Mocking is an essential part of unit testing, and the Mockito library makes it easy to write clean and intuitive unit tests for your Java code.
Get started with mocking and improve your application tests using our Mockito guide:
Handling concurrency in an application can be a tricky process with many potential pitfalls. A solid grasp of the fundamentals will go a long way to help minimize these issues.
Get started with understanding multi-threaded applications with our Java Concurrency guide:
Spring 5 added support for reactive programming with the Spring WebFlux module, which has been improved upon ever since. Get started with the Reactor project basics and reactive programming in Spring Boot:
Since its introduction in Java 8, the Stream API has become a staple of Java development. The basic operations like iterating, filtering, mapping sequences of elements are deceptively simple to use.
But these can also be overused and fall into some common pitfalls.
To get a better understanding on how Streams work and how to combine them with other language features, check out our guide to Java Streams:
Explore Spring Boot 3 and Spring 6 in-depth through building a full REST API with the framework:
Yes, Spring Security can be complex, from the more advanced functionality within the Core to the deep OAuth support in the framework.
I built the security material as two full courses - Core and OAuth, to get practical with these more complex scenarios. We explore when and how to use each feature and code through it on the backing project.
You can explore the course here:
Spring Data JPA is a great way to handle the complexity of JPA with the powerful simplicity of Spring Boot.
Get started with Spring Data JPA through the guided reference course:
Refactor Java code safely — and automatically — with OpenRewrite.
Refactoring big codebases by hand is slow, risky, and easy to put off. That’s where OpenRewrite comes in. The open-source framework for large-scale, automated code transformations helps teams modernize safely and consistently.
Each month, the creators and maintainers of OpenRewrite at Moderne run live, hands-on training sessions — one for newcomers and one for experienced users. You’ll see how recipes work, how to apply them across projects, and how to modernize code with confidence.
Join the next session, bring your questions, and learn how to automate the kind of work that usually eats your sprint time.
Distributed systems often come with complex challenges such as service-to-service communication, state management, asynchronous messaging, security, and more.
Dapr (Distributed Application Runtime) provides a set of APIs and building blocks to address these challenges, abstracting away infrastructure so we can focus on business logic.
In this tutorial, we'll focus on Dapr's pub/sub API for message brokering. Using its Spring Boot integration, we'll simplify the creation of a loosely coupled, portable, and easily testable pub/sub messaging system:
1. Overview
In this short tutorial, we’re going to introduce the keytool command. We’ll learn how to use keytool to create a new certificate and check the information for that certificate.
2. What Is keytool?
Java includes the keytool utility in its releases. We use it to manage keys and certificates and store them in a keystore. The keytool command allows us to create self-signed certificates and show information about the keystore.
In the following sections, we’re going to go through different functionalities of this utility.
3. Creating a Self-Signed Certificate
First of all, let’s create a self-signed certificate that could be used to establish secure communication between projects in our development environment, for example.
In order to generate the certificate, we’re going to open a command-line prompt and use keytool command with the -genkeypair option:
keytool -genkeypair -alias <alias> -keypass <keypass> -validity <validity> -storepass <storepass>Let’s learn more about each of these parameters:
- alias – the name for our certificate
- keypass – the password of the certificate. We’ll need this password to have access to the private key of our certificate
- validity – the time (in days) of the validity of our certificate
- storepass – the password for the keystore. This will be the password of the keystore if the store doesn’t exist
For example, let’s generate a certificate named “cert1” that has a private key of “pass123” and is valid for one year. We’ll also specify “stpass123” as the keystore password:
keytool -genkeypair -alias cert1 -keypass pass123 -validity 365 -storepass stpass123After executing the command, it’ll ask for some information that we’ll need to provide:
What is your first and last name?
[Unknown]: Name
What is the name of your organizational unit?
[Unknown]: Unit
What is the name of your organization?
[Unknown]: Company
What is the name of your City or Locality?
[Unknown]: City
What is the name of your State or Province?
[Unknown]: State
What is the two-letter country code for this unit?
[Unknown]: US
Is CN=Name, OU=Unit, O=Company, L=City, ST=State, C=US correct?
[no]: yesAs mentioned, if we haven’t created the keystore before, creating this certificate will create it automatically.
We could also execute the -genkeypair option without parameters. If we don’t provide them in the command line and they’re mandatory, we’ll be prompted for them.
Note that it’s generally advised not to provide the passwords (-keypass or -storepass) on the command line in production environments.
4. Listing Certificates in the Keystore
Next, we’re going to learn how to view the certificates that are stored in our keystore. For this purpose, we’ll use the -list option:
keytool -list -storepass <storepass> The output for the executed command will show the certificate that we’ve created:
Keystore type: JKS
Keystore provider: SUN
Your keystore contains 1 entry
cert1, 02-ago-2020, PrivateKeyEntry,
Certificate fingerprint (SHA1): 0B:3F:98:2E:A4:F7:33:6E:C4:2E:29:72:A7:17:E0:F5:22:45:08:2FIf we want to get the information for a concrete certificate, we just need to include the -alias option to our command. To get further information than provided by default, we’ll also add the -v (verbose) option:
keytool -list -v -alias <alias> -storepass <storepass> This will provide us all the information related to the requested certificate:
Alias name: cert1
Creation date: 02-ago-2020
Entry type: PrivateKeyEntry
Certificate chain length: 1
Certificate[1]:
Owner: CN=Name, OU=Unit, O=Company, L=City, ST=State, C=US
Issuer: CN=Name, OU=Unit, O=Company, L=City, ST=State, C=US
Serial number: 11d34890
Valid from: Sun Aug 02 20:25:14 CEST 2020 until: Mon Aug 02 20:25:14 CEST 2021
Certificate fingerprints:
MD5: 16:F8:9B:DF:2C:2F:31:F0:85:9C:70:C3:56:66:59:46
SHA1: 0B:3F:98:2E:A4:F7:33:6E:C4:2E:29:72:A7:17:E0:F5:22:45:08:2F
SHA256: 8C:B0:39:9F:A4:43:E2:D1:57:4A:6A:97:E9:B1:51:38:82:0F:07:F6:9E:CE:A9:AB:2E:92:52:7A:7E:98:2D:CA
Signature algorithm name: SHA256withDSA
Subject Public Key Algorithm: 2048-bit DSA key
Version: 3
Extensions:
#1: ObjectId: 2.5.29.14 Criticality=false
SubjectKeyIdentifier [
KeyIdentifier [
0000: A1 3E DD 9A FB C0 9F 5D B5 BE 2E EC E2 87 CD 45 .>.....].......E
0010: FE 0B D7 55 ...U
]
]5. Other Features
Apart from the functionalities that we’ve already seen, there are many additional features available in this tool.
For example, we can delete the certificate we created from the keystore:
keytool -delete -alias <alias> -storepass <storepass>Another example is that we will even be able to change the alias of a certificate:
keytool -changealias -alias <alias> -destalias <new_alias> -keypass <keypass> -storepass <storepass>Finally, to get more information about the tool, we can ask for help through the command line:
keytool -help6. Conclusion
In this quick tutorial, we’ve learned a bit about the keytool utility. We’ve also learned to use some basic features included in this tool.
