book-microservices-v2/chapter03

Learn Microservices with Spring Boot (2nd edition) - Chapter 3

Learn Microservices with Spring Boot - Chapter 3

This repository contains the source code of the practical use case described in the book Learn Microservices with Spring Boot (2nd Edition).

The book follows a pragmatic approach to building a Microservice Architecture. You start with a small monolith and examine the pros and cons that come with a move to microservices.

Chapter 3 version

In Chapter 3, the goal is to build a Spring Boot application according to good practices:

• Domain-Driven Design. We analyze the boundaries of the Users and Challenges domains.
• 3-layer Application Design. This chapter focuses on two of the layers: Controller, and Service.
• Test-Driven Development. You write tests before building the functionalities.
• Monolith First. We keep two domains separate by using different root packages.

The next figure shows the status of the Multiplication application by the end of the Chapter, as it's also included in this repository.

There are two functional domains included in this first application: Users, and Challenges. See the figure below.

Running the app

Note: You need to use at least JDK version 14 to run this project.

To start the Spring Boot application, you can use the command line with the included Maven wrapper:

$ ./mvnw spring-boot:run

Questions

• Do you have questions about how to make this application work?
• Did you get the book and have questions about any concept explained within this chapter?
• Have you found issues using updated dependencies?

Don't hesitate to create an issue in this repository and post your question/problem there.

About the book

Are you interested in building a microservice architecture from scratch? You'll face all the challenges of designing and implementing a distributed system one by one, and will be able to evaluate if it's the best choice for your project.

Visit https://tpd.io/book-extra for all the details about the book.

Purchase

You can buy the book online from these stores:

• Apress
• Amazon
• and other online stores, check the IBAN (9781484261309) on google

Source code by chapter (all repositories are available on Github)

• Chapter 3. A professional 3-tier 3-layer Spring Boot app (this repo).
• Chapter 4. Building a basic frontend in React (backender-friendly)
• Chapter 5. The Data Layer Concepts and Spring Data JPA
• Chapter 6. Starting with Microservices - Synchronous
• Chapter 7. Event-Driven Architectures - Making our system asynchronous
• Chapter 8 (I). The Gateway Pattern in Microservice Architectures (Spring Cloud Gateway)
• Chapter 8 (II). Service Discovery and Load Balancing for Spring Boot Microservices (Consul / Spring Cloud Load Balancer)
• Chapter 8 (III). Centralized Configuration with Consul KV
• Chapter 8 (IV). Centralized Logs, Distributed Tracing, and Containerization with Docker (Buildpacks) and Docker Compose

Extra chapters:

• E.1. End-to-End Microservice tests with Cucumber
• U.2.4.0. Upgrade: Spring Boot 2.4.0, Cloud 2020.0, Java 15

chapter03's Issues

Running of test fails - Mockito cannot mock class

Unfortunately, I am stuck already at page 47 of the book. When running ./mvnw test I am getting this error log

`-------------------------------------------------------------------------------
Test set: microservices.book.multiplication.challenge.ChallengeGeneratorServiceTest

Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.037 s <<< FAILURE! - in microservices.book.multiplication.challenge.ChallengeGeneratorServiceTest
generateRandomFactorIsBetweenExpectedLimits Time elapsed: 0.036 s <<< ERROR!
org.mockito.exceptions.base.MockitoException:
Unable to initialize @SPY annotated field 'random'.

Mockito cannot mock this class: class java.util.Random.

Mockito can only mock non-private & non-final classes, but the root cause of this error might be different.
Please check the full stacktrace to understand what the issue is.
If you're still not sure why you're getting this error, please open an issue on GitHub.

Java : 17
JVM vendor name : Eclipse Adoptium
JVM vendor version : 17.0.5+8
JVM name : OpenJDK 64-Bit Server VM
JVM version : 17.0.5+8
JVM info : mixed mode
OS name : Linux
OS version : 5.15.0-56-generic

Underlying exception : java.lang.IllegalStateException: Cannot access annotation property public abstract boolean jdk.internal.util.random.RandomSupport$RandomGeneratorProperties.isStochastic()
Caused by: org.mockito.exceptions.base.MockitoException:

Mockito cannot mock this class: class java.util.Random.

