protobuf转json

方法介绍

    protobuf的介绍在这里就不详细介绍了，主要是俺也是刚接触，感兴趣的同学可以去搜索相关博客或者直接去看源码以及google的官方文档(官方文档表示很吃力)或者去这个网站：https://developers.google.com/protocol-buffers/docs/overview查看相应内容，这里面内容很全面，可以很方面的查询各个函数的使用方法以及功能。本篇文章主要介绍一下本人最近做的一个protobuf转json的小工具，下面进行拆分讲解，完整的代码在：git@github.com:chengfeiGitHub/P-bToJson.git。

    protobuf自带一个MessageToJson()的函数可以将对应的消息转换成json，一般情况下该函数可以满足转换需求。但是，最近项目的要求使用MessageToJson()无法实现，主要要求是：

1. 选择特定的messge进行转换（主要是提供包含需求字段号的set或者vector，根据提供的字段号进行转换）；
2. 对于Enum类型的消息，可以选择显示枚举名或者枚举值；
3. 对于字段值为0的字段，可以选择显示或者不显示.

    主要有这三个要求，对于功能2、3现在最新的protobuf应该是支持的，但是没有功能1的实现方式，所以只好自己写一个小工具。

    说明：本工具由C++编写完成

    首先是函数的声明：

#pragma once 2 #include <iostream> 3 #include <google/protobuf/message.h> 4 #include <google/protobuf/descriptor.h> 5  6 void ChooseSomeFieldsToJson(std::string& pb2jsonstring, const ::google::protobuf::Message& msg, std::vector<uint>& needs, bool Enum_2_Str, bool Showzero); 7 //Enum_2_Str:　ture显示枚举名，false:显示枚举值；　Showzero: ture显示值为０的fields，false,不显示值为０的fields。 8 void GetRepeatedJson(std::string& pb2jsonstring, const ::google::protobuf::Message& msg, const google::protobuf::FieldDescriptor *field, const ::google::protobuf::Reflection *reflection, bool Enum_2_Str,bool Showzero); 9 void NeedEmptyToJson(std::string& pb2jsonstring, const ::google::protobuf::Message& msg, bool Enum_2_Str, bool Showzero);10 void NeedNotEmptyToJson(std::string& pb2jsonstring, const ::google::protobuf::Message& msg, std::vector<uint>& needs, bool Enum_2_Str, bool Showzero);11 int AppendTmpString1(std::string& pb2jsonstring,std::string& tmp_string, int judge);12 int AppendTmpString2(std::string& pb2jsonstring,std::string& tmp_string, int judge);

 

    pb2jsonstring是存储转换结果的字符串，msg是需要转换的消息，needs是需要转换的字段号；函数GetRepeatedJson()是对重复的字段进行操作；NeedEmptyToJson()是当needs为空时对应的操作(needs为空表示需要转换所有的字段)；NeedNotEmptyToJson()是当needs不为空时对应的操作；AppendTmpStrign1()以及AppendTmpStrign2()是将临时字符串添加到pb2jsonstring后的操作。

    上面的代码保存到一个头文件当中,就叫pbjsontest3.h吧，然后是pbjsontest3.cpp

    

#include <iostream> 2 #include <google/protobuf/descriptor.h>   3 #include <google/protobuf/message.h>   4 #include <set> 5 #include <string> 6 #include "pbjsontest3.h" 7    8 using namespace ::google::protobuf;  9 10 void ChooseSomeFieldsToJson(std::string& pb2jsonstring, const ::google::protobuf::Message& msg, std::vector<uint>& need, bool Enum_2_Str, bool Showzero)  11 {12 13     const Descriptor* descriptor = msg.GetDescriptor();  14     const Reflection* reflection = msg.GetReflection(); 15     if (need.empty())  //如果needs为空，表示需要将所有的字段转换为json16     {    17         NeedEmptyToJson(pb2jsonstring, msg, Enum_2_Str, Showzero);18     }19     else 20     {21         NeedNotEmptyToJson(pb2jsonstring, msg, need, Enum_2_Str, Showzero);22     }23 }

