added data validation and global exception handler

pom.xml

@@ -71,6 +71,12 @@
 			<artifactId>liquibase-maven-plugin</artifactId>
 			<version>4.23.1</version>
 		</dependency>
+		<dependency>
+			<groupId>org.hibernate.validator</groupId>
+			<artifactId>hibernate-validator</artifactId>
+			<version>8.0.1.Final</version>
+		</dependency>
+
 
 	</dependencies>
 

src/main/java/mate/academy/bookstore/controller/BookController.java

@@ -1,5 +1,6 @@
 package mate.academy.bookstore.controller;
 
+import jakarta.validation.Valid;
 import java.util.List;
 import lombok.RequiredArgsConstructor;
 import mate.academy.bookstore.dto.BookDto;
@@ -31,13 +32,13 @@ public BookDto getBookById(Long id) {
     }
 
     @PostMapping
-    public BookDto createBook(@RequestBody CreateBookRequestDto bookDto) {
+    public BookDto createBook(@RequestBody @Valid CreateBookRequestDto bookDto) {
         return bookService.save(bookDto);
     }
 
     @PutMapping("/{id}")
     public BookDto updateBook(@PathVariable Long id,
-                              @RequestBody CreateBookRequestDto requestDto) {
+                              @RequestBody @Valid CreateBookRequestDto requestDto) {
         return bookService.update(id, requestDto);
     }
 

src/main/java/mate/academy/bookstore/dto/CreateBookRequestDto.java

@@ -1,13 +1,20 @@
 package mate.academy.bookstore.dto;
 
+import jakarta.validation.constraints.Min;
+import jakarta.validation.constraints.NotNull;
 import java.math.BigDecimal;
 import lombok.Data;
 
 @Data
 public class CreateBookRequestDto {
+    @NotNull
     private String title;
+    @NotNull
     private String author;
+    @NotNull
     private String isbn;
+    @NotNull
+    @Min(0)
     private BigDecimal price;
     private String description;
     private String coverImage;

src/main/java/mate/academy/bookstore/exceptions/CustomGlobalExceptionHandler.java

@@ -0,0 +1,46 @@
+package mate.academy.bookstore.exceptions;
+
+import java.time.LocalDateTime;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.HttpStatusCode;
+import org.springframework.http.ResponseEntity;
+import org.springframework.validation.FieldError;
+import org.springframework.validation.ObjectError;
+import org.springframework.web.bind.MethodArgumentNotValidException;
+import org.springframework.web.bind.annotation.ControllerAdvice;
+import org.springframework.web.context.request.WebRequest;
+import org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler;
+
+@ControllerAdvice
+public class CustomGlobalExceptionHandler extends ResponseEntityExceptionHandler {
+
+    @Override
+    protected ResponseEntity<Object> handleMethodArgumentNotValid(
+            MethodArgumentNotValidException ex,
+            HttpHeaders headers,
+            HttpStatusCode status,
+            WebRequest request
+    ) {
+        Map<String, Object> body = new LinkedHashMap<>();
+        body.put("timestamp", LocalDateTime.now());
+        body.put("status", HttpStatus.BAD_REQUEST);
+        List<String> errors = ex.getBindingResult().getAllErrors().stream()
+                        .map(this::getErrorMessage)
+                        .toList();
+        body.put("errors", errors);
+        return super.handleMethodArgumentNotValid(ex, headers, status, request);
+    }
+
+    private String getErrorMessage(ObjectError e) {
+        if (e instanceof FieldError) {
+            String field = ((FieldError) e).getField();
+            String message = e.getDefaultMessage();
+            return field + " " + message;
+        }
+        return e.getDefaultMessage();
+    }
+}