Spring RestTemplate – Spring REST Client Example

After learning to build Spring REST API for XML representation and JSON representation, let’s build Spring REST client to consume APIs which we have written in linked examples.

Accessing a third-party REST service inside a Spring application revolves around the use of the Spring RestTemplate class. The RestTemplate class is designed on the same principles as the many other Spring *Template classes (e.g., JdbcTemplate, JmsTemplate ), providing a simplified approach with default behaviors for performing complex tasks.

Given that the RestTemplate class is designed to call REST services, It should come as no surprise that its main methods are closely tied to REST’s underpinnings, which are the HTTP protocol’s methods: HEAD, GET, POST, PUT, DELETE, and OPTIONS. For example, RestTemplate class has methods headForHeaders(), getForObject(), postForObject(), put() and delete() etc.

Read More and Source Code : Spring REST Example – JSON

Read More: RestTemplate Java Configuration with HttpClient

1. Spring RestTemplate – HTTP GET Method Example

1.1. XML Response

REST API Code

Spring REST API for HTTP GET method.

@RequestMapping(value = "/employees", produces = MediaType.APPLICATION_XML_VALUE, method = RequestMethod.GET)
public String getAllEmployeesXML(Model model) 
{
	model.addAttribute("employees", getEmployeesCollection());
	return "xmlTemplate";
}

REST Client Code

Spring REST client using RestTemplate to access HTTP GET api requests.

private static void getEmployees()
{
	final String uri = "http://localhost:8080/springrestexample/employees.xml";
	
	RestTemplate restTemplate = new RestTemplate();
	String result = restTemplate.getForObject(uri, String.class);
	
	System.out.println(result);
}

1.2. JSON Response

REST API Code

@RequestMapping(value = "/employees", produces = MediaType.APPLICATION_JSON_VALUE,  method = RequestMethod.GET)
public String getAllEmployeesJSON(Model model) 
{
	model.addAttribute("employees", getEmployeesCollection());
	return "jsonTemplate";
}

REST Client Code

private static void getEmployees()
{
	final String uri = "http://localhost:8080/springrestexample/employees.json";
	
	RestTemplate restTemplate = new RestTemplate();
	String result = restTemplate.getForObject(uri, String.class);
	
	System.out.println(result);
}

1.3. Custom HTTP Headers with RestTemplate

REST API Code

@RequestMapping(value = "/employees", produces = MediaType.APPLICATION_JSON_VALUE,  method = RequestMethod.GET)
public String getAllEmployeesJSON(Model model) 
{
	model.addAttribute("employees", getEmployeesCollection());
	return "jsonTemplate";
}

REST Client Code

private static void getEmployees()
{
	final String uri = "http://localhost:8080/springrestexample/employees";
	
	RestTemplate restTemplate = new RestTemplate();
	
	HttpHeaders headers = new HttpHeaders();
	headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
	HttpEntity<String> entity = new HttpEntity<String>("parameters", headers);
	
	ResponseEntity<String> result = restTemplate.exchange(uri, HttpMethod.GET, entity, String.class);
	
	System.out.println(result);
}

1.4. Get response as object

REST API Code

@RequestMapping(value = "/employees", produces = MediaType.APPLICATION_XML_VALUE, method = RequestMethod.GET)
public String getAllEmployeesXML(Model model) 
{
	model.addAttribute("employees", getEmployeesCollection());
	return "xmlTemplate";
}

REST Client Code

private static void getEmployees()
{
	final String uri = "http://localhost:8080/springrestexample/employees";
	RestTemplate restTemplate = new RestTemplate();
	
	EmployeeListVO result = restTemplate.getForObject(uri, EmployeeListVO.class);
	