Mockito can only mock non-private & non-final classes, but the root cause of this error might be different.
Please check the full stacktrace to understand what the issue is.
If you're still not sure why you're getting this error, please open an issue on GitHub.

Java : 17
JVM vendor name : Eclipse Adoptium
JVM vendor version : 17.0.5+8
JVM name : OpenJDK 64-Bit Server VM
JVM version : 17.0.5+8
JVM info : mixed mode
OS name : Linux
OS version : 5.15.0-56-generic

Underlying exception : java.lang.IllegalStateException: Cannot access annotation property public abstract boolean jdk.internal.util.random.RandomSupport$RandomGeneratorProperties.isStochastic()
Caused by: java.lang.IllegalStateException: Cannot access annotation property public abstract boolean jdk.internal.util.random.RandomSupport$RandomGeneratorProperties.isStochastic()
Caused by: java.lang.IllegalAccessException: class net.bytebuddy.description.annotation.AnnotationDescription$ForLoadedAnnotation cannot access interface jdk.internal.util.random.RandomSupport$RandomGeneratorProperties (in module java.base) because module java.base does not export jdk.internal.util.random to unnamed module @55a561cf

`
I am not able to solve the issue. Seems to be an incompatibility issue between the Java version and Mockito? Not sure, how to solve this.

Parameters selected in spring initializr:

Spring Boot 3.0.1
Java 17 (also tested with 19)

I saw some hints to add an explicit dependency for Mockito into pom.xml but this actually does not help as it is unclear which version fits to Java 17 or 19 (is there any version which fits?)

JUnit output in book incorrect?

Looking at listing 3-12 on page 47, it says it Actual is null, and Expected is factorA=20, factorB=30. I believe the Expected should be factorA=31, factorB=41. I actually downloaded the code just to debug the test to double check this. Am I correct or am I missing something?

Error while running ChallengeGeneratorServiceTest

Hi- Getting the following error while running the ChallengeGeneratorServiceTest .

org.mockito.exceptions.base.MockitoException: Unable to initialize @SPY annotated field 'random'.

Mockito cannot mock this class: class java.util.Random.

Mockito can only mock non-private & non-final classes.
If you're not sure why you're getting this error, please report to the mailing list.

Java : 18
JVM vendor name : Oracle Corporation
JVM vendor version : 18.0.1.1+2-6
JVM name : OpenJDK 64-Bit Server VM
JVM version : 18.0.1.1+2-6
JVM info : mixed mode, sharing
OS name : Windows 10
OS version : 10.0

Underlying exception : java.lang.IllegalStateException: Cannot access annotation property public abstract java.lang.String jdk.internal.util.random.RandomSupport$RandomGeneratorProperties.name()

at org.mockito.junit.jupiter.MockitoExtension.beforeEach(MockitoExtension.java:153)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeBeforeEachCallbacks$2(TestMethodTestDescriptor.java:163)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeBeforeMethodsOrCallbacksUntilExceptionOccurs$6(TestMethodTestDescriptor.java:199)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeBeforeMethodsOrCallbacksUntilExceptionOccurs(TestMethodTestDescriptor.java:199)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeBeforeEachCallbacks(TestMethodTestDescriptor.java:162)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:129)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:66)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:151)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:35)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:54)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:107)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:114)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:86)
at org.junit.platform.launcher.core.DefaultLauncherSession$DelegatingLauncher.execute(DefaultLauncherSession.java:86)
at org.junit.platform.launcher.core.SessionPerRequestLauncher.execute(SessionPerRequestLauncher.java:53)
at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:71)
at com.intellij.rt.junit.IdeaTestRunner$Repeater$1.execute(IdeaTestRunner.java:38)
at com.intellij.rt.execution.junit.TestsRepeater.repeat(TestsRepeater.java:11)
at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:35)
at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)
Suppressed: java.lang.NullPointerException: Cannot invoke "java.util.Set.forEach(java.util.function.Consumer)" because the return value of "org.junit.jupiter.api.extension.ExtensionContext$Store.remove(Object, java.lang.Class)" is null
	at org.mockito.junit.jupiter.MockitoExtension.afterEach(MockitoExtension.java:184)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeAfterEachCallbacks$12(TestMethodTestDescriptor.java:257)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeAllAfterMethodsOrCallbacks$13(TestMethodTestDescriptor.java:273)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeAllAfterMethodsOrCallbacks$14(TestMethodTestDescriptor.java:273)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeAllAfterMethodsOrCallbacks(TestMethodTestDescriptor.java:272)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeAfterEachCallbacks(TestMethodTestDescriptor.java:256)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:141)
	... 47 more

