Exporting and Importing Data JSON Exporting and Importing Data JSON SoftUni Team Technical Trainers Software University http://softuni.bg © Software University Foundation – http://softuni.org This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike license.

Table of Contents JSON Export JSON Import * (c) 2008 National Academy for Software Development - http://academy.devbg.org. All rights reserved. Unauthorized copying or re-distribution is strictly prohibited.*

Questions sli.do #db-advanced

JSON

JSON Specifics JSON = JavaScript Object Notation JSON is a subset of JavaScript syntax JSON is a lightweight format that is used for data interchanging JSON is easy to read and write JSON is language independent JSON format is primarily used to transmit data between a server and web application The filename extension is .json

JSON Example person.json js object Key Value Variable Value Property { "firstName": "Daniel", "lastName": "Sempre", "age": 24, "isMarried": true } js object Variable Value var person = { firstName: "Daniel", lastName: "Sempre", age: 24, isMarried: true }; Property

JSON Function Client Server person.js person.json car.js car.json JavaScript Java, PHP, C# Client Server JSON PersonController.java person.js person.json CarController.java car.js car.json

JSON Structure Data is represented in name/value pairs. Curly braces hold objects Square brackets hold arrays person.json Object holder Key Value { "firstName": "Daniel", "lastName": "Sempre", "age": 24, "isMarried": true } Comma separeted

Nested array of objects JSON Structure Object holder person.json Key Value { "firstName": "John", "lastName": "Snow", "address": { "country": "Spain", "city": "Barcelona", "street": "Barcelona" }, "phoneNumbers": [ "number": "1e341341" "number": "542152" } ] Nested object Nested array of objects Array holder

JSON Data Types Type Description Number double- precision floating-point String double-quoted Unicode Boolean true or false Array an ordered sequence of values Object an unordered collection of key:value pairs null empty

GSON Provide easy to use mechanisms to convert Java to JSON and vice-versa Generate compact and readability JSON output pom.xml <dependency> <groupId>com.google.code.gson</groupId> <artifactId>gson</artifactId> </dependency>

GSON Initialization Gson objects are responsible for the JSON manipulations GsonBuilder creates an instance of GSON excludeFieldsWithoutExposeAnnotation() – excludes fields without @Expose annotation setPrettyPrinting() – justifies the JSON create() – creates an instance of Gson JsonParser.java Gson gson = new GsonBuilder() .excludeFieldsWithoutExposeAnnotation() .setPrettyPrinting() .create();

Export Single Object to JSON AddressJsonDto.java The filed will be imported/exported public class AddressJsonDto implements Serializable { @Expose private String country; private String city; private String street; } JsonParser.java AddressJsonDto addressJsonDto = new AddressJsonDto(); addressJsonDto.setCountry("Bulgaria"); addressJsonDto.setCity("Sofia"); addressJsonDto.setStreet("Mladost 4"); String content = this.gson.toJson(addressJsonDto); Creates JSON

Export Single Object to JSON JsonParser.java AddressJsonDto addressJsonDto = new AddressJsonDto(); addressJsonDto.setCountry("Bulgaria"); addressJsonDto.setCity("Sofia"); addressJsonDto.setStreet("Mladost 4"); String content = this.gson.toJson(addressJsonDto); address.json { "country": "Bulgaria", "city": "Sofia", "street": "Mladost 4" }

Export Multiple Object to JSON JsonParser.java List<AddressJsonDto> addressJsonDtos = new ArrayList<>(); addressJsonDtos.add(addressJsonDtoBulgaria); addressJsonDtos.add(addressJsonDtoSpain); String content = this.gson.toJson(addressJsonDtos); addresses.json [ { "country": "Bulgaria", "city": "Sofia", "street": "Mladost 4" }, "country": "Spain", "city": "Barcelona", "street": "Las Ramblas" } ]

Import Single Object to JSON AddressJsonDto.java The filed will be imported/exported public class AddressJsonDto implements Serializable { @Expose private String country; private String city; private String street; } JsonParser.java Creates Object AddressJsonDto addressJsonDto = this.gson.fromJson(AddressJsonDto.class, "/files/input/json/address.json");

Import Single Object to JSON AddressJsonDto.java public class AddressJsonDto implements Serializable { @Expose private String country; private String city; private String street; } address.json { "country": "Bulgaria", "city": "Sofia", "street": "Mladost 4" }

Import Multiple Object to JSON JsonParser.java Object Array AddressJsonDto[] addressJsonDtos = this.gson.fromJson(AddressJsonDto[].class, "/files/input/json/addresses.json"); addresses.json [ { "country": "Bulgaria", "city": "Sofia", "street": "Mladost 4" }, "country": "Spain", "city": "Barcelona", "street": "Las Ramblas" } ]

Summary JSON Export JSON Import

JSON https://softuni.bg/courses/databases-advanced-hibernate © Software University Foundation – http://softuni.org This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike license.

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