Spring Batch reader using generics

问题

I'm just new in the spring architecture and I am wondering if it is possible to use a generic T (o what you want) in an ItemStreamReader.

Something like this:

public class Reader implements ItemStreamReader<T extends SomeClass>{
    public T read() {
    .......
    }
    public void open() {
    .......
    }
    public void update() {
    .......
    }
    public void close() {
    .......
    }
}

So I pass to the reader various objects that extends SomeClass.

回答1:

this should work:

public class Reader<T extends SomeClass> implements ItemStreamReader<T>{
    public T read() {
    .......
    }
    public void open() {
    .......
    }
    public void update() {
    .......
    }
    public void close() {
    .......
    }
}

use it like:

Reader<SomeClass> reader = new Reader<>();
Reader<ExtendedFromSomeClass> reader2 = new Reader<>();

回答2:

I recommend you to read first about java generics.

http://www.angelikalanger.com/GenericsFAQ/FAQSections/ParameterizedTypes.html#What is a parameterized (or generic) type?

But if you define your class

public class Reader implements ItemStreamReader<SomeClass>{
    public SomeClass read() {
    .......
    }
    public void open() {
    .......
    }
    public void update() {
    .......
    }
    public void close() {
    .......
    }
}

Your method can return any object that is Subclass of SomeClass.

For example

Reader a = new Reader();
Subclass b = (Subclass)a.read();

来源：https://stackoverflow.com/questions/33627388/spring-batch-reader-using-generics