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I need Freemarker documentation for data model when using #recurse with trees other than XML

I am trying to process a tree structure in Freemarker and would like use the #recurse, #visit directives but I can't find any good documentation on how to set up the data model. The only examples I can see are those that create a data model for an XML structure. I don't need it to be so detailed. My tree is very simple.
In trying to test the functionality I need, I built a unit test but when I run it I get
FreeMarker template error:
For "." left-hand operand: Expected a hash, but this has evaluated to a node
Here is the source code:
public class FreemarkerXmlTests {
static class Element implements TemplateNodeModel {
private final String name;
private final String text;
private Element parent;
private final List<Element> elements = new ArrayList<>();
public Element(String name) {
this(name, null);
}
public Element(String name, String text) {
this.name = name;
this.text = text;
}
public void add(Element element) {
element.parent = this;
this.elements.add(element);
}
public List<Element> getElements() {
return this.elements;
}
public String getName() {
return this.name;
}
public String getText() {
return this.text;
}
public String getTitle() {
return this.name;
}
public TemplateModel get(String key) {
return null;
}
#Override
public TemplateNodeModel getParentNode() throws TemplateModelException {
return this.parent;
}
#Override
public TemplateSequenceModel getChildNodes() throws TemplateModelException {
// TODO Auto-generated method stub
return new SimpleSequence(this.elements, cfg.getObjectWrapper());
}
#Override
public String getNodeName() throws TemplateModelException {
return this.name;
}
#Override
public String getNodeType() throws TemplateModelException {
return this.name;
}
#Override
public String getNodeNamespace() throws TemplateModelException {
return null;
}
}
private static Configuration cfg;
private static final String myTestTemplate = "<#recurse doc>\r\n" +
"\r\n" +
"<#macro book>\r\n" +
" Book element with title ${.node.title} \r\n" +
" <#recurse>\r\n" +
" End book\r\n" +
"</#macro>\r\n" +
"\r\n" +
"<#macro title>\r\n" +
" Title element\r\n" +
"</#macro>\r\n" +
"\r\n" +
"<#macro chapter>\r\n" +
" Chapter element with title: ${.node.title}\r\n" +
"</#macro>";
#BeforeClass
public static void classInit() throws IOException {
StringTemplateLoader stringTemplateLoader = new StringTemplateLoader();
stringTemplateLoader.putTemplate("myTestTemplate", myTestTemplate);
cfg = new Configuration(Configuration.VERSION_2_3_29);
cfg.setTemplateLoader(stringTemplateLoader);
cfg.setDefaultEncoding("UTF-8");
cfg.setTemplateExceptionHandler(TemplateExceptionHandler.RETHROW_HANDLER);
cfg.setLogTemplateExceptions(false);
cfg.setWrapUncheckedExceptions(true);
cfg.setFallbackOnNullLoopVariable(false);
}
#Test
public void basicXmlTest() throws TemplateException, IOException {
Element doc = new Element("doc");
Element book = new Element("book");
book.add(new Element("title", "Test Book"));
doc.add(book);
Element chapter1 = new Element("chapter");
chapter1.add(new Element("title", "Ch1"));
chapter1.add(new Element("para", "p1.1"));
chapter1.add(new Element("para", "p1.2"));
chapter1.add(new Element("para", "p1.3"));
book.add(chapter1);
Element chapter2 = new Element("chapter");
chapter2.add(new Element("title", "Ch2"));
chapter2.add(new Element("para", "p2.1"));
chapter2.add(new Element("para", "p2.2"));
chapter2.add(new Element("para", "p2.3"));
book.add(chapter2);
Map<String, Object> root = new HashMap<>();
// Put string "user" into the root
root.put("doc", doc);
Template temp = cfg.getTemplate("myTestTemplate");
Writer out = new OutputStreamWriter(System.out);
temp.process(root, out);
}
Any ideas?

Take a look at the freemarker.template.TemplateNodeModel interface. Your objects have to implement that, or they have to be wrapped (via the ObjectWrapper) into a TemplateModel the implements that. Then #recurse/#visit/?parent/?children/etc. will work with them.
Here's an example of implementing TemplateNodeModel for traversing JSON: https://github.com/freemarker/fmpp/blob/master/src/main/java/fmpp/models/JSONNode.java
Some templates where above is used:
https://github.com/freemarker/fmpp/tree/master/src/test/resources/tests/dl_json/src
As of the . operator, for that you need to implement TemplateHashModel (or its sub-interfaces, like TemplateHashModelEx2).

