[MWAR-397] Replace XStream with Modello to merge overlays

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Resolved
• Fix Version/s: 3.3.0
• Assignee: Robert Scholte
• Reporter: Robert Scholte
• Created: 05/Nov/16 19:56
• Updated: 19/Jan/20 10:15
• Resolved: 10/Nov/19 20:56

Description

When packaging a war with most recent jigsaw-jdk9-ea releases you will get the following exception:

Caused by: java.lang.reflect.InaccessibleObjectException: Unable to make field private final java.util.Comparator java.util.TreeMap.comparator accessible: module java.base does not "exports private java.util" to unnamed module @17088b23
    at jdk.internal.reflect.Reflection.throwInaccessibleObjectException (Reflection.java:414)
    at java.lang.reflect.AccessibleObject.checkCanSetAccessible (AccessibleObject.java:198)
    at java.lang.reflect.Field.checkCanSetAccessible (Field.java:171)
    at java.lang.reflect.Field.setAccessible (Field.java:165)
    at com.thoughtworks.xstream.core.util.Fields.locate (Fields.java:40)
    at com.thoughtworks.xstream.converters.collections.TreeMapConverter.<clinit> (TreeMapConverter.java:50)
    at com.thoughtworks.xstream.XStream.setupConverters (XStream.java:832)
    at com.thoughtworks.xstream.XStream.<init> (XStream.java:574)
    at com.thoughtworks.xstream.XStream.<init> (XStream.java:496)
    at com.thoughtworks.xstream.XStream.<init> (XStream.java:465)
    at com.thoughtworks.xstream.XStream.<init> (XStream.java:411)
    at com.thoughtworks.xstream.XStream.<init> (XStream.java:378)
    at org.apache.maven.plugins.war.util.WebappStructureSerializer.<clinit> (WebappStructureSerializer.java:47)

Root cause is the change is the jigsaw-jdk-9-ea+135

The changes to setAccessible in #AwkwardStrongEncapsulation is going to
be disruptive and will no doubt expose hacks in many areas. We've run
into several of these already. The command line option to allow existing
code to break into non-public types/members is --add-exports-private.
The format of the value passed to this option is the same--add-exports.
With #AddExportsInManifest then there are equivalents in the application
JAR main manifest to try out too.

The stacktrace exposes that the issue is caused by XStream. It seems that XStream is used to be able to merge overlays. Maven and most other plugins use Modello for these kind of things.

There's still a lot of discussion about #ReflectiveAccessToNonExportedTypes and #AwkwardStrongEncapsulation and but I think we can avoid this issue by simply switching to the well known Modello solution.

Issue Links

• is related to: MWAR-405 Workaround XStream incompatibility with Java9
• is related to: MWAR-429 Failed to execute goal org.apache.maven.plugins:maven-war-plugin:3.2.3:exploded (pre-exploded-war) on project alfresco-platform
• is superceded by: MWAR-375 Remove the useCache with its implementation