Deserializing @JacksonXmlElementWrapper(useWrapping = false) fails on missing (optional) attribute

[nezda]

Attempting to deserialize an unwrapped collection field (@JacksonXmlElementWrapper(useWrapping = false)) fails if element is missing an attribute. For example, given:

static class Optional {
    @JacksonXmlText
    public String number = "NOT SET";
    public String type = "NOT SET";
}
static class MultiOptional {
    @JacksonXmlElementWrapper(useWrapping = false)
    public List<Optional> optional;
}

XmlMapper can handle <MultiOptional><optional type='work'>123-456-7890</optional></MultiOptional>
but not <MultiOptional><optional>123-456-7890</optional></MultiOptional> (since it is missing type property).

Here are some related additions I made to com.fasterxml.jackson.dataformat.xml.failing.TestDeserialization to refine this issue:

        private static class StateAttrLocalName
    {
        @JacksonXmlProperty(localName="state", isAttribute=true)
        public String stateAttr = "NOT SET";

                @Override public String toString() { return "StateAttrLocalName: stateAttr: " + stateAttr; }
    }

        public void testAttrLocalName() throws Exception
    {
        StateAttrLocalName ob = MAPPER.readValue("<Wrapper state='stateAttr'></Wrapper>",
                StateAttrLocalName.class);
        assertNotNull(ob);
                System.err.println("ob: " + ob);
        assertEquals("stateAttr", ob.stateAttr);
    }


        private static class StateAttr
    {
        @JacksonXmlProperty(localName="state", isAttribute=true)
        public String state = "NOT SET";

                @Override public String toString() { return "StateAttr: state: " + state; }
    }

        public void testAttr() throws Exception
    {
        StateAttr ob = MAPPER.readValue("<Wrapper state='stateAttr'></Wrapper>",
                StateAttr.class);
        assertNotNull(ob);
                System.err.println("ob: " + ob);
        assertEquals("stateAttr", ob.state);
    }

        private static class TwoStates
    {
        @JacksonXmlProperty(localName="state", isAttribute=true)
        public String stateAttr = "NOT SET";
        public String state = "NOT SET";

                @Override public String toString() { return "TwoStates: stateAttr: " + stateAttr + " state: " + state; }
    }

    public void testAttrElementConflict() throws Exception
    {
        TwoStates ob = MAPPER.readValue("<Wrapper state='stateAttr'><state>stateElement</state></Wrapper>",
                TwoStates.class);
        assertNotNull(ob);
                System.err.println("ob: " + ob);
        assertEquals("stateElement", ob.state);
        assertEquals("stateAttr", ob.stateAttr); // attribute stateAttr is ignored
    }

        private static class Optional
    {
                @JacksonXmlText
        public String number = "NOT SET";
        //@JacksonXmlProperty(isAttribute=true)
                public String type = "NOT SET";

                @Override public String toString() { return "Optional: number: " + number + " type: " + type; }
    }

    public void testOptionalAttr() throws Exception
    {
        Optional ob = MAPPER.readValue("<phone type='work'>123-456-7890</phone>",
                Optional.class);
        assertNotNull(ob);
                System.err.println("ob: " + ob);
        assertEquals("123-456-7890", ob.number);
        assertEquals("work", ob.type);
    }

    public void testMissingOptionalAttr() throws Exception
    {
        Optional ob = MAPPER.readValue("<phone>123-456-7890</phone>",
                Optional.class);
        assertNotNull(ob);
                System.err.println("ob: " + ob);
        assertEquals("123-456-7890", ob.number);
        assertEquals("NOT SET", ob.type);
    }

        private static class MultiOptional
    {
                @JacksonXmlElementWrapper(useWrapping = false)
                public List<Optional> optional;

                @Override public String toString() { return "MultiOptional: optional's: " + optional; }
    }

        public void testMultiOptional() throws Exception
    {
        MultiOptional ob = MAPPER.readValue("<MultiOptional><optional type='work'>123-456-7890</optional></MultiOptional>",
                MultiOptional.class);
        assertNotNull(ob);
                System.err.println("ob: " + ob); // works fine
//        assertEquals("123-456-7890", ob.number);
//        assertEquals("NOT SET", ob.type);
    }

        public void testMultiOptionalWithMissingType() throws Exception
    {
            MultiOptional ob = MAPPER.readValue("<MultiOptional><optional>123-456-7890</optional></MultiOptional>",
                MultiOptional.class);
        assertNotNull(ob);
                System.err.println("ob: " + ob); // fails: 
//        assertEquals("123-456-7890", ob.number);
//        assertEquals("NOT SET", ob.type);
    }

[cowtowncoder]

Thanks, sounds like a bug.

[nezda]

Would be awesome to not have to use JAXB or JiBX for this project.

[cowtowncoder]

Yes. I hope to find time to fix this for 2.2.2 release. Thank you for providing the test case!