    这一部分主要就是判断need是否为空，然后选择相应的函数进行操作，不在做详细的叙述，下面是NeedEmptyToJson()的介绍。由于这一部分代码太长，所以相应的介绍在代码中进行注释说明。

void NeedEmptyToJson(std::string& pb2jsonstring, const ::google::protobuf::Message& msg, bool Enum_2_Str, bool Showzero)  2 {  3     const Descriptor* descriptor = msg.GetDescriptor();    4     const Reflection* reflection = msg.GetReflection();   5     const uint count = descriptor->field_count();  //count为当前消息中所有的字段总数  6     uint judge = 0;//ｊｕｄｇｅ用来判断是否在当前ｊｓｏｎ元素前加“，”用来分隔前后元素，如果ｊｕｄｇｅ＝＝０，则不加，如果ｊｕｇｄｇｅ＝＝１，则加“，”  7     std::string tmp_string;  //临时变量  8     std::int32_t v32=0;  9     std::uint32_t vu32=0; 10     std::int64_t v64=0; 11     std::uint64_t vu64=0; 12     double vd=0; 13     std::string str; 14     pb2jsonstring.append("{");  //添加第一个"{" 15     for (int it = 0; it <count; ++it)  16     {          17         const FieldDescriptor* goal_field=descriptor->field(it);   18         /*这里要用field()来取字段，因为field()是按字段的实际标号来取字段，而不是根据字段号来进行取字段，这样就避免的字段号不连续造成的某些字段取不到的问题。 */    19         if(nullptr==goal_field)  //不存在字段 20         { 21             continue; 22         }  23  24         if (goal_field->is_repeated())  //判断字段是否为repeated 25         {   26             if (reflection->FieldSize(msg, goal_field) > 0)   27             {  28                 tmp_string=""; 29                 tmp_string.append("\"").append(goal_field->name()).append("\":"); 30                 tmp_string .append("[");  //重复的字段用[]包围 31                 GetRepeatedJson(tmp_string, msg, goal_field, reflection, Enum_2_Str,Showzero);  32                 tmp_string.append("]");  33                 judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);   34             } 35             continue;   36         } 37         switch (goal_field->type())   38         {   39         case FieldDescriptor::TYPE_MESSAGE:   40             {   41                 const Message& tmp_msg = reflection->GetMessage(msg, goal_field);   42                 if (0 != tmp_msg.ByteSize())   43                 {  44                     tmp_string=""; 45                     tmp_string.append("\"").append(goal_field->name()).append("\":"); 46                     NeedEmptyToJson(tmp_string,tmp_msg, Enum_2_Str, Showzero); 47                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge); 48                 }   49             }   50             break;   51              52         case FieldDescriptor::TYPE_INT32:  53             { 54                 v32=reflection->GetInt32(msg, goal_field); 55                 if(v32==0) 56                 { 57                     if(Showzero)   //字段值为０，也需要进行打印 58                     {                         59                         tmp_string=""; 60                         tmp_string.append("\"").append(goal_field->name()).append("\":"); 61                         tmp_string.append(std::to_string(v32)); //需要抓换成字符型 62                         judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);  63                     } 64                 } 65                 else 66                 { 67                     tmp_string=""; 68                     tmp_string.append("\"").append(goal_field->name()).append("\":"); 69                     tmp_string.append(std::to_string(v32));                      70                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);  71                 }  72             } 73             break;   74  75         case FieldDescriptor::TYPE_UINT32: 76             {   77                 vu32=reflection->GetUInt32(msg, goal_field); 78                 if(vu32==0) 79                 { 80                     if(Showzero) 81                     { 82                         tmp_string=""; 83                         tmp_string.append("\"").append(goal_field->name()).append("\":"); 84                         tmp_string.append(std::to_string(vu32));   85                         judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);  86                     } 87                 } 88                 else 89                 { 90                     tmp_string=""; 91                     tmp_string.append("\"").append(goal_field->name()).append("\":"); 92                     tmp_string.append(std::to_string(vu32)); 93                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);  94                 }        95              } 96             break;   97  98         case FieldDescriptor::TYPE_INT64:   99             {  100                 v64=reflection->GetInt64(msg, goal_field);101                 if(v64==0)102                 {103                     if(Showzero)104                     {105                         tmp_string="";106                         tmp_string.append("\"").append(goal_field->name()).append("\":");         107                         tmp_string.append(std::to_string(v64));108                         judge = AppendTmpString1(pb2jsonstring,tmp_string,judge); 109                     }110                 }111                 else112                 {113                     tmp_string="";114                     tmp_string.append("\"").append(goal_field->name()).append("\":");115                     