EDJSON: Echo DTO JSON ✨

EDJSON is a small, utility-focused Go library that simplifies data mapping and JSON response generation within the Echo web framework. It builds upon robust deep-copy functionality to ensure clean, reliable data transfer from backend models to public-facing Data Transfer Objects (DTOs).

Its primary goal is to provide a single, clean function for mapping complex data structures into a defined response format before delivery.

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🚀 Main Feature: The JSON Helper

The core of EDJSON is the generic JSON function. It is designed to eliminate boilerplate code in your HTTP handlers by combining error checking, deep-copying, DTO instantiation, and JSON response delivery into one clean call.

How It Works

The JSON function handles three essential steps for you:

1. Error Check: Immediately returns if a previous error (e.g., from a data service call) is passed to it.
2. DTO Mapping: Deep-copies the data from your source object into a newly created instance of the specified DTO type T.
3. JSON Response: Sends the resulting DTO as a JSON response using the Echo context with the provided HTTP status.

Usage Example

// T is the DTO type (e.g., UserResponseDTO)
// source is the internal data structure (e.g., *User)
func GetUser(c echo.Context) error {
    user, dataServiceErr := service.Users.Get(c.Param("id"))
    
    // Maps 'user' to UserResponseDTO, handles dataServiceErr, and sends the JSON response.
    return edjson.JSON[UserResponseDTO](c, http.StatusOK, user, dataServiceErr)
}

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🛠️ Data Copying & Custom Conversion

EDJSON ensures all data copying is performed as a deep copy, meaning nested structs, maps, and slices are copied by value, preventing unexpected side effects or mutation of your source data.

Custom Converters

EDJSON manages a global list of Type Converters which allow you to define custom logic for copying between fields of different types. This is essential for:

• Custom Types: Handling conversions between library-specific types and standard Go structs.
• Encoding/Decoding: Automatic encoding/decoding during the copy process (e.g., converting a []byte field to a Base64-encoded string).

You can easily register your custom converters during application startup:

func init() {
    // Add built-in converters for []byte -> Base64 string
    edjson.Converters.Add(edjson.BytesToBase64Converter()...)
}

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