Add Stackdriver Trace samples.

trace/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+ Copyright 2018 Google LLC
+
+ 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.
+-->
+<project>
+  <modelVersion>4.0.0</modelVersion>
+  <packaging>jar</packaging>
+  <groupId>com.example</groupId>
+  <artifactId>trace-samples</artifactId>
+  <version>1.0</version>
+
+  <!--
+    The parent pom defines common style checks and testing strategies for our samples.
+    Removing or replacing it should not affect the execution of the samples in anyway.
+  -->
+  <parent>
+    <groupId>com.google.cloud.samples</groupId>
+    <artifactId>shared-configuration</artifactId>
+    <version>1.0.10</version>
+    <relativePath></relativePath>
+  </parent>
+
+  <properties>
+    <maven.compiler.source>1.8</maven.compiler.source>
+    <maven.compiler.target>1.8</maven.compiler.target>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    <opencensus.version>0.12.2</opencensus.version>
+  </properties>
+
+  <dependencies>
+    <!-- [START trace_setup_java_maven ] -->
+    <dependency>
+      <groupId>io.opencensus</groupId>
+      <artifactId>opencensus-api</artifactId>
+      <version>${opencensus.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>io.opencensus</groupId>
+      <artifactId>opencensus-exporter-trace-stackdriver</artifactId>
+      <version>${opencensus.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>io.opencensus</groupId>
+      <artifactId>opencensus-impl</artifactId>
+      <version>${opencensus.version}</version>
+      <scope>runtime</scope>
+    </dependency>
+    <!-- [END trace_setup_java_maven ] -->
+
+    <!-- Test dependencies -->
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <version>4.12</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>com.google.truth</groupId>
+      <artifactId>truth</artifactId>
+      <version>0.42</version>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+</project>

trace/src/main/java/com/example/trace/TraceSample.java

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+/*
+ * Copyright 2018 Google LLC
+ *
+ * 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 com.example.trace;
+
+import com.google.auth.oauth2.AccessToken;
+import com.google.auth.oauth2.GoogleCredentials;
+
+import io.opencensus.common.Scope;
+import io.opencensus.exporter.trace.stackdriver.StackdriverTraceConfiguration;
+import io.opencensus.exporter.trace.stackdriver.StackdriverTraceExporter;
+import io.opencensus.trace.Tracer;
+import io.opencensus.trace.Tracing;
+import io.opencensus.trace.samplers.Samplers;
+
+import java.io.IOException;
+import java.util.Date;
+
+import org.joda.time.DateTime;
+
+public class TraceSample {
+
+  // [START trace_setup_java_custom_span]
+  private static final Tracer tracer = Tracing.getTracer();
+
+  public static void doWork() {
+    // Create a child Span of the current Span.
+    try (Scope ss = tracer.spanBuilder("MyChildWorkSpan").startScopedSpan()) {
+      doInitialWork();
+      tracer.getCurrentSpan().addAnnotation("Finished initial work");
+      doFinalWork();
+    }
+  }
+
+  private static void doInitialWork() {
+    // ...
+    tracer.getCurrentSpan().addAnnotation("Doing initial work");
+    // ...
+  }
+
+  private static void doFinalWork() {
+    // ...
+    tracer.getCurrentSpan().addAnnotation("Hello world!");
+    // ...
+  }
+  // [END trace_setup_java_custom_span]
+
+  // [START trace_setup_java_full_sampling]
+  public static void doWorkFullSampled() {
+    try (Scope ss = tracer.spanBuilder("MyChildWorkSpan")
+        .setSampler(Samplers.alwaysSample())
+        .startScopedSpan()) {
+      doInitialWork();
+      tracer.getCurrentSpan().addAnnotation("Finished initial work");
+      doFinalWork();
+    }
+  }
+  // [END trace_setup_java_full_sampling]
+
+  // [START trace_setup_java_create_and_register]
+  public static void createAndRegister() throws IOException {
+    StackdriverTraceExporter.createAndRegister(
+        StackdriverTraceConfiguration.builder().build());
+  }
+  // [END trace_setup_java_create_and_register]
+
+  // [START trace_setup_java_create_and_register_with_token]
+  public static void createAndRegisterWithToken(String accessToken) throws IOException {
+    Date expirationTime = DateTime.now().plusSeconds(60).toDate();
+
+    StackdriverTraceExporter.createAndRegister(
+        StackdriverTraceConfiguration.builder()
+            .setProjectId("MyStackdriverProjectId")
+            .setCredentials(GoogleCredentials.create(new AccessToken(accessToken, expirationTime)))
+            .build());
+  }
+  // [END trace_setup_java_create_and_register_with_token]
+
+  // [START trace_setup_java_register_exporter]
+  public static void createAndRegisterGoogleCloudPlatform(String projectId) throws IOException {
+    StackdriverTraceExporter.createAndRegister(
+        StackdriverTraceConfiguration.builder()
+            .setProjectId(projectId)
+            .build());
+  }
+  // [END trace_setup_java_register_exporter]
+}

trace/src/test/java/com/example/trace/TraceSampleIT.java

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+/*
+ * Copyright 2018 Google LLC
+ *
+ * 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 com.example.trace;
+
+import io.opencensus.exporter.trace.stackdriver.StackdriverTraceExporter;
+
+import java.io.IOException;
+
+import org.junit.After;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/**
+ * Tests for stackdriver tracing sample.
+ */
+@RunWith(JUnit4.class)
+@SuppressWarnings("checkstyle:abbreviationaswordinname")
+public class TraceSampleIT {
+
+  @After
+  public void tearDown() {
+    StackdriverTraceExporter.unregister();
+  }
+
+  @Test
+  public void testCreateAndRegister() throws IOException {
+    TraceSample.createAndRegister();
+    TraceSample.doWork();
+  }
+
+  @Test
+  public void testCreateAndRegisterFullSampled() throws IOException {
+    TraceSample.createAndRegister();
+    TraceSample.doWorkFullSampled();
+  }
+
+  @Test
+  public void testCreateAndRegisterGoogleCloudPlatform() throws IOException {
+    TraceSample.createAndRegisterGoogleCloudPlatform(System.getenv("GOOGLE_CLOUD_PROJECT"));
+    TraceSample.doWork();
+  }
+}