Obtendo um usuário por id

src/main/java/com/miguelaugusto/workshopmongo/resources/UserResource.java

@@ -5,6 +5,7 @@
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
 import org.springframework.web.bind.annotation.RestController;
@@ -30,4 +31,11 @@ public ResponseEntity<List<UserDTO>> findAll(){
 		return ResponseEntity.ok().body(listDTO);
 	}
 
+	@RequestMapping(value = "/{id}", method=RequestMethod.GET)
+	public ResponseEntity<UserDTO> findById(@PathVariable String id){
+
+		User obj = service.findById(id);
+
+		return ResponseEntity.ok().body(new UserDTO(obj));
+	}
 }

src/main/java/com/miguelaugusto/workshopmongo/resources/exception/ResourceExceptionHandler.java

@@ -0,0 +1,24 @@
+package com.miguelaugusto.workshopmongo.resources.exception;
+
+import javax.servlet.http.HttpServletRequest;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.ControllerAdvice;
+import org.springframework.web.bind.annotation.ExceptionHandler;
+
+import com.miguelaugusto.workshopmongo.services.ObjectNotFoundException;
+
+@ControllerAdvice
+public class ResourceExceptionHandler {
+
+	@ExceptionHandler(ObjectNotFoundException.class)
+	public ResponseEntity<StandardError> objectNotFound(ObjectNotFoundException e, HttpServletRequest request){
+		HttpStatus status = HttpStatus.NOT_FOUND;
+		StandardError err = new StandardError(System.currentTimeMillis(), 
+				status.value(), "Não encontrado", e.getMessage(), 
+				request.getRequestURI());
+		return ResponseEntity.status(status).body(err);
+	}
+
+}

src/main/java/com/miguelaugusto/workshopmongo/resources/exception/StandardError.java

@@ -0,0 +1,59 @@
+package com.miguelaugusto.workshopmongo.resources.exception;
+
+import java.io.Serializable;
+
+public class StandardError implements Serializable{
+
+	private static final long serialVersionUID = 1L;
+	private Long timestamp;
+	private Integer status;
+	private String error;
+	private String message;
+	private String path;
+
+	public StandardError() {
+	}
+
+	public StandardError(Long timestamp, Integer status, String error, String message, String path) {
+		super();
+		this.timestamp = timestamp;
+		this.status = status;
+		this.error = error;
+		this.message = message;
+		this.path = path;
+	}
+
+	public Long getTimestamp() {
+		return timestamp;
+	}
+
+	public void setTimestamp(Long timestamp) {
+		this.timestamp = timestamp;
+	}
+
+	public Integer getStatus() {
+		return status;
+	}
+
+	public void setStatus(Integer status) {
+		this.status = status;
+	}
+
+	public String getError() {
+		return error;
+	}
+
+	public void setError(String error) {
+		this.error = error;
+	}
+
+	public String getPath() {
+		return path;
+	}
+
+	public void setPath(String path) {
+		this.path = path;
+	}
+
+
+}

src/main/java/com/miguelaugusto/workshopmongo/services/ObjectNotFoundException.java

@@ -0,0 +1,11 @@
+package com.miguelaugusto.workshopmongo.services;
+
+public class ObjectNotFoundException extends RuntimeException {
+
+	private static final long serialVersionUID = 1L;
+
+	public ObjectNotFoundException(String msg) {
+		super(msg);
+	}
+
+}

src/main/java/com/miguelaugusto/workshopmongo/services/UserService.java

@@ -1,6 +1,7 @@
 package com.miguelaugusto.workshopmongo.services;
 
 import java.util.List;
+import java.util.Optional;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Service;
@@ -17,4 +18,10 @@ public class UserService {
 	public List<User> findAll(){
 		return repo.findAll();
 	}
+
+	public User findById(String id) {
+
+		Optional<User> obj = repo.findById(id);
+		return obj.orElseThrow(() -> new ObjectNotFoundException("Não foi encontrado nenhum usuário com o id " + id));
+	}
 }