Add support to use SemanticAttributes with Span.Builder.

api/src/main/java/io/opentelemetry/common/Acceptor.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2020, OpenTelemetry 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.opentelemetry.common;
+
+/**
+ * A function to be executed with a single argument, having a side effect.
+ *
+ * <p>Adapted from Java 8's {@code java.util.function.Consumer}.
+ *
+ * @param <T> Type of the input argument.
+ */
+public interface Acceptor<T> {
+
+  /**
+   * Performs this operation on the given argument.
+   *
+   * @param arg the input argument
+   */
+  void exec(T arg);
+}

api/src/main/java/io/opentelemetry/trace/DefaultTracer.java

@@ -16,6 +16,7 @@
 
 package io.opentelemetry.trace;
 
+import io.opentelemetry.common.Acceptor;
 import io.opentelemetry.common.AttributeValue;
 import io.opentelemetry.context.Scope;
 import io.opentelemetry.internal.Utils;
@@ -157,6 +158,12 @@ public NoopSpanBuilder setStartTimestamp(long startTimestamp) {
       return this;
     }
 
+    @Override
+    public Span.Builder apply(Acceptor<Span.Builder> acceptor) {
+      acceptor.exec(this);
+      return this;
+    }
+
     private NoopSpanBuilder(String name) {
       Utils.checkNotNull(name, "name");
     }

api/src/main/java/io/opentelemetry/trace/Span.java

@@ -16,6 +16,7 @@
 
 package io.opentelemetry.trace;
 
+import io.opentelemetry.common.Acceptor;
 import io.opentelemetry.common.AttributeValue;
 import java.util.Map;
 import javax.annotation.Nullable;
@@ -544,6 +545,17 @@ interface Builder {
      */
     Builder setStartTimestamp(long startTimestamp);
 
+    /**
+     * Applies the given consumer to this {@link Builder}.
+     *
+     * <p>This is indented to be used with {@link
+     * io.opentelemetry.trace.attributes.StringAttributeSetter#set(String)}, etc.
+     *
+     * @param acceptor The {@link Acceptor} to apply to this
+     * @return this.
+     */
+    Builder apply(Acceptor<Builder> acceptor);
+
     /**
      * Starts a new {@link Span}.
      *

api/src/main/java/io/opentelemetry/trace/attributes/BooleanAttributeSetter.java

@@ -16,6 +16,7 @@
 
 package io.opentelemetry.trace.attributes;
 
+import io.opentelemetry.common.Acceptor;
 import io.opentelemetry.trace.Span;
 import javax.annotation.concurrent.Immutable;
 
@@ -60,4 +61,21 @@ public String key() {
   public void set(Span span, boolean value) {
     span.setAttribute(key(), value);
   }
+
+  /**
+   * Returns a {@link Acceptor} for use set {@link Span.Builder#apply(Acceptor)} that sets the
+   * attribute to {@code value}.
+   *
+   * @param value the value for this attribute
+   * @return A {@link Acceptor} for use set {@link Span.Builder#apply(Acceptor)}.
+   */
+  @SuppressWarnings("InconsistentOverloads")
+  public Acceptor<Span.Builder> set(final boolean value) {
+    return new Acceptor<Span.Builder>() {
+      @Override
+      public void exec(Span.Builder arg) {
+        arg.setAttribute(key(), value);
+      }
+    };
+  }
 }

api/src/main/java/io/opentelemetry/trace/attributes/DoubleAttributeSetter.java

@@ -16,6 +16,7 @@
 
 package io.opentelemetry.trace.attributes;
 
+import io.opentelemetry.common.Acceptor;
 import io.opentelemetry.trace.Span;
 import javax.annotation.concurrent.Immutable;
 
@@ -60,4 +61,21 @@ public String key() {
   public void set(Span span, double value) {
     span.setAttribute(key(), value);
   }
+
+  /**
+   * Returns a {@link Acceptor} for use set {@link Span.Builder#apply(Acceptor)} that sets the
+   * attribute to {@code value}.
+   *
+   * @param value the value for this attribute
+   * @return A {@link Acceptor} for use set {@link Span.Builder#apply(Acceptor)}.
+   */
+  @SuppressWarnings("InconsistentOverloads")
+  public Acceptor<Span.Builder> set(final double value) {
+    return new Acceptor<Span.Builder>() {
+      @Override
+      public void exec(Span.Builder arg) {
+        arg.setAttribute(key(), value);
+      }
+    };
+  }
 }

api/src/main/java/io/opentelemetry/trace/attributes/LongAttributeSetter.java

@@ -16,6 +16,7 @@
 
 package io.opentelemetry.trace.attributes;
 
+import io.opentelemetry.common.Acceptor;
 import io.opentelemetry.trace.Span;
 import javax.annotation.concurrent.Immutable;
 
