I wrote a project A which contains a class KMeans.java. The class contains a public local varaible iteration. I build the project to a jar and add the jar to my spring boot web project B.
/**
ProjectA.jar
--KMeans.java
*/
public class KMeans{
public int iteration;
public void run(){
for( iteration=0; iteration<1000; iteration++){
....
}
}
}
I try to obtain the iteration value in B to show it in web page dynamically. However, I dont know how to obtain the value. Thus, I decide to write the value into database.
I create a class ModelStatusUtils.java in A which contains save(int iteration) method.
public abstract class ModelStatusUtils{
public abstract void save(int iteration);
}
And I put the class as a parameter in run() method in KMeans.java so that I can save the iteration which can be controlled by external class.
....
public void run(ModelStatusUtils model){
for( iteration=0; iteration<1000; iteration++){
....
model.save(iteration);
}
}
...
Next, I create a class WebModelStatusUtils.java in B (I think the following error is because WebModelStatusUtils extends ModelStatusUtils in A, so spring boot cannot scan the package and could not autowired jpa correctly) that extends ModelStatusUtils.java . I used jpa and autowired the jpa in WebModelStatusUtils.java.
public class WebModelStatusUtils extends ModelStatusUtils{
@Autowired
private ModelStatusRepository modelStatusRepository;
@Override
public int saveIteration(int i) {
ModelStatus modelStatus = new ModelStatus(i);
modelStatusRepository.save(modelStatus);
return 1;
}
}
And repository is:
public interface ModelStatusRepository extends JpaRepository<ModelStatus, Long> {
}
However, it calls error:
java.lang.NullPointerException: null, at WebModelStatusUtils .saveIteration(WebModelStatusUtils .java:23) ~[classes/:na]
My question is:
1) how to obtain instance's local variable of the external jar in web project
2) Why it throws null exception. How should i to solve it
