Unmarshalling complex nested list of xml items using JAXB

Question

I am trying to unmarshall this complex xml, but not able to do it successfully. Below is my xml:

This is my ImportSession.java

import java.io.Serializable;
import java.util.List;

import javax.xml.bind.annotation.*;

import lombok.Getter;
import lombok.Setter;
import lombok.AllArgsConstructor;
import lombok.NoArgsConstructor;
import lombok.ToString;

@XmlRootElement(name = "ImportSession")
@XmlAccessorType(XmlAccessType.FIELD)
@ToString
public class ImportSession {
    @XmlElement(name = "Batches")
    private Batches batches;
    
    @XmlAccessorType(XmlAccessType.FIELD)
    @ToString
    public static class Batches implements Serializable {
        @XmlElement(name = "Batch")
        private Batch batch;
        
        @XmlAccessorType(XmlAccessType.FIELD)
        @ToString
        public static class Batch implements Serializable {
            @XmlElement(name = "Documents")
            private Documents documents;
            
            @XmlAccessorType(XmlAccessType.FIELD)
            @ToString
            public static class Documents implements Serializable {
                @XmlElement(name = "Document")
                private Document document;
                
                @XmlAccessorType(XmlAccessType.FIELD)
                @ToString
                public static class Document implements Serializable {
                    @XmlElement(name = "IndexFields")
                    private IndexFields indexFields;
                    @XmlElement(name = "Pages")
                    private Pages pages;
                    
                    @XmlAccessorType(XmlAccessType.FIELD)
                    @ToString
                    public static class IndexFields implements Serializable {
                        @XmlElement(name = "IndexField")
                        private List indexField;
                        
                        @XmlAccessorType(XmlAccessType.FIELD)
                        @ToString
                        public static class IndexField implements Serializable {
                            @XmlAttribute(name = "Name")
                            private String name;
                            
                            @XmlAttribute(name = "Value")
                            private String value;
                        }
                    }
                    
                    @XmlAccessorType(XmlAccessType.FIELD)
                    @ToString
                    public static class Pages implements Serializable {
                        @XmlElement(name = "Page")
                        private List page;
                        
                        @XmlAccessorType(XmlAccessType.FIELD)
                        @ToString
                        public static class Page implements Serializable {
                            @XmlAttribute(name = "ImportFileName")
                            private String importFileName;
                        }
                    }
                }
            }
        }
    }
}

Below is my unmarshalling code:

private static void main(String xmlFile) {
        try {
            JAXBContext jaxbContext = JAXBContext.newInstance(ImportSession.class);
            
            Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
            ImportSession ImportSession = (ImportSession) unmarshaller.unmarshal(new File(xmlFile));
            System.out.println("output = " + ImportSession);
        } catch (Exception e) {
            System.err.println(e.getMessage());
            e.printStackTrace();
        }
    }

In my Documents class, if I have

private Document document;

It works fine, but then it only gives me last document of my xml. But if I try to put:

private List document;

Code just comes out with nothing, no errors as well. Need help in analyzing what I am missing.

I don't want BatchFields/BatchField in my output, so I don't have that same in my class schema.

user_3681607 · Answer

I have generated the java class ImportSession.java with xjc and got different result.

import java.util.ArrayList;
import java.util.List;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "", propOrder = {
    "batches"
})
@XmlRootElement(name = "ImportSession")
public class ImportSession {

    @XmlElement(name = "Batches", required = true)
    protected ImportSession.Batches batches;

    public ImportSession.Batches getBatches() {
        return batches;
    }

    public void setBatches(ImportSession.Batches value) {
        this.batches = value;
    }

    @XmlAccessorType(XmlAccessType.FIELD)
    @XmlType(name = "", propOrder = {
        "batch"
    })
    public static class Batches {

        @XmlElement(name = "Batch", required = true)
        protected ImportSession.Batches.Batch batch;

        public ImportSession.Batches.Batch getBatch() {
            return batch;
        }

        public void setBatch(ImportSession.Batches.Batch value) {
            this.batch = value;
        }

        @XmlAccessorType(XmlAccessType.FIELD)
        @XmlType(name = "", propOrder = {
            "batchFields",
            "documents"
        })
        public static class Batch {

            @XmlElement(name = "BatchFields", required = true)
            protected ImportSession.Batches.Batch.BatchFields batchFields;
            @XmlElement(name = "Documents", required = true)
            protected ImportSession.Batches.Batch.Documents documents;
            @XmlAttribute(name = "BatchClassName", required = true)
            protected String batchClassName;

            public ImportSession.Batches.Batch.BatchFields getBatchFields() {
                return batchFields;
            }

            public void setBatchFields(ImportSession.Batches.Batch.BatchFields value) {
                this.batchFields = value;
            }

            public ImportSession.Batches.Batch.Documents getDocuments() {
                return documents;
            }

            public void setDocuments(ImportSession.Batches.Batch.Documents value) {
                this.documents = value;
            }

            public String getBatchClassName() {
                return batchClassName;
            }

            public void setBatchClassName(String value) {
                this.batchClassName = value;
            }

            @XmlAccessorType(XmlAccessType.FIELD)
            @XmlType(name = "", propOrder = {
                "batchField"
            })
            public static class BatchFields {

                @XmlElement(name = "BatchField", required = true)
                protected List batchField;

                public List getBatchField() {
                    if (batchField == null) {
                        batchField = new ArrayList();
                    }
                    return this.batchField;
                }