tmp_string.append(std::to_string(v64));         116                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);  117                 } 118             } 119             break;  120         case FieldDescriptor::TYPE_UINT64:  121              {  122                 vu64=reflection->GetUInt64(msg, goal_field);123                 if(vu64==0)124                 {125                     if(Showzero)126                     {127                         tmp_string="";                128                         tmp_string.append("\"").append(goal_field->name()).append("\":");      129                         tmp_string.append(std::to_string(vu64));130                         judge = AppendTmpString1(pb2jsonstring,tmp_string,judge); 131                     }132                 }133                 else134                 {135                     tmp_string="";                136                     tmp_string.append("\"").append(goal_field->name()).append("\":");      137                     tmp_string.append(std::to_string(vu64));138                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge); 139                 }140              } 141             break;  142         case FieldDescriptor::TYPE_STRING:  143         case FieldDescriptor::TYPE_BYTES:  144             {  145                 146                 str=reflection->GetString(msg, goal_field);147                 if(str.empty())148                 {149                     if(Showzero)150                     {151                         tmp_string="";152                         tmp_string.append("\"").append(goal_field->name()).append("\":");153                         tmp_string.append("\"").append(str).append("\"");154                         judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);155                     }156                 }157                 else158                 {159                     tmp_string="";160                     tmp_string.append("\"").append(goal_field->name()).append("\":");161                     tmp_string.append("\"").append(str).append("\"");162                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);163 164                 }165             }  166             break; 167         case FieldDescriptor::TYPE_DOUBLE:168             {169                 vd=reflection->GetDouble(msg, goal_field);170                 if(vd==0)171                 {172                     if(Showzero)173                     {174                         tmp_string="";175                         tmp_string.append("\"").append(goal_field->name()).append("\":");176                         tmp_string.append(std::to_string(vd));177                         judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);178                     }179                 }180                 else 181                 {182                     tmp_string="";183                     tmp_string.append("\"").append(goal_field->name()).append("\":");184                     tmp_string.append(std::to_string(vd));185                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);186                 }          187             } 188             break;189         case FieldDescriptor::TYPE_BOOL:190             {191                 tmp_string="";192                 tmp_string.append("\"").append(goal_field->name()).append("\":");193                 if (reflection->GetBool(msg, goal_field))194                     tmp_string.append("true");195                 else 196                     tmp_string.append("false");197                 judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);198               199             } 200             break;201         case FieldDescriptor::TYPE_ENUM:202             {203                 tmp_string="";204                 tmp_string.append("\"").append(goal_field->name()).append("\":");205                 if (Enum_2_Str) //判断显示枚举名还是枚举值206                 {       207                     tmp_string.append("\"").append(reflection->GetEnum(msg,goal_field)->name()).append("\"");208                 }209                 else 210                 {211                     static char enumstr[8];212                     memset(enumstr, 0, sizeof(enumstr)); 213                     snprintf(enumstr, sizeof(enumstr), "%d", reflection->GetEnum(msg,goal_field)->number());214                     tmp_string.append(enumstr);                    215                 }216                 judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);217             }218             break;219         default:  220             break;  221         }222     }223     pb2jsonstring.append("}");224 }225 226 int AppendTmpString1(std::string &pb2jsonstring,std::string &tmp_string, int judge)227 {228     if ( judge!=0 && tmp_string.length()!=0)229     {230         pb2jsonstring.append(",").append(tmp_string);231         return judge;232     }233     else if(judge==0 && tmp_string.length()!=0)234     {235         pb2jsonstring.append(tmp_string);236         return 1;237     }238     return judge;239 }

