HADOOP-19375: Organize JDK version-specific code in IDEA friendly approach

Closes #7245

Reviewed-by: Steve Loughran <stevel@apache.org>
Signed-off-by: Chris Nauroth <cnauroth@apache.org>

hadoop-common-project/hadoop-annotations/pom.xml

@@ -52,27 +52,25 @@
           <systemPath>${java.home}/../lib/tools.jar</systemPath>
         </dependency>
       </dependencies>
-    </profile>
-    <profile>
-      <id>jdk10</id>
-      <activation>
-        <jdk>[10,)</jdk>
-      </activation>
       <build>
         <plugins>
           <plugin>
-            <artifactId>maven-compiler-plugin</artifactId>
-            <configuration>
-              <excludes>
-                <exclude>org/apache/hadoop/classification/tools/</exclude>
-              </excludes>
-            </configuration>
-          </plugin>
-          <plugin>
-            <artifactId>maven-javadoc-plugin</artifactId>
-            <configuration>
-              <excludePackageNames>org.apache.hadoop.classification.tools</excludePackageNames>
-            </configuration>
+            <groupId>org.codehaus.mojo</groupId>
+            <artifactId>build-helper-maven-plugin</artifactId>
+            <executions>
+              <execution>
+                <id>add-source</id>
+                <phase>generate-sources</phase>
+                <goals>
+                  <goal>add-source</goal>
+                </goals>
+                <configuration>
+                  <sources>
+                    <source>${basedir}/src/main/java8</source>
+                  </sources>
+                </configuration>
+              </execution>
+            </executions>
           </plugin>
         </plugins>
       </build>

hadoop-hdfs-project/hadoop-hdfs/pom.xml

@@ -549,19 +549,29 @@ https://maven.apache.org/xsd/maven-4.0.0.xsd">
       </build>
     </profile>
     <profile>
-      <id>java9</id>
+      <id>jdk1.8</id>
       <activation>
-        <jdk>[9,)</jdk>
+        <jdk>1.8</jdk>
       </activation>
       <build>
         <plugins>
           <plugin>
-            <artifactId>maven-compiler-plugin</artifactId>
-            <configuration>
-              <testExcludes>
-                <testExclude>org/apache/hadoop/hdfs/TestDFSClientFailover.java</testExclude>
-              </testExcludes>
-            </configuration>
+            <groupId>org.codehaus.mojo</groupId>
+            <artifactId>build-helper-maven-plugin</artifactId>
+            <executions>
+              <execution>
+                <id>add-source</id>
+                <phase>generate-sources</phase>
+                <goals>
+                  <goal>add-source</goal>
+                </goals>
+                <configuration>
+                  <sources>
+                    <source>${basedir}/src/main/java8</source>
+                  </sources>
+                </configuration>
+              </execution>
+            </executions>
           </plugin>
         </plugins>
       </build>