view.html", "layout.html") -- or
local view = template.new[[
{{message}}
]] -- or
local view = template.new([[
{{message}}
]], [[
{*view*}
]])
Example
local template = require "resty.template"
local view = template.new"view.html"
view.message = "Hello, World!"
view:render()
-- You may also replace context on render
view:render{ title = "Testing lua-resty-template" }
-- If you want to include view context in replacement context
view:render(setmetatable({ title = "Testing lua-resty-template" }, { __index = view }))
-- To get rendered template as a string, you can use tostring
local result = tostring(view)
boolean template.caching(boolean or nil)
This function enables or disables template caching, or if no parameters are passed, returns current state of
template caching. By default template caching is enabled, but you may want to disable it on development or
low-memory situations.
local template = require "resty.template"
-- Get current state of template caching
local enabled = template.caching()
-- Disable template caching
template.caching(false)
-- Enable template caching
template.caching(true)
Please note that if the template was already cached when compiling a template, the cached version will be returned.
You may want to flush cache with template.cache = {} to ensure that your template really gets recompiled.
function, boolean template.compile(view, cache_key, plain)
Parses, compiles and caches (if caching is enabled) a template and returns the compiled template as a function
that takes context as a parameter and returns rendered template as a string. Optionally you may pass cache_key that
is used as a cache key. If cache key is not provided view wil be used as a cache key. If cache key is no-cache
the template cache will not be checked and the resulting function will not be cached. You may also optionally
pass plain with a value of true if the view is plain text string (this will skip template.load and binary
chunk detection in template.parse phase). If plain is false the template is considered to be a file,
and all the issues with file reading are considered as errors. If the plain is set to nil (the default)
the template does not consider file reading errors as fatal, and returns back the view (usually the path of
the template).
local func = template.compile("template.html") -- or
local func = template.compile([[
{{message}}
]])
Example
local template = require "resty.template"
local func = template.compile("view.html")
local world = func{ message = "Hello, World!" }
local universe = func{ message = "Hello, Universe!" }
print(world, universe)
Also note the second return value which is a boolean. You may discard it, or use it to determine if
the returned function was cached.
function, boolean template.compile_string(view, cache_key)
This just calls template.compile(view, cache_key, true)
function, boolean template.compile_file(view, cache_key)
This just calls template.compile(view, cache_key, false)
template.visit(func)
Allows you to register template parser visitor functions. Visitors are called in the order they
are registered. And once registered, cannot be removed from parser. Perhaps it is easier to show
how it works:
local template = require "resty.template.safe".new()
local i = 0
template.visit(function(content, type, name)
local trimmed = content:gsub("^%s+", ""):gsub("%s+$", "")
if trimmed == "" then return content end
i = i + 1
print(" visit: ", i)
if type then print(" type: ", type) end
if name then print(" name: ", name) end
print("content: ", trimmed)
print()
return content
end)
local func = template.compile([[
How are you, {{user.name}}?
Here is a new cooking recipe for you!
{% for i, ingredient in ipairs(ingredients) do %}
{*i*}. {{ingredient}}
{% end %}
{-ad-}`lua-resty-template` the templating engine for OpenResty!{-ad-}
]])
local content = func{
user = {
name = "bungle"
},
ingredients = {
"potatoes",
"sausages"
}
}
print(content)
This will output the following:
visit: 1
content: How are you,
visit: 2
type: {
content: user.name
visit: 3
content: ?
Here is a new cooking recipe for you!
visit: 4
type: %
content: for i, ingredient in ipairs(ingredients) do
visit: 5
type: *
content: i
visit: 6
content: .
visit: 7
type: {
content: ingredient
visit: 8
type: %
content: end
visit: 9
type: -
name: ad
content: `lua-resty-template` the templating engine for OpenResty!
visit: 10
content: `lua-resty-template` the templating engine for OpenResty!
How are you, bungle?
Here is a new cooking recipe for you!
1. potatoes
2. sausages
The visitor functions should have this signature:
string function(content, type, name)
If the function doesn't modify the content it should return the content back, like the visitor
above does.
