Add constants for standard span tags (#30)

According to http://opentracing.io/data-semantics/

opentracing-api/pom.xml

@@ -22,7 +22,7 @@
     <parent>
         <groupId>io.opentracing</groupId>
         <artifactId>parent</artifactId>
-        <version>0.1.0-SNAPSHOT</version>
+        <version>0.2.0-SNAPSHOT</version>
     </parent>
 
     <artifactId>opentracing-api</artifactId>
@@ -32,4 +32,13 @@
     <properties>
         <main.basedir>${project.basedir}/..</main.basedir>
     </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-all</artifactId>
+            <version>1.10.19</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
 </project>

opentracing-api/src/main/java/io/opentracing/tag/AbstractTag.java

@@ -0,0 +1,28 @@
+/**
+ * Copyright 2016 The OpenTracing 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.opentracing.tag;
+
+public abstract class AbstractTag<T> {
+    protected final String key;
+
+    protected AbstractTag(String tagKey) {
+        this.key = tagKey;
+    }
+
+    public String getKey() {
+        return key;
+    }
+
+    abstract void set(io.opentracing.Span span, T tagValue);
+}

opentracing-api/src/main/java/io/opentracing/tag/BooleanTag.java

@@ -0,0 +1,25 @@
+/**
+ * Copyright 2016 The OpenTracing 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.opentracing.tag;
+
+public class BooleanTag extends AbstractTag<Boolean> {
+    BooleanTag(String key) {
+        super(key);
+    }
+
+    @Override
+    public void set(io.opentracing.Span span, Boolean tagValue) {
+        span.setTag(super.key, tagValue);
+    }
+}

opentracing-api/src/main/java/io/opentracing/tag/IntTag.java

@@ -0,0 +1,25 @@
+/**
+ * Copyright 2016 The OpenTracing 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.opentracing.tag;
+
+public class IntTag extends AbstractTag<Integer> {
+    IntTag(String key) {
+        super(key);
+    }
+
+    @Override
+    public void set(io.opentracing.Span span, Integer tagValue) {
+        span.setTag(super.key, tagValue);
+    }
+}

opentracing-api/src/main/java/io/opentracing/tag/ShortTag.java

@@ -0,0 +1,25 @@
+/**
+ * Copyright 2016 The OpenTracing 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.opentracing.tag;
+
+public class ShortTag extends AbstractTag<Short> {
+    ShortTag(String key) {
+        super(key);
+    }
+
+    @Override
+    public void set(io.opentracing.Span span, Short tagValue) {
+        span.setTag(super.key, tagValue);
+    }
+}

opentracing-api/src/main/java/io/opentracing/tag/StringTag.java

@@ -0,0 +1,29 @@
+/**
+ * Copyright 2016 The OpenTracing 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.opentracing.tag;
+
+public class StringTag extends AbstractTag<String> {
+    StringTag(String key) {
+        super(key);
+    }
+
+    @Override
+    public void set(io.opentracing.Span span, String tagValue) {
+        span.setTag(super.key, tagValue);
+    }
+
+    public void set(io.opentracing.Span span, StringTag tag) {
+        span.setTag(super.key, tag.key);
+    }
+}

