Add three test utils, prepare for removing the “get” method from the Tag classes.

apm-commons/apm-trace/src/main/java/org/skywalking/apm/trace/tag/AbstractTag.java

@@ -24,5 +24,12 @@ public abstract class AbstractTag<T> {
 
     protected abstract void set(Span span, T tagValue);
 
+    /**
+     * @return the key of this tag.
+     */
+    public String key() {
+        return this.key;
+    }
+
     public abstract T get(Span span);
 }

apm-commons/apm-trace/src/main/java/org/skywalking/apm/trace/tag/ShortTag.java

-package org.skywalking.apm.trace.tag;
-
-import org.skywalking.apm.trace.Span;
-
-/**
- * Do the same thing as {@link StringTag}, just with a {@link Short} value.
- * <p>
- * Created by wusheng on 2017/2/17.
- */
-public class ShortTag extends AbstractTag<Short> {
-    public ShortTag(String key) {
-        super(key);
-    }
-
-    @Override
-    public void set(Span span, Short tagValue) {
-        span.setTag(super.key, (int) tagValue.shortValue());
-    }
-
-    /**
-     * Get a tag value, type of {@link Short}.
-     * After akka-message/serialize, all tags values are type of {@link String}, convert to {@link Short}, if necessary.
-     *
-     * @param span
-     * @return tag value
-     */
-    @Override
-    public Short get(Span span) {
-        Integer tagValue = span.getIntTag(super.key);
-        if (tagValue == null) {
-            return null;
-        } else {
-            return Short.valueOf(tagValue.toString());
-        }
-    }
-}

apm-commons/apm-trace/src/test/java/org/skywalking/apm/trace/tag/TagsTest.java

@@ -40,15 +40,4 @@ public class TagsTest {
         tag.set(span, 123);
         Assert.assertEquals(123, tag.get(span).intValue());
     }
-
-    @Test
-    public void testShortTag() {
-        ShortTag tag = new ShortTag("test.key");
-        Span span = new Span(1, "/test");
-        Assert.assertNull(tag.get(span));
-
-        short value = 123;
-        tag.set(span, value);
-        Assert.assertEquals(value, tag.get(span).intValue());
-    }
 }

apm-sniffer/apm-sniffer-mock/src/main/java/org/skywalking/apm/sniffer/mock/trace/tag/BooleanTagGetter.java

+package org.skywalking.apm.sniffer.mock.trace.tag;
+
+import org.skywalking.apm.trace.Span;
+import org.skywalking.apm.trace.tag.BooleanTag;
+
+/**
+ * Test case util for getting the {@link Boolean} type of the tag value.
+ *
+ * @author wusheng
+ */
+public class BooleanTagGetter {
+    public static Boolean get(Span span, BooleanTag tag) {
+        return span.getBoolTag(tag.key());
+    }
+}

apm-sniffer/apm-sniffer-mock/src/main/java/org/skywalking/apm/sniffer/mock/trace/tag/IntTagGetter.java

+package org.skywalking.apm.sniffer.mock.trace.tag;
+
+import org.skywalking.apm.trace.Span;
+import org.skywalking.apm.trace.tag.IntTag;
+
+/**
+ * Test case util for getting the {@link Integer} type of the tag value.
+ *
+ * @author wusheng
+ */
+public class IntTagGetter {
+    public static Integer get(Span span, IntTag tag) {
+        return span.getIntTag(tag.key());
+    }
+}

apm-sniffer/apm-sniffer-mock/src/main/java/org/skywalking/apm/sniffer/mock/trace/tag/StringTagGetter.java

+package org.skywalking.apm.sniffer.mock.trace.tag;
+
+import org.skywalking.apm.trace.Span;
+import org.skywalking.apm.trace.tag.StringTag;
+
+/**
+ * Test case util for getting the {@link String} type of the tag value.
+ *
+ * @author wusheng
+ */
+public class StringTagGetter {
+    public static String get(Span span, StringTag tag) {
+        return span.getStrTag(tag.key());
+    }
+}