[FLINK-5067] Make Flink compile with 1.8 Java compiler

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.2.0
• Fix Version/s: 1.3.0
• Component/s: Build System

Environment

macOS Sierra 10.12.1, java version "1.8.0_112", Apache Maven 3.3.9

• Assignee: Andrey Melentyev
• Reporter: Andrey Melentyev
• Created: 14/Nov/16 20:44
• Updated: 22/Mar/17 19:53
• Resolved: 04/Mar/17 11:16

Description

Flink fails to compile when using 1.8 as source and target in Maven. There are two types of issue that are both related to the new type inference rules:

• Call to TypeSerializer.copy method in TupleSerializer.java:112 now resolves to a different overload than before causing a compilation error: [ERROR] /Users/andrey.melentyev/Dev/github.com/apache/flink/flink-core/src/main/java/org/apache/flink/api/java/typeutils/runtime/TupleSerializer.java:[112,63] incompatible types: void cannot be converted to java.lang.Object
• A number of unit tests using assertEquals fail to compile:
  [ERROR] /Users/andrey.melentyev/Dev/github.com/apache/flink/flink-java/src/test/java/org/apache/flink/api/common/operators/CollectionExecutionAccumulatorsTest.java:[50,25] reference to assertEquals is ambiguous
  [ERROR] both method assertEquals(long,long) in org.junit.Assert and method assertEquals(java.lang.Object,java.lang.Object) in org.junit.Assert match

In both of the above scenarios explicitly casting one of the arguments helps the compiler to resolve overloaded method call correctly.

It is possible to maintain Flink's code base in a state when it can be built by both 1.7 and 1.8. For this purpose we need minor code fixes and an automated build in Travis to keep the new good state.

Issue Links

• links to: GitHub Pull Request #2804