With the help of the examples posted by ddekany, I added the following:
implements TemplateHashModel to the Element class
static class Element implements TemplateNodeModel, TemplateHashModel {
a method to the Element class and the unit test worked:
#Override
public TemplateModel get(String key) throws TemplateModelException {
switch (key) {
case "title":
case "name":
return cfg.getObjectWrapper().wrap(this.name);
default:
throw new TemplateModelException("unknown hash get: " + key);
}
}

How to define array of objects in a properties file and read from Java program

I have a properties file like this.
property[0].name=A
property[0].value=1
property[1].name=B
property[1].value=2
property[2].name=C
property[2].value=3
How to read this file as a list of objects of a class {name, value} in plain java program using ResourceBundle or Properties?
Here is the class.
public class XYZ {
private String name;
private String value;
// Getters & Setters
}
I need to get like this.
ArrayList<XYZ> propertiesList = SomeUtility.getProperties("property", XYZ.class);
Utility class might be like this.
public class SomeUtility {
public static ArrayList getProperties(String key, Class cls) {
//logic
}
}

I might not understand exactly what you want so feel free to correct me and give me more constraints to work with but here is a simple way to read a Properties file located somewhere in your project:
private static void readPropertiesFile(String path) throws IOException {
java.util.Map<String, String> map = new java.util.LinkedHashMap<>();
Properties properties = new Properties();
InputStream inputStream = new FileInputStream(path);
properties.load(inputStream);
for (String name : properties.stringPropertyNames()) {
map.put(name, properties.getProperty(name));
}
for (java.util.Map.Entry<String, String> entry : map.entrySet()) {
System.out.printf("Property Key: %s, Property Value: %s%n", entry.getKey(), entry.getValue());
}
}
Output
Property Key: property[0].name, Property Value: A
Property Key: property[1].name, Property Value: B
Property Key: property[0].value, Property Value: 1
Property Key: property[1].value, Property Value: 2
Property Key: property[2].name, Property Value: C
Property Key: property[2].value, Property Value: 3

This is the solution I wrote, but it involves Reflect and Gson. Is there any better way to do this? Anything already available which is fine tuned like Apache's.
import com.google.gson.Gson;
import com.google.gson.JsonObject;
import java.lang.reflect.Field;
import java.util.*;
public class ListResourceBundle {
public static final Gson gson = new Gson();
private final ResourceBundle bundle;
public ListResourceBundle(ResourceBundle bundle) {
this.bundle = bundle;
}
public List<?> getProperties(String key, Class<?> cls) {
final int maxArraySize = getMaxArraySize(key, getMatchingKeys(key));
final List<String> fields = getFields(cls);
final List<Object> result = new ArrayList<>();
for (int i = 0; i < maxArraySize; i++) {
JsonObject jsonObject = new JsonObject();
for (String field : fields) {
jsonObject.addProperty(field, getStringOrNull(key + "[" + i + "]." + field));
}
result.add(gson.fromJson(jsonObject, cls));
}
System.out.println("result.toString() = " + result.toString());
return result;
}
public List<String> getMatchingKeys(String key) {
Enumeration<String> keys = bundle.getKeys();
List<String> matchingKeys = new ArrayList<>();
while(keys.hasMoreElements()) {
String k = keys.nextElement();
if(k.startsWith(key)) {
matchingKeys.add(k);
}
}
Collections.sort(matchingKeys);
return matchingKeys;
}
public int getMaxArraySize(String key, List<String> matchingKeys) {
int maxArraySize = 0;
for (int i = 0; ; i++) {
boolean indexAvailable = false;
for (String matchingKey : matchingKeys) {
if(matchingKey.startsWith(key + "[" + i + "]")) {
indexAvailable = true;
break;
}
}
if(indexAvailable) {
maxArraySize++;
} else {
break;
}
}
return maxArraySize;
}
public String getStringOrNull(String key) {
try {
return bundle.getString(key);
} catch (MissingResourceException e) {
return null;
}
}
public List<String> getFields(Class<?> cls) {
final List<String> fields = new ArrayList<>();
for (Field field : cls.getDeclaredFields()) {
fields.add(field.getName());
}
return fields;
}
public static void main(String[] args) {
ResourceBundle bundle = ResourceBundle.getBundle("com.example.application.resources.Resource");
ListResourceBundle applicationResourceBundle = new ListResourceBundle(bundle);
applicationResourceBundle.getProperties("property", ReportParam.class);
}
}
Resource:
property[0].name=A
property[0].value=1
property[1].name=B
property[1].value=2
property[2].name=C
property[2].value=3
Output:
result.toString() = [
ReportParam{name='A', value='1'},
ReportParam{name='B', value='2'},
ReportParam{name='C', value='3'}]
Process finished with exit code 0

