How to get all the headers from HttpServletRequest? - https://stackoverflow.com/a/49771639

HttpHeadersTest.java

package io.github.cepr0.demo;

import org.junit.Before;
import org.junit.Test;
import org.springframework.http.HttpHeaders;

import javax.servlet.http.HttpServletRequest;
import java.util.*;
import java.util.function.Function;
import java.util.stream.Collectors;

import static org.assertj.core.api.Assertions.assertThat;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;

public class HttpHeadersTest {

  private HttpServletRequest httpRequest;

  @SuppressWarnings("unchecked")
  @Before
  public void setUp() throws Exception {
    httpRequest = mock(HttpServletRequest.class);

    Enumeration headers = new StringTokenizer("header1 header2", " ");
    when(httpRequest.getHeaderNames()).thenReturn(headers);

    Enumeration header1Values = new StringTokenizer("value1_1 value1_2", " ");
    when(httpRequest.getHeaders("header1")).thenReturn(header1Values);

    Enumeration header2Values = new StringTokenizer("value2_1 value2_2", " ");
    when(httpRequest.getHeaders("header2")).thenReturn(header2Values);
  }

  @Test
  public void map() {
    Map<String, List<String>> headersMap = Collections
        .list(httpRequest.getHeaderNames())
        .stream()
        .collect(Collectors.toMap(
          Function.identity(), 
          h -> Collections.list(httpRequest.getHeaders(h))
        ));

    assertThat(headersMap.get("header1")).containsOnly("value1_1", "value1_2");
    assertThat(headersMap.get("header2")).containsOnly("value2_1", "value2_2");
  }

  @Test
  public void httpHeaders() {
    HttpHeaders httpHeaders = Collections
        .list(httpRequest.getHeaderNames())
        .stream()
        .collect(Collectors.toMap(
            Function.identity(),
            h -> Collections.list(httpRequest.getHeaders(h)),
            (oldValue, newValue) -> newValue,
            HttpHeaders::new
        ));

    assertThat(httpHeaders.get("header1")).containsOnly("value1_1", "value1_2");
    assertThat(httpHeaders.get("header2")).containsOnly("value2_1", "value2_2");
  }
}