119 lines
4.0 KiB
Go
119 lines
4.0 KiB
Go
package main
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import (
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"encoding/json"
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"errors"
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"fmt"
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"io"
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"maps"
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"net/http"
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"strconv"
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"strings"
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"github.com/julienschmidt/httprouter"
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)
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// Define an envelope type.
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type envelope map[string]any
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// Retrieve the "id" URL parameter from the current request context, then convert it to
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// an integer and return it. If the operation isn't successful, return 0 and an error.
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func (app *application) readIDParam(r *http.Request) (int64, error) {
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params := httprouter.ParamsFromContext(r.Context())
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id, err := strconv.ParseInt(params.ByName("id"), 10, 64)
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if err != nil || id < 1 {
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return 0, errors.New("invalid id parameter")
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}
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return id, nil
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}
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// Change the data parameter to have the type envelope instead of interface{}.
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func (app *application) writeJSON(w http.ResponseWriter, status int, data envelope, headers http.Header) error {
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js, err := json.MarshalIndent(data, "", "\t")
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if err != nil {
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return err
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}
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js = append(js, '\n')
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maps.Copy(w.Header(), headers)
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w.Header().Set("Content-Type", "application/json")
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w.WriteHeader(status)
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w.Write(js)
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return nil
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}
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func (app *application) readJSON(w http.ResponseWriter, r *http.Request, dst any) error {
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// Use http.MaxBytesReader() to limit the size of the request body to 1MB.
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maxBytes := 1_048_576
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r.Body = http.MaxBytesReader(w, r.Body, int64(maxBytes))
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// Initialize the json.Decoder, and call the DisallowUnknownFields() method on it
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// before decoding. This means that if the JSON from the client now includes any
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// field which cannot be mapped to the target destination, the decoder will return
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// an error instead of just ignoring the field.
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dec := json.NewDecoder(r.Body)
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dec.DisallowUnknownFields()
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// Decode the request body to the destination.
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err := dec.Decode(dst)
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if err != nil {
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var syntaxError *json.SyntaxError
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var unmarshalTypeError *json.UnmarshalTypeError
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var invalidUnmarshalError *json.InvalidUnmarshalError
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switch {
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case errors.As(err, &syntaxError):
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return fmt.Errorf("body contains badly-formed JSON (at character %d)", syntaxError.Offset)
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case errors.Is(err, io.ErrUnexpectedEOF):
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return errors.New("body contains badly-formed JSON")
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case errors.As(err, &unmarshalTypeError):
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if unmarshalTypeError.Field != "" {
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return fmt.Errorf("body contains incorrect JSON type for field %q", unmarshalTypeError.Field)
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}
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return fmt.Errorf("body contains incorrect JSON type (at character %d)", unmarshalTypeError.Offset)
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case errors.Is(err, io.EOF):
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return errors.New("body must not be empty")
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// If the JSON contains a field which cannot be mapped to the target destination
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// then Decode() will now return an error message in the format "json: unknown
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// field "<name>"". We check for this, extract the field name from the error,
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// and interpolate it into our custom error message. Note that there's an open
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// issue at https://github.com/golang/go/issues/29035 regarding turning this
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// into a distinct error type in the future.
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case strings.HasPrefix(err.Error(), "json: unknown field "):
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fieldName := strings.TrimPrefix(err.Error(), "json: unknown field ")
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return fmt.Errorf("body contains unknown key %s", fieldName)
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// If the request body exceeds 1MB in size the decode will now fail with the
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// error "http: request body too large". There is an open issue about turning
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// this into a distinct error type at https://github.com/golang/go/issues/30715.
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case err.Error() == "http: request body too large":
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return fmt.Errorf("body must not be larger than %d bytes", maxBytes)
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case errors.As(err, &invalidUnmarshalError):
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panic(err)
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default:
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return err
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}
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}
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// Call Decode() again, using a pointer to an empty anonymous struct as the
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// destination. If the request body only contained a single JSON value this will
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// return an io.EOF error. So if we get anything else, we know that there is
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// additional data in the request body and we return our own custom error message.
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err = dec.Decode(&struct{}{})
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if err != io.EOF {
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return errors.New("body must only contain a single JSON value")
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}
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return nil
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}
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