@@ -60,4 +61,21 @@ public String key() {
   public void set(Span span, long value) {
     span.setAttribute(key(), value);
   }
+
+  /**
+   * Returns a {@link Acceptor} for use set {@link Span.Builder#apply(Acceptor)} that sets the
+   * attribute to {@code value}.
+   *
+   * @param value the value for this attribute
+   * @return A {@link Acceptor} for use set {@link Span.Builder#apply(Acceptor)}.
+   */
+  @SuppressWarnings("InconsistentOverloads")
+  public Acceptor<Span.Builder> set(final long value) {
+    return new Acceptor<Span.Builder>() {
+      @Override
+      public void exec(Span.Builder arg) {
+        arg.setAttribute(key(), value);
+      }
+    };
+  }
 }

api/src/main/java/io/opentelemetry/trace/attributes/StringAttributeSetter.java

@@ -16,6 +16,7 @@
 
 package io.opentelemetry.trace.attributes;
 
+import io.opentelemetry.common.Acceptor;
 import io.opentelemetry.trace.Span;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
@@ -61,4 +62,21 @@ public String key() {
   public void set(Span span, @Nullable String value) {
     span.setAttribute(key(), value);
   }
+
+  /**
+   * Returns a {@link Acceptor} for use set {@link Span.Builder#apply(Acceptor)} that sets the
+   * attribute to {@code value}.
+   *
+   * @param value the value for this attribute
+   * @return A {@link Acceptor} for use set {@link Span.Builder#apply(Acceptor)}.
+   */
+  @SuppressWarnings("InconsistentOverloads")
+  public Acceptor<Span.Builder> set(@Nullable final String value) {
+    return new Acceptor<Span.Builder>() {
+      @Override
+      public void exec(Span.Builder arg) {
+        arg.setAttribute(key(), value);
+      }
+    };
+  }
 }

api/src/test/java/io/opentelemetry/trace/attributes/SemanticAttributesTest.java

@@ -17,6 +17,7 @@
 package io.opentelemetry.trace.attributes;
 
 import static com.google.common.truth.Truth.assertThat;
+import static io.opentelemetry.trace.attributes.SemanticAttributes.HTTP_METHOD;
 
 import io.opentelemetry.OpenTelemetry;
 import io.opentelemetry.trace.Span;
@@ -33,16 +34,17 @@
 @RunWith(JUnit4.class)
 public class SemanticAttributesTest {
 
-  private Span span;
+  private Span.Builder spanBuilder;
 
   @Before
   public void setUp() {
     Tracer tracer = OpenTelemetry.getTracerProvider().get("io.telemetry.api");
-    span = tracer.spanBuilder("junit").startSpan();
+    spanBuilder = tracer.spanBuilder("junit");
   }
 
   @Test
   public void shouldEnableSetAttributeOnSpan() throws IllegalAccessException {
+    Span span = spanBuilder.startSpan();
     Set<String> keys = new HashSet<>();
     Field[] fields = SemanticAttributes.class.getFields();
     for (Field field : fields) {
@@ -65,6 +67,35 @@ public void shouldEnableSetAttributeOnSpan() throws IllegalAccessException {
     assertThat(keys.size()).isEqualTo(fields.length);
   }
 
+  @Test
+  public void shouldEnableSetAttributeOnSpanBuilder() throws IllegalAccessException {
+    Set<String> keys = new HashSet<>();
+    Field[] fields = SemanticAttributes.class.getFields();
+    for (Field field : fields) {
+      Object attribute = field.get(null);
+      if (attribute instanceof StringAttributeSetter) {
+        keys.add(((StringAttributeSetter) attribute).key());
+        spanBuilder.apply(((StringAttributeSetter) attribute).set("TestValue"));
+        spanBuilder.apply(((StringAttributeSetter) attribute).set(null));
+      } else if (attribute instanceof LongAttributeSetter) {
+        keys.add(((LongAttributeSetter) attribute).key());
+        spanBuilder.apply(((LongAttributeSetter) attribute).set(42));
+      } else if (attribute instanceof DoubleAttributeSetter) {
+        keys.add(((DoubleAttributeSetter) attribute).key());
+        spanBuilder.apply(((DoubleAttributeSetter) attribute).set(3.14));
+      } else if (attribute instanceof BooleanAttributeSetter) {
+        keys.add(((BooleanAttributeSetter) attribute).key());
+        spanBuilder.apply(((BooleanAttributeSetter) attribute).set(true));
+      }
+    }
+    assertThat(keys.size()).isEqualTo(fields.length);
+  }
+
+  @Test
+  public void setBuilderDemo() {
+    spanBuilder.apply(HTTP_METHOD.set("GET"));
+  }
+
   @Test
   public void shouldCreateAllSetterTypes() {
     assertThat(BooleanAttributeSetter.create("attr.one"))

sdk/src/main/java/io/opentelemetry/sdk/trace/SpanBuilderSdk.java

@@ -17,6 +17,7 @@
 package io.opentelemetry.sdk.trace;
 
 import io.grpc.Context;
+import io.opentelemetry.common.Acceptor;
 import io.opentelemetry.common.AttributeValue;
 import io.opentelemetry.internal.Utils;
 import io.opentelemetry.sdk.common.Clock;
@@ -198,6 +199,12 @@ public Span.Builder setStartTimestamp(long startTimestamp) {
     return this;
   }
 
+  @Override
+  public Span.Builder apply(Acceptor<Span.Builder> acceptor) {
+    acceptor.exec(this);
+    return this;
+  }
+
   @Override
   public Span startSpan() {
     SpanContext parentContext = parent(parentType, parent, remoteParent);