Golang custom json marshal Dec 9, 2019 · JSON Tricks: "Slightly" Custom Marshaling December 9, 2019 For more content like this, buy my in-progress eBook, Data Serialization in Go, and get updates immediately as they are added! Apr 10, 2015 · Custom JSON Marshalling in Go Fri, Apr 10, 2015 Go’s encoding/json package makes it really easy to marshal struct s to JSON data. Unmarshal to encode/decode JSON. (coinex exchange API) First, we make our request like this: Jan 1, 2024 · The json package provides encoders like json. Unmarshal and without you doing some extra work Either unmarshal it first into the map and then loop over that map to construct your slice of Status structs, or create a type like type Result []Status and implement the unmarshaler interface for that type. Jun 26, 2020 · JSON Tricks: Extending an Embedded Marshaler June 26, 2020 How can you embed a struct with a custom MarshalJSON () method? Aug 4, 2022 · When I was working on gocoinex library for the first time, I needed some custom configuration on JSON unmarshalling process, I want to share my learnings with you here, but before that, we're going to have a recap on how we can unmarshall JSON in golang. Dec 28, 2014 · How do I marshal a nested struct into JSON? I know how to marshal the struct without any nested structs. Mastering JSON Jun 15, 2016 · Go has a robust JSON library for consuming and outputting JSON. It's an essential function when you need to convert your Go program's data into JSON, making it easy to transmit data across the network or save it in a file format that is readable by other applications. It only exists when building We would like to show you a description here but the site won’t allow us. Beyond the basic types you will have to create custom marshaling methods on your types and write some logic to handle the conversion process. It's easier to implement by using automatic code generation for performance or by using a dedicated interface, but go-json dares to stick to compatibility with encoding/json and is the simple interface. Marshaler interface, since MarshalJSON is not in the method set for myStruct (only for *myStruct). Now this alone would be absolute painful to work with but: struct tags do not play a role in convertibility between types which lets you convert from AlphaIn to AlphaOut with a simple type conversion: Nov 26, 2024 · Go’s JSON package (encoding/json) provides straightforward capabilities for marshaling and unmarshaling data structures. Marshal() choose to (de Nov 5, 2025 · Marshal returns the JSON encoding of v. May 7, 2023 · Golang Custom JSON Marshal Example In this article we are going to see how to perform custom JSON Marshalling in Go (Golang). This means I have an map with a Jun 22, 2024 · As one of the most efficient and performant programming languages, Go, also known as Golang, has gained significant traction among developers, particularly for applications involving high concurrency and networked services. At line 330, marshal() calls e. In the realm of web development, JSON (JavaScript Object Notation) stands as a pivotal format for data interchange between servers and web applications. #golang #json. Marshal traverses the value v recursively. Jan 20, 2015 · I have seen plenty of ways to marshal/unmarshal structs that only have unexported fields. I'm trying to create a response struct with a generic message body. The fix is to either (a) make your MarshalJSON method take a non-pointer Mar 19, 2025 · Making YAML do what we want The yaml. We will go over writing these Dec 13, 2020 · I create my own type as enum value in other languages (like java). The `json:""` strings that follow the field declarations are struct tags. Jul 5, 2023 · Custom JSON marshaling in Go empowers you to define your own rules for encoding Go structs into JSON, tailoring the output to specific requirements. Advanced JSON customization By using struct tags, adding whitespace and enveloping the data, we’ve been able to add quite a lot of customization to our JSON responses already. At line 161, Marshal() calls e. Feb 17, 2025 · Discover 8 essential Go JSON processing techniques with practical code examples. The tags in this struct set the names of the struct's fields when marshaling to and from JSON. (The same general problem exists for UnmarshalJSON, too, but I’ll focus on just marshaling for demonstration purposes. Oct 22, 2021 · Therefore, instead of explicit mappings we wanted to implement a custom marshaller for the dto s that contains the enumeration value to help us customize the way that json. Here, we'll explore how to implement custom marshaling and unmarshaling logic. Marshal() and json. Marshal() function in Go is used to encode a Go data structure into JSON format. I understand I need to implement my own Unmarshaler for the d Mar 8, 2023 · Let's explore the encode. Both have Marshal and Unmarshal, as well as a couple of similar interfaces - and we are about to use them! First step would be to create a type alias for []string and change our Config type to use it: Jan 6, 2016 · I want to Marshal / Unmarshal Golang object (json) with a custom tag. Unmarshal() functions do a great job of aligning primitive types and converting them from Go into JSON, and vise versa. go file in the encoding/json package. Unmarshal and use AlphaOut to serialise a struct with encoding/json. However, certain scenarios require customization, such as handling non-standard JSON formats or manipulating data during these transformations. MarshalWrite and UnmarshalRead Jul 23, 2023 · This article aims to provide an introduction on how JSON can be handled in Go, and as always, with a bit of customization. The basic use case with Marshal and As far as I know that's not possible with plain encoding/json. The… Jun 6, 2019 · I am trying to write a simple custom marshaler and failing. marshal(). Aug 3, 2016 · In Golang, is there a way to make the generic encoding/json Marshal to use a different layout when Marshaling the time. Weekday int values but allows for the string value in request/response json and in the database Feb 24, 2022 · I have a struct with one of the fields type equal to that of another struct: type Developer struct { Name string `json:"name,omitempty"` ProjectRef *Ref `json:"project,omitempty"` } type Ref struct { ID string `json:"id,omitempty"` } In my implementation I cannot guarantee if there is or isn't