2020-09-29 非商品模板化代码层次 rapidjson库

业务

'''
MatBuilderBase:
  Build()  //调用FillMat()填写JSON.
  FillMat()=0
XXXBuilder:MatBuilderBase   //六种非商品的Builder类对纯虚函数FillMat()做实现.
  FillMat(){
    xxx}
NowareMatHelper:
  GetBuilder(AD_TYPE_ACTIVITY){
    return xxxBuilder}  //根据AD_TYPE_ACTIVITY选择使用对应的builder,对应的builder会写对应的JSON
  Init()
  GetMatByType()  //根据广告类型给模板或不给
  UseMat()  //判断某广告类型用不用模板
  mat_ctrl_  //读取的哪些广告位用模板的配置字符串
  
noware和general的WriteBidResponse()调用父类的RecommendRequestHandler::WriteBidResponse()
做的事是初始化了NowareMatHelper的mat_ctrl_，从词表中读取的哪些广告位用模板的配置字符串
'''

rapidjson库

腾讯搞的headeronly的库，又小又快（竟然是褒义hh）又不依赖别的库。
简单用法是JSON->DOM->对DOM进行修改->写回JSON
（看起来意思是不能直接修改JSON）

参考文档http://rapidjson.org/zh-cn/index.html
例子：

// rapidjson/example/simpledom/simpledom.cpp`
#include "rapidjson/document.h"
#include "rapidjson/writer.h"
#include "rapidjson/stringbuffer.h"
#include <iostream>
 
using namespace rapidjson;
 
int main() {
    
    // 1. 把 JSON 解析至 DOM。
    const char* json = "{\"project\":\"rapidjson\",\"stars\":10}";
    Document d;
    d.Parse(json);
 
    // 2. 利用 DOM 作出修改。
    Value& s = d["stars"];
    s.SetInt(s.GetInt() + 1);
 
    // 3. 把 DOM 转换（stringify）成 JSON。
    StringBuffer buffer;
    Writer<StringBuffer> writer(buffer);
    d.Accept(writer);
 
    // Output {"project":"rapidjson","stars":11}
    std::cout << buffer.GetString() << std::endl;
    return 0;
}

---

std::string（）构造函数

之string(const char *s, size_type n, const Allocator &a = Allocator());
生成的是s的前n个字符组成的字符串，s不够长会拿内存中字符串位置后的随机值扩充。

附录1 rapidjson写json

	rapidjson::StringBuffer buf;
	//rapidjson::Writer<rapidjson::StringBuffer> writer(buf);
	rapidjson::PrettyWriter<rapidjson::StringBuffer> writer(buf); // it can word wrap
 
	writer.StartObject();
 
	writer.Key("name"); writer.String("spring");
	writer.Key("address"); writer.String("北京");
	writer.Key("age"); writer.Int(30);
 
	writer.Key("value1");
	writer.StartArray();
	writer.StartArray();
 
	writer.StartObject();
 
	writer.Key("name"); writer.String("spring");
	writer.Key("address"); writer.String("北京");
	writer.Key("age"); writer.Int(30);
 
	writer.Key("value1");
	writer.StartArray();
	writer.StartArray();
	writer.Double(23); writer.Double(43); writer.Double(-2.3); writer.Double(6.7);     
    writer.Double(90);
	writer.EndArray();
 
	writer.StartArray();
	writer.Int(-9); writer.Int(-19); writer.Int(10); writer.Int(2);
	writer.EndArray();
 
	writer.StartArray();
	writer.Int(-5); writer.Int(-55);
	writer.EndArray();
	writer.EndArray();
 
	writer.Key("value2");
	writer.StartArray();
	writer.Double(13.3); writer.Double(1.9); writer.Double(2.10);
	writer.EndArray();
 
	writer.Key("bei_jing");
	writer.StartObject();
	writer.Key("address"); writer.String("海淀");
	writer.Key("car"); writer.Bool(false);
	writer.Key("cat"); writer.Bool(true);
	writer.EndObject();
 
	writer.Key("shan_dong");
	writer.StartObject();
	writer.Key("address"); writer.String("济南");
	writer.Key("value1");
	writer.StartArray();
	writer.Key("ji_nan"); writer.String("趵突泉");
	writer.Key("tai_an"); writer.String("泰山");
	writer.EndArray();
	writer.EndObject();
 

结果

{
  "name": "spring",
  "address": "北京",
  "age": 30,
  "value1": [[23, 43, -2.3, 6.7, 90],
             [-9, -19, 10, 2],
             [-5, -55]],
  "value2": [13.3, 1.9, 2.10],
  
  "bei_jing": {
    "address": "海淀",
    "car": false,
    "cat": true
  },
  "shan_dong": {
    "address": "济南",
    "value1": [{"ji_nan": "趵突泉"}, {"tai_an": "泰山"}]
  }
}