英文:
Findone() always return blank with mongodb driver in golang
问题
我正在尝试使用Golang的MongoDB驱动程序搜索文档，但结果始终为空。
这是我的代码：
var bsonString bson.Mvar jsonString stringfmt.Printf("[%s] > request for url\n", req.RemoteAddr)w.Header().Set("Access-Control-Allow-Origin", "*")dataSource := client.Database(dbName)collection := dataSource.Collection(collectionName)err := collection.FindOne(context.Background(), bson.D{{"question.title", "Question"}}).Decode(&bsonString)if err != nil {if err == mongo.ErrNoDocuments {// 这个错误意味着你的查询没有匹配到任何文档。log.Println("No matched documents!")return}panic(err)}finalBytes, _ := bson.Marshal(bsonString)bson.Unmarshal(finalBytes, &jsonString)fmt.Println(jsonString)
我的数据是：
{"_id":{"$oid":"631c5c78e606582e2ad78e2d"},"question":{"title":"Question","create_by":"AZ","time":{"$numberLong":"1661394765044"},"detail":"<h4>info</h4>"},"answers":[{"create_by":"baa","time":{"$numberLong":"1661394765044"},"detail":"<h4>abc</h4>"}]}
英文:
I'm trying to search a document in golang using mongodb driver. But the result is always blank.
This is my code:
var bsonString bson.Mvar jsonString stringfmt.Printf("[%s] > request for url\n", req.RemoteAddr)w.Header().Set("Access-Control-Allow-Origin", "*")dataSource := client.Database(dbName)collection := dataSource.Collection(collectionName)err := collection.FindOne(context.Background(), bson.D{{"question.title", "Question"}}).Decode(&bsonString)if err != nil {if err == mongo.ErrNoDocuments {// This error means your query did not match any documents.log.Println("No matched documents!")return}panic(err)}finalBytes, _ := bson.Marshal(bsonString)bson.Unmarshal(finalBytes, &jsonString)fmt.Println(jsonString)
My data is:
{"_id":{"$oid":"631c5c78e606582e2ad78e2d"},"question":{"title":"Question","create_by":"AZ","time":{"$numberLong":"1661394765044"},"detail":"<h4>info</h4>"},"answers":[{"create_by":"baa","time":{"$numberLong":"1661394765044"},"detail":"<h4>abc</h4>"}]}
答案1
得分: 0
你正在将一个文档解组成一个字符串。如果你进行错误处理，你会看到错误信息：
// 没有错误处理json.Unmarshal(finalBytes, &jsonString)// 带有错误处理err = json.Unmarshal(finalBytes, &jsonString)if err != nil {fmt.Println(err)// 输出: json: 无法将对象解组为类型为 string 的 Go 值}
你可以创建一个与你的数据匹配的结构体，或者解组到接口中（用于非结构化数据）。
// 声明变量var bsonString bson.Mvar jsonString stringdataSource := client.Database(dbName)collection := dataSource.Collection(collectionName)//dataObject := map[string]interface{}{}fmt.Printf("[%s] > 请求 URL\n", req.RemoteAddr)// 设置头部信息w.Header().Set("Access-Control-Allow-Origin", "*")err := collection.FindOne(context.Background(), bson.D{{"question.title", "Question"}}).Decode(&bsonString)if err != nil {if err == mongo.ErrNoDocuments {// 这个错误意味着你的查询没有匹配到任何文档。log.Println("没有匹配的文档！")return}panic(err)}// 编组和解组finalBytes, _ := bson.Marshal(bsonString)bson.Unmarshal(finalBytes, &dataObject)fmt.Println(dataObject)
英文:
You are unmarshalling a document into a string. If you did error handling you would see the error:
// no error haldlingjson.Unmarshal(finalBytes, &jsonString)// with error handlingerr = json.Unmarshal(finalBytes, &jsonString)if err != nil {fmt.Println(err)// prints: json: cannot unmarshal object into Go value of type string}
You can create a struct to match your data or unmarshal into interface (for unstructured data).
// declare variablesvar bsonString bson.Mvar jsonString stringdataSource := client.Database(dbName)collection := dataSource.Collection(collectionName)//dataObject := map[string]interface{}{}fmt.Printf("[%s] > request for url\n", req.RemoteAddr)// set headersw.Header().Set("Access-Control-Allow-Origin", "*")err := collection.FindOne(context.Background(), bson.D{{"question.title", "Question"}}).Decode(&bsonString)if err != nil {if err == mongo.ErrNoDocuments {// This error means your query did not match any documents.log.Println("No matched documents!")return}panic(err)}// marshal & unmarshallfinalBytes, _ := bson.Marshal(bsonString)bson.Unmarshal(finalBytes, &dataObject)fmt.Println(dataObject)
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