Here is a bit more advanced visitor example that handles run-time errors on expressions:
local template = require "resty.template".new()
template.render "Calculation: {{i*10}}"
This will runtime error with:
ERROR: [string "context=... or {}..."]:7: attempt to perform arithmetic on global 'i' (a nil value)
stack traceback:
resty/template.lua:652: in function 'render'
a.lua:52: in function 'file_gen'
init_worker_by_lua:45: in function <43>43>
[C]: in function 'xpcall'
init_worker_by_lua:52: in function <50>50>
Now let's add a visitor that handles this error:
local template = require "resty.template".new()
template.visit(function(content, type)
if type == "*" or type == "{" then
return "select(3, pcall(function() return nil, " .. content .. " end)) or ''"
end
return content
end)
template.render "Calculation: {{i*10}}\n"
template.render("Calculation: {{i*10}}\n", { i = 1 })
This will output:
Calculation:
Calculation: 10
string template.process(view, context, cache_key, plain)
Parses, compiles, caches (if caching is enabled) and returns output as string. You may optionally also
pass cache_key that is used as a cache key. If plain evaluates to true, the view is considered
to be plain string template (template.load and binary chunk detection is skipped on template.parse).
If plain is false" the template is considered to be a file, and all the issues with file reading are
considered as errors. If the plain is set to nil (the default) the template does not consider file
reading errors as fatal, and returns back the view.
local output = template.process("template.html", { message = "Hello, World!" }) -- or
local output = template.process([[
{{message}}
]], { message = "Hello, World!" })
string template.process_string(view, context, cache_key)
This just calls template.process(view, context, cache_key, true)
string template.process_file(view, context, cache_key)
This just calls template.process(view, context, cache_key, false)
template.render(view, context, cache_key, plain)
Parses, compiles, caches (if caching is enabled) and outputs template either with ngx.print if available,
or print. You may optionally also pass cache_key that is used as a cache key. If plain evaluates to
true, the view is considered to be plain string template (template.load and binary chunk detection
is skipped on template.parse). If plain is false" the template is considered to be a file, and
all the issues with file reading are considered as errors. If the plain is set to nil (the default)
the template does not consider file reading errors as fatal, and returns back the view.
template.render("template.html", { message = "Hello, World!" }) -- or
template.render([[
{{message}}
]], { message = "Hello, World!" })
template.render_string(view, context, cache_key)
This just calls template.render(view, context, cache_key, true)
template.render_file(view, context, cache_key)
This just calls template.render(view, context, cache_key, false)
string template.parse(view, plain)
Parses template file or string, and generates a parsed template string. This may come useful when debugging
templates. You should note that if you are trying to parse a binary chunk (e.g. one returned with
template.compile), template.parse will return that binary chunk as is. If plain evaluates to
true, the view is considered to be plain string template (template.load and binary chunk detection
is skipped on template.parse). If plain is false" the template is considered to be a file, and
all the issues with file reading are considered as errors. If the plain is set to nil (the default)
the template does not consider file reading errors as fatal, and returns back the view.
local t1 = template.parse("template.html")
local t2 = template.parse([[
{{message}}
]])
string template.parse_string(view, plain)
This just calls template.parse(view, plain, true)
string template.parse_file(view, plain)
This just calls template.parse(view, plain, false)
string template.precompile(view, path, strip, plain)
Precompiles template as a binary chunk. This binary chunk can be written out as a file (and you may use it
directly with Lua's load and loadfile). For convenience you may optionally specify path argument to
output binary chunk to file. You may also supply strip parameter with value of false to make precompiled
templates to have debug information as well (defaults to true). The last parameter plain means that
should complilation treat the view as string (plain = true) or as file path (plain = false) or
try first as a file, and fallback to string (plain = nil). In case the plain=false (a file) and there
is error with file io the function will also error with an assertion failure.
local view = [[
{{title}}
{% for _, v in ipairs(context) do %}
{{v}}
{% end %}
]]
local compiled = template.precompile(view)
local file = io.open("precompiled-bin.html", "wb")
file:write(compiled)
file:close()
-- Alternatively you could just write (which does the same thing as above)
template.precompile(view, "precompiled-bin.html")
template.render("precompiled-bin.html", {
title = "Names",
"Emma", "James", "Nicholas", "Mary"
})
string template.precompile_string(view, path, strip)
This just calls template.precompile(view, path, strip, true).
string template.precompile_file(view, path, strip)
This just calls template.precompile(view, path, strip, false).
string template.load(view, plain)
This field is used to load templates. template.parse calls this function before it starts parsing the template
(assuming that optional plain argument in template.parse evaluates to false or nil (the default).