 

    下面need不为空时候的转换：

    

void NeedNotEmptyToJson(std::string& pb2jsonstring, const ::google::protobuf::Message& msg, std::vector<uint>& needs, bool Enum_2_Str, bool Showzero)  2 {  3     const Descriptor* descriptor = msg.GetDescriptor();    4     const Reflection* reflection = msg.GetReflection();   5      6     uint judge = 0;  7     std::string tmp_string;  8     std::int32_t v32=0;  9     std::uint32_t vu32=0; 10     std::int64_t v64=0; 11     std::uint64_t vu64=0; 12     double vd=0; 13     std::string str; 14  15     pb2jsonstring.append("{"); 16     17     for (auto it=needs.begin(); it != needs.end(); ++it)  18     {          19         const FieldDescriptor* goal_field=descriptor->FindFieldByNumber(*it);  20         //need为空的转换和不为空的几乎一样，主要差别是对字段的提取，不为空时需要使用FindFieldByNumber()来进行操作，这样可以取任意字段号对应的字段。将need为空和不为空分开写主要是测试中这样可以节省时间，其实是可以写到一块的，有兴趣的同学可以进行修改。 21  22         if(nullptr==goal_field)  //不存在字段 23         { 24             continue; 25         }  26  27         if (goal_field->is_repeated())   28         {   29             if (reflection->FieldSize(msg, goal_field) > 0)   30             {  31                 tmp_string=""; 32                 tmp_string.append("\"").append(goal_field->name()).append("\":"); 33                 tmp_string .append("["); 34                 GetRepeatedJson(tmp_string, msg, goal_field, reflection, Enum_2_Str,Showzero);  35                 tmp_string.append("]");  36                 judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);   37             } 38             continue;   39         } 40         switch (goal_field->type())   41         {   42         case FieldDescriptor::TYPE_MESSAGE:   43             {   44                 const Message& tmp_msg = reflection->GetMessage(msg, goal_field);   45                 if (0 != tmp_msg.ByteSize())   46                 {  47                     tmp_string=""; 48                     tmp_string.append("\"").append(goal_field->name()).append("\":"); 49                     NeedEmptyToJson(tmp_string,tmp_msg, Enum_2_Str, Showzero); 50                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge); 51                 }   52             }   53             break;   54              55         case FieldDescriptor::TYPE_INT32:  56             { 57                 v32=reflection->GetInt32(msg, goal_field); 58                 if(v32==0) 59                 { 60                     if(Showzero)   //字段值为０，也需要进行打印 61                     {                         62                         tmp_string=""; 63                         tmp_string.append("\"").append(goal_field->name()).append("\":"); 64                         tmp_string.append(std::to_string(v32));  65                         judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);  66                     } 67                 } 68                 else 69                 { 70                     tmp_string=""; 71                     tmp_string.append("\"").append(goal_field->name()).append("\":"); 72                     tmp_string.append(std::to_string(v32));                      73                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);  74                 }  75             } 76             break;   77  78         case FieldDescriptor::TYPE_UINT32: 79             {   80                 vu32=reflection->GetUInt32(msg, goal_field); 81                 if(vu32==0) 82                 { 83                     if(Showzero) 84                     { 85                         tmp_string=""; 86                         tmp_string.append("\"").append(goal_field->name()).append("\":"); 87                         tmp_string.append(std::to_string(vu32));   88                         judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);  89                     } 90                 } 91                 else 92                 { 93                     tmp_string=""; 94                     tmp_string.append("\"").append(goal_field->name()).append("\":"); 95                     tmp_string.append(std::to_string(vu32)); 96                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);  97                 }        98              } 99             break;  100 101         case FieldDescriptor::TYPE_INT64:  102             {  103                 v64=reflection->GetInt64(msg, goal_field);104                 if(v64==0)105                 {106                     if(Showzero)107                     {108                         tmp_string="";109                         tmp_string.append("\"").append(goal_field->name()).append("\":");         110                         tmp_string.append(std::to_string(v64));111                         judge = AppendTmpString1(pb2jsonstring,tmp_string,judge); 112                     }113                 }114                 else115                 {116                     tmp_string="";117                     tmp_string.append("\"").append(goal_field->name()).append("\":");118                     tmp_string.append(std::to_string(v64));         119                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);  120                 } 121             } 122             break;  123         case FieldDescriptor::TYPE_UINT64:  124              {  125                 vu64=reflection->GetUInt64(msg, goal_field);126                 if(vu64==0)127                 {128                     if(Showzero)129                     {130                         tmp_string="";                131                         tmp_string.append("\"").append(goal_field->name()).append("\":");      132                         tmp_string.append(std::to_string(vu64));133                         judge = AppendTmpString1(pb2jsonstring,tmp_string,judge); 134                     }135                 }136                 else137                 {138                     tmp_string="";                139                     tmp_string.append("\"").append(goal_field->name()).append("\":");      140                     tmp_string.append(std::to_string(vu64));141                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge); 142                 }143              } 144             break;  145         case FieldDescriptor::TYPE_STRING:  146         case FieldDescriptor::TYPE_BYTES:  147             {  148                 149                 str=reflection->GetString(msg, goal_field);150                 if(str.empty())151                 {152                     if(Showzero)153                     {154                         tmp_string="";155                         tmp_string.append("\"").append(goal_field->name()).append("\":");156                         tmp_string.append("\"").append(str).append("\"");157                         judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);158                     }159                 }160                 else161                 {162                     tmp_string="";163                     tmp_string.append("\"").append(goal_field->name()).append("\":");164                     tmp_string.append("\"").append(str).append("\"");165                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);166 167                 }168             }  169             break; 170         case FieldDescriptor::TYPE_DOUBLE:171             {172                 vd=reflection->GetDouble(msg, goal_field);173                 if(vd==0)174                 {175                     if(Showzero)176                     {177                         tmp_string="";178                         tmp_string.append("\"").append(goal_field->name()).append("\":");179                         tmp_string.append(std::to_string(vd));180                         judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);181                     }182                 }183                 else 184                 {185                     tmp_string="";186                     tmp_string.append("\"").append(goal_field->name()).append("\":");187                     tmp_string.append(std::to_string(vd));188                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);189                 }          190             } 191             break;192         case FieldDescriptor::TYPE_BOOL:193             {194                 tmp_string="";195                 tmp_string.append("\"").append(goal_field->name()).append("\":");196                 if (reflection->GetBool(msg, goal_field))197                     tmp_string.append("true");198                 else 199                     tmp_string.append("false");200                 judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);201               202             } 203             break;204         case FieldDescriptor::TYPE_ENUM:205             {206                 tmp_string="";207                 tmp_string.append("\"").append(goal_field->name()).append("\":");208                 if (Enum_2_Str)209                 {       210                     tmp_string.append("\"").append(reflection->GetEnum(msg,goal_field)->name()).append("\"");211                 }212                 else 213                 {214                     static char enumstr[8];215                     memset(enumstr, 0, sizeof(enumstr)); 216                     snprintf(enumstr, sizeof(enumstr), "%d", reflection->GetEnum(msg,goal_field)->number());217                     tmp_string.append(enumstr);                    218                 }219                 judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);220             }221             break;222         default:  223             break;  224         }225     }226     pb2jsonstring.append("}");227 }

