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org.hibernate.MappingException: collection foreign key mapping has wrong number of columns

I have a class Subject as such, Its composite Id is defined in SubjectId class as such, On compiling, I get the error org.hibernate.MappingException: collection foreign key mapping has wrong number of columns: com.example.Subject.students type: component[name,teacher] While this points the error to students element, the error occured after I removed the autogenerated id of Subject, and replaced it with combination

Something wrong with armstrong number java code

I wrote a code for school in java that verifies if a number is an armstrong number. I programmed it so that it runs as many times until the user inputs 0, at which the program will terminate. I am having 2 problems. The code only works the first time through, if the user inputs 371 (an armstrong number) the

Graphviz’s dot tool on Windows

I’ve created a java program to write a .dot file as I’m using Graphviz software to visualize some data. There is nothing wrong with a code itself, but when I try to execute the following command in command prompt: dot -Tpdf data.dot -o data.pdf in a folder where my java code is located, I get the following error: ‘dot’ is

What is C++ version of Java’s cyclic barrier?

In java, multiple threads can wait all others at a certain point so that they don’t start a new block of codes before all others finish first block: is there an exact or easy convertion to C++? Also with OpenCL, there is a similar instruction: so all neighbor threads wait each other but it is only a constrained C implementation.

Spring save locale and change locale when user logs in

I have a spring application that I want users to be able to change the preferred locale. Currently users can change the locale for the current session but I want to be able to save the users option so that whenever they log in, the saved locale is used if one exists. I have a mysql database which I’m using

Replacements for deprecated JPMS modules with Java EE APIs

Java 9 deprecated six modules that contain Java EE APIs and they are going to be removed soon: java.activation with javax.activation package java.corba with javax.activity, javax.rmi, javax.rmi.CORBA, and org.omg.* packages java.transaction with javax.transaction package java.xml.bind with all javax.xml.bind.* packages java.xml.ws with javax.jws, javax.jws.soap, javax.xml.soap, and all javax.xml.ws.* packages java.xml.ws.annotation with javax.annotation package Which maintained third-party artifacts provide those APIs? It

how to traverse a Boolean recursion array

The exercise: Build a recursion(with no loops) that every cell that you go inside is the number of steps that you can go, it could be right/left until you get to the last cell. if you can’t get to the last cell return false, else return true. you must start from index 0. My problem: I build the program, it’s

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