Problem phenomenon: add a message (Booklist) in an existing proto file (recommendresponse. Proto). When compiling the proto file with maven, an error is reported:

E:\workspace\ms-selection-service\ms-selection-api>mvn clean install
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Detecting the operating system and CPU architecture
[INFO] ------------------------------------------------------------------------
[INFO] os.detected.name: windows
[INFO] os.detected.arch: x86_64
[INFO] os.detected.version: 10.0
[INFO] os.detected.version.major: 10
[INFO] os.detected.version.minor: 0
[INFO] os.detected.classifier: windows-x86_64
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building ms-selection-api 1.0.18061
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ ms-selection-api ---
[INFO] Deleting E:\workspace\ms-selection-service\ms-selection-api\target
[INFO]
[INFO] --- protobuf-maven-plugin:0.5.0:compile (default) @ ms-selection-api ---
[INFO] Compiling 84 proto file(s) to E:\workspace\ms-selection-service\ms-selection-api\target\generated-sources\protobuf\java
[ERROR] PROTOC FAILED: recommend/RecommendResponse.proto:34:16: "BookList.bookName" is already defined in file "contentrecommend/ContentRecommendResponse.proto".
recommend/RecommendResponse.proto:35:16: "BookList.authorName" is already defined in file "contentrecommend/ContentRecommendResponse.proto".
recommend/RecommendResponse.proto:36:16: "BookList.bookCover" is already defined in file "contentrecommend/ContentRecommendResponse.proto".
recommend/RecommendResponse.proto:37:16: "BookList.bookUrl" is already defined in file "contentrecommend/ContentRecommendResponse.proto".
recommend/RecommendResponse.proto:38:16: "BookList.coPercent" is already defined in file "contentrecommend/ContentRecommendResponse.proto".
recommend/RecommendResponse.proto:39:16: "BookList.contentType" is already defined in file "contentrecommend/ContentRecommendResponse.proto".
recommend/RecommendResponse.proto:33:9: "BookList" is already defined in file "contentrecommend/ContentRecommendResponse.proto".
recommend/RecommendResponse.proto:13:19: "BookList" seems to be defined in "contentrecommend/ContentRecommendResponse.proto", which is not imported by "recommend/RecommendResponse.proto".  To use it here, please add the necessary import.

See RecommendResponse.proto:

syntax = "proto3";

option java_package = "cn.wlf.selection.proto.base";

message RecommendResponse {
    
     string pluginCode=1;
     string status=2;
     string isvisable=3;
     string isShowLine=4; 
     Recommend data=5; 
     string messageDesc=6;
     repeated BookList bookList= 7;

}

message Recommend{

    repeated RecommendData   buttons=1;
    map<string, string> ctag = 2;
    string isMarginTop=3;
    string isMarginBottom=4;

}

message RecommendData{

    string name=1;
    
    string url=2;    
}

message BookList{
    string bookName=1;
    string authorName=2;
    string bookCover=3;
    string bookUrl=4;
    string coPercent=5;
    string contentType=6;

}

20877;- 30475;- ContentRecommendResponse.proto:

syntax = "proto3";

option java_package = "cn.wlf.selection.proto.base";

message  ContentRecommendResponse {
    string pluginCode=1;
    
    string status=2;
    
    string isvisable=3;
    
    string messageDesc=4;

    ContentRecommendData data=5;

}
message ContentRecommendData{
    
    string isMarginTop = 1;
    
    string isMarginBottom = 2;
    
    string isPaddingTop = 3;
    
    string isShowLine = 4;
    
    string dataFrom = 5;
    
    string title = 6;
    
    string style = 7;

    repeated BookList bookList=8;
    
    BiData biData = 9;
    
}
message BookList{
    string bookName=1;
    string authorName=2;
    string bookCover=3;
    string bookUrl=4;
    string coPercent=5;
    string contentType=6;
}

message BiData{
    
    string msisdn = 1;
    string bid = 2;
    string pageNo = 3;
    string showNum = 4;
    string clientVersion = 5;
    string instanceId = 6;
}

Problem location: the error message actually tells us that the message booklist already exists in contentrecommendresponse.proto. You can also see that there are messages with the same name in the two PROTOS

Problem solving:

1. If the new booklist is the same as the existing data structure, you only need to import it. Recommendresponse.proto is changed to:

syntax = "proto3";

option java_package = "cn.wlf.selection.proto.base";
import "contentrecommend/ContentRecommendResponse.proto";

message RecommendResponse {
    
     string pluginCode=1;
     string status=2;
     string isvisable=3;
     string isShowLine=4; 
     Recommend data=5; 
     string messageDesc=6;
     repeated BookList bookList= 7;

}

message Recommend{

    repeated RecommendData   buttons=1;
    map<string, string> ctag = 2;
    string isMarginTop=3;
    string isMarginBottom=4;

}

message RecommendData{

    string name=1;
    
    string url=2;    
}

2. If the booklist data structure is changed, it cannot be reused. Only the class name can be changed. Recommendresponse.proto is changed to:

syntax = "proto3";

option java_package = "cn.wlf.selection.proto.base";

message RecommendResponse {
    
     string pluginCode=1;
     string status=2;
     string isvisable=3;
     string isShowLine=4; 
     Recommend data=5; 
     string messageDesc=6;
     repeated BookListNew bookList= 7;

}

message Recommend{

    repeated RecommendData   buttons=1;
    map<string, string> ctag = 2;
    string isMarginTop=3;
    string isMarginBottom=4;

}

message RecommendData{

    string name=1;
    
    string url=2;    
}

message BookListNew{
    string bookCover=1;
}

Although the class name is changed from booklist to booklistnew, the instance name is still booklist, and the final output response field name is still called booklist

In the above two cases, running Maven after modification can successfully compile java files