1 files changed, 118 insertions, 0 deletions
diff --git a/api/src/main/java/io/opencensus/trace/TraceComponent.java b/api/src/main/java/io/opencensus/trace/TraceComponent.java
new file mode 100644
index 00000000..d98d0f9e
--- /dev/null
+++ b/api/src/main/java/io/opencensus/trace/TraceComponent.java
@@ -0,0 +1,118 @@
+/*
+ * Copyright 2016-17, 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;
+
+import io.opencensus.common.Clock;
+import io.opencensus.internal.ZeroTimeClock;
+import io.opencensus.trace.config.TraceConfig;
+import io.opencensus.trace.export.ExportComponent;
+import io.opencensus.trace.propagation.PropagationComponent;
+
+/**
+ * Class that holds the implementation instances for {@link Tracer}, {@link PropagationComponent},
+ * {@link Clock}, {@link ExportComponent} and {@link TraceConfig}.
+ *
+ * <p>Unless otherwise noted all methods (on component) results are cacheable.
+ *
+ * @since 0.5
+ */
+public abstract class TraceComponent {
+
+  /**
+   * Returns the {@link Tracer} with the provided implementations. If no implementation is provided
+   * then no-op implementations will be used.
+   *
+   * @return the {@code Tracer} implementation.
+   * @since 0.5
+   */
+  public abstract Tracer getTracer();
+
+  /**
+   * Returns the {@link PropagationComponent} with the provided implementation. If no implementation
+   * is provided then no-op implementation will be used.
+   *
+   * @return the {@code PropagationComponent} implementation.
+   * @since 0.5
+   */
+  public abstract PropagationComponent getPropagationComponent();
+
+  /**
+   * Returns the {@link Clock} with the provided implementation.
+   *
+   * @return the {@code Clock} implementation.
+   * @since 0.5
+   */
+  public abstract Clock getClock();
+
+  /**
+   * Returns the {@link ExportComponent} with the provided implementation. If no implementation is
+   * provided then no-op implementations will be used.
+   *
+   * @return the {@link ExportComponent} implementation.
+   * @since 0.5
+   */
+  public abstract ExportComponent getExportComponent();
+
+  /**
+   * Returns the {@link TraceConfig} with the provided implementation. If no implementation is
+   * provided then no-op implementations will be used.
+   *
+   * @return the {@link TraceConfig} implementation.
+   * @since 0.5
+   */
+  public abstract TraceConfig getTraceConfig();
+
+  /**
+   * Returns an instance that contains no-op implementations for all the instances.
+   *
+   * @return an instance that contains no-op implementations for all the instances.
+   */
+  static TraceComponent newNoopTraceComponent() {
+    return new NoopTraceComponent();
+  }
+
+  private static final class NoopTraceComponent extends TraceComponent {
+    private final ExportComponent noopExportComponent = ExportComponent.newNoopExportComponent();
+
+    @Override
+    public Tracer getTracer() {
+      return Tracer.getNoopTracer();
+    }
+
+    @Override
+    public PropagationComponent getPropagationComponent() {
+      return PropagationComponent.getNoopPropagationComponent();
+    }
+
+    @Override
+    public Clock getClock() {
+      return ZeroTimeClock.getInstance();
+    }
+
+    @Override
+    public ExportComponent getExportComponent() {
+      return noopExportComponent;
+    }
+
+    @Override
+    public TraceConfig getTraceConfig() {
+      return TraceConfig.getNoopTraceConfig();
+    }
+
+    private NoopTraceComponent() {}
+  }
+}