Guava version compatibility issue

Spring Boot errors Pure Java exceptions Suggested solutions Method Guava version com.google.common.base.Preconditions.checkArgument 26.0-jre / 26.0-android com.google.common.base.Preconditions.checkState 21.0 com.google.common.util.concurrent.MoreExecutors.sameThreadExecutor 18.0 / 19.0 Let me remind you that guava with maven is connected like this: If suggested verions don’t fix the problem, you can try connecting the specified versions in order: 18.0 / 19.0 / 21.0 / […]

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Generate SSL certificate with User Principal Name openssl

We assume that openssl is already installed. User certificate with a UPN field Create a new file named ext.cnf in the folder where we are going to generate certificates. Write the line to the file: Replace text your_text_here with your own. The rest does not need to be touched. Now, you need to add a […]

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Load x509 certificate from keystore Java

We have a keystore with an imported certificate and we need to work with it in code. We are going to import cert into an X509Certificate class object. After that, you can work with it further, or simply display some information about it, for example: Subject X500 Principal, Issuer X500 Principal Subject DN, Issuer DN […]

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Failed to find reentrant lock with given name Ignite

Full text of the exception in Apache Ignite: The code that uses the reentrant lock looks something like this: Check that when creating a lock, the last argument = true is passed to the reentrantLock method: If the error is still repeated, then this is a bug: https://issues.apache.org/jira/browse/IGNITE-3386. It appears when one of the server […]

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How to find out what is taking up disk space in Linux

Sometimes disk space suddenly runs out, and you need to quickly identify the cause. Let’s find the problematic partition using the command: Output example: We are looking partitions, which 95% full or more. Use the /cd command to navigate to the folder from the corresponding “Mounted on” column. In our case it is /data folder. […]

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Error creating shaded jar target\classes (Access is denied)

The error looks like this: Stacktrace: maven-shade-plugin tries to open classes folder as zip file. This happens when one of the dependencies is found on the local filesystem and not in the local maven repository. Before unpacking, the plugin should check whether target\classes is a directory or a zip file, but it doesn’t. One solution […]

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WordPress XML Sitemap problem

Let’s imagine that we have just installed a plugin for generating a Sitemap, check certain Sitemap URL, and received the following error: This page contains the following errors: error on line * at column *: XML declaration allowed only at the start of the document Below is a rendering of the page up to the […]

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WordPress plugin conflict

There are some cases when at a certain moment something breaks on the WordPress site. One of the possible reasons is a conflict of installed plugins. If we cannot disable plugins in a productive environment, it will be convenient to use the plugin (yes, another one) Health Check & Troubleshooting. It is available at https://wordpress.org/plugins/health-check. […]

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Speed ​​up WordPress site

Speed ​​check You measure the site loading time and get recommendations for speeding up using the PageSpeed ​​Insights tool. We will look at 3 simple steps that are going to reduce the load time of your WordPress site. Async JavaScript Plugin The plugin is available at https://www.wordpress.org/plugins/async-javascript. Render-blocking Javascript prevents your content loading until the […]

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                   Mark Chesnavsky. Email me or connect via LinkedIn.