going to be a ProjectRef for a Developer. MarshalJSON] method is present but the value implements encoding. Time fields? Basically I have this struct: s := {"starttime":time. TextMarshaler instead, Marshal calls encoding. Sep 4, 2018 · The things I often search for include: encode custom type to sql database json encode enum int as string json encode map key but not value In this example I make a custom Weekday type which matches time. But what happens when these things aren’t enough, and you need the freedom to customize your JSON even more? To answer this question, we first need to talk some theory about how Go handles JSON encoding behind the Dec 12, 2020 · The problem The general problem I aim to solve here, is a struct (or any data type, really), that implements a custom MarshalJSON method, but that method needs to access the non-custom JSON representation of itself. Upvoting indicates when questions and answers are useful. Marshal and Unmarshal encode and decode Go values to/from JSON text contained within a []byte. ) But why? Feb 25, 2024 · Introduction Golang is increasingly popular for backend services, where JSON stands as the pivotal data format for communication. This process is known as marshaling. Jun 22, 2025 · JSON evolution in Go: from v1 to v2 The second version of the json package coming in Go 1. If no [Marshaler. Golang has a powerful builting json encoding package that can be used right from the standard library without using any third party dependencies. Learn custom marshaling, streaming, validation, and performance optimization for robust data handling. For the sake of simplicity, our emphasis will be on handling JSON data that can be marshaled or unmarshaled as a single string or an array of strings. Marshal and decoders like json. Marshal to JSON. Now(), "na Aug 22, 2024 · Learn how to master Go JSON Marshal with custom marshalers. Marshal(ms); err != nil { The problem is that this variable does not implement the json. MarshalText and encodes the result as a JSON May 18, 2021 · } Use AlphaIn to deserialise JSON with encoding/json. 25 is a big update, and it has a lot of breaking changes. JSON is a simple data interchange format that can represent primitive data types such as booleans, strings, and numbers, in addition to structured data types such as objects and arrays. I implement for deserialising UnmarshalJSON method for this type and see that marshal can't transform into custom type package main May 21, 2023 · In this article, we will delve into the process of marshaling and unmarshaling a JSON property that has the flexibility to hold either a single value or an array of values. MarshalJSON] to produce JSON. Understand the challenges and solutions for struct embedding and JSON marshaling in Go to avoid common pitfalls and enhance your Go code. However when I try to make the JSON response look like this: Jun 21, 2017 · You'll need to complete a few actions and gain 15 reputation points before being able to upvote. How it works go-json is very fast in both encoding and decoding compared to other libraries. The v2 package adds new features, fixes API issues and behavioral flaws, and boosts performance. v3 package has a very similar API to the standard library’s json package. Go by Example: JSON Next example: XML. Nov 27, 2024 · The json. But i run into issues. Jan 24, 2024 · How to override JSON values in Golang using custom marshalling and using alias types to extend this to external types and field Apr 26, 2022 · This example allows us to see a couple of edge cases and features of JSON You can specify a JSON tag json:"full_name" and specify a custom name for your JSON field When specifying json:"<field name>,omitempty" as a json tag, the field will be disarcarded in the JSON output if the value has a zero value. If an encountered value implements Marshaler and is not a nil pointer, Marshal calls [Marshaler. TextMarshaler. These are real world examples. Mastery of JSON marshaling and unmarshaling — the conversion of Go data structures to JSON and back — is essential for developers engaged in building web Jul 20, 2023 · Taking Control of JSON Marshalling in Golang. This flexibility allows you to control structure… Apr 13, 2023 · I am working with a JSON response that can sometimes return a string or an object with string keys but values that are string and bool. reflectValue(), which identifies the type at runtime and marshals it accordingly. How to Override Default Behavior and Tailor JSON Encoding to Suit Your Needs. What's reputation and how do I get it? Instead, you can save this post to reference later. Nearly 4 years later, I've come up with an answer that is fundamentally similar to @jcbwlkr's, but does not require the intermediate unmarshal/re-marshal step, by using a little bit of byte-slice manipulation to join two JSON segments. There are equivalent encoders and decoders for other formats like XML, YAML, and more. Background Let's consider a situation where we map the WHERE clause to Oct 27, 2025 · Package json implements semantic processing of JSON as specified in RFC 8259. May 26, 2022 · How to customize JSON serialization for your data types while avoiding pointer and receiver problems -- a story in three parts. At line 358, reflectValue() calls valueEncoder(), which returns an encoder function for the type. Mar 27, 2017 · I'm working on s small server-client project based on JSON communication. This package (encoding/json/v2) is experimental, and not subject to the Go 1 compatibility promise. In this part of the code, ms gets copied into an interface{} variable: // Trying another method (UNSUCCESSFUL) if ret, err := json. Both Happy and Sad structs implement this interface by embedding the emotion struct Nov 5, 2025 · Package json implements semantic processing of JSON as specified in RFC 8259. Notice I have an interface that has three functions. But how can I do this with mixed fields? Given a struct: type Test struct { fieldA string `json:"fie Nov 13, 2014 · Reading Time: 2 minutesIn this post I want to go through an example of data marshaling in the Go language. Its robust built-in support for JSON, a universally accepted data interchange format, is a key strength. Let's take a look at what's changed! All examples are interactive, so you can read and practice at the same time. The standard json. ge91 hd s4j9i eulu yf iymazcy grna 5cjgp 0b0p ipnio