adding controlleradvice for common exceptions

Author: mouaadaassou

README.md

@@ -17,3 +17,25 @@ HATEOAS.
 #### Content Negotiation:
 Content Negotiation is one of the most powerful features of HTTP: the same service may serve clients
 that accept different protocols.
+
+#### Little Bite of Servlet Container Terminology:
+In a typical Servlet Container implementation (Like Apache tomcat, ...) each http request is handled
+via a thread that is obtained from that Servlet Container's thread pool.
+
+Threads pool are necessary to control the amount of the threads that are being executed simultaneously.
+
+``` 
+In a regular basis, each thread consumes ~1MB of memory just to allocate a single thread stack, 
+so 1000 simultaneous requests could use ~1GB of memory only for the thread stacks. Therefore, 
+thread pool comes as a solution to limit the amount of threads being executed, fitting the application
+to a scenario where it doesn’t throw an OutOfMemoryError.
+```
+
+#### Error Handling:
+@ControllerAdvie is a special type of component that may introduce behavior (and respond to exceptions) for
+any number of controllers. They are natural place to stick centralized @ExceptionHandler handlers.
+
+
+### Useful Resources:
+* [Using Asynchronuous Calls With Spring MVC](https://adrianobrito.github.io/2018/01/11/using-callable-responses-in-spring-mvc/)
+<!-- * [the difference between Callable and WebAsyncTask in Spring MVC]() -->

pom.xml

@@ -37,6 +37,17 @@
       <artifactId>spring-data-rest-hal-browser</artifactId>
     </dependency>
 
+    <dependency>
+      <groupId>com.google.protobuf</groupId>
+      <artifactId>protobuf-java</artifactId>
+      <version>3.11.4</version>
+    </dependency>
+    <dependency>
+      <groupId>com.googlecode.protobuf-java-format</groupId>
+      <artifactId>protobuf-java-format</artifactId>
+      <version>1.4</version>
+    </dependency>
+
     <dependency>
       <groupId>org.springdoc</groupId>
       <artifactId>springdoc-openapi-ui</artifactId>

protos/customer.proto

@@ -0,0 +1,14 @@
+package io.nodom.cnj;
+
+option java_package = "io.nodom.cnj.customer.proto";
+
+message Customer {
+  optional int64 id = 1;
+  required string firstName = 2;
+  required string lastName = 3;
+}
+
+message Customers {
+  repeated Customer customer = 1;
+}
+

protos/gen.sh

@@ -0,0 +1,23 @@
+#!/bin/bash
+
+SRC_DIR='pwd'
+DST_DIR='pwd/../src/main/'
+
+function ensure_implementations() {
+  gem list | grep ruby-protocol-buffers || gem install ruby-protocol-buffers
+  go get -u github.com/golang/protobuf/{proto,protoc-gen-go}
+}
+
+function gen() {
+  D=$1
+  echo $D
+  OUT=$DST_DIR/$D
+  mkdir -p $OUT
+  protoc -I=$SRC_DIR --${D}_out=$OUT $SRC_DIR/customer.proto
+}
+
+ensure_implementations
+
+gen java
+gen python
+gen ruby

src/main/java/io/nodom/cnj/CloudNativeJavaRestApplication.java

@@ -2,7 +2,9 @@
 
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.web.servlet.config.annotation.EnableWebMvc;
 
+@EnableWebMvc
 @SpringBootApplication
 public class CloudNativeJavaRestApplication {
 

src/main/java/io/nodom/cnj/customer/controller/CustomerController.java

@@ -1,6 +1,7 @@
 package io.nodom.cnj.customer.controller;
 
 
+import io.nodom.cnj.customer.exception.CustomerNotFoundException;
 import io.nodom.cnj.customer.model.Customer;
 import io.nodom.cnj.customer.service.CustomerService;
 import java.net.URI;
@@ -46,7 +47,9 @@ public ResponseEntity<List<Customer>> getAllCustomer() {
   @GetMapping(value = "/{id}", produces = {MediaType.APPLICATION_JSON_VALUE,
       MediaType.APPLICATION_XML_VALUE})
   public ResponseEntity<Customer> getCustomerById(@PathVariable Long id) {
-    return ResponseEntity.ok(this.customerService.findCustomerById(id));
+    Customer customer = this.customerService.findCustomerById(id)
+        .orElseThrow(() -> new CustomerNotFoundException(id));
+    return ResponseEntity.ok(customer);
   }
 
   @PostMapping(produces = {MediaType.APPLICATION_JSON_VALUE, MediaType.APPLICATION_XML_VALUE})

src/main/java/io/nodom/cnj/customer/controller/CustomerControllerAdvice.java

@@ -0,0 +1,34 @@
+package io.nodom.cnj.customer.controller;
+
+import io.nodom.cnj.customer.exception.CustomerNotFoundException;
+import java.util.Optional;
+import org.springframework.hateoas.mediatype.vnderrors.VndErrors;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.ExceptionHandler;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.bind.annotation.RestControllerAdvice;
+
+
+@RequestMapping(produces = "application/vnd.error+json")
+@RestControllerAdvice(annotations = RestController.class)
+public class CustomerControllerAdvice {
+
+  @ExceptionHandler(CustomerNotFoundException.class)
+  ResponseEntity<VndErrors> notFoundException(CustomerNotFoundException ex) {
+    return this.error(ex, HttpStatus.NOT_FOUND, ex.getCustomerId());
+  }
+
+  @ExceptionHandler(IllegalArgumentException.class)
+  ResponseEntity<VndErrors> assertionException(IllegalArgumentException ex) {
+    return this.error(ex, HttpStatus.BAD_REQUEST, 0L);
+  }
+
+  private <E extends Exception> ResponseEntity<VndErrors> error(E error, HttpStatus httpSatatus,
+      Long logref) {
+    String msg = Optional.of(error.getMessage()).orElse(error.getClass().getSimpleName());
+    return new ResponseEntity<>(new VndErrors("CustomerId: ".concat(logref.toString()), msg), httpSatatus);
+  }
+
+}

src/main/java/io/nodom/cnj/customer/controller/CustomerProfilePhotoController.java

