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Unsupported major.minor version 52.0 with web app built with eclipse, server is tomcat 7 [duplicate]

This question already has answers here:
How to fix java.lang.UnsupportedClassVersionError: Unsupported major.minor version
(51 answers)
Closed 4 years ago.
I have recently upgraded my development machine to Ubuntu 18.04 and have been revisiting and checking some old projects, one of which is built under Eclipse oxygen and deployed using Tomcat 7.
To the best of my memory this project worked when deploying the .war file to the private instance of tomcat (running on port 10080) and the main, autostarting instance on 8080.
It still works on 10080 but when I deploy to 8080 and open through a browser, I see
javax.servlet.ServletException: java.lang.UnsupportedClassVersionError: org/eclipse/jdt/internal/compiler/env/INameEnvironment : Unsupported major.minor version 52.0
I have $JAVA_HOME as JAVA_HOME="/usr/lib/jvm/java-8-oracle"
The main tomcat manager page shows :
Apache Tomcat/7.0.68 (Ubuntu) JVM version 1.7.0_80-b15
I have set the the eclipse compiler compliance level to 1.7.
I am completely baffled as to why one instance is OK and the other not. I don't want to change the JAVA_HOME, so I think it must be something to do with the tomcat configuration or the internal compiler but can't seem to sort it out.
All sensible suggestions will be gratefully received.
Edit:
This is not a duplicate of a question, as I have built one war file and exported it to ~/junk. After that I have copied and pasted it to the separate webapps folders for the two Tomcat instances. I think it's a tomact configuration issue but I can't see what. Please don't mark it as duplicate
Edit 2:
Looking at how the tomcat was started as a service with systemctl I see:
nick#nick-X555LAB:~$ systemctl status tomcat7.service
tomcat7.service - LSB: Start Tomcat.
Loaded: loaded (/etc/init.d/tomcat7; generated)
Active: active (running) since Mon 2018-08-20 12:04:29 BST; 55s ago
Docs: man:systemd-sysv-generator(8)
Process: 10050 ExecStart=/etc/init.d/tomcat7 start (code=exited, status=0/SUCC
Tasks: 20 (limit: 4915)
CGroup: /system.slice/tomcat7.service
└─10109 /usr/lib/jvm/java-7-oracle/bin/java -Djava.util.logging.confi
Aug 20 12:04:24 nick-X555LAB systemd[1]: Starting LSB: Start Tomcat....
Aug 20 12:04:24 nick-X555LAB tomcat7[10050]: * Starting Tomcat servlet engine t
Aug 20 12:04:29 nick-X555LAB tomcat7[10050]: ...done.
Aug 20 12:04:29 nick-X555LAB systemd[1]: Started LSB: Start Tomcat..
Note the reference to java7 - I'd like to switch this to java 8
Solved
Solved it. Found a reference to java 7 in /etc/default/tomcat7, changed it to java 8 and all is well.

Use update-alternatives to change the default JDK to java8
as
sudo update-alternatives --config java
see https://linux.die.net/man/8/update-alternatives

java permission error on first run of newly installed Neo4J server

I'm setting up a new server for an application (node.js with Neo4j 1.8.3) that hasn't been used for a while. I installed Oracle JDK 7 (latest), which might explain this issue, as it's not recommended
for 1.8.3, will retest with JDK 6 tomorrow.
I installed Neo4J 1.8.3 on Thursday, on Ubuntu 14.04 running on Linode. Today I reviewed the log file (neo4j.0.0.log) and saw the following error:
Oct 02, 2014 5:02:48 PM java.util.prefs.FileSystemPreferences$1 run
WARNING: Couldn't create user preferences directory. User preferences are unusable.
After that there are numerous errors as follows:
WARNING: java.io.IOException: No such file or directory
Oct 02, 2014 12:00:46 PM java.util.prefs.FileSystemPreferences checkLockFile0ErrorCode
This discussion seems relevant,
java system preferences under different users in linux
But before trying this I wanted to ask here. Is this a known problem with a standard solution?

How to resolve java.lang.ClassNotFoundException: DerbyLogSetting

I am dealing with derby to perform database related functions in a Java Project. The java project is a command line project. To accomplish this, I have added derby.jar into libs folder of my project, though on running application into netbeans, I am getting this error :
Mon Aug 18 17:32:23 IST 2014 Thread[AWT-EventQueue-0,6,main] java.lang.ClassNotFoundException: DerbyLogSetting
----------------------------------------------------------------
Mon Aug 18 17:32:23 IST 2014:
Booting Derby version The Apache Software Foundation - Apache Derby - 10.8.1.2 - (1095077): instance a816c00e-0147-e8ff-2d32-000003436058
on database directory My_Database_Path\Database_Path with class loader sun.misc.Launcher$AppClassLoader#430e468f
Loaded from file:/My_Project_Path/derby.jar
java.vendor=Oracle Corporation
java.runtime.version=1.7.0_45-b18
user.dir=My_Project_Path
derby.system.home=null
derby.stream.error.method=DerbyLogSetting.disableDerbyLogFile
Database Class Loader started - derby.database.classpath=''
Same happening when I am running the exe of my project on command prompt. On goggling about the issue, I got that on adding derby-client into class path can solve my problem, but adding this jar (derbyclient-10.8.1.2.jar) into libs of my project not solving the issue.
What else needed to solve the issue ?

