Global Exception Handling support added

2023/03/31

src/main/java/com/nisum/bookstore/components/MyCustomErrorAttributes.java

+package com.nisum.bookstore.components;
+
+import org.springframework.boot.web.error.ErrorAttributeOptions;
+import org.springframework.boot.web.reactive.error.DefaultErrorAttributes;
+import org.springframework.stereotype.Component;
+import org.springframework.web.reactive.function.server.ServerRequest;
+
+import java.util.Map;
+
+@Component
+public class MyCustomErrorAttributes extends DefaultErrorAttributes {
+
+    @Override
+    public Map<String, Object> getErrorAttributes(ServerRequest request, ErrorAttributeOptions options) {
+        Map<String, Object> errorAttributes = super.getErrorAttributes(request, options);
+        errorAttributes.remove("error");
+        errorAttributes.put("cause", errorAttributes.get("message"));
+        errorAttributes.remove("message");
+        return errorAttributes;
+
+    }
+}

src/main/java/com/nisum/bookstore/config/ResourceWebPropertiesConfig.java

+package com.nisum.bookstore.config;
+
+import org.springframework.boot.autoconfigure.web.WebProperties;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+public class ResourceWebPropertiesConfig {
+    @Bean
+    public WebProperties.Resources resources() {
+        return new WebProperties.Resources();
+    }
+}

src/main/java/com/nisum/bookstore/controller/BookController.java

 package com.nisum.bookstore.controller;
 
 import com.nisum.bookstore.dto.BookDto;
+import com.nisum.bookstore.exceptions.BookNotFoundException;
 import com.nisum.bookstore.service.BookService;
 import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.http.HttpStatus;
 import org.springframework.web.bind.annotation.*;
+import org.springframework.web.server.ResponseStatusException;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
@@ -16,27 +19,35 @@ public class BookController {
 
     @GetMapping
     public Flux<BookDto> getBooks() {
-        return bookService.getBooks();
+        return bookService.getBooks().log();
+    }
+
+    @GetMapping("/dummy/{id}")
+    public Mono<BookDto> getBookDummyById( @PathVariable String id ) {
+        return bookService.getBookById( id ).log().switchIfEmpty(
+                Mono.just( new BookDto("1", "name", "author", "publications", "description") ) );
     }
 
     @GetMapping("/{id}")
     public Mono<BookDto> getBookById( @PathVariable String id ) {
-        return bookService.getBookById( id );
+        return bookService.getBookById( id ).log().switchIfEmpty(
+            BookNotFoundException.monoResponseBookNotFoundException( id )
+        );
     }
 
     @PostMapping
     public Mono<BookDto> addBook( @RequestBody BookDto bookDto ) {
-        return bookService.addBook( Mono.just(bookDto) );
+        return bookService.addBook( Mono.just(bookDto) ).log();
     }
 
     @PutMapping( "/{id}" )
     public Mono<BookDto> updateBook( @PathVariable String id, @RequestBody BookDto bookDto ) {
-        return bookService.updateBook( id, Mono.just(bookDto) );
+        return bookService.updateBook( id, Mono.just(bookDto) ).log();
     }
 
     @DeleteMapping( "/{id}" )
     public Mono<Void> deleteBook( @PathVariable String id ) {
-        return bookService.deleteBook( id );
+        return bookService.deleteBook( id ).log();
     }
 
 }

src/main/java/com/nisum/bookstore/exceptions/BookNotFoundException.java

+package com.nisum.bookstore.exceptions;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.web.server.ResponseStatusException;
+import reactor.core.publisher.Mono;
+
+public class BookNotFoundException {
+
+    public static <T> Mono<T> monoResponseBookNotFoundException( String id ) {
+        return Mono.error(new ResponseStatusException(HttpStatus.NOT_FOUND, "Book ["+ id + "] not found"));
+    }
+}

src/main/java/com/nisum/bookstore/exceptions/GlobalExceptionHandler.java

+package com.nisum.bookstore.exceptions;
+
+import com.nisum.bookstore.components.MyCustomErrorAttributes;
+import org.springframework.boot.autoconfigure.web.WebProperties;
+import org.springframework.boot.autoconfigure.web.reactive.error.AbstractErrorWebExceptionHandler;
+import org.springframework.boot.web.error.ErrorAttributeOptions;
+import org.springframework.boot.web.reactive.error.ErrorAttributes;
+import org.springframework.context.ApplicationContext;
+import org.springframework.core.annotation.Order;
+import org.springframework.http.MediaType;
+import org.springframework.http.codec.ServerCodecConfigurer;
+import org.springframework.stereotype.Component;
+import org.springframework.web.reactive.function.BodyInserters;
+import org.springframework.web.reactive.function.server.*;
+import reactor.core.publisher.Mono;
+
+import java.util.Map;
+import java.util.Optional;
+
+@Component
+@Order(-2)
+public class GlobalExceptionHandler extends AbstractErrorWebExceptionHandler {
+
+    ErrorAttributes errorAttributes = null;
+
+    public GlobalExceptionHandler(ErrorAttributes errorAttributes,
+                                  WebProperties.Resources resources,
+                                  ApplicationContext applicationContext,
+                                  ServerCodecConfigurer serverCodecConfigurer) {
+        super(errorAttributes, resources, applicationContext);
+        this.setMessageWriters( serverCodecConfigurer.getWriters() );
+        this.errorAttributes = errorAttributes;
+    }
+
+    @Override
+    protected RouterFunction<ServerResponse> getRoutingFunction(ErrorAttributes errorAttributes) {
+        return RouterFunctions.route(RequestPredicates.all(), this::formatErrorResponse);
+    }
+
+    private Mono<ServerResponse> formatErrorResponse( ServerRequest serverRequest ) {
+        Map<String, Object> errorAttributesMap = getErrorAttributes(serverRequest,
+                ErrorAttributeOptions.defaults()
+                .including(ErrorAttributeOptions.Include.MESSAGE)
+                .including(ErrorAttributeOptions.Include.BINDING_ERRORS) );
+
+        int status = (int) Optional.ofNullable(errorAttributesMap.get("status")).orElse(500);
+
+        return ServerResponse
+                .status(status)
+                .contentType(MediaType.APPLICATION_JSON)
+                .body(BodyInserters.fromValue(errorAttributesMap));
+    }
+
+}

src/main/java/com/nisum/bookstore/service/impl/BookServiceImpl.java

@@ -23,7 +23,7 @@ public class BookServiceImpl implements BookService {
 
     @Override
     public Mono<BookDto> getBookById(String id) {
-        return bookRepo.findById(id).map( book -> AppUtils.entityToDto(book) );
+        return bookRepo.findById(id).map( book -> AppUtils.entityToDto(book) ).switchIfEmpty(Mono.empty());
     }
 
     @Override