Switch to java 8, use CompletionStage in async API

Commit changes source and target java version to 1.8 and makes all
public async APIs use `CompletionStage` instead of `Response`, which
is now removed. This allows easier future chaining and makes API much
more usable. Currently all internal futures are converted to
`CompletionStage` at the highest level before returning to the user.

Author: lutovich

driver/pom.xml

@@ -104,8 +104,8 @@
         <artifactId>maven-compiler-plugin</artifactId>
         <version>2.3.2</version>
         <configuration>
-          <source>1.7</source>
-          <target>1.7</target>
+          <source>${java.version}</source>
+          <target>${java.version}</target>
         </configuration>
       </plugin>
       <plugin>

driver/src/main/java/org/neo4j/driver/internal/ExplicitTransaction.java

@@ -20,6 +20,7 @@
 
 import java.util.Collections;
 import java.util.Map;
+import java.util.concurrent.CompletionStage;
 
 import org.neo4j.driver.ResultResourcesHandler;
 import org.neo4j.driver.internal.async.AsyncConnection;
@@ -35,7 +36,6 @@
 import org.neo4j.driver.internal.types.InternalTypeSystem;
 import org.neo4j.driver.internal.util.BiConsumer;
 import org.neo4j.driver.v1.Record;
-import org.neo4j.driver.v1.Response;
 import org.neo4j.driver.v1.Statement;
 import org.neo4j.driver.v1.StatementResult;
 import org.neo4j.driver.v1.StatementResultCursor;
@@ -47,6 +47,7 @@
 import org.neo4j.driver.v1.types.TypeSystem;
 import org.neo4j.driver.v1.util.Function;
 
+import static org.neo4j.driver.internal.async.Futures.asCompletionStage;
 import static org.neo4j.driver.internal.util.ErrorUtil.isRecoverable;
 import static org.neo4j.driver.v1.Values.ofValue;
 import static org.neo4j.driver.v1.Values.value;
@@ -215,9 +216,9 @@ private void rollbackTx()
     }
 
     @Override
-    public Response<Void> commitAsync()
+    public CompletionStage<Void> commitAsync()
     {
-        return internalCommitAsync();
+        return asCompletionStage( internalCommitAsync() );
     }
 
     InternalFuture<Void> internalCommitAsync()
@@ -238,9 +239,9 @@ else if ( state == State.ROLLED_BACK )
     }
 
     @Override
-    public Response<Void> rollbackAsync()
+    public CompletionStage<Void> rollbackAsync()
     {
-        return internalRollbackAsync();
+        return asCompletionStage( internalRollbackAsync() );
     }
 
     InternalFuture<Void> internalRollbackAsync()
@@ -317,7 +318,7 @@ public StatementResult run( String statementText, Value statementParameters )
     }
 
     @Override
-    public Response<StatementResultCursor> runAsync( String statementText, Value parameters )
+    public CompletionStage<StatementResultCursor> runAsync( String statementText, Value parameters )
     {
         return runAsync( new Statement( statementText, parameters ) );
     }
@@ -329,7 +330,7 @@ public StatementResult run( String statementText )
     }
 
     @Override
-    public Response<StatementResultCursor> runAsync( String statementTemplate )
+    public CompletionStage<StatementResultCursor> runAsync( String statementTemplate )
     {
         return runAsync( statementTemplate, Values.EmptyMap );
     }
@@ -342,7 +343,8 @@ public StatementResult run( String statementText, Map<String,Object> statementPa
     }
 
     @Override
-    public Response<StatementResultCursor> runAsync( String statementTemplate, Map<String,Object> statementParameters )
+    public CompletionStage<StatementResultCursor> runAsync( String statementTemplate,
+            Map<String,Object> statementParameters )
     {
         Value params = statementParameters == null ? Values.EmptyMap : value( statementParameters );
         return runAsync( statementTemplate, params );
@@ -356,7 +358,7 @@ public StatementResult run( String statementTemplate, Record statementParameters
     }
 
     @Override
-    public Response<StatementResultCursor> runAsync( String statementTemplate, Record statementParameters )
+    public CompletionStage<StatementResultCursor> runAsync( String statementTemplate, Record statementParameters )
     {
         Value params = statementParameters == null ? Values.EmptyMap : value( statementParameters.asMap() );
         return runAsync( statementTemplate, params );
@@ -388,10 +390,10 @@ public StatementResult run( Statement statement )
     }
 
     @Override
-    public Response<StatementResultCursor> runAsync( Statement statement )
+    public CompletionStage<StatementResultCursor> runAsync( Statement statement )
     {
         ensureNotFailed();
-        return QueryRunner.runAsync( asyncConnection, statement, this );
+        return asCompletionStage( QueryRunner.runAsync( asyncConnection, statement, this ) );
     }
 
     @Override