By default there are two loaders in lua-resty-template: one for Lua and the other for Nginx / OpenResty.
Users can overwrite this field with their own function. For example you may want to write a template loader
function that loads templates from a database.
The default template.load for Lua (attached as template.load when used directly with Lua):
function(view, plain)
if plain == true then return view end
local path, root = view, template.root
if root and root ~= EMPTY then
if byte(root, -1) == SOL then root = sub(root, 1, -2) end
if byte(view, 1) == SOL then path = sub(view, 2) end
path = root .. "/" .. path
end
return plain == false and assert(read_file(path)) or read_file(path) or view
end
The default template.load for Nginx / OpenResty (attached as template.load when used in context
of Nginx / OpenResty):
function(view, plain)
if plain == true then return view end
local vars = VAR_PHASES[phase()]
local path = view
local root = template.location
if (not root or root == EMPTY) and vars then
root = var.template_location
end
if root and root ~= EMPTY then
if byte(root, -1) == SOL then root = sub(root, 1, -2) end
if byte(path, 1) == SOL then path = sub(path, 2) end
path = root .. "/" .. path
local res = capture(path)
if res.status == 200 then return res.body end
end
path = view
root = template.root
if (not root or root == EMPTY) and vars then
root = var.template_root
if not root or root == EMPTY then root = var.document_root or prefix end
end
if root and root ~= EMPTY then
if byte(root, -1) == SOL then root = sub(root, 1, -2) end
if byte(path, 1) == SOL then path = sub(path, 2) end
path = root .. "/" .. path
end
return plain == false and assert(read_file(path)) or read_file(path) or view
end
As you can see, lua-resty-template always tries (by default) to load a template from a file
(or with ngx.location.capture) even if you provided template as a string. lua-resty-template.
But if you know that your templates are always strings, and not file paths, you may use plain
argument in template.compile, template.render, and template.parse OR replace template.load
with the simplest possible template loader there is (but be aware that if your templates use
{(file.html)} includes, those are considered as strings too, in this case file.html will
be the template string that is parsed) - you could also setup a loader that finds templates in
some database system, e.g. Redis:
local template = require "resty.template"
template.load = function(view, plain) return view end
If the plain parameter is false (nil is not treated as false), all the issues with file
io are considered assertion errors.
string template.load_string(view)
This just calls template.load(view, true)
string template.load_file(view)
This just calls template.load(view, false)
template.print
This field contains a function that is used on template.render() or
template.new("example.html"):render() to output the results. By default this holds either
ngx.print (if available) or print. You may want to (and are allowed to) overwrite this
field, if you want to use your own output function instead. This is also useful if you are
using some other framework, e.g. Turbo.lua (http://turbolua.org/).
local template = require "resty.template"
template.print = function(s)
print(s)
print("")
end
Template Precompilation
lua-resty-template supports template precompilation. This can be useful when you want to
skip template parsing (and Lua interpretation) in production or if you do not want your
templates distributed as plain text files on production servers. Also by precompiling,
you can ensure that your templates do not contain something, that cannot be compiled
(they are syntactically valid Lua). Although templates are cached (even without precompilation),
there are some performance (and memory) gains. You could integrate template precompilation in
your build (or deployment) scripts (maybe as Gulp, Grunt or Ant tasks).
Precompiling template, and output it as a binary file
local template = require "resty.template"
local compiled = template.precompile("example.html", "example-bin.html")
Load precompiled template file, and run it with context parameters
local template = require "resty.template"
template.render("example-bin.html", { "Jack", "Mary" })
Template Helpers
Built-in Helpers
echo(...)
Echoes output. This is useful with {% .. %}:
require "resty.template".render[[
begin
{%
for i=1, 10 do
echo("\tline: ", i, "\n")
end
%}
end
]]
This will output:
begin
line: 1
line: 2
line: 3
line: 4
line: 5
line: 6
line: 7
line: 8
line: 9
line: 10
end
This can also be written as but echo might come handy in some cases:
require "resty.template".render[[
begin
{% for i=1, 10 do %}
line: {* i *}
{% end %}
end
]]
include(view, context)
This is mainly used with internally with {(view.hmtl)}, {["view.hmtl"]} and
with blocks {-block-name-}..{-block-name-}. If context is not given the context
used to compile parent view is used. This function will compile the view and call
the resulting function with context (or the context of parent view if not given).
