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.M
var jsonString string
fmt.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":{"$numberLong":"1661394765044"},"detail":"<h4>abc</h4>"}]}
英文:
I'm trying to search a document in golang using mongodb driver. But the result is always blank.
This is my code:
var bsonString bson.M
var jsonString string
fmt.Printf("[%s] > request for url\n", req.RemoteAddr)
w.Header().Set("Access-Control-Allow-Origin", "*")
dataSource := client.Database(dbName)
collection := dataSource.Collection(collectionName)
err := collection.FindOne(context.Background(), bson.D{{"question.title", "Question"}}).Decode(&bsonString)
if err != nil {
if err == mongo.ErrNoDocuments {
// This error means your query did not match any documents.
log.Println("No matched documents!")
return
}
panic(err)
}
finalBytes, _ := bson.Marshal(bsonString)
bson.Unmarshal(finalBytes, &jsonString)
fmt.Println(jsonString)
My data is:
{"_id":{"$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.M
var jsonString string
dataSource := 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 haldling
json.Unmarshal(finalBytes, &jsonString)
// with error handling
err = 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 variables
var bsonString bson.M
var jsonString string
dataSource := client.Database(dbName)
collection := dataSource.Collection(collectionName)
//
dataObject := map[string]interface{}{}
fmt.Printf("[%s] > request for url\n", req.RemoteAddr)
// set headers
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 {
// This error means your query did not match any documents.
log.Println("No matched documents!")
return
}
panic(err)
}
// marshal & unmarshall
finalBytes, _ := bson.Marshal(bsonString)
bson.Unmarshal(finalBytes, &dataObject)
fmt.Println(dataObject)
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