                @XmlAccessorType(XmlAccessType.FIELD)
                @XmlType(name = "")
                public static class BatchField {

                    @XmlAttribute(name = "Name", required = true)
                    protected String name;
                    @XmlAttribute(name = "Value", required = true)
                    protected String value;

                    public String getName() {
                        return name;
                    }

                    public void setName(String value) {
                        this.name = value;
                    }

                    public String getValue() {
                        return value;
                    }

                    public void setValue(String value) {
                        this.value = value;
                    }
                }
            }

            @XmlAccessorType(XmlAccessType.FIELD)
            @XmlType(name = "", propOrder = {
                "document"
            })
            public static class Documents {

                @XmlElement(name = "Document", required = true)
                protected List document;

                public List getDocument() {
                    if (document == null) {
                        document = new ArrayList();
                    }
                    return this.document;
                }

                @XmlAccessorType(XmlAccessType.FIELD)
                @XmlType(name = "", propOrder = {
                    "indexFields",
                    "pages"
                })
                public static class Document {

                    @XmlElement(name = "IndexFields", required = true)
                    protected ImportSession.Batches.Batch.Documents.Document.IndexFields indexFields;
                    @XmlElement(name = "Pages", required = true)
                    protected ImportSession.Batches.Batch.Documents.Document.Pages pages;
                    @XmlAttribute(name = "FormTypeName", required = true)
                    protected String formTypeName;

                    public ImportSession.Batches.Batch.Documents.Document.IndexFields getIndexFields() {
                        return indexFields;
                    }

                    public void setIndexFields(ImportSession.Batches.Batch.Documents.Document.IndexFields value) {
                        this.indexFields = value;
                    }

                    public ImportSession.Batches.Batch.Documents.Document.Pages getPages() {
                        return pages;
                    }

                    public void setPages(ImportSession.Batches.Batch.Documents.Document.Pages value) {
                        this.pages = value;
                    }

                    public String getFormTypeName() {
                        return formTypeName;
                    }

                    public void setFormTypeName(String value) {
                        this.formTypeName = value;
                    }

                    @XmlAccessorType(XmlAccessType.FIELD)
                    @XmlType(name = "", propOrder = {
                        "indexField"
                    })
                    public static class IndexFields {

                        @XmlElement(name = "IndexField", required = true)
                        protected List indexField;

                        public List getIndexField() {
                            if (indexField == null) {
                                indexField = new ArrayList();
                            }
                            return this.indexField;
                        }

                        @XmlAccessorType(XmlAccessType.FIELD)
                        @XmlType(name = "")
                        public static class IndexField {

                            @XmlAttribute(name = "Name", required = true)
                            protected String name;
                            @XmlAttribute(name = "Value", required = true)
                            protected String value;

                            public String getName() {
                                return name;
                            }

                            public void setName(String value) {
                                this.name = value;
                            }

                            public String getValue() {
                                return value;
                            }

                            public void setValue(String value) {
                                this.value = value;
                            }
                        }
                    }

                    @XmlAccessorType(XmlAccessType.FIELD)
                    @XmlType(name = "", propOrder = {
                        "page"
                    })
                    public static class Pages {

                        @XmlElement(name = "Page", required = true)
                        protected ImportSession.Batches.Batch.Documents.Document.Pages.Page page;

                        public ImportSession.Batches.Batch.Documents.Document.Pages.Page getPage() {
                            return page;
                        }

                        public void setPage(ImportSession.Batches.Batch.Documents.Document.Pages.Page value) {
                            this.page = value;
                        }

                        @XmlAccessorType(XmlAccessType.FIELD)
                        @XmlType(name = "")
                        public static class Page {

                            @XmlAttribute(name = "ImportFileName", required = true)
                            protected String importFileName;

                            public String getImportFileName() {
                                return importFileName;
                            }

                            public void setImportFileName(String value) {
                                this.importFileName = value;
                            }
                        }
                    }
                }
            }
        }
    }
}

I have first generated the xsd file from your xml file with this online site: https://www.liquid-technologies.com/online-xml-to-xsd-converter
Generated xsd (I name it "test.xsd"):

Generation of ImportSession.java (xjc is included in JDK8):

$ xjc test.xsd 
analyse dun schéma...
compilation dun schéma...
generated/ImportSession.java
generated/ObjectFactory.java

I have remove the first line package generated; and many many auto-generated comments.

Now,
System.out.println("output = " + ImportSession.getBatches().getBatch().getDocuments().getDocument().size());
show 3.

user_7248342 · Answer

Your XML element contains several elements.

Therefore in your Documents Java class you don't need a member of type Document, but instead of type List. So in your Documents class you need to replace

@XmlElement(name = "Document")
private Document document;

by

@XmlElement(name = "Document")
private List documents;

I also changed the member name from document to documents, because using a plural word is common practice for lists.

While the above modification already fixes your problem, there is even more room for improvement:

Currently you have two separate classes Documents and Document for modeling XML content like:


  ...
  ...
  ...

You can simplify the Java code by using the @XmlElementWrapper annotation. In your Batch class you can replace

@XmlElement(name = "Documents")
private Documents documents;

by

@XmlElementWrapper(name = "Documents")
@XmlElement(name = "Document")
private List documents;

By doing so you don't need the Documents class anymore.

You might want to do similar modifications for the other lists in your Java code corresponding to

containing several elements
containing several elements
containing several elements
containing several elements

Unmarshalling complex nested list of xml items using JAXB

2 Answers