Other Ways to Extend
While lua-resty-template does not have much infrastucture or ways to extend it,
you still have a few possibilities that you may try.
Adding methods to global string, and table types (not encouraged, though)
Wrap your values with something before adding them in context (e.g. proxy-table)
Create global functions
Add local functions either to template table or context table
Use metamethods in your tables
While modifying global types seems convenient, it can have nasty side effects.
That's why I suggest you to look at these libraries, and articles first:
You could for example add Moses' or Underscore's _ to template table or context table.
Example
local _ = require "moses"
local template = require "resty.template"
template._ = _
Then you can use _ inside your templates. I created one example template helper
that can be found from here:
https://github.com/bungle/lua-resty-template/blob/master/lib/resty/template/html.lua
Lua
local template = require "resty.template"
local html = require "resty.template.html"
template.render([[
{% for _, person in ipairs(context) do %}
{*html.li(person.name)*}
{% end %}
{% for _, person in ipairs(context) do %}
{*html.td{ id = person.id }(person.name)*}
{% end %}
]], {
{ id = 1, name = "Emma"},
{ id = 2, name = "James" },
{ id = 3, name = "Nicholas" },
{ id = 4 }
})
Output
• Emma
• James
• Nicholas
•
Emma
James
Nicholas
Usage Examples
Template Including
You may include templates inside templates with {(template)} and {(template, context)} syntax.
The first one uses the current context as a context for included template, and the second one replaces
it with a new context. Here is example of using includes and passing a different context to include file:
Lua
local template = require "resty.template"
template.render("include.html", { users = {
{ name = "Jane", age = 29 },
{ name = "John", age = 25 }
}})
include.html
{% for _, user in ipairs(users) do %}
{(user.html, user)}
{% end %}
user.html
User {{name}} is of age {{age}}
Outut
• User Jane is of age 29
• User John is of age 25
Views with Layouts
Layouts (or Master Pages) can be used to wrap a view inside another view (aka layout).
Lua
local template = require "resty.template"
local layout = template.new "layout.html"
layout.title = "Testing lua-resty-template"
layout.view = template.compile "view.html" { message = "Hello, World!" }
layout:render()
-- Or like this
template.render("layout.html", {
title = "Testing lua-resty-template",
view = template.compile "view.html" { message = "Hello, World!" }
})
-- Or maybe you like this style more
-- (but please remember that context.view is overwritten on rendering the layout.html)
local view = template.new("view.html", "layout.html")
view.title = "Testing lua-resty-template"
view.message = "Hello, World!"
view:render()
-- Well, maybe like this then?
local layout = template.new "layout.html"
layout.title = "Testing lua-resty-template"
local view = template.new("view.html", layout)
view.message = "Hello, World!"
view:render()
view.html
{{message}}
layout.html
{{title}}
{*view*}
Alternatively you can define the layout in a view as well:
Lua
local view = template.new("view.html", "layout.html")
view.title = "Testing lua-resty-template"
view.message = "Hello, World!"
view:render()
view.html
{% layout="section.html" %}
{{message}}
section.html
{*view*}
layout.html
{{title}}
{*view*}
Output
Testing lua-resty-template
Hello, World!
Using Blocks
Blocks can be used to move different parts of the views to specific places in layouts. Layouts have placeholders
for blocks.
Lua
local view = template.new("view.html", "layout.html")
view.title = "Testing lua-resty-template blocks"
view.message = "Hello, World!"
view.keywords = { "test", "lua", "template", "blocks" }
view:render()
view.html
{{message}}
{-aside-}
{% for _, keyword in ipairs(keywords) do %}
{{keyword}}
{% end %}
{-aside-}
layout.html
{*title*}
{*view*}
{% if blocks.aside then %}
{*blocks.aside*}
{% end %}
Output
Testing lua-resty-template blocks
Hello, World!
• test
• lua
• template
• blocks
Grandfather-Father-Son Inheritance
Say you have base.html, layout1.html, layout2.html and page.html. You want an inheritance like this:
base.html ➡ layout1.html ➡ page.html or base.html ➡ layout2.html ➡ page.html (actually this nesting is
not limited to three levels).
