Add method to create Headers from Map<String, String>

okhttp-tests/src/test/java/com/squareup/okhttp/internal/http/HeadersTest.java

@@ -22,7 +22,11 @@ import com.squareup.okhttp.Response;
 import com.squareup.okhttp.internal.spdy.Header;
 import java.io.IOException;
 import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
+
 import org.junit.Test;
 
 import static com.squareup.okhttp.TestUtil.headerEntries;
@@ -234,4 +238,68 @@ public final class HeadersTest {
     } catch (IllegalArgumentException expected) {
     }
   }
+
+  @Test public void ofMapThrowsOnNull() {
+    try {
+      Headers.of(Collections.<String, String>singletonMap("User-Agent", null));
+      fail();
+    } catch (IllegalArgumentException expected) {
+    }
+  }
+
+  @Test public void ofMapThrowsOnEmptyName() {
+    try {
+      Headers.of(Collections.singletonMap("", "OkHttp"));
+      fail();
+    } catch (IllegalArgumentException expected) {
+    }
+  }
+
+  @Test public void ofMapThrowsOnBlankName() {
+    try {
+      Headers.of(Collections.singletonMap(" ", "OkHttp"));
+      fail();
+    } catch (IllegalArgumentException expected) {
+    }
+  }
+
+  @Test public void ofMapAcceptsEmptyValue() {
+    Headers headers = Headers.of(Collections.singletonMap("User-Agent", ""));
+    assertEquals("", headers.value(0));
+  }
+
+  @Test public void ofMapTrimsKey() {
+    Headers headers = Headers.of(Collections.singletonMap(" User-Agent ", "OkHttp"));
+    assertEquals("User-Agent", headers.name(0));
+  }
+
+  @Test public void ofMapTrimsValue() {
+    Headers headers = Headers.of(Collections.singletonMap("User-Agent", " OkHttp "));
+    assertEquals("OkHttp", headers.value(0));
+  }
+
+  @Test public void ofMapMakesDefensiveCopy() {
+    Map<String, String> namesAndValues = new HashMap<>();
+    namesAndValues.put("User-Agent", "OkHttp");
+
+    Headers headers = Headers.of(namesAndValues);
+    namesAndValues.put("User-Agent", "Chrome");
+    assertEquals("OkHttp", headers.value(0));
+  }
+
+  @Test public void ofMapRejectsNulCharInName() {
+    try {
+      Headers.of(Collections.singletonMap("User-Agent", "Square\u0000OkHttp"));
+      fail();
+    } catch (IllegalArgumentException expected) {
+    }
+  }
+
+  @Test public void ofMapRejectsNulCharInValue() {
+    try {
+      Headers.of(Collections.singletonMap("User-\u0000Agent", "OkHttp"));
+      fail();
+    } catch (IllegalArgumentException expected) {
+    }
+  }
 }

okhttp/src/main/java/com/squareup/okhttp/Headers.java

@@ -22,6 +22,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Date;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import java.util.TreeSet;
 
@@ -167,6 +168,33 @@ public final class Headers {
     return new Headers(namesAndValues);
   }
 
+  /**
+   * Returns headers for the header names and values in the {@link Map}.
+   */
+  public static Headers of(Map<String, String> headers) {
+    if (headers == null) {
+      throw new IllegalArgumentException("Expected map with header names and values");
+    }
+
+    // Make a defensive copy and clean it up.
+    final String[] namesAndValues = new String[headers.size() * 2];
+    int i = 0;
+    for (Map.Entry<String, String> header : headers.entrySet()) {
+      if (header.getKey() == null || header.getValue() == null)
+        throw new IllegalArgumentException("Headers cannot be null");
+      final String name = header.getKey().trim();
+      final String value = header.getValue().trim();
+      if (name.length() == 0 || name.indexOf('\0') != -1 || value.indexOf('\0') != -1) {
+        throw new IllegalArgumentException("Unexpected header: " + name + ": " + value);
+      }
+      namesAndValues[i] = name;
+      namesAndValues[i + 1] = value;
+      i += 2;
+    }
+
+    return new Headers(namesAndValues);
+  }
+
   public static final class Builder {
     private final List<String> namesAndValues = new ArrayList<>(20);