get user with id

src/main/java/restful/app/resources/UserResource.java

@@ -6,6 +6,7 @@
 
 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;
@@ -27,4 +28,10 @@ public ResponseEntity<List<UserDTO>> findAll(){
         List<UserDTO> listDto = list.stream().map(x -> new UserDTO(x)).collect(Collectors.toList());
         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/restful/app/resources/exception/ResourceExceptionHandler.java

@@ -0,0 +1,21 @@
+package restful.app.resources.exception;
+
+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 jakarta.servlet.http.HttpServletRequest;
+import restful.app.services.exception.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(), "Not found", e.getMessage(), request.getRequestURI());
+        return ResponseEntity.status(status).body(err);
+    }
+}

src/main/java/restful/app/resources/exception/StandardError.java

@@ -0,0 +1,64 @@
+package restful.app.resources.exception;
+
+import java.io.Serializable;
+
+public class StandardError implements Serializable{
+    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) {
+        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 getMessage() {
+        return message;
+    }
+
+    public void setMessage(String message) {
+        this.message = message;
+    }
+
+    public String getPath() {
+        return path;
+    }
+
+    public void setPath(String path) {
+        this.path = path;
+    }
+
+
+}

src/main/java/restful/app/services/UserService.java

@@ -1,12 +1,14 @@
 package restful.app.services;
 
 import java.util.List;
+import java.util.Optional;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Service;
 
 import restful.app.domain.User;
 import restful.app.repository.UserRepository;
+import restful.app.services.exception.ObjectNotFoundException;
 
 @Service
 public class UserService {
@@ -16,4 +18,9 @@ public class UserService {
     public List<User> findAll(){
         return repository.findAll();
     }
+
+    public User findById(String id){
+        Optional<User> obj = repository.findById(id);
+        return obj.orElseThrow(() -> new ObjectNotFoundException("Object not found!"));
+    }
 }

src/main/java/restful/app/services/exception/ObjectNotFoundException.java

@@ -0,0 +1,8 @@
+package restful.app.services.exception;
+
+public class ObjectNotFoundException extends RuntimeException{
+
+    public ObjectNotFoundException(String msg){
+        super(msg);
+    }
+}