{"id":95115,"date":"2019-08-19T10:00:57","date_gmt":"2019-08-19T07:00:57","guid":{"rendered":"https:\/\/www.javacodegeeks.com\/?p=95115"},"modified":"2019-08-14T13:38:43","modified_gmt":"2019-08-14T10:38:43","slug":"how-to-convert-a-java-object-into-a-json-string","status":"publish","type":"post","link":"https:\/\/www.javacodegeeks.com\/2019\/08\/how-to-convert-a-java-object-into-a-json-string.html","title":{"rendered":"How to Convert a Java Object into a JSON String"},"content":{"rendered":"
When learning how to write Java-based software, one of the first snags developers hit is how to connect their code with other software. This is usually where JSON comes in. While you might be a wizard with Java, JSON is another animal. Regardless, this blog post explains all you need to get the job done.<\/p>\n
What is a Java Object? <\/strong><\/h2>\n
A Java object is a combination of data and procedures that work on the available data<\/strong>.<\/p>\n
\n
<\/figure>\n<\/div>\n
Objects have both states<\/strong> and behaviors<\/strong>. In Java, an object is created using the keyword \u201cnew\u201d.<\/p>\n
Objects are created from templates known as classes. <\/p>\n
An object is an instance of a class.<\/strong><\/p>\n
For example, our \u201cCat object<\/strong>\u201d has:States<\/strong> \u2013 color, name, breed the state of an object is stored in fields (variables). Behavior<\/strong> \u2013 purring, eating, sleeping methods (functions) display the object\u2019s behavior.<\/p>\n
What is a JSON String?<\/strong><\/h2>\n
\n
JSON<\/strong> is an acronym for JavaScript Object Notation<\/strong>. <\/li>\n
JSON <\/strong>was designed as a data interchange format and has a syntax that is a subset of JavaScript.<\/li>\n
Context which is surrounded by quotes (single or double), loaded from a text file etc. are called JSON strings. e.g. {\u201cid\u201d:1,\u201dname\u201d:\u201dSiAm\u201d,\u201dcolor\u201d:\u201dCream\u201d,\u201deyecolor\u201d:\u201dBlue\u201d,\u201dbreed\u201d:\u201dSiamese\u201d}<\/li>\n
JSON is interoperable meaning that it\u2019s language\/platform independent. <\/li>\n
JSON format is used for serializing and transmitting structured data over a network connection. It is used primarily to transmit data between a server and mobile\/web application, serving as an alternative to XML. <\/li>\n<\/ul>\n
Common Uses for Converting Java Obj. to JSON String<\/strong><\/h2>\n
The example below demonstrates a client server scenario where the RESTful Web Service accepts data in XML\/JSON. <\/p>\n
\n
The RESTful web server app is designed using java: <\/li>\n
enduser doesn\u2019t understand the xml\/json but that\u2019s not an issue<\/li>\n
the enduser communicates with a mobile app which might be android<\/li>\n
the enduser communicates with a mobile app which might be php<\/li>\n
the mobile\/web app communicates with the RESTful web service via XML\/JSON<\/li>\n<\/ul>\n
\n
<\/figure>\n<\/div>\n
When would you want to convert from Java Obj to JSON string?<\/strong><\/h2>\n
In our example diagram above, our RESTful web service was designed using Java. <\/p>\n
\n
<\/figure>\n<\/div>\n
Since Java objects are only understood by Java applications we need to convert the java object to JSON when creating a web service for the android app. Let\u2019s say the mobile app is a hybrid app where the front end is handled by android view and the data transactions are sent through its own web services using JSON. In this instance we need to send\/receive requests from the android app to\/from our database using web services\/api using JSON data structure.<\/p>\n
\n
JSON is a simple string format data. JSON is readable format<\/strong>. It is very easy to read and infer information from it.<\/li>\n
JSON format is simple<\/strong> to use.<\/li>\n
JSON is quite light-weight<\/strong> compared to other formats like XML etc,.<\/li>\n
JSON format can be <\/strong>easily converted into Java objects<\/strong> in an Object oriented manner.<\/li>\n
JSON is interoperable:<\/strong> program and platform independent.<\/li>\n<\/ul>\n
Java Object to Json String: Tutorial<\/strong><\/h2>\n
Step by step examples of how to convert Java Object to JSON string<\/h3>\n
The most common way to convert Java Object to JSON string is to use an API<\/strong>. The most common APIs for this purpose are Jackson and GSON.<\/p>\n
JACKSON API example<\/strong><\/em><\/h3>\n
This example shows how to use JACKSON API to convert a Java Object into a JSON String.<\/strong><\/p>\n
We can use the ObjectMapper class<\/strong> provided by the Jackson API for our conversion.<\/p>\n
\n
writeValueAsString() is used to convert java obj to JSON<\/strong><\/li>\n
readValue() is used to convert JSON into java obj<\/li>\n
<\/li>\n<\/ul>\n
Step 1: Include the JACKSON JAR files into your classpath. <\/strong><\/h3>\n
When using MAVEN for dependency management (recommended) you can include the following dependency to download JAR files, any dependency for JACKSON and automatically include it in your project\u2019s classpath.<\/p>\n
Add the following dependency to the pom file:<\/p>\n
![\"\"](\"https:\/\/www.javacodegeeks.com\/wp-content\/uploads\/2019\/08\/color.png\")
<\/figure>\n<\/div>\n![\"\"](\"https:\/\/www.javacodegeeks.com\/wp-content\/uploads\/2019\/08\/diagram-768x367.png\")
<\/figure>\n<\/div>\n![\"\"](\"https:\/\/www.javacodegeeks.com\/wp-content\/uploads\/2019\/08\/json-java.png\")
<\/figure>\n<\/div>\n