Spring RestTemplate.getForEntity()
April 19, 2020
RestTemplate.getForEntity() method example. The getForEntity method retrieves resources from the given URI or URL templates. It returns response as ResponseEntity using which we can get response status code, response body etc. To fetch data on the basis of some key properties, we can send them as path variables. We need to use URI template and pass a Map or Object varargs to getForEntity method to expand it on URI template. Now let us discuss using getForEntity in our REST client application.
Contents
1. Technologies Used
Find the technologies being used in our example.1. Java 11
2. Spring 5.2.5.RELEASE
3. Spring Boot 2.2.6.RELEASE
4. Maven 3.5.2
2. Maven Dependencies
Find the Maven dependencies to run the example.<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency>
3. Using getForEntity()
Find thegetForEntity method declaration with URI + responseType from Spring doc.
ResponseEntity<T> getForEntity(URI url, Class<T> responseType)
responseType: Type of object returned by
getForEntity method.
Client code
URI uri = new URI("http://localhost:8080/employee");
RestTemplate restTemplate = new RestTemplate();
ResponseEntity<Employee[]> responseEntity = restTemplate.getForEntity(uri, Employee[].class);
@GetMapping("employee")
public ResponseEntity<List<Employee>> getAllEmployees() {
------
}
4. URI Variables as Object Varargs
Find thegetForEntity method declaration with url + responseType + uriVariables as Object Varargs from Spring doc.
ResponseEntity<T> getForEntity(String url, Class<T> responseType, Object... uriVariables)
responseType: Type of object returned by
getForEntity method.
uriVariables: URI variables as Object Varargs.
Client code
String url = "http://localhost:8080/employee/{id}";
Integer empId= 101;
ResponseEntity<Employee> responseEntity = restTemplate.getForEntity(url, Employee.class, empId);
@GetMapping("employee/{id}")
public ResponseEntity<Employee> getEmployeeById(@PathVariable("id") Integer empId) {
------
}
5. URI Variables as Map
Find thegetForEntity method declaration with url + responseType + uriVariables as Map from Spring doc.
ResponseEntity<T> getForEntity(String url, Class<T> responseType, Map<String,?> uriVariables)
Map.
Client code
String url = "http://localhost:8080/employee/{profile}/{tech}";
Map<String, String> map = new HashMap<>();
map.put("profile", "Developer");
map.put("tech", "Java");
ResponseEntity<Employee[]> responseEntity = restTemplate.getForEntity(url, Employee[].class, map);
Map. If we want to use object varargs in the above code, we can do it as following.
String profile = "Developer"; String tech = "Java"; ResponseEntity<Employee[]> responseEntity = restTemplate.getForEntity(url, Employee[].class, profile, tech);
@GetMapping("employee/{profile}/{tech}")
public ResponseEntity<List<Employee>> getEmployeesByProfileNTech(@PathVariable("profile") String profile,
@PathVariable("tech") String technology) {
------
}
6. Complete Example
Find the client code.RestClientUtil.java
package com.concretepage.client;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.HashMap;
import java.util.Map;
import org.springframework.http.ResponseEntity;
import org.springframework.web.client.RestTemplate;
import com.concretepage.domain.Employee;
public class RestClientUtil {
public void getEmployeeDemo1() throws URISyntaxException {
URI uri = new URI("http://localhost:8080/employee");
RestTemplate restTemplate = new RestTemplate();
ResponseEntity<Employee[]> responseEntity = restTemplate.getForEntity(uri, Employee[].class);
System.out.println("Status Code: " + responseEntity.getStatusCode());
for (Employee e : responseEntity.getBody()) {
System.out.println(e);
}
}
public void getEmployeeDemo2() {
String url = "http://localhost:8080/employee/{id}";
Integer empId= 101;
RestTemplate restTemplate = new RestTemplate();
ResponseEntity<Employee> responseEntity = restTemplate.getForEntity(url, Employee.class, empId);
System.out.println("Status Code: " + responseEntity.getStatusCode());
Employee emp = responseEntity.getBody();
System.out.println(emp);
}
public void getEmployeeDemo3() {
String url = "http://localhost:8080/employee/{profile}/{tech}";
Map<String, String> map = new HashMap<>();
map.put("profile", "Developer");
map.put("tech", "Java");
RestTemplate restTemplate = new RestTemplate();
ResponseEntity<Employee[]> responseEntity = restTemplate.getForEntity(url, Employee[].class, map);
System.out.println("Status Code: " + responseEntity.getStatusCode());
for (Employee e : responseEntity.getBody()) {
System.out.println(e);
}
}
public static void main(String args[]) throws URISyntaxException {
RestClientUtil util = new RestClientUtil();
util.getEmployeeDemo1();
util.getEmployeeDemo2();
util.getEmployeeDemo3();
}
}
Find the Server code.
EmployeeController.java
package com.concretepage.controller;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;
import com.concretepage.domain.Employee;
import com.concretepage.service.EmployeeService;
@RestController
public class EmployeeController {
@Autowired
private EmployeeService empService;
@GetMapping("employee")
public ResponseEntity<List<Employee>> getAllEmployees() {
List<Employee> list = empService.getAllEmployees();
return new ResponseEntity<List<Employee>>(list, HttpStatus.OK);
}
@GetMapping("employee/{id}")
public ResponseEntity<Employee> getEmployeeById(@PathVariable("id") Integer empId) {
Employee emp = empService.getEmployeeById(empId);
return new ResponseEntity<Employee>(emp, HttpStatus.OK);
}
@GetMapping("employee/{profile}/{tech}")
public ResponseEntity<List<Employee>> getEmployeesByProfileNTech(@PathVariable("profile") String profile,
@PathVariable("tech") String technology) {
List<Employee> list = empService.getEmployeesByProfileNTech(profile, technology);
return new ResponseEntity<List<Employee>>(list, HttpStatus.OK);
}
}
package com.concretepage.domain;
public class Employee {
private int empId;
private String name;
private String city;
public Employee() {}
public Employee(int empId, String name, String city) {
this.empId = empId;
this.name = name;
this.city = city;
}
//Setters and Getters
}
package com.concretepage.service;
import java.util.Arrays;
import java.util.List;
import org.springframework.stereotype.Service;
import com.concretepage.domain.Employee;
@Service
public class EmployeeService {
public Employee getEmployeeById(int empId) {
// Perform database operation
System.out.println("empId: " + empId);
return new Employee(101, "Lakshman", "Agra");
}
public List<Employee> getEmployeesByProfileNTech(String profile, String technology) {
// Perform database operation
System.out.println(profile);
System.out.println(technology);
Employee e1 = new Employee(101, "Lakshman", "Agra");
Employee e2 = new Employee(102, "Bharat", "Mathura");
return Arrays.asList(e1, e2);
}
public List<Employee> getAllEmployees() {
// Perform database operation
Employee e1 = new Employee(101, "Lakshman", "Agra");
Employee e2 = new Employee(102, "Bharat", "Mathura");
Employee e3 = new Employee(103, "Shatrughan", "Noida");
return Arrays.asList(e1, e2, e3);
}
}
getEmployeeDemo1() method of RestClientUtil class.
Status Code: 200 OK 101, Lakshman, Agra 102, Bharat, Mathura 103, Shatrughan, Noida
7. Run Application
Download the project and run the following command from root folder of the project using command prompt.mvn spring-boot:run
RestClientUtil as Java Application.