Caused by: org.mockito.exceptions.base.MockitoException:
Mockito cannot mock this class: class java.util.Random.

Mockito can only mock non-private & non-final classes.
If you're not sure why you're getting this error, please report to the mailing list.

Java : 18
JVM vendor name : Oracle Corporation
JVM vendor version : 18.0.1.1+2-6
JVM name : OpenJDK 64-Bit Server VM
JVM version : 18.0.1.1+2-6
JVM info : mixed mode, sharing
OS name : Windows 10
OS version : 10.0

Underlying exception : java.lang.IllegalStateException: Cannot access annotation property public abstract java.lang.String jdk.internal.util.random.RandomSupport$RandomGeneratorProperties.name()
... 54 more
Caused by: java.lang.IllegalStateException: Cannot access annotation property public abstract java.lang.String jdk.internal.util.random.RandomSupport$RandomGeneratorProperties.name()
at net.bytebuddy.description.annotation.AnnotationDescription$ForLoadedAnnotation.getValue(AnnotationDescription.java:824)
at net.bytebuddy.implementation.attribute.AnnotationAppender$Default.handle(AnnotationAppender.java:314)
at net.bytebuddy.implementation.attribute.AnnotationAppender$Default.doAppend(AnnotationAppender.java:377)
at net.bytebuddy.implementation.attribute.AnnotationAppender$Default.append(AnnotationAppender.java:354)
at net.bytebuddy.implementation.attribute.TypeAttributeAppender$ForInstrumentedType.apply(TypeAttributeAppender.java:93)
at net.bytebuddy.dynamic.scaffold.TypeWriter$Default$ForCreation.create(TypeWriter.java:5916)
at net.bytebuddy.dynamic.scaffold.TypeWriter$Default.make(TypeWriter.java:2213)
at net.bytebuddy.dynamic.scaffold.subclass.SubclassDynamicTypeBuilder.make(SubclassDynamicTypeBuilder.java:232)
at net.bytebuddy.dynamic.scaffold.subclass.SubclassDynamicTypeBuilder.make(SubclassDynamicTypeBuilder.java:204)
at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase.make(DynamicType.java:3668)
at org.mockito.internal.creation.bytebuddy.SubclassBytecodeGenerator.mockClass(SubclassBytecodeGenerator.java:288)
at org.mockito.internal.creation.bytebuddy.TypeCachingBytecodeGenerator.lambda$mockClass$0(TypeCachingBytecodeGenerator.java:47)
at net.bytebuddy.TypeCache.findOrInsert(TypeCache.java:168)
at net.bytebuddy.TypeCache$WithInlineExpunction.findOrInsert(TypeCache.java:399)
at net.bytebuddy.TypeCache.findOrInsert(TypeCache.java:190)
at net.bytebuddy.TypeCache$WithInlineExpunction.findOrInsert(TypeCache.java:410)
at org.mockito.internal.creation.bytebuddy.TypeCachingBytecodeGenerator.mockClass(TypeCachingBytecodeGenerator.java:40)
at org.mockito.internal.creation.bytebuddy.SubclassByteBuddyMockMaker.createMockType(SubclassByteBuddyMockMaker.java:77)
at org.mockito.internal.creation.bytebuddy.SubclassByteBuddyMockMaker.createMock(SubclassByteBuddyMockMaker.java:43)
at org.mockito.internal.creation.bytebuddy.ByteBuddyMockMaker.createMock(ByteBuddyMockMaker.java:42)
at org.mockito.internal.util.MockUtil.createMock(MockUtil.java:53)
at org.mockito.internal.MockitoCore.mock(MockitoCore.java:96)
at org.mockito.Mockito.mock(Mockito.java:1965)
at org.mockito.internal.configuration.SpyAnnotationEngine.spyNewInstance(SpyAnnotationEngine.java:130)
at org.mockito.internal.configuration.SpyAnnotationEngine.process(SpyAnnotationEngine.java:70)
at org.mockito.internal.configuration.InjectingAnnotationEngine.processIndependentAnnotations(InjectingAnnotationEngine.java:75)
at org.mockito.internal.configuration.InjectingAnnotationEngine.process(InjectingAnnotationEngine.java:47)
at org.mockito.MockitoAnnotations.openMocks(MockitoAnnotations.java:81)
at org.mockito.internal.framework.DefaultMockitoSession.(DefaultMockitoSession.java:43)
at org.mockito.internal.session.DefaultMockitoSessionBuilder.startMocking(DefaultMockitoSessionBuilder.java:83)
... 54 more
Caused by: java.lang.IllegalAccessException: class net.bytebuddy.description.annotation.AnnotationDescription$ForLoadedAnnotation cannot access interface jdk.internal.util.random.RandomSupport$RandomGeneratorProperties (in module java.base) because module java.base does not export jdk.internal.util.random to unnamed module @71c7db30
at java.base/jdk.internal.reflect.Reflection.newIllegalAccessException(Reflection.java:394)
at java.base/java.lang.reflect.AccessibleObject.checkAccess(AccessibleObject.java:674)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
at net.bytebuddy.description.annotation.AnnotationDescription$ForLoadedAnnotation.getValue(AnnotationDescription.java:803)
... 83 more