@@ -36,18 +36,30 @@ public ResponseEntity<Resource> getCustomerProfilePhoto(@PathVariable Long id) {
     return ResponseEntity.ok().contentType(MediaType.IMAGE_JPEG).body(customerPhoto);
   }
 
-  @RequestMapping(method = {RequestMethod.POST, RequestMethod.PUT}, consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
+  /**
+   * It could be an intensive IO Operation, for this reason, we decided to do it the non-blocking
+   * way, using Asynchronous Calls, note that is recommended to use only the heavy operation inside
+   * the callable lambda - {@link Callable}.
+   *
+   * @param id    of the customer's profile.
+   * @param photo to be uploaded.
+   * @return a response with the HTTP Status.
+   */
+  @RequestMapping(method = {RequestMethod.POST,
+      RequestMethod.PUT}, consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
   public Callable<ResponseEntity<?>> uploadImage(@PathVariable Long id,
       @RequestParam MultipartFile photo) {
     log.info(
-        String.format("====== upload start: /customer/%s/photo (%S bytes)", id, photo.getSize()));
+        String.format("====== upload start: /customer/%s/photo (%S bytes) ======", id,
+            photo.getSize()));
+    return () -> {
+      Long customerId = this.customerProfilePhotoService.uploadPhoto(id, photo);
 
-    Long customerId = this.customerProfilePhotoService.uploadPhoto(id, photo);
+      URI location = ServletUriComponentsBuilder.fromCurrentContextPath().path("{id}")
+          .buildAndExpand(customerId).toUri();
 
-    URI location = ServletUriComponentsBuilder.fromCurrentContextPath().path("{id}")
-        .buildAndExpand(customerId).toUri();
-
-    return () -> ResponseEntity.created(location).build();
+      return ResponseEntity.created(location).build();
+    };
   }
 
 }

src/main/java/io/nodom/cnj/customer/exception/CustomerNotFoundException.java

@@ -1,11 +1,15 @@
 package io.nodom.cnj.customer.exception;
 
+
+import lombok.Getter;
+
+@Getter
 public class CustomerNotFoundException extends RuntimeException {
 
-  private String message;
+  private final Long customerId;
 
-  public CustomerNotFoundException(String message) {
-    super(message);
-    this.message = message;
+  public CustomerNotFoundException(Long customerId) {
+    super("cannot find customer with id: " + customerId);
+    this.customerId = customerId;
   }
 }

src/main/java/io/nodom/cnj/customer/service/CustomerProfilePhotoService.java

@@ -33,7 +33,7 @@ public Resource readPhoto(Long customerId) {
           File file = new File(this.rootFile, Arrays.toString(this.encode(customer.getId())));
           return new FileSystemResource(file);
         }).orElseThrow(
-            () -> new CustomerNotFoundException("No Customer found with Id: " + customerId));
+            () -> new CustomerNotFoundException(customerId));
   }
 
   public Long uploadPhoto(Long customerId, MultipartFile photo) {
@@ -42,7 +42,7 @@ public Long uploadPhoto(Long customerId, MultipartFile photo) {
           this.writeBinaryDateByCustomer(photo, customer.getId());
           return customer.getId();
         }).orElseThrow(
-            () -> new CustomerNotFoundException("No Customer found with Id: " + customerId));
+            () -> new CustomerNotFoundException(customerId));
   }
 
   private void writeBinaryDateByCustomer(MultipartFile photo, Long customerId) {

src/main/java/io/nodom/cnj/customer/service/CustomerService.java

@@ -23,9 +23,8 @@ public List<Customer> findAllCustomers() {
     return this.customerRepository.findAll();
   }
 
-  public Customer findCustomerById(Long customerId) {
-    return this.customerRepository.findById(customerId)
-        .orElseThrow(() -> new CustomerNotFoundException("No Customer with Id: " + customerId));
+  public Optional<Customer> findCustomerById(Long customerId) {
+    return this.customerRepository.findById(customerId);
   }
 
   public Customer createCustomer(@Valid Customer customer) {
@@ -35,7 +34,7 @@ public Customer createCustomer(@Valid Customer customer) {
 
   public Customer deleteCustomerById(Long id) {
     Customer customer = this.customerRepository.findById(id)
-        .orElseThrow(() -> new CustomerNotFoundException("No Customer With Id" + id));
+        .orElseThrow(() -> new CustomerNotFoundException(id));
 
     this.customerRepository.delete(customer);
     return customer;
@@ -50,6 +49,6 @@ public Customer updateCustomer(Customer customer) {
           existingCustomer.setLastName(customer.getLastName());
           this.customerRepository.save(existingCustomer);
           return customer;
-        }).orElseThrow(() -> new CustomerNotFoundException("Customer Not Found"));
+        }).orElseThrow(() -> new CustomerNotFoundException(customer.getId()));
   }
 }

src/test/restClient.http

@@ -0,0 +1,3 @@
+GET localhost:8080/v1/customers/1
+
+###