On Wed, Jul 31, 2019 at 4:42 PM Rajesh KSV <rajeshks...@gmail.com> wrote:
>
>
> If there are multiple custom XML Serializers (XMLStreamWriter) in a class,
> serialization fails
>
> I have two classes. CustomClass1, CustomClass2. There is a wrapping class
> TestJacksonXml1. When I am trying to serialize TestJacksonXml1, it throws an
> exception.
Ok, the problem here is pretty fundamental: you should NOT use
underlying `XMLStreamWriter` directly,
but `JsonGenerator` (or if necessary you can cast that as `ToXmlGenerator`.
If you try to by-pass it, state maintained by Jackson will be out of
sync with actually writer and things
will probably not work very well.
Output methods via `JsonGenerator` will be translated so it may be bit
cumbersome but that
is necessary for all serializers to function same way regardless of
underlying format.
XMLStreamWriter access may be needed in rare cases (for example, to
add XML comments),
but care needs to be taken if so.
-+ Tatu +-
>
> CustomClass1
>
> class CustomClass1 {
> int prop1;
>
> public CustomClass1(int prop1) {
> this.prop1 = prop1;
> }
>
> public int getProp1() {
> return prop1;
> }
>
> static class CustomClass1Serializer extends StdSerializer<CustomClass1> {
> public CustomClass1Serializer() { this(null); }
>
> public CustomClass1Serializer(Class<CustomClass1> t) {
> super(t);
> }
>
> @Override
> public void serialize(CustomClass1 customClass1, JsonGenerator
> jsonGenerator, SerializerProvider serializerProvider) throws IOException {
> final ToXmlGenerator toXmlGenerator = (ToXmlGenerator)
> jsonGenerator;
> final XMLStreamWriter staxWriter =
> (toXmlGenerator).getStaxWriter();
> try {
> staxWriter.writeStartElement("class1");
>
> staxWriter.writeCharacters(String.valueOf(customClass1.prop1));
> staxWriter.writeEndElement();
> } catch (XMLStreamException e){
> e.printStackTrace();
> }
> }
> }
> }
>
>
> CustomClass2
>
> class CustomClass2 {
> int prop2;
>
> public CustomClass2(int prop2) {
> this.prop2 = prop2;
> }
>
> public int getProp2() {
> return prop2;
> }
>
> static class CustomClass2Serializer extends
> StdSerializer<CustomClass2> {
> public CustomClass2Serializer() { this(null); }
>
> public CustomClass2Serializer(Class<CustomClass2> t) {
> super(t);
> }
>
> @Override
> public void serialize(CustomClass2 customClass2, JsonGenerator
> jsonGenerator, SerializerProvider serializerProvider) throws IOException {
> final ToXmlGenerator toXmlGenerator = (ToXmlGenerator)
> jsonGenerator;
> final XMLStreamWriter staxWriter =
> (toXmlGenerator).getStaxWriter();
> try {
> staxWriter.writeStartElement("class2");
>
> staxWriter.writeCharacters(String.valueOf(customClass2.prop2));
> staxWriter.writeEndElement();
> } catch (XMLStreamException e){
> e.printStackTrace();
> }
> }
> }
> }
>
>
> Enclosing Class
>
> public class TestJacksonXml1 {
> @JsonSerialize(using = CustomClass1.CustomClass1Serializer.class)
> CustomClass1 obj1;
>
> @JsonSerialize(using = CustomClass2.CustomClass2Serializer.class)
> CustomClass2 obj2;
>
> public TestJacksonXml1(CustomClass1 obj1, CustomClass2 obj2) {
> this.obj1 = obj1;
> this.obj2 = obj2;
> }
>
> public CustomClass1 getObj1() {
> return obj1;
> }
>
> public CustomClass2 getObj2() {
> return obj2;
> }
>
> public static void main(String[] args) throws JsonProcessingException {
> XmlMapper xmlMapper = new XmlMapper();
> System.out.println(xmlMapper.writeValueAsString(new
> TestJacksonXml1(new CustomClass1(10), new CustomClass2(20))));
> }
> }
>
>
> The exception I get is
>
> Exception in thread "main"
> com.fasterxml.jackson.core.JsonGenerationException: Can not write a field
> name, expecting a value
> at
> com.fasterxml.jackson.core.JsonGenerator._reportError(JsonGenerator.java:1961)
> at
> com.fasterxml.jackson.dataformat.xml.ser.ToXmlGenerator.writeFieldName(ToXmlGenerator.java:435)
> at
> com.fasterxml.jackson.dataformat.xml.ser.ToXmlGenerator.writeFieldName(ToXmlGenerator.java:577)
> at
> com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:725)
> at
> com.fasterxml.jackson.dataformat.xml.ser.XmlBeanSerializerBase.serializeFields(XmlBeanSerializerBase.java:202)
> at
> com.fasterxml.jackson.dataformat.xml.ser.XmlBeanSerializer.serialize(XmlBeanSerializer.java:117)
> at
> com.fasterxml.jackson.dataformat.xml.ser.XmlSerializerProvider.serializeValue(XmlSerializerProvider.java:107)
> at
> com.fasterxml.jackson.databind.ObjectMapper._configAndWriteValue(ObjectMapper.java:3905)
> at
> com.fasterxml.jackson.databind.ObjectMapper.writeValueAsString(ObjectMapper.java:3219)
> at fk.reportsvc.common.TestJacksonXml1.main(TestJacksonXml1.java:39)
>
>
> When I comment out one of the custom serializers, the other one works.
> Shouldn't we use two/multiple custom serializers (with XMLStreamWriter) at
> once ?
>
>
> If I use JsonGenerator directly instead of XMLStreamWriter, then I am able to
> use both custom serializers at once.
>
>
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