Lua
local res = require"resty.template".compile("page.html"){}
base.html
{* blocks.page_css *}
{* blocks.main *}
{* blocks.page_js *}
layout1.html
{% layout = "base.html" %}
{-main-}
{* blocks.sidebar *}
{* blocks.content *}
{-main-}
layout2.html
{% layout = "base.html" %}
{-main-}
{* blocks.sidebar *}
{* blocks.content *}
I am different from layout1
{-main-}
page.html
{% layout = "layout1.html" %}
{-sidebar-}
this is sidebar
{-sidebar-}
{-content-}
this is content
{-content-}
{-page_css-}
{-page_css-}
{-page_js-}
{-page_js-}
Or:
page.html
{% layout = "layout2.html" %}
{-sidebar-}
this is sidebar
{-sidebar-}
{-content-}
this is content
{-content-}
{-page_css-}
{-page_css-}
{-page_js-}
{-page_js-}
Macros
@DDarko mentioned in an issue #5
that he has a use case where he needs to have macros or parameterized views. That is a nice feature that you can
use with lua-resty-template.
To use macros, let's first define some Lua code:
template.render("macro.html", {
item = "original",
items = { a = "original-a", b = "original-b" }
})
And the macro-example.html:
{% local string_macro = [[
{{item}}
]] %}
{* template.compile(string_macro)(context) *}
{* template.compile(string_macro){ item = "string-macro-context" } *}
This will output:
original
string-macro-context
Now let's add function macro, in macro-example.html (you can omit local if you want):
{% local function_macro = function(var, el)
el = el or "div"
return "{{" .. var .. "}}" .. el .. ">\n"
end %}
{* template.compile(function_macro("item"))(context) *}
{* template.compile(function_macro("a", "span"))(items) *}
This will output:
original
original-a
But this is even more flexible, let's try another function macro:
{% local function function_macro2(var)
return template.compile("
{{" .. var .. "}}
\n")
end %}
{* function_macro2 "item" (context) *}
{* function_macro2 "b" (items) *}
This will output:
original
original-b
And here is another one:
{% function function_macro3(var, ctx)
return template.compile("
{{" .. var .. "}}
\n")(ctx or context)
end %}
{* function_macro3("item") *}
{* function_macro3("a", items) *}
{* function_macro3("b", items) *}
{* function_macro3("b", { b = "b-from-new-context" }) *}
This will output:
original
original-a
original-b
b-from-new-context
Macros are really flexible. You may have form-renderers and other helper-macros to have a reusable and
parameterized template output. One thing you should know is that inside code blocks (between {% and %})
you cannot have %}, but you can work around this using string concatenation "%" .. "}".
Calling Methods in Templates
You can call string methods (or other table functions) in templates too.
Lua
local template = require "resty.template"
template.render([[
{{header:upper()}}
]], { header = "hello, world!" })
Output
HELLO, WORLD!
Embedding Angular or other tags / templating inside the Templates
Sometimes you need to mix and match other templates (say client side Javascript templates like Angular) with
server side lua-resty-templates. Say you have this kind of Angular template:
{{buttonText}}
Now you can see that there is {{buttonText}} that is really for Angular templating, and not for lua-resty-template.
You can fix this by wrapping either the whole code with {-verbatim-} or {-raw-} or only the parts that you want:
{-raw-}
{{buttonText}}
{-raw-}
or (see the {(head.html)} is processed by lua-resty-template):
{(head.html)}
{-raw-}{{buttonText}}{-raw-}
You may also use short escaping syntax:
...
\{{buttonText}}
...
Embedding Markdown inside the Templates
If you want to embed Markdown (and SmartyPants) syntax inside your templates you can do it by using for example
lua-resty-hoedown (it depends on LuaJIT). Here is an example of
using that:
Lua
local template = require "resty.template"
template.markdown = require "resty.hoedown"
template.render[=[
{*markdown[[
#Hello, World
Testing Markdown.
]]*}
]=]
Output
Hello, World
Testing Markdown.
You may also add config parameters that are documented in lua-resty-hoedown project.
Say you want also to use SmartyPants:
Lua
local template = require "resty.template"
template.markdown = require "resty.hoedown"
template.render[=[
{*markdown([[
#Hello, World
Testing Markdown with "SmartyPants"...
