MediaType Annotations and HttpStatus

MediaType Annotations and HttpStatus | Here we will discuss @RequestBody, @ResponseBody, and HttpStatus.

@RequestBody and @ResponseBody in Spring REST

• @ResponseBody:- It is a return type representing non-String. Here, and returns in JSON/XML format. The object will be converted to JSON/XML.
• @RequestBody:- It is a parameter (non-String). Here, JSON/XML is converted to an object.

Using @ResponseBody is optional because @RestController will take care of that. But @RequestBody annotation must be applied externally.

• @RequestBody should be used as the method parameter.
• It will read the HTTP Request Body (XML/JSON) and convert it to Object Format.
• Syntax:- @RequestBody ClassName objectName
• The end client/consumer must specify one header parameter:- 'Content-Type:__'
• To send data from consumer to producer GET request is not supported. (GET request never supports @RequestBody).

Example Application

Create a Spring starter project and add the following dependencies:- Lombok, Spring Web.

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Employee {
    private Integer eid;
    private String ename;
    private Double esal;
}

@RestController
@RequestMapping("/employee")
public class EmployeeRestController {

    @PostMapping("/read")
    public ResponseEntity<String> readEmp(@RequestBody Employee employee) {
        return ResponseEntity.ok(employee.toString());
    }
}

Start the application. API:- http://localhost:8080/employee/read

Example JSON:-

{
  "eid" : 10,
  "ename" : "ABC",
  "esal" : 300.2
}

It will create the following object:- Employee(eid=10, ename=ABC, esal=300.2)

Even { } in the request body is a valid JSON, that indicates objects created with default values:- Employee(eid=null, ename=null, esal=null)

In the postman, in the body change the type to XML and try to send the below data:-

<Employee>
  <eid>101</eid>
  <ename>ABC</ename>
  <esal>250.0</esal>
</Employee>

If we try to send XML Input using @RequestBody but the application is not supporting XML, then FrontController returns Http Status – 415 Unsupported MediaType. Response:-

{
    "timestamp": "2024-06-21T01:15:18.107+00:00",
    "status": 415,
    "error": "Unsupported Media Type",
    "trace": "org.springframework.web.HttpMediaTypeNotSupportedException: Content-Type 'application/xml;charset=UTF-8' is not supported...",
    "message": "Content-Type 'application/xml;charset=UTF-8' is not supported.",
    "path": "/employee/read"
}

Whereas If output XML (ResponseBody) is not supported then 406 – Not Acceptable.

To Enable XML support, Add XML Dependency in pom.xml file, and restart the application:-

<dependency>
  <groupId>com.fasterxml.jackson.dataformat</groupId>
  <artifactId>jackson-dataformat-xml</artifactId>
</dependency>

Different Combination

Accept	Return
JSON	JSON
XML	JSON
XML	XML
JSON	XML

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Employee {
    private Integer eid;
    private String ename;
    private Double esal;
    private Double hra;
    private Double ta;
}

@RestController
@RequestMapping("/employee")
public class EmployeeRestController {

    @PostMapping("/read")
    public ResponseEntity<Employee> readEmp(@RequestBody Employee employee) {
        var sal = employee.getEsal();
        var hra = sal * 10 / 100.0;
        var ta = sal * 6 / 100.0;

        employee.setHra(hra);
        employee.setTa(ta);

        return ResponseEntity.ok(employee);
    }
}

Sample XML Input:-

<Employee>
  <eid>101</eid>
  <ename>AA</ename>
  <esal>1000.0</esal>
</Employee>

Sample JSON Input:-

{
  "eid" : 999, 
  "ename" : "SYED", 
  "esal" : 500.0
}

Case#1:- Accept JSON and return JSON.
It is the default one. In body => raw => JSON.

Case#2:- Accept XML and return JSON.
In body => raw => XML. Send the XML data, it will return JSON data.

Case#3:- Accept XML and return XML.
In Headers mention KEY=Accept and VALUE=application/xml. In body => raw => XML.

Case#4:- Accept JSON and return XML.
In Headers mention KEY=Accept and VALUE=application/xml. In body => raw => JSON.

At a time only one type of input/output.

HttpStatus

• It indicates what is the final response status for a request.
• It is a global type i.e. every language can understand.
• It is the combination of Number and Code (message).
• For every request, one response is given.
• For every response, one status code is provided.
• These are categorized into 5 types.

Message	Code	Description	Sample Code
Information	1xx	Details about processing	100, 101, 102, …
Success	2xx	Processed Successfully	200, 201, 202, …
Redirect	3xx	Redirect Moved From one server/link to another server/link	300, 301, 302, …
Client Side Error	4xx	User Data Problem, Invalid Format	400, 401, 403, 404, …
Server Side Error	5xx	Issue in code. Exceptions like NullPointerException, SQLException	500, 501, 502, …

HttpStatus Success

• If the request is processed successfully (no exception/no error) then return Http Status 200 -OK
• For the current request something new data(Resource) is created at the server side – then Return Http Status 201-CREATED. (ex: Database Table#Row[inserted], one PDF is created..etc)
• For the Void type, the response recommended Status code is 204-No Content. For example, delete one record.
• Accepted Header Param is considered and expected data format is given back then return Http Status code – 202 Accepted.

Client Side Error

• 400 - BAD REQUEST:- Input Data Type mismatch or required params missing then HTTP Status code is 400 -BAD Request. Ex: int sid = __URL?sid=ABC
• 404 - Not Found:- If Entered URL, doesn’t match with any RestController method then FrontController returns 404-Not Found.
• 405 - Method Not Allowed:- If the code is GET type but the request is POST type then FrontController returns 405 – Method Not Allowed.
• 406 - Not Acceptable:- If we request using Accept= __ Header, Content-Type is not supported then FC returns 406 – Not Acceptable
• 415 - Unsupported Media Type:- If Request Body MediaType (Content-Type= _ ) is not supported then FrontController returns 415 – Unsupported Media Type
• 401 - Unauthorized (Security):- Try to access the URL without Login.
• 403- FORBIDDEN:- (Security) [invalid role access]. Logged in as Clerk, but trying to access Manager Services.

See more:- HTTP response status codes

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