Spring boot: RestEntity: Enhancing rest application

In my previous post, I explained simple REST application. You can download previous working application from this link.

Areas of improvement

a.   We are not done any validations while performing CRUD operations on Employee. For example, we should return not found response code when employee not exist, we should return internal server error in exceptional cases and we should return status code 201 for new object creation.

How can we improve previous application?

We can user ResponseEntity object, to send the response properly. ResponseEntity class is used to set the response body, status code and headers.

For example, below snippet return collection of employee as ResponseEntity.

@RequestMapping(value = "employees", method = RequestMethod.GET)

public ResponseEntity<Collection<Employee>> all() {

    return ResponseEntity.ok(EmployeeUtil.all());

}

You can even set different status code for different scenarios. For example, below snippet return 404 status code if employee not found.

@RequestMapping(value = "employees/{id}", method = RequestMethod.GET)

public ResponseEntity<Employee> byId(@PathVariable int id) {

    Employee emp = EmployeeUtil.byId(id);

    if (emp == null) {

        return new ResponseEntity<>(HttpStatus.NOT_FOUND);

    }

    return ResponseEntity.ok(emp);

}

You can even set response header using below constructor.

ResponseEntity(@Nullable T body, @Nullable MultiValueMap<String, String> headers, HttpStatus status)

Use ok method to send the response payload with status code 200.

ResponseEntity.ok(emp);

Update EmployeeController of previous application like below.

EmployeeController.java

package com.sample.app.controller;

import java.util.Collection;

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import com.sample.app.model.Employee;
import com.sample.app.util.EmployeeUtil;

@RestController
@RequestMapping("api/v1/")
public class EmployeeController {

    @RequestMapping(value = "employees", method = RequestMethod.GET)
    public ResponseEntity<Collection<Employee>> all() {
        return ResponseEntity.ok(EmployeeUtil.all());
    }

    @RequestMapping(value = "employees", method = RequestMethod.POST)
    public ResponseEntity<Employee> create(@RequestBody Employee emp) {
        return new ResponseEntity<>(EmployeeUtil.create(emp), HttpStatus.CREATED);

    }

    @RequestMapping(value = "employees/{id}", method = RequestMethod.GET)
    public ResponseEntity<Employee> byId(@PathVariable int id) {
        Employee emp = EmployeeUtil.byId(id);

        if (emp == null) {
            return new ResponseEntity<>(HttpStatus.NOT_FOUND);
        }

        return ResponseEntity.ok(emp);

    }

    @RequestMapping(value = "employees/{id}", method = RequestMethod.DELETE)
    public ResponseEntity<Employee> deleteById(@PathVariable int id) {
        Employee emp = EmployeeUtil.byId(id);

        if (emp == null) {
            return new ResponseEntity<>(HttpStatus.NOT_FOUND);
        }

        return ResponseEntity.ok(EmployeeUtil.delete(id));
    }

    @RequestMapping(value = "employees/{id}", method = RequestMethod.PUT)
    public ResponseEntity<Employee> updateById(@PathVariable int id, @RequestBody Employee emp) {

        Employee currentEmp = EmployeeUtil.byId(id);

        if (currentEmp == null) {
            return new ResponseEntity<>(HttpStatus.NOT_FOUND);
        }

        return ResponseEntity.ok(EmployeeUtil.updateById(id, emp));
    }

}

Run App.java.

Request for non-exist employee

As you see above image, when I request for non-exist employee, I got response status code as 404.

Create new employee

As you see above image, when I create new employee, I got response status code as 201.

You can download complete working example from this link.

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