Code generation fails with "Prefix '' is already bound to ''" when episode generation is on on Java 9

On Java 9 with episode generation turned on, code generation fails:

[ERROR] Failed to execute goal org.jvnet.jaxb2.maven2:maven-jaxb23-plugin:0.13.3-SNAPSHOT:generate (generate) on project maven-jaxb2-plugin-tests-java-9: Execution generate of goal org.jvnet.jaxb2.maven2:maven-jaxb23-plugin:0.13.3-SNAPSHOT:generate failed: Prefix '' is already bound to '' -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.jvnet.jaxb2.maven2:maven-jaxb23-plugin:0.13.3-SNAPSHOT:generate (generate) on project maven-jaxb2-plugin-tests-java-9: Execution generate of goal org.jvnet.jaxb2.maven2:maven-jaxb23-plugin:0.13.3-SNAPSHOT:generate failed: Prefix '' is already bound to ''
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:212)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
	at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
	at org.apache.maven.cli.MavenCli.execute(MavenCli.java:863)
	at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:288)
	at org.apache.maven.cli.MavenCli.main(MavenCli.java:199)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:564)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
	at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
	at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
Caused by: org.apache.maven.plugin.PluginExecutionException: Execution generate of goal org.jvnet.jaxb2.maven2:maven-jaxb23-plugin:0.13.3-SNAPSHOT:generate failed: Prefix '' is already bound to ''
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:145)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:207)
	... 20 more
Caused by: java.lang.IllegalArgumentException: Prefix '' is already bound to ''
	at com.sun.xml.txw2.StartTag.addNamespaceDecl(StartTag.java:191)
	at com.sun.xml.txw2.ContainerElement._namespace(ContainerElement.java:333)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:564)
	at com.sun.xml.txw2.ContainerElement.invoke(ContainerElement.java:134)
	at com.sun.proxy.$Proxy46._namespace(Unknown Source)
	at com.sun.tools.xjc.addon.episode.PluginImpl.run(PluginImpl.java:174)
	at com.sun.tools.xjc.model.Model.generateCode(Model.java:292)
	at org.jvnet.mjiip.v_2_3.XJC23Mojo.generateCode(XJC23Mojo.java:66)
	at org.jvnet.mjiip.v_2_3.XJC23Mojo.doExecute(XJC23Mojo.java:41)
	at org.jvnet.mjiip.v_2_3.XJC23Mojo.doExecute(XJC23Mojo.java:28)
	at org.jvnet.jaxb2.maven2.RawXJC2Mojo.doExecute(RawXJC2Mojo.java:473)
	at org.jvnet.jaxb2.maven2.RawXJC2Mojo.execute(RawXJC2Mojo.java:317)
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
	... 21 more

[mw84367]

It seems that XJC has a bug. When I provide an additional dummy XML schema without the normal header <xs:schema targetNamespace="my.namespace" elementFormDefault="qualified" xmlns="my.namespace" xmlns:xs="http://www.w3.org/2001/XMLSchema">

,i.e. the “targetNamespace”, “elementFormDefault” and “xmlns” attributes, the error is gone.

Thus one just need to add a dummy XSD file like <xs:schema id="Dummy" xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:element name="Dummy"> <xs:complexType> <xs:sequence> <xs:element name="test"/> </xs:sequence> </xs:complexType> </xs:element> </xs:schema>

and it works. 😃

[highsource]

OK, I’ll release the new version in the next days then. I don’t see the need for extra pre-java9/post-java9 versions at the moment, So I’ll risk releasing just one version.