Akka: custom HttpHeader, convert HashMap to Iterable<HttpHeader> in java-CodePudding

I'm trying to generate custom HttpHeader in akka. I've a HashMap of header entries which I need to convert to Iterable. Here's my code:

import akka.http.javadsl.model.HttpHeader;
HashMap<String, String> headersMap = new HashMap<>();
headersMap.put("key1","value1");
return (Iterable<HttpHeader>) headersMap;
//HttpRequest.create().withUri("uri").addHeaders(Iterable<HttpHeader> iterable)
public static Iterable<HttpHeader> convertToRecordHttpHeaders(Map<String, String> headersMap){
    return headersMap.entrySet().stream()
            .map(x -> new HttpHeader(x.getKey(), x.getValue()))
            .collect(Collectors.toList());
}

What's the efficient way to convert the map to HttpHeader and convert it to Iterable as I want to create a HttpRequest in akka.

CodePudding user response：

A HashMap is not an Iterable anything. Its entrySet(), keySet() and values() are, but for your map those are Iterable<Map.Entry<String, String>>, Iterable<String> and Iterable<String> respectively. That means that you cannot cast the map in any way to an Iterable<HttpHeader>.

What you can do is convert:

List<HttpHeader> headersList = headersMap.entrySet().stream()
        .map(entry -> new HttpHeader(entry.getKey(), entry.getValue())
        .collect(Collectors.toList()); // or just toList() with Java 17

This assumes that HttpHeader has a constructor that takes a header name and value. If it doesn't, replace the constructor call with something else that creates an HttpHeader.

CodePudding user response：

Lets say your Header class is something like this

class HttpHeader{
    public HttpHeader(Map.Entry<String,String> header){}
}

then just use constructor reference in place of lambda or else you can provide your parsing using lambda expression

headersMap.entrySet().stream().map(HttpHeader::new).iterator();

But still i don't understand the use case of creating HashMap for return HttpHeader iterator.

i guess you used to keep header keys unique viva map however you can use TreeSet that will maintain unique objects too


class HttpHeader implements Comparable<HttpHeader>{
    String key;
    String value;
    
    public HttpHeader(String key, String value){
        this.key = key;
        this.value = value;
    }

    @Override
    public int compareTo(HttpHeader o) {
        return key.compareTo(o.key);
    }
}