CXF Compilation Episode Issue

This example demonstrates a problem in CXF referencing types in the WSDL that are part of previous compilation episodes.

Versions

The test uses JDK 1.8u121 (JAXB 2.2.11) and CXF 3.1.10

The 2 classes of interst are:

org.apache.cxf.tools.wsdlto.databinding.jaxb.JAXBDataBinding
com.sun.tools.xjc.reader.xmlschema.BGMBuilder

Problem

CXF fails when using existing compilation expisodes of schemata in same or other namespace.

Expected

Generation of a SEI that references {model}SomeRQ type as the request and {model}SomeRS as response type.

Actual

[ERROR] Failed to execute goal org.apache.cxf:cxf-codegen-plugin:3.1.10:wsdl2java (generate-wsdl-bindings) on project cxf-wsdlgen-issue-service:
  Execution generate-wsdl-bindings of goal org.apache.cxf:cxf-codegen-plugin:3.1.10:wsdl2java failed:
    Failed to create java parameter for part [body] in method [invoke] - this wsdl is invalid, please use the wsdlvalidator tool to validate this wsdl -> [Help 1]

Description

Including a schema from an earlier compilation episode in a wsdl schema with the same namespace will cause to CXF fail when resolving the Java type when constructing the wsdl operation parameter.

parent
  |
  +-- model (with episode)
  |     |
  |     +-- model schema in urn:model
  |     |
  |     +-- xjc generated episode
  |
  +-- service
        |
        +-- message schema in urn:model
        |    |
        |    +-- include model schema
        |    |
        |    +-- the wsdl operation message element is defined in this schema file
        |
        +-- wsdl in urn:service
             |
             +-- import message schema
             |
             +-- wsdl messages reference request and response payload from message schema
             |
             +-- wsdl operation references above wsdl messages

The test case is setup in a way that one can see the wsdl generation failing in its original form:

mvn clean install

and with a workaround where the episode from the previous compilation is pre-processed and the map attribute is set to true:

mvn clean install -Dworkaround=true

CXF does not see the types of the previous episode. The ClassSelector it registers with the XJC schema builder is not populated with the type information of the current schema set and neither with any types that have been included into the XJC compilation with reference to previous compilation episodes.

In com.sun.tools.xjc.reader.xmlschema.BGMBuilder:L299 any schema that has it's binding attribute map set to false will be excluded from being pushed into any provided ClassSelector:

for( XSSchema s : Ring.get(XSSchemaSet.class).getSchemas() ) {
    BISchemaBinding sb = getBindInfo(s).get(BISchemaBinding.class);

    if(sb!=null && !sb.map) {
        sb.markAsAcknowledged();
        continue;       // no mapping for this package  <<<<<<<<<<<<<<<< schema is part of a previous episode
    }

    getClassSelector().pushClassScope( new CClassInfoParent.Package(
        getClassSelector().getPackage(s.getTargetNamespace())) );

    checkMultipleSchemaBindings(s);
    processPackageJavadoc(s);
    populate(s.getAttGroupDecls(),s);
    populate(s.getAttributeDecls(),s);
    populate(s.getElementDecls(),s);                    <<<<<<<<<<<<<<<< XJC would have to reach here to populate the supplied CXF ClassSelector
    populate(s.getModelGroupDecls(),s);
    ...
}

I argue this is not a XJC bug but a flaw in the approach of the CXF JAXBDataBinding module to get type information from XJC. It uses XJC to process the schemata but then it only registers a handler with XJC to receive the type information that is part of the current compilation episode but not any previous ones. This will cause any references to types defined in previous compilation episodes to be not available to CXF when building the WSDL model.

