Manually read JSON values

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In Go I usually unmarshal my JSON into a struct and read values from the struct.. it works very well.

This time around I am only concerned with a certain element of a JSON object and because the overall JSON object is very large, I don't want to have to create a struct.

Is there a way in Go so that I can lookup values in the JSON object using keys or iterate arrays as per usual.

Considering the following JSON how could I pull out the title field only.

{
  "title": "Found a bug",
  "body": "I'm having a problem with this.",
  "assignee": "octocat",
  "milestone": 1,
  "labels": [
    "bug"
  ]
}

To extend Darigaaz's answer, you can also use an anonymous struct declared within the parsing function. This avoids having to have package-level type declarations litter the code for single-use cases.

https://play.golang.org/p/MkOo1KNVbs

package main

import (
    "encoding/json"
    "fmt"
)

func main() {
    test := `{
        "title": "Found a bug",
        "body": "I'm having a problem with this.",
        "assignee": "octocat",
        "milestone": 1,
        "labels": [
          "bug"
        ]
    }`

    var s struct {
        Title string `json:"title"`
    }
    json.Unmarshal([]byte(test), &s)

    fmt.Printf("%#v", s)

}

Manually read JSON values, To extend Darigaaz's answer, you can also use an anonymous struct declared within the parsing function. This avoids having to have� The simplest way to extract data from a JSON file is to provide a key name to obtain its data value. Type a period and the key name without a space between them. This creates a filter from the key name. We also need to tell jq which JSON file to use. We type the following to retrieve the message value: jq .message iss.json

Dont declare fields you dont want.

https://play.golang.org/p/cQeMkUCyFy

package main

import (
    "fmt"
    "encoding/json"
)

type Struct struct {
    Title   string  `json:"title"`
}

func main() {
    test := `{
        "title": "Found a bug",
        "body": "I'm having a problem with this.",
        "assignee": "octocat",
        "milestone": 1,
        "labels": [
          "bug"
        ]
    }`

    var s Struct
    json.Unmarshal([]byte(test), &s)

    fmt.Printf("%#v", s)

}

Or if you want to completely get rid of structs:

var i interface{}
json.Unmarshal([]byte(test), &i)

fmt.Printf("%#v\n", i)
fmt.Println(i.(map[string]interface{})["title"].(string))

Or. It will swallow all conversion errors.

m := make(map[string]string)

json.Unmarshal([]byte(test), interface{}(&m))

fmt.Printf("%#v\n", m)
fmt.Println(m["title"])

How to Parse JSON in Java, A JSON object is an unordered set of key/value pairs. A JSON array is an ordered collection of values. The values themselves could be objects or� Null values in the JSON are ignored only if they are valid. Null values for non-nullable value types cause exceptions. Utf8JsonReader, Utf8JsonWriter, and JsonDocument. System.Text.Json.Utf8JsonReader is a high-performance, low allocation, forward-only reader for UTF-8 encoded JSON text, read from a ReadOnlySpan<byte> or ReadOnlySequence<byte>.

Check out go-simplejson

Example:

js, err := simplejson.NewJson([]byte(`{
  "test": {
    "string_array": ["asdf", "ghjk", "zxcv"],
    "string_array_null": ["abc", null, "efg"],
    "array": [1, "2", 3],
    "arraywithsubs": [{"subkeyone": 1},
    {"subkeytwo": 2, "subkeythree": 3}],
    "int": 10,
    "float": 5.150,
    "string": "simplejson",
    "bool": true,
    "sub_obj": {"a": 1}
  }
}`))

if _, ok = js.CheckGet("test"); !ok {
  // Missing test struct
}

aws := js.Get("test").Get("arraywithsubs")
aws.GetIndex(0)

How to parse JSON in Java, JSON can represent two structured types: objects and arrays. An object is an unordered collection of zero or more name/value pairs. An array is� JSON (JavaScript Object Notation) is a lightweight, text-based, language-independent data exchange format that is easy for humans and machines to read and write. JSON can represent two structured types: objects and arrays. An object is an unordered collection of zero or more name/value pairs. An array is an ordered sequence of zero or more values.

package main

import (
    "encoding/json"
    "fmt"
)


type Seller struct {
  Name string
  ShareName string
  Holdings int
  Quantity int
  PerShare float64
}

type Buyer struct {
  Name string
  ShareName string
  Holdings int
  Quantity int
  PerShare float64

