JavaでJSONを解析する方法?

この記事では、JavaでJSONを解析する方法について説明します.JSON Java、GSON、JSONのようなJSONライブラリを使います
JSONはJavaScriptのオブジェクト表記を表します.データを格納して、輸送することは、使いやすくて、開いている標準的なファイル形式を軽くします.
としてjson.org ,

It is easy for humans to read and write. It is easy for machines to parse and generate.

JSONの例

{
  "name": "coderolls",
  "type": "blog",
  "address": {
    "street": "1600 Pennsylvania Avenue NW",
    "city": "Washington",
    "state": "DC"
  },
  "employees": [
    {
      "firstName": "John",
      "lastName": "Doe"
    },
    {
      "firstName": "Anna",
      "lastName": "Smith"
    },
    {
      "firstName": "Peter",
      "lastName": "Jones"
    }
  ]
}

上記のJSONではname がキーでありcoderolls それは価値ですか.For address キー、値はキーと値を含む別のJSONオブジェクトです.
For employees キー、それはJSONオブジェクトの配列です.
今日、Javaで3つのJSONライブラリを見てJSON文字列を解析します.以下に列挙します.

ジャンソン

ギャルソン

シンプルソン

JavaでJSONを解析するために、すべての3つのライブラリの例を示します.

JavaでJOSNを解析する方法
JSON JavaはJavaのための最もシンプルなJSONライブラリの一つです.
ここでは、我々はJSONObject JSON Javaライブラリのクラス.JSONObject has a constructor which accepts string . 私たちは、JSONストリングを解析するために、ths建設者を使用しています.

public JSONObject(String source) throws JSONException

Construct a JSONObject from a source JSON text string. This is the most commonly used JSONObject constructor.

Parameters:

source  - A string beginning with  `{` (left brace)  and ending with  `}`  (right brace).

Throws:

JSONException  - If there is a syntax error in the source string or a duplicated key.

参照することができますJSON-java Docs .
マベン

<dependency>
    <groupId>org.json</groupId>
    <artifactId>json</artifactId>
    <version>20201115</version>
</dependency>

グレード

compile group: 'org.json', name: 'json', version: '20201115'

例:

package com.coderolls.JSONExample;

import org.json.JSONArray;
import org.json.JSONObject;

/**
 * A program to parse JSON strin in Java using JSON-Java
 * @author Gaurav Kukade at coderolls.com
 */

public class ParseJSONUsingJSONJava {

    public static void main(String[] args) {

        String jsonString = "{"
                + "  \"name\": \"coderolls\","
                + "  \"type\": \"blog\","
                + "  \"address\": {"
                + "    \"street\": \"1600 Pennsylvania Avenue NW\","
                + "    \"city\": \"Washington\","
                + "    \"state\": \"DC\""
                + "  },"
                + "  \"employees\": ["
                + "    {"
                + "      \"firstName\": \"John\","
                + "      \"lastName\": \"Doe\""
                + "    },"
                + "    {"
                + "      \"firstName\": \"Anna\","
                + "      \"lastName\": \"Smith\""
                + "    },"
                + "    {"
                + "      \"firstName\": \"Peter\","
                + "      \"lastName\": \"Jones\""
                + "    }"
                + "  ]"
                + "}";

        System.out.println("Parsing the json string in java using JSON-Java......\n");

        //add jsonString to the constructor
        JSONObject coderollsJSONObject = new JSONObject(jsonString);

        //now we can access the values 
        String name = coderollsJSONObject.getString("name");
        System.out.println("Name: "+name+"\n");

        //we can get the JSON object present as value of any key in the parent JSON
        JSONObject addressJSONObject = coderollsJSONObject.getJSONObject("address");

        //access the values of the addressJSONObject 
        String street = addressJSONObject.getString("street");
        System.out.println("Street: "+street+"\n");


        //we can get the json array present as value of any key in the parent JSON
        JSONArray employeesJSONArray = coderollsJSONObject.getJSONArray("employees");
        System.out.println("Printing the employess json array: \n"+employeesJSONArray.toString()+"\n");

        //we can get individual json object at an index from the employeesJSONArray
        JSONObject employeeJSONObject = employeesJSONArray.getJSONObject(0);
        String firstName = employeeJSONObject.getString("firstName");
        System.out.println("First Name of the employee at index 0: "+firstName);
    }
}

コードを得るParseJSONUsingJSON.Java
出力:

Parsing the json string in java using JSON-Java......

