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1. 安装必要的工具和库

apt-get install capnproto luarocksluarocks install lua-capnproto
luarocks install lua-cjson

lua-cjson 库不是必须的，是由于后面的演示程序要使用，就一起装上了。

可以看下库的安装位置：

root@350983744ebf:~# luarocks show lua-capnprotolua-capnproto 0.1.4-5 - Lua-capnproto is a pure lua implementation of capnproto based on LuaJIT.Lua-capnproto is a pure lua implementation of capnproto based on LuaJIT.License:        BSD
Homepage:       https://github.com/calio/lua-capnproto
Installed in:   /usr/localModules:capnp (/usr/local/share/lua/5.1/capnp.lua)capnp.compile (/usr/local/share/lua/5.1/capnp/compile.lua)capnp.util (/usr/local/share/lua/5.1/capnp/util.lua)handwritten_capnp (/usr/local/share/lua/5.1/handwritten_capnp.lua)handwritten_data_generator (/usr/local/share/lua/5.1/handwritten_data_generator.lua)random (/usr/local/share/lua/5.1/random.lua)schema_capnp (/usr/local/share/lua/5.1/schema_capnp.lua)test (/usr/local/share/lua/5.1/test.lua)tool (/usr/local/share/lua/5.1/tool.lua)Depends on:lua ~> 5.1 (using 5.1-1)

默认库都是安装到了 /usr/local/share/lua/5.1/ 目录下。

2. 编译 capnp 文件

先将 openresty 自带的 luajit 程序目录加入 PATH 路径中：

export PATH=$PATH:/usr/local/openresty/luajit/bin

新建一个AddressBook.capnp 文件，内容如下：

@0xdbb9ad1f14bf0b36;  # unique file ID, generated by `capnp id`struct Person {id @0 :UInt32;name @1 :Text;email @2 :Text;phones @3 :List(PhoneNumber);struct PhoneNumber {number @0 :Text;type @1 :Type;enum Type {mobile @0;home @1;work @2;}}employment :union {unemployed @4 :Void;employer @5 :Text;school @6 :Text;selfEmployed @7 :Void;# We assume that a person is only one of these.}
}struct AddressBook {people @0 :List(Person);
}

然后编译 capnp 文件：

root@350983744ebf:~# capnp compile -olua AddressBook.capnp
root@350983744ebf:~# ls -lh
total 36K
-rw-r--r-- 1 root root  532 Oct 22 21:18 AddressBook.capnp
-rw-r--r-- 1 root root  21K Oct 22 21:20 AddressBook_capnp.lua

得到 AddressBook_capnp.lua 文件。

3. 写一个测试程序

新建一个目录，将 AddressBook_capnp.lua 文件放到这个目录。

root@350983744ebf:~# mkdir /usr/local/openresty/lua
root@350983744ebf:~# cd /usr/local/openresty/lua
root@350983744ebf:/usr/local/openresty/lua# cp /root/AddressBook_capnp.lua .

在这目录新建一个 lua 程序文件 main.lua，内容如下：

local addressBook = require "AddressBook_capnp"
local capnp = require "capnp"
local cjson = require "cjson"
local util = require "capnp.util"local data = {people = {{id = 123,name = "Alice",email = "alice@example.com",phones = {{number = "555-1212",["type"] = "MOBILE",},},employment = {school = "MIT",},},{id = 456,name = "Bob",email = "bob@example.com",phones = {{number = "555-4567",["type"] = "HOME",},{number = "555-7654",["type"] = "WORK",},},employment = {unemployed = "Void",},},}
}local bin = addressBook.AddressBook.serialize(data)
local decoded = addressBook.AddressBook.parse(bin)ngx.say(cjson.encode(decoded))

这个程序将一个 lua 数据【数据格式是按照 AddressBook.capnp 文件定义的】序列化成 capnp 二进制数据，然后将二进制数据反序列化成 lua 数据，最后使用 cjson 库将 lua 数据序列化成 json 格式，使用 nginx 输出。

4. 验证程序

修改 nginx 配置文件【 /usr/local/openresty/nginx/conf/nginx.conf】内容为：

worker_processes  1;events {worker_connections  1024;
}http {lua_package_path "/usr/local/openresty/lua/?.lua;;";server {listen       80;server_name  localhost;location /capnp {content_by_lua_file /usr/local/openresty/lua/main.lua;}}
}

启动 nginx 并验证结果：

root@350983744ebf:~# /usr/local/openresty/nginx/sbin/nginx        root@350983744ebf:~# 
root@350983744ebf:~# curl 127.0.0.1/capnp
{"people":[{"phones":[{"number":"555-1212","type":"MOBILE"}],"id":123,"name":"Alice","employment":{"school":"MIT"},"email":"alice@example.com"},{"phones":[{"number":"555-4567","type":"HOME"},{"number":"555-7654","type":"WORK"}],"id":456,"name":"Bob","employment":{"unemployed":"Void"},"email":"bob@example.com"}]}

和预期相符。