	System.out.println(result);
}

1.5. URL Parameters

REST API Code

@RequestMapping(value = "/employees/{id}")
public ResponseEntity<EmployeeVO> getEmployeeById (@PathVariable("id") int id) 
{
	if (id <= 3) {
		EmployeeVO employee = new EmployeeVO(1,"Lokesh","Gupta","howtodoinjava@gmail.com");
		return new ResponseEntity<EmployeeVO>(employee, HttpStatus.OK);
	}
	return new ResponseEntity(HttpStatus.NOT_FOUND);
}

REST Client Code

private static void getEmployeeById()
{
	final String uri = "http://localhost:8080/springrestexample/employees/{id}";
	
	Map<String, String> params = new HashMap<String, String>();
	params.put("id", "1");
	
	RestTemplate restTemplate = new RestTemplate();
	EmployeeVO result = restTemplate.getForObject(uri, EmployeeVO.class, params);
	
	System.out.println(result);
}

2. Spring RestTemplate – HTTP POST Method Example

REST API Code

Spring REST API for HTTP POST method.

@RequestMapping(value = "/employees", method = RequestMethod.POST)
public ResponseEntity<String> createEmployee(@RequestBody EmployeeVO employee) 
{
	System.out.println(employee);
	return new ResponseEntity(HttpStatus.CREATED);
}

REST Client Code

Spring REST client using RestTemplate to access HTTP POST api requests.

private static void createEmployee()
{
	final String uri = "http://localhost:8080/springrestexample/employees";

	EmployeeVO newEmployee = new EmployeeVO(-1, "Adam", "Gilly", "test@email.com");

	RestTemplate restTemplate = new RestTemplate();
	EmployeeVO result = restTemplate.postForObject( uri, newEmployee, EmployeeVO.class);

	System.out.println(result);
}

3. Spring RestTemplate – HTTP PUT Method Example

REST API Code

Spring REST API for HTTP PUT method.

@RequestMapping(value = "/employees/{id}", method = RequestMethod.PUT)
public ResponseEntity<EmployeeVO> updateEmployee(@PathVariable("id") int id, @RequestBody EmployeeVO employee) 
{
	System.out.println(id);
	System.out.println(employee);
	return new ResponseEntity<EmployeeVO>(employee, HttpStatus.OK);
}

REST Client Code

Spring REST client using RestTemplate to access HTTP PUT api requests.

private static void updateEmployee()
{
	final String uri = "http://localhost:8080/springrestexample/employees/{id}";
	
	Map<String, String> params = new HashMap<String, String>();
	params.put("id", "2");
	
	EmployeeVO updatedEmployee = new EmployeeVO(2, "New Name", "Gilly", "test@email.com");
	
	RestTemplate restTemplate = new RestTemplate();
	restTemplate.put ( uri, updatedEmployee, params);
}

4. Spring RestTemplate – HTTP DELETE Method Example

REST API Code

Spring REST API for HTTP DELETE method.

@RequestMapping(value = "/employees/{id}", method = RequestMethod.DELETE)
public ResponseEntity<String> updateEmployee(@PathVariable("id") int id) 
{
	System.out.println(id);
	return new ResponseEntity(HttpStatus.OK);
}

REST Client Code

Spring REST client using RestTemplate to access HTTP DELETE api requests.

private static void deleteEmployee()
{
	final String uri = "http://localhost:8080/springrestexample/employees/{id}";
	
	Map<String, String> params = new HashMap<String, String>();
	params.put("id", "2");
	
	RestTemplate restTemplate = new RestTemplate();
	restTemplate.delete ( uri,  params );
}

Feel free to copy and modify above Spring RestTemplate examples for building the Spring REST client in your MVC application

5. More RestTemplate Examples

Spring RestTemplate basic authentication example
Spring RestTemplate timeout configuration example
Spring RestTemplateBuilder Example
Spring RestTemplate – HttpClient configuration example
Spring Boot RestTemplate GET Example
Spring Boot RestTemplate POST Example
Spring boot JUnit example with RestTemplate
Spring boot TestRestTemplate POST with headers example
Spring ClientHttpRequestInterceptor with RestTemplate

Happy Learning !!