Process finished with exit code -1

The constructor Challenge(int, int) is undefined

When I am running the test, I am getting this error:

The constructor Challenge(int, int) is undefined

It is caused by this line of code inside ChallengeGeneratorServiceTest

then(challenge).isEqualTo(new Challenge(31, 41));

It is possible to solve the issue by explicitly adding a constructor which accepts two int values to the Challenge class:

`package microservices.book.multiplication.challenge;

import lombok.*;

/**

• This class represents a Challenge to solve a Multiplication (a * b).
  */
  @getter
  @tostring
  @EqualsAndHashCode
  @AllArgsConstructor
  public class Challenge {
  private int factorA;
  private int factorB;

  public Challenge(int i, int j) {
  this.factorA = i;
  this.factorB = j;
  }
  }`

However, as we use the @AllArgsConstructor of Lombock it should not be necessary to add this constructor. Am I missing something?

getCorrect?

chapter03/multiplication/src/test/java/microservices/book/multiplication/challenge/ChallengeServiceTest.java

Line 28 in ecf489e

then(resultAttempt.isCorrect()).isTrue();

should this be getCorrect instead of isCorrect?

book and code are different

chapter03/multiplication/src/main/java/microservices/book/multiplication/challenge/ChallengeAttempt.java

Line 15 in ecf489e

private User user;

chapter 3 in the book mention
Long userId
and code here is using
User user

javax.validation cannot be resolved

Dear Moisés,

I had an issue while importing

javax.validation.constraints.*

for the ChallengeAttemptDTO. I found that this solves the issue:

jakarta.validation.constraints.*

Is this already documented somewhere, I do not find anything related to this on your web page.

Many thanks and best regards,
Matthias

same as above

chapter03/multiplication/src/test/java/microservices/book/multiplication/challenge/ChallengeServiceTest.java

Line 42 in ecf489e

then(resultAttempt.isCorrect()).isFalse();

http://localhost:8080/challenges/random not found

Hey Moisés,

I finished the implementation of the controller but when running the application with mvnw spring-boot:run there is nothing found under http://localhost:8080/challenges/random. I only receive this error:

`This application has no explicit mapping for /error, so you are seeing this as a fallback.

Sun Jan 15 16:48:24 CET 2023
There was an unexpected error (type=Not Found, status=404).`

I do not see what could be the error in my code which causes the issue. Maybe you want to have a look into my coding on GitHub.

Thanks and best regards,
Matthias