neo4j cannot find JAVA_HOME when checking service status

I installed neo4j 1.8.2 on opensuse 12.2/64. To do so I had to add the JAVA_HOME path in the /etc/profile file as:
export JAVA_HOME=/opt/java/64/jdk1.7.0_21/jre/:
export PATH=$PATH:/opt/java/64/jdk1.7.0_21/jre/bin/;
Now when I try to check the server status I get the following error
>service neo4j-service status
neo4j-service.service - LSB: The Neo4J graph database server. See http://neo4j.org
Loaded: loaded (/etc/init.d/neo4j-service)
Active: failed (Result: exit-code) since Fri, 26 Apr 2013 17:13:56 +0200; 10s ago
Process: 7234 ExecStart=/etc/init.d/neo4j-service start (code=exited, status=1/FAILURE)
CGroup: name=systemd:/system/neo4j-service.service
Apr 26 17:13:56 linux-wwcz neo4j-service[7234]: which: no java in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/...bin)
Apr 26 17:13:56 linux-wwcz neo4j-service[7234]: Error: JAVA_HOME is not defined correctly.
Apr 26 17:13:56 linux-wwcz neo4j-service[7234]: We cannot execute
It's quite puzzling considering neo4j-service links to ./bin/neo4j, namely the file used at installation time with
./bin/neo4j install
Some ideas on what is going on here?
Thanks
SOLVED
Actually I was using jdk 7 instead of jdk 6
EDIT 2
According to the official neo4j page one runs the server using neo4j start. But I got into troubles when trying to run service neo4j start/status/stop as suggested in the Installing Neo4j in Linux how-to.

Try changing them to this:
export JAVA_HOME=/opt/java/64/jdk1.7.0_21/:
export PATH=$PATH:/opt/java/64/jdk1.7.0_21/bin/;

Not exactly for the question, but I reached here because I also though Neo4j could not find the environment variable JAVA_HOME when
sudo neo4j start
My problem was that OS reset environment variables when using sudo.
sudo -E neo4j start
solved my problem.

Google App Engine - How to get demos to work?

I'm embarrassed to have to ask this, but I can't for the life of me figure out what I'm doing wrong.
I've downloaded the appengine-java-sdk-1.4.2 via the eclipse 3.6 plugin as per the instructions on Installing the Java SDK page. I am running Mac OSX 10.5.8 with JRE version 1.5.0_26. I have made the dev_appserver.sh file executable (chmod u+x dev_appserver.sh) and when I attempt to start the app server with one of the demos via the command
bin/dev_appserver.sh demos/guestbook/war/
I get the following output, but the server does not start up:
2011-03-13 17:52:43.404 java[839:80f] [Java CocoaComponent compatibility mode]: Enabled
2011-03-13 17:52:43.405 java[839:80f] [Java CocoaComponent compatibility mode]: Setting timeout for SWT to 0.100000
********************************************************
Warning: Future versions of the Dev App Server will require Java 1.6 or later. Please upgrade your JRE.
********************************************************
Mar 13, 2011 9:52:44 PM com.google.apphosting.utils.jetty.JettyLogger info
INFO: Logging to JettyLogger(null) via com.google.apphosting.utils.jetty.JettyLogger
Mar 13, 2011 9:52:44 PM com.google.apphosting.utils.config.AppEngineWebXmlReader readAppEngineWebXml
INFO: Successfully processed /Applications/eclipse_3.6/plugins/com.google.appengine.eclipse.sdkbundle.1.4.2_1.4.2.v201102111811/appengine-java-sdk-1.4.2/demos/guestbook/war/WEB-INF/appengine-web.xml
Mar 13, 2011 9:52:44 PM com.google.apphosting.utils.config.AbstractConfigXmlReader readConfigXml
INFO: Successfully processed /Applications/eclipse_3.6/plugins/com.google.appengine.eclipse.sdkbundle.1.4.2_1.4.2.v201102111811/appengine-java-sdk-1.4.2/demos/guestbook/war/WEB-INF/web.xml
I see the warning about upgrading the JRE, but I don't think this is the problem, as there are no exceptions reported. It just won't start up. I've tried creating a hello world app from within Eclipse using the plugin and running as Web server, but that also spits out the same text but does not start up the web server.
Any idea what I'm doing wrong and how to remedy the problem?

By changing the line in dev_appserver.sh to
/System/Library/Frameworks/JavaVM.framework/Versions/1.6.0/Commands/java -ea -cp "$JAR_FILE" \
com.google.appengine.tools.KickStart \
com.google.appengine.tools.development.DevAppServerMain $*
instead of using the default java (which is set to 1.5.0_26 as I mentioned earlier) the web server starts up.

I had the same problem and simply tried running Eclipse as Administrator and then debugging worked fine.