This tutorial shows how to convert a Java map to JSON string using Jackson’s data binding. In the previous tutorials, I explained converting Java Objects/Arrays to JSON String using Jackson API. You can refer to the below tutorials.
Serialization – How to create JSON Payload from Java Object – Jackson API
How to create JSON Array Payload using POJO – Jackson API
How to create Nested JSON Object using POJO – Jackson API
To start off, add the latest Jackson dataformat Maven dependency to the project.
<dependency>
<groupId>com.fasterxml.jackson.dataformat</groupId>
<artifactId>jackson-dataformat-xml</artifactId>
<version>2.13.0</version>
</dependency>
Sample JSON
{
"skillset" : [
"Java",
"Teradata",
"Python",
"Power BI"
],
"gender" : "female",
"DOB" : "12-02-1985",
"name" : "Vibha Singh",
"contactNumber" : "+919999988822",
"employeeId" : "10342256",
"location" : "Dublin",
"emailId" : "abc@test.com",
"salary" : "75000.0"
}
First, we will populate a Map, then convert them into JSON and later write that JSON to a file.
@Test
public void SerializationMapTest() {
ObjectMapper mapper = new ObjectMapper();
Map<String, Object> inputMap = new HashMap<String, Object>();
inputMap.put("employeeId", "10342256");
inputMap.put("name", "Vibha Singh");
inputMap.put("DOB", "12-02-1985");
inputMap.put("salary", "75000.0");
inputMap.put("location", "Dublin");
inputMap.put("contactNumber", "+919999988822");
inputMap.put("emailId", "abc@test.com");
inputMap.put("gender", "female");
List<String> skillset = new ArrayList<String>();
skillset.add("Java");
skillset.add("Teradata");
skillset.add("Python");
skillset.add("Power BI");
inputMap.put("skillset", skillset);
// Converting map to a JSON payload as string
try {
String employeePrettyJson = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(inputMap);
System.out.println(employeePrettyJson);
} catch (JsonProcessingException e) {
e.printStackTrace();
}
String userDir = System.getProperty("user.dir");
//Writing JSON on a file
try {
mapper.writerWithDefaultPrettyPrinter()
.writeValue(new File(userDir + "\\src\\test\\resources\\JSONFromMap.json"), inputMap);
} catch (IOException e) {
e.printStackTrace();
}
}
}
Output
As mentioned above, the new JSON is saved in a file and placed under src/test/resources.
Below is the file with JSON.
Congratulations, we are done. We have successfully created a JSON using HashMap.
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