    然后就是需要对repeated的字段进行相应的转换，

void GetRepeatedJson(std::string& pb2jsonstring, const ::google::protobuf::Message& msg, const google::protobuf::FieldDescriptor *goal_field, const ::google::protobuf::Reflection *reflection, bool Enum_2_Str,bool Showzero)    2 {       3     std::string tmp_string;  4     int judge=0;  5     std::int32_t v32=0;  6     std::uint32_t vu32=0;  7     std::int64_t v64=0;  8     std::uint64_t vu64=0;  9     double vd=0; 10     std::string str; 11     for (int i = 0; i < reflection->FieldSize(msg, goal_field); ++i)   12     {       13         switch (goal_field->type())                  14         {   15         case FieldDescriptor::TYPE_MESSAGE:   16             {   17                 const Message& tmp_msg = reflection->GetRepeatedMessage(msg, goal_field, i); 18                 if (0 != tmp_msg.ByteSize())   19                 {                     20                     tmp_string=""; 21                     //当重复的是message时，需要全部进行转换，不需要选择特定的字段进行转换，当然有这个需求的也可以进行相应的改进，不过会麻烦一些。重复字段的提取主要就是Get方式的不同，这个可以查阅文章开头中提到的文档，里面有详细说明 22                     NeedEmptyToJson(tmp_string, tmp_msg, Enum_2_Str,Showzero);  23                     judge = AppendTmpString2(pb2jsonstring,tmp_string,judge); 24                 } 25             }   26             break;   27         case FieldDescriptor::TYPE_INT32:  28             {                29                 v32=reflection->GetRepeatedInt32(msg, goal_field,i); 30                 if(v32==0) 31                 { 32                     if(Showzero) 33                     {                         34                         tmp_string=""; 35                         tmp_string.append(std::to_string(v32));  36                         judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);  37                     } 38                 } 39                 else 40                 { 41                     tmp_string=""; 42                     tmp_string.append(std::to_string(v32));             43                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);  44                 }  45             }  46              47             break;   48         case FieldDescriptor::TYPE_UINT32: 49             {                50                 vu32=reflection->GetRepeatedUInt32(msg, goal_field,i); 51                 if(vu32==0) 52                 { 53                     if(Showzero) 54                     { 55                         tmp_string=""; 56                         tmp_string.append(std::to_string(vu32));   57                         judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);  58                     } 59                 } 60                 else 61                 { 62                     tmp_string=""; 63                     tmp_string.append(std::to_string(vu32));  64                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);  65                 }        66              }           67             break;   68         case FieldDescriptor::TYPE_INT64:   69             {   70                 v64=reflection->GetRepeatedInt64(msg, goal_field,i); 71                 if(v64==0) 72                 { 73                     if(Showzero) 74                     { 75                         tmp_string="";       76                         tmp_string.append(std::to_string(v64)); 77                         judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);  78                     } 79                 } 80                 else 81                 { 82                     tmp_string=""; 83                     tmp_string.append(std::to_string(v64));          84                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);   85                 } 86             }   87             break;   88         case FieldDescriptor::TYPE_UINT64:   89             {   90                 vu64=reflection->GetRepeatedUInt64(msg, goal_field,i); 91                 if(vu64==0) 92                 { 93                     if(Showzero) 94                     { 95                         tmp_string="";                       96                         tmp_string.append(std::to_string(vu64)); 97                         judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);  98                     } 99                 }100                 else101                 {102                     tmp_string="";                    103                     tmp_string.append(std::to_string(vu64));104                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge); 105                 }106 107             }  108             break;  109         case FieldDescriptor::TYPE_STRING:  110         case FieldDescriptor::TYPE_BYTES: 111             {112                 str="";113                 str=reflection->GetRepeatedString(msg, goal_field,i);114                 if(str.empty())115                 {116                     if(Showzero)117                     {118                         tmp_string="";119                         tmp_string.append("\"").append(str).append("\"");120                         judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);121                     }122                 }123                 else124                 {125                     tmp_string="";126                     tmp_string.append("\"").append(str).append("\"");127                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);128 129                 }130             }131             break; 132         case FieldDescriptor::TYPE_DOUBLE:  133             {134                 vd=reflection->GetRepeatedDouble(msg, goal_field,i);135                 if(vd==0)136                 {137                     if(Showzero)138                     {139                         tmp_string="";140                         tmp_string.append(std::to_string(vd));141                         judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);142                     }143                 }144                 else 145                 {146                     tmp_string="";147                     tmp_string.append(std::to_string(vd));148                     judge = AppendTmpString1(pb2jsonstring,tmp_string,judge);149                 }150 151             }           152             break; 153          case FieldDescriptor::TYPE_BOOL:  154         {155             tmp_string="";156             if(reflection->GetRepeatedBool(msg, goal_field,i))157                 tmp_string.append("true");158             else159                 tmp_string.append("false");160             judge = AppendTmpString2(pb2jsonstring,tmp_string,judge);161 162         }           163         break; 164         case FieldDescriptor::TYPE_ENUM:165             {166                tmp_string="";167                if (Enum_2_Str)168                     {                       169                         tmp_string.append("\"").append(reflection->GetRepeatedEnum(msg,goal_field,i)->name()).append("\"");                170                     }171                 else 172                     {173                         static char enumstr[8];174                         memset(enumstr, 0, sizeof(enumstr)); 175                         snprintf(enumstr, sizeof(enumstr), "%d", reflection->GetRepeatedEnum(msg,goal_field,i)->number());176                         tmp_string.append(enumstr);177                     }178                 judge = AppendTmpString2(pb2jsonstring,tmp_string,judge);179             }       180             break;  181         default:  182             break;  183         }        184     }    185 }  186 int AppendTmpString2(std::string &pb2jsonstring,std::string &tmp_string, int judge)187 {188     if( judge!=0 && tmp_string.length()!=0)189     {190         pb2jsonstring.append(",").append(tmp_string);191         return judge;192     }193     else if( judge==0 && tmp_string.length()!=0)194     {195         pb2jsonstring.append(tmp_string);196         return 1;197     }198     return judge;199 }

总结说明

    本文中介绍的方法从逻辑上来说没有什么特别的地方，就是读取字段名，字段值然后添加到对应的字符串当中，代码比较繁琐，还有很大的改进空间，后来使用宏定义的##操作减少了很多代码量，比如GetInt()与GetRepeatedInt()可以通过使用“##”操作合并到一个函数中进行操作。

    文中有不合理的地方希望各位批评指正。