Name: coderolls

Street: 1600 Pennsylvania Avenue NW

Printing the employess json array: 
[{"firstName":"John","lastName":"Doe"},{"firstName":"Anna","lastName":"Smith"},{"firstName":"Peter","lastName":"Jones"}]

First Name of the employee at index 0: John

JavaでJOSNを解析する方法
GSONは、Javaで開発されたJavaオブジェクトをシリアル化し、Javaで開発したJavaライブラリです.
JSON文字列を等価Javaオブジェクトに変換するために使用できます.
ここでは、我々はJsonObject GSONライブラリのクラス.
あなたはdocs of JsonObject .
マベン

<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.8.6</version>
</dependency>

グレード

compile group: 'com.google.code.gson', name: 'gson', version: '2.8.6'

例:

package com.coderolls.JSONExample;

import com.google.gson.Gson;
import com.google.gson.JsonArray;
import com.google.gson.JsonObject;

/**
 * A program to parse JSON strin in Java using Gson
 * @author Gaurav Kukade at coderolls.com
 */

public class ParseJSONUsingGSON {

    public static void main(String[] args) {

        //take json as string
        String jsonString = "{"
                + "  \"name\": \"coderolls\","
                + "  \"type\": \"blog\","
                + "  \"address\": {"
                + "    \"street\": \"1600 Pennsylvania Avenue NW\","
                + "    \"city\": \"Washington\","
                + "    \"state\": \"DC\""
                + "  },"
                + "  \"employees\": ["
                + "    {"
                + "      \"firstName\": \"John\","
                + "      \"lastName\": \"Doe\""
                + "    },"
                + "    {"
                + "      \"firstName\": \"Anna\","
                + "      \"lastName\": \"Smith\""
                + "    },"
                + "    {"
                + "      \"firstName\": \"Peter\","
                + "      \"lastName\": \"Jones\""
                + "    }"
                + "  ]"
                + "}";
        System.out.println("Parsing the json string in java using Gson......\n");

        Gson gson = new Gson();

        //get json object from the json string
        JsonObject coderollsJsonObject = gson.fromJson(jsonString, JsonObject.class);

        //now we can access the values 
        String name = coderollsJsonObject.get("name").getAsString();
        System.out.println("Name: "+name+"\n");

        //we can get the JSON object present as value of any key in the parent JSON
        JsonObject addressJsonObject = coderollsJsonObject.get("address").getAsJsonObject();

        //access the values of the addressJSONObject 
        String street = addressJsonObject.get("street").getAsString();
        System.out.println("Street: "+street+"\n");


        //we can get the json array present as value of any key in the parent JSON
        JsonArray employeesJsonArray = coderollsJsonObject.get("employees").getAsJsonArray();
        System.out.println("Printing the employess json array: \n"+employeesJsonArray.toString()+"\n");

        //we can get individual json object at an index from the employeesJSONArray
        JsonObject employeeJsonObject = employeesJsonArray.get(0).getAsJsonObject();
        String firstName = employeeJsonObject.get("firstName").getAsString();
        System.out.println("First Name of the employee at index 0: "+firstName);
    }
}

コードを得るParseJSONUsingGSON.java
出力:

Parsing the json string in java using Gson......