]], { smartypants = true })*}
]=]
Output
Hello, World
Testing Markdown with “SmartyPants”…
You may also want to add caching layer for your Markdowns, or a helper functions instead of placing
Hoedown library directly as a template helper function in template.
Lua Server Pages (LSP) with OpenResty
Lua Server Pages or LSPs is similar to traditional PHP or Microsoft Active Server Pages (ASP)
where you can just place source code files in your document root (of your web server) and have
them processed by compilers of the respective languages (PHP, VBScript, JScript, etc.).
You can emulate quite closely this, sometimes called spaghetti-style of develoment, easily with
lua-resty-template. Those that have been doing ASP.NET Web Forms development, know a concept
of Code Behind files. There is something similar, but this time we call it Layout in Front here
(you may include Lua modules with normal require calls if you wish in LSPs). To help you
understand the concepts, let's have a small example:
nginx.conf:
http {
init_by_lua '
require "resty.core"
template = require "resty.template"
template.caching(false); -- you may remove this on production
';
server {
location ~ \.lsp${
default_type text/html;
content_by_lua 'template.render(ngx.var.uri)';
}
}
}
The above configuration creates a global template variable in Lua environment (you may not want that).
We also created location to match all .lsp files (or locations), and then we just render the template.
Let's imagine that the request is for index.lsp.
index.lsp
{%
layout = "layouts/default.lsp"
local title = "Hello, World!"
%}
{{title}}
Here you can see that this file includes a little bit of a view (
{{title}}
) in addition to some
Lua code that we want to run. If you want to have a pure code file with Layout in Front, then just don't
write any view code in this file. The layout variable is already defined in views as documented else
where in this documentation. Now let's see the other files too.
layouts/default.lsp
{(include/header.lsp)}
{*view*}
Here we have a layout to decorate the index.lsp, but we also have include here, so let's look at it.
include/header.lsp
Testing Lua Server Pages
Static stuff here only.
Output
The final output will look like this:
Testing Lua Server Pages
Hello, World!
As you can see, lua-resty-template can be quite flexibile and easy to start with. Just place
files under your document root and use the normal save-and-refresh style of development. The
server will automatically pick the new files and reload the templates (if the caching is turned
of) on save.
If you want to pass variables to layouts or includes you can add stuff to context table (in the
example below see context.title):
{%
layout = "layouts/default.lsp"
local title = "Hello, World!"
context.title = 'My Application - ' .. title
%}
{{title}}
FAQ
How Do I Clear the Template Cache
lua-resty-template automatically caches (if caching is enabled) the resulting template functions
in template.cache table. You can clear the cache by issuing template.cache = {}.
Where is lua-resty-template Used
jd.com – Jingdong Mall (Chinese: 京东商城; pinyin: Jīngdōng Shāngchéng),
formerly 360Buy, is a Chinese electronic commerce company
Please let me know if there are errors or old information in this list.
Alternatives
You may also look at these (as alternatives, or to mix them with lua-resty-template):
lua-resty-template was originally forked from Tor Hveem's tirtemplate.lua that he had extracted
from Zed Shaw's Tir web framework (http://tir.mongrel2.org/). Thank you Tor, and Zed for your earlier
contributions.
Benchmarks
There is also a regression in LuaJIT that affects the results. If you want your LuaJIT patched against this,
you need to merge this pull request: https://github.com/LuaJIT/LuaJIT/pull/174.
Others have reported
that in simple benchmarks running this template engine actually beats Nginx serving static files by
a factor of three. So I guess this engine is quite fast.
