Adds TextFormat and usage example. (#724)

* Adds TextFormat and usage example.

* Remove multiple encodings support.

* Run google java formatter.

* Remove getTextFormat from PropagationComponent.

* Update comments.

* Improve javadoc.

2 files changed, 76 insertions, 1 deletions

diff --git a/api/src/test/java/io/opencensus/trace/propagation/PropagationComponentTest.java b/api/src/test/java/io/opencensus/trace/propagation/PropagationComponentTest.java
index 62f04d98..ba64e98e 100644
--- a/api/src/test/java/io/opencensus/trace/propagation/PropagationComponentTest.java
+++ b/api/src/test/java/io/opencensus/trace/propagation/PropagationComponentTest.java
@@ -29,7 +29,7 @@ public class PropagationComponentTest {
       PropagationComponent.getNoopPropagationComponent();
 
   @Test
-  public void implementationOfBinary() {
+  public void implementationOfBinaryFormat() {
     assertThat(propagationComponent.getBinaryFormat())
         .isEqualTo(BinaryFormat.getNoopBinaryFormat());
   }
diff --git a/api/src/test/java/io/opencensus/trace/propagation/TextFormatTest.java b/api/src/test/java/io/opencensus/trace/propagation/TextFormatTest.java
new file mode 100644
index 00000000..c2e6e127
--- /dev/null
+++ b/api/src/test/java/io/opencensus/trace/propagation/TextFormatTest.java
@@ -0,0 +1,75 @@
+/*
+ * Copyright 2017, OpenCensus Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.opencensus.trace.propagation;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import io.opencensus.trace.SpanContext;
+import io.opencensus.trace.propagation.TextFormat.Getter;
+import io.opencensus.trace.propagation.TextFormat.Setter;
+import javax.annotation.Nullable;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Unit tests for {@link TextFormat}. */
+@RunWith(JUnit4.class)
+public class TextFormatTest {
+  private static final TextFormat textFormat = TextFormat.getNoopTextFormat();
+
+  @Test(expected = NullPointerException.class)
+  public void inject_NullSpanContext() {
+    textFormat.inject(
+        null,
+        new Object(),
+        new Setter<Object>() {
+          @Override
+          public void put(Object carrier, String key, String value) {}
+        });
+  }
+
+  @Test
+  public void inject_NotNullSpanContext_DoesNotFail() {
+    textFormat.inject(
+        SpanContext.INVALID,
+        new Object(),
+        new Setter<Object>() {
+          @Override
+          public void put(Object carrier, String key, String value) {}
+        });
+  }
+
+  @Test(expected = NullPointerException.class)
+  public void fromHeaders_NullGetter() throws SpanContextParseException {
+    textFormat.extract(new Object(), null);
+  }
+
+  @Test
+  public void fromHeaders_NotNullGetter() throws SpanContextParseException {
+    assertThat(
+            textFormat.extract(
+                new Object(),
+                new Getter<Object>() {
+                  @Nullable
+                  @Override
+                  public String get(Object carrier, String key) {
+                    return null;
+                  }
+                }))
+        .isSameAs(SpanContext.INVALID);
+  }
+}