i try to serialize a List of Objects in Java using Xstream, my code in core is:
//register alias
xstream.alias("category", ServerCategory.class);
//register converter
xstream.registerConverter(new ServerCategoryConverter());
// get all categories
List<ServerCategory> categoryList = categoryDao.getAllEager();
// serialize all categories
for(ServerCategory category : categoryList) {
xstream.toXML(category, streamWriter);
}
This works well, but i get no linebreak after the </category>-tag and this seems to conflict with xml specification cause every reader breaks at this line.
is there any fix for this?
Your current code will generate something like below :
<category>
<id>1</id>
<name>One</name>
<description>One</description>
<syncversion>V1</syncversion>
<parents/>
</category>
<category>
<id>2</id>
<name>Two</name>
<description>Two</description>
<syncversion>V1</syncversion>
<parents>
<parent>1</parent>
</parents>
</category>
This is invalid xml as it should have one root element (this xml has multiple root element category) Ideally you should generate like this. You will be able to open below in the browser.
<list> <!-- one root element required!!-->
<category>
<id>1</id>
<name>One</name>
<description>One</description>
<syncversion>V1</syncversion>
<parents/>
</category>
<category>
<id>2</id>
<name>Two</name>
<description>Two</description>
<syncversion>V1</syncversion>
<parents>
<parent>1</parent>
</parents>
</category>
<list>
What needs to be done is instead of
for(ServerCategory category : categoryList) {
xstream.toXML(category, streamWriter);
}
you should serialize the whole list
xstream.toXML(categoryList, streamWriter);
and your ServerCategoryConverter canCovert() should be overridden with
public boolean canConvert(Class foo) {
//dont use this converter for the Arraylist. Arraylist will be handeld by the default converter
if (foo.getName().equals("java.util.ArrayList")) {
return false;
}
return true;
}
I have attached my full code for reference. It works with the above fixes :
import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.converters.Converter;
import com.thoughtworks.xstream.converters.MarshallingContext;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
import java.io.*;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;
public class XSTReamTest {
/*
* ExpertService.class
*/
public static void main(String args[]) throws Exception {
XSTReamTest tst = new XSTReamTest();
tst.createXmlExport();
}
public File createXmlExport() throws Exception {
XStream xstream = new XStream();
File xmlExportFile = null;
BufferedOutputStream outputStream = null;
OutputStreamWriter streamWriter = null;
try {
xmlExportFile = new File("easylearncards1_exportRequest_.xml");
System.out.println("Path = " + xmlExportFile.getAbsolutePath());
outputStream = new BufferedOutputStream(new FileOutputStream(xmlExportFile));
streamWriter = new OutputStreamWriter(outputStream, Charset.forName("UTF-8"));
exportCategories(xstream, streamWriter);
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
streamWriter.close();
outputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return xmlExportFile;
}
private void exportCategories(XStream xstream, OutputStreamWriter streamWriter) {
// register alias
xstream.alias("category", ServerCategory.class);
// register converter
xstream.registerConverter(new ServerCategoryConverter());
// get all categories
List<ServerCategory> categoryList = new ArrayList<ServerCategory>();
ServerCategory root = new ServerCategory("1", "One", "One", "V1", null);
ServerCategory child1 = new ServerCategory("2", "Two", "Two", "V1", new ServerCategory[]{root});
ServerCategory child2 = new ServerCategory("3", "Three", "Three", "V1", new ServerCategory[]{root});
ServerCategory child3 = new ServerCategory("4", "Four", "Four", "V1", new ServerCategory[]{child1, child2});
categoryList.add(root);
categoryList.add(child1);
categoryList.add(child2);
categoryList.add(child3);
// convert all categories
// for (ServerCategory category : categoryList) {
// xstream.toXML(category, streamWriter);
// }
xstream.toXML(categoryList, streamWriter);
}
static class ServerCategory {
String id;
String name;
String description;
String syncVersion;
ServerCategory parents[];
ServerCategory(String id, String name, String description, String syncVersion, ServerCategory[] parents) {
this.id = id;
this.name = name;
this.description = description;
this.syncVersion = syncVersion;
this.parents = parents;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public String getSyncVersion() {
return syncVersion;
}
public void setSyncVersion(String syncVersion) {
this.syncVersion = syncVersion;
}
public ServerCategory[] getParents() {
return parents;
}
public void setParents(ServerCategory[] parents) {
this.parents = parents;
}
}
/*
* ServerCategoryConverter.class
*/
static class ServerCategoryConverter implements Converter {
public void marshal(Object value, HierarchicalStreamWriter writer, MarshallingContext context) {
ServerCategory category = (ServerCategory) value;
writer.startNode("id");
writer.setValue(category.getId().toString());
writer.endNode();
writer.startNode("name");
writer.setValue(category.getName());
writer.endNode();
writer.startNode("description");
writer.setValue(category.getDescription());
writer.endNode();
writer.startNode("syncversion");
writer.setValue(category.getSyncVersion().toString());
writer.endNode();
writer.startNode("parents");
if (category.getParents() != null) {
for (ServerCategory parent : category.getParents()) {
writer.startNode("parent");
writer.setValue(parent.getId().toString());
writer.endNode();
}
}
writer.endNode();
}
public java.lang.Object unmarshal(com.thoughtworks.xstream.io.HierarchicalStreamReader hierarchicalStreamReader, com.thoughtworks.xstream.converters.UnmarshallingContext unmarshallingContext) {
return null;
}
public boolean canConvert(Class foo) {
if (foo.getName().equals("java.util.ArrayList")) {
return false;
}
return true;
}
}
}