Armeria: How pass object from a decorator to next decorator ?

[iEAmi]

I need get some header value from request and validate that and then pass that value to next decorator.
I can not find a way to do this .
What is the best way for doing this ?

[iEAmi]

I think find a way. I create a custom ServiceRequestContextWrapper and put a ConcurrentHashMap in it and save all objects that need in this ConcurrentHashMap then i can get this object using RequestContext.current(). i test this solution, this work.
Is this a optimal solution ? I want to use this method in production.

[hyangtack]

You can attach your object to the ServiceRequestContext. It may be simpler. Please refer to Central Dogma source code.

Attach MetadataService instance to the context:
https://github.com/line/centraldogma/blob/master/server/src/main/java/com/linecorp/centraldogma/server/internal/metadata/MetadataServiceInjector.java#L54

Get the attatched object from the context in the next decorator:
https://github.com/line/centraldogma/blob/master/server/src/main/java/com/linecorp/centraldogma/server/internal/api/auth/RequiresPermissionDecorator.java#L61
https://github.com/line/centraldogma/blob/master/server/src/main/java/com/linecorp/centraldogma/server/internal/metadata/MetadataServiceInjector.java#L61

[iEAmi]

Thank you. :)

[trustin]

For completeness, let me explain the detail here. You can attach one or more attributes to a RequestContext. To attach attributes, you need to define AttributeKeys first:

public final class MyAttributeKeys {
    public static final AttributeKey<Integer> INT_ATTR =
            AttributeKey.valueOf(MyAttributeKeys.class, "INT_ATTR");
    public static final AttributeKey<MyBean> BEAN_ATTR =
            AttributeKey.valueOf(MyAttributeKeys.class, "BEAN_ATTR");
    ...
}

Then, you can access them via RequestContext.attr(AttributeKey):

// Setting:
ctx.attr(INT_ATTR).set(42);
ctx.attr(BEAN_ATTR).set(new MyBean());

// Getting;
Integer i = ctx.attr(INT_ATTR).get();
MyBean bean = ctx.attr(BEAN_ATTR);

[trustin]

You can also iterate over all the attributes in a context using RequestContext.attrs():

for (Attribute<?> a : ctx.attrs()) {
    System.err.println(a.key() + ": " + a.get());
}

If you are only interested in checking whether an attribute exists or not, it would be better using hasAttr(AttributeKey) because it does not perform any allocation for a non-existent attribute unlike attr(AttributeKey):

if (ctx.hasAttr(INT_ATTR)) {
    int i = ctx.attr(INT_ATTR).get();
    ...
}

[trustin]

Please feel free to reopen this issue if your question was not solved.