opentracing-api/src/main/java/io/opentracing/tag/Tags.java

@@ -0,0 +1,91 @@
+/**
+ * Copyright 2016 The OpenTracing 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.opentracing.tag;
+
+/**
+ * The following span tags are recommended for instrumentors who are trying to capture more
+ * semantic information about the spans. Tracers may expose additional features based on these
+ * standardized data points. Tag names follow a general structure of namespacing.
+ *
+ * @see http://opentracing.io/data-semantics/
+ */
+
+public final class Tags {
+    private Tags(){}
+
+    /**
+    * A constant for setting the span kind to indicate that it represents a server span.
+    */
+    public static final String SPAN_KIND_SERVER = "server";
+
+    /**
+     * A constant for setting the span kind to indicate that it represents a client span.
+     */
+    public static final String SPAN_KIND_CLIENT = "client";
+
+    /**
+     *  HTTP_URL records the url of the incoming request.
+     */
+    public static final StringTag HTTP_URL = new StringTag("http.url");
+
+    /**
+     *  HTTP_STATUS records the http status code of the response.
+     */
+    public static final IntTag HTTP_STATUS = new IntTag("http.status_code");
+
+    /**
+     *  PEER_HOST_IPV4 records IPv4 host address of the peer.
+     */
+    public static final IntTag PEER_HOST_IPV4 = new IntTag("peer.ipv4");
+
+    /**
+     *  PEER_HOST_IPV6 records the IPv6 host address of the peer.
+     */
+    public static final StringTag PEER_HOST_IPV6 = new StringTag("peer.ipv6");
+
+    /**
+     *  PEER_SERVICE records the service name of the peer.
+     */
+    public static final StringTag PEER_SERVICE = new StringTag("peer.service");
+
+    /**
+     * PEER_HOSTNAME records the host name of the peer.
+     */
+    public static final StringTag PEER_HOSTNAME = new StringTag("peer.hostname");
+
+    /**
+     *  PEER_PORT records the port number of the peer.
+     */
+    public static final ShortTag PEER_PORT = new ShortTag("peer.port");
+
+    /**
+     *  SAMPLING_PRIORITY determines the priority of sampling this Span.
+     */
+    public static final ShortTag SAMPLING_PRIORITY = new ShortTag("sampling.priority");
+
+    /**
+     *  SPAN_KIND hints at the relationship between spans, e.g. client/server.
+     */
+    public static final StringTag SPAN_KIND = new StringTag("span.kind");
+
+    /**
+     *  COMPONENT is a low-cardinality identifier of the module, library, or package that is instrumented.
+     */
+    public static final StringTag COMPONENT  = new StringTag("component");
+
+    /**
+     * ERROR indicates whether a Span ended in an error state.
+     */
+    public static final BooleanTag ERROR = new BooleanTag("error");
+}

opentracing-api/src/test/java/io/opentracing/tag/BooleanTagTest.java

@@ -0,0 +1,34 @@
+/**
+ * Copyright 2016 The OpenTracing 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.opentracing.tag;
+
+import io.opentracing.Span;
+import org.junit.Test;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+
+public class BooleanTagTest {
+    @Test
+    public void testSetBoolean() {
+        Boolean value = true;
+        String key = "expected.key";
+        Span span = mock(Span.class);
+
+        BooleanTag tag = new BooleanTag(key);
+        tag.set(span, value);
+
+        verify(span).setTag(key, value);
+    }
+}

opentracing-api/src/test/java/io/opentracing/tag/IntTagTest.java

@@ -0,0 +1,34 @@
+/**
+ * Copyright 2016 The OpenTracing 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.opentracing.tag;
+
+import io.opentracing.Span;
+import org.junit.Test;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+
+public class IntTagTest {
+    @Test
+    public void testSetInt() {
+        Integer value = 7;
+        String key = "expected.key";
+        Span span = mock(Span.class);
+
+        IntTag tag = new IntTag(key);
+        tag.set(span, value);
+
+        verify(span).setTag(key, value);
+    }
+}

opentracing-api/src/test/java/io/opentracing/tag/ShortTagTest.java

@@ -0,0 +1,33 @@
+/**
+ * Copyright 2016 The OpenTracing 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.opentracing.tag;
+
+import io.opentracing.Span;
+import org.junit.Test;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+
+public class ShortTagTest {
+    @Test
+    public void testSetShort() {
+        Short value = 4;
+        String key = "expected.key";
+
+        Span span = mock(Span.class);
+        ShortTag tag = new ShortTag(key);
+        tag.set(span, value);
+        verify(span).setTag(key, value);
+    }
+}

opentracing-api/src/test/java/io/opentracing/tag/StringTagTest.java

@@ -0,0 +1,35 @@
+/**
+ * Copyright 2016 The OpenTracing 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.opentracing.tag;
+
+import io.opentracing.Span;
+import org.junit.Test;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+
+public class StringTagTest {
+
+    @Test
+    public void testSetString() {
+        String value = "expected.value";
+        String key = "expected.key";
+
+        Span span = mock(Span.class);
+        StringTag tag = new StringTag(key);
+        tag.set(span, value);
+
+        verify(span).setTag(key, value);
+    }
+}