Java Reading XML with XStream

java xml parsing xstream

16,429

You are missing Authors?

//ListOfDBook.java
public class ListOfDBook {
    public ArrayList<DBook> DBook; 
}

//DBook.java
public class DBook {
    public ArrayList<Author> Authors;
}

//Author.java
public class Author {
    public ArrayList<DAuthor> DAuthors;
}

//DAuthor.java
public class DAuthor {
    String Name;
    String Url;
}

EDIT 2:

You need to use addImplicitCollection.

import java.util.*;
import com.thoughtworks.xstream.*;
import com.thoughtworks.xstream.io.*;
import com.thoughtworks.xstream.io.xml.*;
import java.io.*;

public class Test {

    public static void main(String[] args) throws Exception {

        XStream xstream = new XStream(new DomDriver());
        xstream.alias("ListOfDBook", ListOfDBook.class);
        xstream.alias("DBook", DBook.class);
        xstream.alias("Authors", Authors.class);
        xstream.alias("DAuthor", DAuthor.class);
        xstream.addImplicitCollection(Authors.class, "dauthors");
        xstream.addImplicitCollection(DBook.class, "authors");
        xstream.addImplicitCollection(ListOfDBook.class, "dbooks");
        InputStream in = new FileInputStream("Books.xml");
        ListOfDBook var = (ListOfDBook)xstream.fromXML(in);

    }

}

//ListOfDBook.java
class ListOfDBook {
    public List<DBook> dbooks = new LinkedList<DBook>(); 
}

//DBook.java
class DBook {
    public List<Authors> authors = new LinkedList<Authors>();
}

//Authors.java
class Authors {
    public List<DAuthor> dauthors = new LinkedList<DAuthor>();
}

//DAuthor.java
class DAuthor {
    public String Name;
    public String Url;
}

16,429

Author by

user2686811

Updated on June 04, 2022

Comments

user2686811 almost 2 years

I'm trying to deserialize this XML file using XStream and I'm getting this error

Exception in thread "main" com.thoughtworks.xstream.converters.ConversionException: Authors : Authors
---- Debugging information ----
message             : Authors
cause-exception     : com.thoughtworks.xstream.mapper.CannotResolveClassException
cause-message       : Authors
class               : java.util.ArrayList
required-type       : java.util.ArrayList
converter-type      : com.thoughtworks.xstream.converters.collections.CollectionConverter
path                : /ListOfDBook/DBook/Authors
class[1]            : com.test.books.ListOfDBook
converter-type[1]   : com.thoughtworks.xstream.converters.reflection.ReflectionConverter
version             : null
-------------------------------
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:79)
    at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
    at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.unmarshallField(AbstractReflectionConverter.java:355)
    at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.doUnmarshal(AbstractReflectionConverter.java:306)
    at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.unmarshal(AbstractReflectionConverter.java:234)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
    at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:134)
    at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:32)
    at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1058)
    at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1042)
    at com.thoughtworks.xstream.XStream.fromXML(XStream.java:922)
    at com.test.booktest.BookImport.getBooks(BookImport.java:34)
    at com.test.booktest.Client.main(Client.java:6)
Caused by: com.thoughtworks.xstream.mapper.CannotResolveClassException: Authors
    at com.thoughtworks.xstream.mapper.DefaultMapper.realClass(DefaultMapper.java:56)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.DynamicProxyMapper.realClass(DynamicProxyMapper.java:55)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.PackageAliasingMapper.realClass(PackageAliasingMapper.java:88)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.ClassAliasingMapper.realClass(ClassAliasingMapper.java:79)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.ArrayMapper.realClass(ArrayMapper.java:74)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.CachingMapper.realClass(CachingMapper.java:45)
    at com.thoughtworks.xstream.core.util.HierarchicalStreams.readClassType(HierarchicalStreams.java:29)
    at com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter.readItem(AbstractCollectionConverter.java:70)
    at com.thoughtworks.xstream.converters.collections.CollectionConverter.addCurrentElementToCollection(CollectionConverter.java:79)
    at com.thoughtworks.xstream.converters.collections.CollectionConverter.populateCollection(CollectionConverter.java:72)
    at com.thoughtworks.xstream.converters.collections.CollectionConverter.populateCollection(CollectionConverter.java:66)
    at com.thoughtworks.xstream.converters.collections.CollectionConverter.unmarshal(CollectionConverter.java:61)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
    ... 16 more

With this XML

<ListOfDBook xmlns="Test.Books" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
    <DBook>
        <Authors>
            <DAuthor>
                <Name>Google</Name>
                <Url>http://google.com</Url>
            </DAuthor>
        </Authors>
    </DBook>
</ListOfDBook>

With these classes

//ListOfDBook.java
public class ListOfDBook {
    public ArrayList<DBook> DBook; 
}

//DBook.java
public class DBook {
    public ArrayList<DAuthor> Authors;
}

//DAuthor.java
public class DAuthor {
    String Name;
    String Url;
}

//BookImport.java
import com.test.books.*;
XStream xstream = new XStream(new DomDriver());
xstream.alias("ListOfDBook", ListOfDBook.class);
InputStream in = new FileInputStream("Books.xml");
ListOfDBook = (ListOfDBook)xstream.fromXML(in);

I recreated the classes from reading the XML file and changing the XML file is not an option. Am I doing something completely wrong?

user2686811 over 10 years

You are correct I was missing Author. It then moves onto the Name element and have the same error. com.thoughtworks.xstream.converters.ConversionException: Name : Name I feel like I don't completely understand how I should be setting out the classes.
jn1kk over 10 years

Try aliasing the custom classes, check this link: xstream.codehaus.org/tutorial.html Also, try lowercase variable names.
user2686811 over 10 years

Creating the Class 'Name' fixes that and the same happens for the next element, 'Url'. I can't be making a new class for every different element when the element should be part of the parent element right?
jn1kk over 10 years

No You do not need a custom class for the Strings. Try using lowercase variable names first.
user2686811 over 10 years

Same error with lowercase. Tried adding this to DAuthor class public DAuthor(String Name, String URL) { this.name = Name; this.url = URL; } also did nothing.
user2686811 over 10 years

If I set xstream.alias("Name", DAuthor.class); it works. Is this correct? Do I need to set an alias for each variable? EDIT: I don't think that's right though, even if I set the alias to point to ArrayOfDBook it accepts it even though there is no Name variable in that class.
user2686811 over 10 years

Thanks! That seems to have fixed it. I guess I need to do that for all the Lists of custom objects. Thanks a lot for your time