-
How to enable WiFi auto reconnect on a Raspberry Pi
In recent times my WiFi seems to have become a bit unstable. As if this wouldn’t be annoying enough, this also means that all my Rasperry Pis loose their WiFi connections as well and thus become unreachable. Yet the sollution is pretty simple: Well, there is a very simple solution: cd /etc/ifplugd/action.d/ sudo mv ifupdown …
-
Windows install error 0x80070002 unable to install App
Yesterday I tried to install a Windows App via its built in App Store. Usually this works like a charm. This time the download seemed to succees (judged by the progress bar) but the installation failed with error 0x80070002; Googling (and Bing’ing) found various issues with kind of the same description, ranging from “download failed”…
-
What to do in case of org.apache.spark.sql.catalyst.errors.package$TreeNodeException: Unresolved attributes
I’m currently gathering my first experiences with Apache Spark and in particular Spark SQL. While I was playing a bit with Spark SQL Joins I suddenly faced an exception like Exception in thread “main” org.apache.spark.sql.catalyst.errors.package$TreeNodeException: Unresolved attributes: foo. Followed by the parsed SQL statement etc … Well, in MySQL the error message would have been…
-
How to ignore Maven build erros due to JavaDoc with Java 8
Java 8 is a bit more strict in JavaDoc parsing. This can lead to build failures in Maven when building the repo with warnings like: Failed to execute goal org.apache.maven.plugins:maven-javadoc-plugin:2.7:jar (attach-javadocs) on project [projectname]: MavenReportException: Error while creating archive: Exit code: 1 – [path-to-file]:[linenumber]: warning: no description for @param Sure, the good solution would be…
-
How to get List of Objects from deeper level in Json via GSON
Sometimes you get a quite nested Json response but the only thing you need is a list of classes in a certain branch of the Json document (like a response of Yahoo’s YQL query). Assume just the following json document: And the only thing you need is the fields array. A Java8 way to get…
-
Java 8 Streams: Collecting items into a Map of (Key, Item)
Once in a while I come across the task where I have a list of Items that I want to filter and afterwards store in a map. Usually the key is a property of the Item: anItem.name -> anItem In the usual Java way this looked like the following: Nothing really special, but it somehow…
-
How to rename a GIT tag
Once in a while (yet often enough) it happens that I have to change an already pushed git tag. Usually because I violated my own naming scheme. Yet I also somehow can’t keep the necesserry commands in mind: Basically it is just: copy/link newTag to oldTag, remove oldTag, delete remote oldTag. Also see the git…
-
Windows Tomcat start failed command 127.0.0.1 could not be found
I just installed Tomcat 7 on my Windows machine and tried to fire it up through Netbeans. But instead of a running server, I just got an error message that command 127.0.0.1 could not be found (Localized error message: Der Befehl “127.0.0.1” ist entweder falsch geschrieben oder konnte nicht gefunden werden.). I remember that I…
-
Epson XP-205 Scanner in Windows 8.1 – How to get it back to work
Now it’s time for a Epson XP-205 Scanner to work with Windows 8.1 It took me a while now to get the XP-205 scanner component to run on my new Windows 8.1 via WiFi: The problem is, that when you install the scan software, you might get a communication error telling you that the scanner…