[ShijunK]

something may or may not related
unwrapped property's XMLStreamReader is not reset/cleanup properly before being reused for a different property

test case:

  @JacksonXmlRootElement(localName = "root")
    public static class Root {

        @JacksonXmlProperty(localName = "unwrapped")
        @JacksonXmlElementWrapper(useWrapping = false)
        private List<UnwrappedElement> unwrapped;

        @JacksonXmlProperty
        private String name;

        public static class UnwrappedElement {
            @JacksonXmlProperty(isAttribute = true)
            private String id;

            @JacksonXmlProperty(isAttribute = true)
            private String type;
        }
    }

    @Test
    public void testUnwrappedWithOptionalAttribute() throws Exception {
        Root twoAttributes = xmlMapper.readValue("<root><unwrapped id=\"1\" type=\"string\"/><unwrapped id=\"2\" type=\"string\"/><name>text</name></root>", Root.class);
        assertThat(twoAttributes.name, equalTo("test"));
    }

exception

java.lang.IllegalArgumentException: Invalid index 0; current element has only 0 attributes
    at com.ctc.wstx.sr.AttributeCollector.throwIndex(AttributeCollector.java:1018)
    at com.ctc.wstx.sr.AttributeCollector.getLocalName(AttributeCollector.java:325)
    at com.ctc.wstx.sr.BasicStreamReader.getAttributeLocalName(BasicStreamReader.java:576)
    at com.fasterxml.jackson.dataformat.xml.deser.XmlTokenStream._next(XmlTokenStream.java:306)
    at com.fasterxml.jackson.dataformat.xml.deser.XmlTokenStream.next(XmlTokenStream.java:162)
    at com.fasterxml.jackson.dataformat.xml.deser.FromXmlParser.nextToken(FromXmlParser.java:451)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:291)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:121)
    at com.fasterxml.jackson.dataformat.xml.deser.WrapperHandlingDeserializer.deserialize(WrapperHandlingDeserializer.java:109)
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:2888)
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2034)

[nezda]

@ShijunK if you are using

<dependency>
  <groupId>org.codehaus.woodstox</groupId>
  <artifactId>woodstox-core-asl</artifactId>
  <version>4.x</version>
</dependency>

and you can remove it (i.e., use default), see if problem goes away - that solved this problem for me. I don't think that problem is related to this issue.

[ShijunK]

@nezda , thanks, that's does not fix the problem. I was using 4.1.5, tried the latest 4.2.0. still get the same exception.

[nezda]

@ShijunK did you remove the dependency as I suggested or upgrade the version?

[ShijunK]

@nezda thanks. I misread your comment.

after removing the woodstox dependency, com.sun's implementation works.
thank you

[cowtowncoder]

No, please do NOT remove Woodstox dependency: Stax parser included in JDK (SJSXP) is known to have issues and even if it happened to work around one, you most likely hit something else. While I have submitted a dozen fixes for SJSXP, it is lagging far behind Woodstox in about all aspects, including both correctness and performance.

[ShijunK]

@cowtowncoder , thanks for the advice. I did double check other test cases. and I did hit some strange exceptions after removing woodstox. For now, I will just do the dirty work to use DOM parse xml for my use case.

one strange exception after removing woodstox dependency:

public static class Node {

        @JacksonXmlProperty(localName = "unwrapped")
        @JacksonXmlElementWrapper(useWrapping = false)
        private List<UnwrappedElement> unwrapped;

        @JacksonXmlProperty
        private String name;

        @JacksonXmlProperty(localName = "node")
        @JacksonXmlElementWrapper(useWrapping = false)
        private List<Node> node;

        public static class UnwrappedElement {
            @JacksonXmlProperty(isAttribute = true)
            private String id;

            @JacksonXmlProperty(isAttribute = true)
            private String type;
        }
    }

    @Test
    public void testUnwrappedWithOptionalAttribute() throws Exception {
        xmlMapper.configure(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY, true);
        Node node = xmlMapper.readValue(
                "<node>\n" +
                        "    <unwrapped id=\"1\"/>\n" +
                        "    <unwrapped id=\"2\" type=\"string\"/>\n" +
                        "    <name>parent</name>\n" +
                        "    <node>\n" +
                        "        <unwrapped id=\"3\"></unwrapped>\n" +
                        "        <name>child</name>\n" +
                        "    </node>\n" +
                        "</node>",
                Node.class);
        assertThat(node.name, equalTo("parent"));
        assertThat(node.node.get(0).name, equalTo("child"));
    }

Caused by: java.lang.IllegalStateException: Current state not XML_START_ELEMENT (1) but 6
    at com.fasterxml.jackson.dataformat.xml.deser.XmlTokenStream.repeatStartElement(XmlTokenStream.java:228)
    at com.fasterxml.jackson.dataformat.xml.deser.FromXmlParser.addVirtualWrapping(FromXmlParser.java:280)
    at com.fasterxml.jackson.dataformat.xml.deser.WrapperHandlingDeserializer._configureParser(WrapperHandlingDeserializer.java:140)
    at com.fasterxml.jackson.dataformat.xml.deser.WrapperHandlingDeserializer.deserialize(WrapperHandlingDeserializer.java:108)
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.handleNonArray(CollectionDeserializer.java:270)
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:217)
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:207)
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:23)
    at com.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:449)
    at com.fasterxml.jackson.databind.deser.impl.FieldProperty.deserializeAndSet(FieldProperty.java:107)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:295)
    ... 32 more

[cowtowncoder]

You can also try JAXB -- it is fairly solid, and much faster than playing with DOM.

[cowtowncoder]

FWIW, while I am happy to accept patches to make module work better with default Stax parser from JDK, I will not be investigating problems specific to it (i.e. things that work with Woodstox). Others are free to pursue these aspects of course.

[cowtowncoder]

Another note: each bug entry should be for specific problem; new ones should be filed for other problems, unless they are known to be directly related. I mention this since unit test included seems to point out different issues.
I will focus on one initially mentioned; problems with missing attributes, on (un)wrapper lists.

[cowtowncoder]

I believe this is finally properly fixed. The problem turned out to be related to "auto-detection" of leaf-level String values: in case where this may occur, need to add explicit support for serializing POJO from a String value.