}
func validateTransaction(seller Seller,buyer Buyer) bool{         
    var isallowTransact bool =false
    if (seller.Quantity >=buyer.Quantity &&seller.PerShare == buyer.PerShare && seller.ShareName ==buyer.ShareName){
         isallowTransact=true; 
    }  

    return isallowTransact
    }

func executeTransaction(seller Seller,buyer Buyer) {         
       seller.Holdings -=seller.Quantity;
       buyer.Holdings +=seller.Quantity;
    fmt.Printf("seller current holding : %d, \n buyyer current holding: %d",seller.Holdings,buyer.Holdings)

}

func main() {   
    sellerJson :=`{"name":"pavan","ShareName":"TCS","holdings":100,"quantity":30,"perShare":11.11}`
    buyerJson :=`{"name":"Raju","ShareName":"TCS","holdings":0,"quantity":30,"perShare":14.11}`
    var seller Seller 
    var buyer Buyer 
    json.Unmarshal([]byte(sellerJson ), &seller)
    json.Unmarshal([]byte(buyerJson ), &buyer)

    //fmt.Printf("seller name : %s, shares of firm: %s,total holdings: %d, want to sell: %d,unit cost: %f", seller.Name , seller.ShareName,seller.Holdings , seller.Quantity,seller.PerShare )
      var isallowExecute bool =false
    isallowExecute  =validateTransaction(seller,buyer)

    if(isallowExecute){ 
    executeTransaction(seller,buyer)
    }else{
     fmt.Print("\n seems buyer quotes are not matching with seller so we are not able to perform transacrion ,Please check and try again");

    }
    fmt.Println("\n Happy Trading...!!");

    }

How to Parse JSON Data From a REST API Using a Simple JSON , This tutorial shows you how to use JAVA to leverage JSON data categorically from a REST API, and parse a URL object as a JSON object� I have set up my AppSettings data in file appsettings/Config .json like this: { "AppSettings": { "token": "1234" } } I have searched online on how to read AppSettings values from .json file, but I could not get anything useful.

Update: This answer is wrong; I'm leaving it as an example of what not to do.

You should look it up with a regex then (pseudocode):

String s = {json source};
int i = s.indexOf("\"title\": \"")
s.substring(i,s.indexOf("\"",i))

more on substrings in Java

Parsing JSON Object using JObject.Parse, Return Values �. Returns the value encoded in json in appropriate PHP type. < ?php // http://www.php.net/manual/en/function.json-decode.php#95782 function� There you have it! You can now parse JSON into .NET objects using C#! If you would like to retrieve and read the JSON via Objective-C and Node.js, feel free to read these two articles: iOS QuickTip: Getting and Reading JSON Data from a URL and How to Use JSON files in Node.js. Other Useful references: www.json.org; www.json2code.com

json_decode - Manual, JSON - Quick Guide - JSON or JavaScript Object Notation is a lightweight text- based open standard designed for JSON is easy to read and write. Step 1 of the process is to start Power BI Desktop. Next, as shown below, you will either use the Get Data Splash screen option or the Get Data button from the Ribbon to start the Get Data Wizard. Next select JSON as the data source. Finally, you select the file you want to work with: Get Quotes.JSON in our example.

JSON - Quick Guide, Parse. JObject class has parse method; it parses the JSON string and converts it into a Key-value dictionary object. In the following example, I� Given that JSON is typically snake or camel case, and properties in C# are pascal case, someone is going to have to give in and change their casing style. This is also ignoring the fact that you are now locked into using dynamic objects which come with their own set of headaches around dynamic typing.

Working With JSON String In C#, The JSON Parser node can parse JSON objects, arrays of objects, single values or arrays of values. In contrast to XML, which only knows the string type, JSON�

Comments
  • You can make a struct exclusively for the parts you want. This from the json package under Unmarshal(): "To unmarshal JSON into a struct, Unmarshal matches incoming object keys to the keys used by Marshal (either the struct field name or its tag), preferring an exact match but also accepting a case-insensitive match. Unmarshal will only set exported fields of the struct." If the field doesn't exist the json key/value pair should simply be ignored.
  • Ah ok, I thought it would complain about unmatched fields. Thanks.
  • Thanks but, imho, this is too trivial a problem to add an external dependency.
  • @conor Of course, it all depends on your needs. I particularly like this library when I have to unit test JSON payloads for instance. But good habit to not add 3rd party libs for small tasks :)
  • Hi, while this code may answer the question, providing additional context regarding how and/or why it solves the problem would improve the answer's long-term value.
  • { "body": "here goes \"title\":\"pick me\"", "title": "catch me if you can" }
  • @Darigaaz ? Is that because I'm over complicating a simple solution or a ray of inspiration?
  • Parsing "structured" text like json/html/xml with regex is a bad idea in general. And i gave you an example.
  • Aaaah, I apologize. I won't delete the answer to serve it as an example for the future, risking my reputation nonetheless