[OLINGO-328] improve multi valued headers of ODataRequest

lib/server-api/src/main/java/org/apache/olingo/server/api/ODataRequest.java

@@ -19,6 +19,7 @@
 package org.apache.olingo.server.api;
 
 import java.io.InputStream;
+import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -44,13 +45,25 @@ public class ODataRequest {
   }
 
   /**
-   * Add header to request where name handled as case insensitive key.
+   * Add header to request where name handled as case insensitive key. If a header already exists then the list of
+   * values will just be extended.
    * @param name case insensitive header name
    * @param values
    */
   public void addHeader(String name, List<String> values) {
+    String key = name.toUpperCase();
+    if (headers.containsKey(key)) {
+      List<String> oldValues = headers.get(key);
+      
+      List<String> newValues = new ArrayList<String>();
+      newValues.addAll(oldValues);
+      newValues.addAll(values);
+
+      headers.put(name.toUpperCase(), newValues);
+    } else {
       headers.put(name.toUpperCase(), values);
     }
+  }
 
   /**
    * Returns header value for name where name is a case insensitive key.

lib/server-test/src/test/java/org/apache/olingo/server/api/ODataRequestTest.java

@@ -36,10 +36,31 @@ public class ODataRequestTest {
     assertEquals("cc", r.getHeader("aA").get(0));
     assertEquals("cc", r.getHeader("AA").get(0));
 
+  }
+
+  @Test
+  public void testHeader2() {
+    ODataRequest r = new ODataRequest();
     r.addHeader("AA", Arrays.asList("dd"));
 
     assertEquals("dd", r.getHeader("aa").get(0));
     assertEquals("dd", r.getHeader("aA").get(0));
     assertEquals("dd", r.getHeader("AA").get(0));
   }
+
+  @Test
+  public void testMultiValueHeader() {
+    ODataRequest r = new ODataRequest();
+
+    r.addHeader("aa", Arrays.asList("a", "b"));
+
+    assertEquals("a", r.getHeader("aa").get(0));
+    assertEquals("b", r.getHeader("aA").get(1));
+
+    r.addHeader("Aa", Arrays.asList("c"));
+
+    assertEquals("a", r.getHeader("aa").get(0));
+    assertEquals("b", r.getHeader("aA").get(1));
+    assertEquals("c", r.getHeader("aA").get(2));
+  }
 }