Lua
local benchmark = require "resty.template.microbenchmark"
benchmark.run()
-- You may also pass iteration count (by default it is 1,000)
benchmark.run(100)
Here are some results from my desktop (old 2010 Mac Pro):
-e 'require "resty.template.microbenchmark".run()'
`
Lua 5.1.5 Copyright (C) 1994-2012 Lua.org, PUC-Rio
Running 1000 iterations in each test
Parsing Time: 0.010759
Compilation Time: 0.054640 (template)
Compilation Time: 0.000213 (template, cached)
Execution Time: 0.061851 (same template)
Execution Time: 0.006722 (same template, cached)
Execution Time: 0.092698 (different template)
Execution Time: 0.009537 (different template, cached)
Execution Time: 0.092452 (different template, different context)
Execution Time: 0.010106 (different template, different context, cached)
Total Time: 0.338978
Lua 5.2.4 Copyright (C) 1994-2015 Lua.org, PUC-Rio
Running 1000 iterations in each test
Parsing Time: 0.011633
Compilation Time: 0.060598 (template)
Compilation Time: 0.000243 (template, cached)
Execution Time: 0.068009 (same template)
Execution Time: 0.007307 (same template, cached)
Execution Time: 0.071339 (different template)
Execution Time: 0.007150 (different template, cached)
Execution Time: 0.066766 (different template, different context)
Execution Time: 0.006940 (different template, different context, cached)
Total Time: 0.299985
Lua 5.3.5 Copyright (C) 1994-2018 Lua.org, PUC-Rio
Running 1000 iterations in each test
Parsing Time: 0.012458
Compilation Time: 0.050013 (template)
Compilation Time: 0.000249 (template, cached)
Execution Time: 0.057579 (same template)
Execution Time: 0.006959 (same template, cached)
Execution Time: 0.065352 (different template)
Execution Time: 0.007133 (different template, cached)
Execution Time: 0.060965 (different template, different context)
Execution Time: 0.007726 (different template, different context, cached)
Total Time: 0.268434
Lua 5.4.0 Copyright (C) 1994-2019 Lua.org, PUC-Rio
Running 1000 iterations in each test
Parsing Time: 0.009466
Compilation Time: 0.053116 (template)
Compilation Time: 0.000209 (template, cached)
Execution Time: 0.059017 (same template)
Execution Time: 0.006129 (same template, cached)
Execution Time: 0.061882 (different template)
Execution Time: 0.006613 (different template, cached)
Execution Time: 0.059104 (different template, different context)
Execution Time: 0.005761 (different template, different context, cached)
Total Time: 0.261297
LuaJIT 2.0.5 -- Copyright (C) 2005-2017 Mike Pall. http://luajit.org/
Running 1000 iterations in each test
Parsing Time: 0.005198
Compilation Time: 0.029687 (template)
Compilation Time: 0.000082 (template, cached)
Execution Time: 0.033824 (same template)
Execution Time: 0.003130 (same template, cached)
Execution Time: 0.075899 (different template)
Execution Time: 0.007027 (different template, cached)
Execution Time: 0.070269 (different template, different context)
Execution Time: 0.007456 (different template, different context, cached)
Total Time: 0.232572
LuaJIT 2.1.0-beta3 -- Copyright (C) 2005-2017 Mike Pall. http://luajit.org/
Running 1000 iterations in each test
Parsing Time: 0.003647
Compilation Time: 0.027145 (template)
Compilation Time: 0.000083 (template, cached)
Execution Time: 0.034685 (same template)
Execution Time: 0.002801 (same template, cached)
Execution Time: 0.073466 (different template)
Execution Time: 0.010836 (different template, cached)
Execution Time: 0.068790 (different template, different context)
Execution Time: 0.009818 (different template, different context, cached)
Total Time: 0.231271
resty (resty 0.23, nginx version: openresty/1.15.8.2)
Running 1000 iterations in each test
Parsing Time: 0.003980
Compilation Time: 0.025983 (template)
Compilation Time: 0.000066 (template, cached)
Execution Time: 0.032752 (same template)
Execution Time: 0.002740 (same template, cached)
Execution Time: 0.036111 (different template)
Execution Time: 0.005559 (different template, cached)
Execution Time: 0.032453 (different template, different context)
Execution Time: 0.006057 (different template, different context, cached)
Total Time: 0.145701
I have not yet compared the results against the alternatives.
Changes
The changes of every release of this module is recorded in
Changes.md file.
See Also
lua-resty-route — Routing library
lua-resty-reqargs — Request arguments parser
lua-resty-session — Session library
lua-resty-validation — Validation and filtering library
Roadmap
Some things I and the community wishes to be added:
Better debugging capabilities and better error messages
Proper sandboxing
License
lua-resty-template uses three clause BSD license (because it was originally forked from one that uses it).
Copyright (c) 2014 - 2020, Aapo Talvensaari
All rights reserved.
Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright notice, this
list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright notice, this
list of conditions and the following disclaimer in the documentation and/or
other materials provided with the distribution.
* Neither the name of the {organization} nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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