Name: coderolls

Street: 1600 Pennsylvania Avenue NW

Printing the employess json array: 
[{"firstName":"John","lastName":"Doe"},{"firstName":"Anna","lastName":"Smith"},{"firstName":"Peter","lastName":"Jones"}]

First Name of the employee at index 0: John

JSONシンプルを使用してJavaでJOSNを解析する方法
JSONシンプルなJSONのJavaツールキットです.JSONを使用できます.JSONテキストをエンコードまたはデコードするのに簡単です.
マベン

<dependency>
    <groupId>com.googlecode.json-simple</groupId>
    <artifactId>json-simple</artifactId>
    <version>1.1.1</version>
</dependency>

グレード

compile group: 'com.googlecode.json-simple', name: 'json-simple', version: '1.1.1'

あなたはjson-simple project page.java .
例:

package com.coderolls.JSONExample;

import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;

/**
 * A program to parse JSON strin in Java using json-simple
 * @author Gaurav Kukade at coderolls.com
 */

public class ParseJSONUsingJsonSimple {

    public static void main(String[] args) {
        //take json as string
        String jsonString = "{"
                        + "  \"name\": \"coderolls\","
                        + "  \"type\": \"blog\","
                        + "  \"address\": {"
                        + "    \"street\": \"1600 Pennsylvania Avenue NW\","
                        + "    \"city\": \"Washington\","
                        + "    \"state\": \"DC\""
                        + "  },"
                        + "  \"employees\": ["
                        + "    {"
                        + "      \"firstName\": \"John\","
                        + "      \"lastName\": \"Doe\""
                        + "    },"
                        + "    {"
                        + "      \"firstName\": \"Anna\","
                        + "      \"lastName\": \"Smith\""
                        + "    },"
                        + "    {"
                        + "      \"firstName\": \"Peter\","
                        + "      \"lastName\": \"Jones\""
                        + "    }"
                        + "  ]"
                        + "}";

        System.out.println("Parsing the json string in java using json-simple......\n");

        JSONParser parser = new JSONParser();
        JSONObject coderollsJSONObject = new JSONObject();
        try {
            coderollsJSONObject = (JSONObject) parser.parse(jsonString);
        } catch (ParseException e) {
            e.printStackTrace();
        }

        //now we can access the values 
        String name = (String) coderollsJSONObject.get("name");
        System.out.println("Name: "+name+"\n");

        //we can get the JSON object present as value of any key in the parent JSON
        JSONObject addressJSONObject = (JSONObject) coderollsJSONObject.get("address");

        //access the values of the addressJSONObject 
        String street = (String) addressJSONObject.get("street");
        System.out.println("Street: "+street+"\n");


        //we can get the json array present as value of any key in the parent JSON
        JSONArray employeesJSONArray = (JSONArray) coderollsJSONObject.get("employees");
        System.out.println("Printing the employess json array: \n"+employeesJSONArray.toString()+"\n");

        //we can get individual json object at an index from the employeesJSONArray
        JSONObject employeeJSONObject = (JSONObject) employeesJSONArray.get(0);
        String firstName = (String) employeeJSONObject.get("firstName");
        System.out.println("First Name of the employee at index 0: "+firstName);
    }
}

コードを得るParseJSONUsingJsonSimple.java
出力:

Parsing the json string in java using json-simple......

Name: coderolls

Street: 1600 Pennsylvania Avenue NW

Printing the employess json array: 
[{"firstName":"John","lastName":"Doe"},{"firstName":"Anna","lastName":"Smith"},{"firstName":"Peter","lastName":"Jones"}]

First Name of the employee at index 0: John

結論
すべての3つのライブラリでJSON文字列からJSONオブジェクトを作成できますが、JSON Javaは使いやすいです.
このブログ記事はすでに公開されています.https://coderolls.com/parse-json-in-java/
あなたはより多くのビデオチュートリアルを見つけるために私の訪問することができます.
あなたは私をサポートすることができますgiving a cup of Coffee ☕

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