Case 1: Original Episode provided to wsdl2java

mvn clean install

Using following episode file:

<?xml version="1.0" encoding="utf-8"?>
<bindings version="2.1" xmlns="http://java.sun.com/xml/ns/jaxb" if-exists="true">

  <bindings xmlns:tns="urn:model" scd="x-schema::tns">
    <!-- package model is flagged as already excluded -->
    <schemaBindings map="false">
      <package name="model"/>
    </schemaBindings>
    ...
  </bindings>

</bindings>

BGMBuilder:L306 Schema populated correctly with an original episode file:

ClassCollector on JAXBDataBinding:L462 does not contain any of the types of previous episodes:

Case2: Edited Episode provided to wsdl2java

mvn clean install -Dworkaround=true

Using following episode file:

<?xml version="1.0" encoding="utf-8"?>
<bindings version="2.1" xmlns="http://java.sun.com/xml/ns/jaxb" if-exists="true">

  <bindings xmlns:tns="urn:model" scd="x-schema::tns">
    <!-- package model is flagged as included but types of previous episode are listed as already present -->
    <schemaBindings map="false">
      <package name="model"/>
    </schemaBindings>
    
    <bindings if-exists="true" scd="~tns:SomeDomainEntity">
      <class ref="model.SomeDomainEntity"/>
    </bindings>
    ...
  </bindings>

</bindings>

BGMBuilder Schema populated correctly with an altered episode file:

ClassCollector on JAXBDataBinding:L462 now contains a type reference to any types in the current xjc compilation episode (which in this test case is the wsdl message types) but still missing any types of previous episodes:

The cxf ClassSelector provided to BGMBuilder is not populated with all known classes but only those that have been in schemata that are not part of a prior compilation episodes.

ClassSelector provided to BGMBuilder on line JAXBDataBinding:L365 (wrapped in allocator) would normally need to be populated by the BGMBuilder:L311 > BGMBuilder:L352.

This problem is also the root cause for CXF-7074 as in this case the u:Fault type is imported from a prior compilation episode.

How to fix it?

In org.apache.cxf.tools.wsdlto.databinding.jaxb.JAXBDataBinding.initialize we have a CXF parsed list of schema types available under this.context.get("xmlSchemaCollection") but we don't know what Java classes they are mapped to. The mapping of Java classes to schema types is only known by XJC as the processor of episode files and newly generated code.

The org.apache.cxf.tools.util.ClassCollector is "injected" into the XJC via the org.apache.cxf.tools.wsdlto.databinding.jaxb.ClassNameAllocatorImpl and collects the class names that are generated by XJC. This does neither collect inner classes (see comment in com.sun.tools.xjc.api.ClassNameAllocator javadocs) nor does it have any exposure to the mapped classes from prior schema episodes.

Inject a "harvester" plugin into the XJC compiler to process the parsed schemata in Plugin#postProcessModel method. Here we simply iterate the schemata and element declarations. An episode referenced element declaration will carry bind info accordingly. This information can then be stored and used during the SEI generation.

The TypeHarvesterPlugin can successfully retrieve following type information from the example:

{urn:util}Fault => util.Fault
{urn:model}SomeDomainEntity => model.SomeDomainEntity
{urn:model}HomeContact => model.HomeContact
{urn:model}BusinessContact => model.BusinessContact
{urn:service}Dummy => util.Fault

The other much simpler alternative is to just parse the episode files supplied to the XJC context and assume it would have used those to resolve {namspace}Type types to Java names.

Creating a Fully Qualified Class Name

I coded a simple XJC module and injected the known episode references into the ClassCollector here here.

To tie this together with the CXF binding module following needs to happen. The method JAXBDataBinding.getType() is consulted by ProcessorUtil.getFullClzName() to produce a fully qualified classname when constructing the message parts. This method only looks at the raw class model generated by the XJC compiler which is not including the episode classes. At this point we could also inspect the content of the ClassCollector. If the getType() method returns null (QName unknown) the ProcessorUtil.resolvePartType() method is called. This method is speculating wildly about the full classname. It looks a bit like a previous attempt to prevent a NPE when the referenced element in the WSDL is unknown by the XJC generated model.

Thoughts:

JAXBDataBinding.getType() should never return null because if the class is unknown from either generated XJC code model or prior episode file(s), the WSDL is invalid.
Enhancing JAXBDataBinding.getType() to also return a class name for any types known from a prior compilation episode will be sufficient to fix this issue reliably. The fix would be local to the JAXB binding context.
The solution is quite complex and we should submit a patch to JAXB project to implement an XJC interface to also extract a list of prior known model types from compilation episodes.

bertramn/cxf-wsdlgen-issue