Speaking Java

I have used Keycloak  in its very early stage ( when it is was in 2.x version). But now it has come a long way (at this time of writing it is in 21.x) In this article let's configure Keycloak behind Nginx. Here are the points to consider.  If you want to configure Apache2 as a proxy server for your java application, please check  this article . We are going to use a domain name other than localhost Anything other than localhost will require Keycloak to run in production mode which requires SSL configurations etc. Or it requires a proxy server. Lets begin. Requirements Keycloak distribution Ubuntu 22.04 server Configuring Keycloak 1. Download Keycloak from here . 2. Extract it using tar -xvzf  keycloak-21.0.1.tar.gz 3. Create a script file called keycloak.sh with the following contents #!/bin/bash export KEYCLOAK_ADMIN=<admin-username-here> export KEYCLOAK_ADMIN_PASSWORD=<admin-password-here> nohup keycloak-21.0.0/bin/kc.sh start-dev --proxy edge --hos...

Sometimes if prebuilt binaries of electron are not available for your platform or if you want to modify the electron source to customize to your need, you are at the right place. I had a requirement to have a <webview> tag inside another <webview> tag. Seems it is not supported out of the box. As per the suggestion provided in the above link, I thought I could modify a couple of lines and see if it works. Coincidentally I am running Kubuntu arm64 build on M1 mac via parallels. So I wanted a aarch64 (a.k.a arm64 ) build. So I provisioned a  t4g.medium (2vCPU , 4 GB RAM)   with Ubuntu 22.04 LTS.   I tried checking out the code as mentioned below. But within 30 mins I ran out of CPU credits and had to switch to   r6g.large (2vCPU , 16 GB RAM) . Code was checked out pretty fast (fast for 50GB of code). Yes you will need at least 60GB of disk. Ok, lets go through the steps for checking out and compiling. Step-1: Prepare the build environment su...

If you are one among those who like Groovy for its simplicity and tight integration with Java (and not for its dynamic capabilities) and wondered how to write Groovy code in a Quarkus application and compile it to native using GraalVM? I have you covered. You dont have to look anywhere else. Scope groovy code as part of quarkus application statically compilable groovy code with no dynamic feature compile the final application to native code using graalvm Code example can be found here . Steps Create a quarkus application as outlined here Add your groovy class under src/main/java Annotate your groovy class with @groovy.transform. CompileStatic create a file called application.properies under src/main/resources folder with the following content. quarkus.native.additional-build-args=\ --allow-incomplete-classpath, \ --report-unsupported-elements-at-runtime, \ --initialize-at-build-time, \ --initialize-at-run-time=org.codehaus.groovy.control.XStreamUtils\\,groov...

Have you ever come across a situation where you wanted to retry a method invocation automatically? Let's say you are calling a stock ticker service for a given stock and get a transient error. Since it is a transient error, you will try again and it may work in second attempt. But what if it doesn't? Well, you will try third time. But how many times can you try like that? More importantly after how much time will you retry? Imagine if you have a handful of methods like this. Your code will become convoluted with retry logic. Is there a better way? Well, if you are using spring/spring boot, you are in luck. Here is how you can do that using spring. Let's write our business service as follows. import java.time.LocalDateTime; import java.util.concurrent.CompletableFuture; import lombok.extern.slf4j.Slf4j; import org.springframework.retry.annotation.Backoff; import org.springframework.retry.annotation.Retryable; import org.springframework.scheduling.annotation.Async; import...

In the last post we saw how to spin a http/2 server using embedded jetty. In this post we will see, how to use asynchronous servlet (as well as AIO a.k.a non-blocking IO) and why that is important? Asynchronous Servlets ≠ Asynchronous IO [1] The concept of Asynchronous Servlets is often confused with Asynchronous IO or the use of NIO. However, Asynchronous Servlets are not primarily motivated by asynchronous IO, since: HTTP Requests are mostly small and arrive in a single packet. Servlets rarely block on requests. Many responses are small and fit within the server buffers, so servlets often do not block writing responses. Asynchronous Servlets Use-case The main use-case for asynchronous servlets is waiting for non-IO events or resources. Many web applications need to wait at some stage during the processing of a HTTP request, for example: waiting for a resource to be available before processing the request (e.g., thread, JDBC Connection) waiting for an applica...

Have you ever wanted to configure internal Java servers using HTTP/2 (or H2 in short), because of the following advantages? Internal clients making concurrent calls, can now use a single connection by utilizing the multiplexing nature of HTTP/2. Server will/can use less threads as there are less connections overall. Servers can also push resources/data and can communicate using websockets But what if you don’t want to go through tedious process of setting up SSL/TLS certificates? HTTP/2 insists on SSL/TLS as no browser supports HTTP/2 on insecure mode. Or what if you want to save every bit of CPU and time by skipping encryption and decryption? You are at the right place. Since everyone nowadays is moving towards (or talking about) micro services, we will also configure Jetty HTTP/2 server in embedded mode. What more? We are also going to configure our server to use Asynchronous Servlets and Asynchronous IO (aka non-blocking IO or NIO) in Part-2 of this article. ...