I know it's bit late of an answer, but if I understand your problem statement correctly, you can use :
#ConfigurationProperties
to get your job done.
Here is my spring-boot example with a YAML file for the sake of convenience (same can be achieved through properties file as well).
application.yaml:
xyz:
xyzprops :
-
name: cbc
value: 441
-
name: obc
value: 443
XYZ class:
#Component
#ConfigurationProperties(prefix = "xyz")
public class XYZ{
private List<XYZProps> xyzprops;
public List<XYZProps> getXyzprops() {
return xyzprops;
}
public void setXyzprops(List<XYZProps> xyzprops) {
this.xyzprops = xyzprops;
}
public class XYZProps{
String name;
String value;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
}
}
And then #Autowire XYZ where you want to use it.

I would use JSON:
in your file:
property=[{"name":"A","value":"1"},{"name":"B","value":"2"},{"name":"C","value":"3"}]
and then deserialize it using com.google.gson.gson (or any other) library:
ArrayList<XYZ> propertiesList;
propertiesList = new gsonbuilder().create().fromjson(property, propertiesList.class);
NOTE: I haven't tested this code, and i'm not very familiar with java so i am sure there is a better,cleaner way to implement this.

How can I use BeanUtils converter to List?

Here, the request Param string is :
firstName=jack&lastName=lily&gender=1&foods=Steak&foods=Pizza&quote=Enter+your+favorite+quote!&education=Jr.High&tOfD=Day
And Mapped class is :
public class Student {
private String firstName;
private String lastName;
private Integer gender;
private List<String> foods;
private String quote;
private String education;
private String tOfD;
getXxx()....;
setXxx()....;
}
And Now, I want to write a generic util class to convert the string to a bean.
public final class InjectUtil<T> {
private static final Logger LOGGER = LoggerFactory.getLogger(InjectUtil.class);
public static <T> T converter2Obj(String source, Class<T> tClass) {
T t = null;
try {
t = tClass.newInstance();
if(source != null && source.length() > 0) {
String[] fields = source.split("&");
for(String field : fields) {
String[] fieldKeyValue = field.split("\\=");
String fieldKey = fieldKeyValue[0];
String fieldValue = fieldKeyValue[1];
// help
}
}
} catch(InstantiationException | IllegalAccessException | InvocationTargetException e) {
e.printStackTrace();
}
return t;
}
}
take care of the help, how can i use BeanUtils converter the "foods=Steak&foods=Pizza" to the List attribute.

Here is a way of doing it :
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import org.apache.commons.beanutils.BeanUtils;
public final class InjectUtil<T> {
// private static final Logger LOGGER =
// LoggerFactory.getLogger(InjectUtil.class);
public static <T> T converter2Obj(String source, Class<T> tClass) {
T t = null;
try {
t = tClass.newInstance();
Map<String, Object> params = new HashMap<String, Object>();
if (source != null && source.length() > 0) {
String[] fields = source.split("&");
for (String field : fields) {
String[] fieldKeyValue = field.split("\\=");
String fieldKey = fieldKeyValue[0];
String fieldValue = fieldKeyValue[1];
if (params.containsKey(fieldKey)) {
//the key does not exist as yet
Object keyValueRetrieved = params.get(fieldKey);
if (keyValueRetrieved instanceof String) {
//key exists , it is single value that has been added now.
//change that now to a list to add more values
ArrayList<String> values = new ArrayList<String>();
values.add(keyValueRetrieved.toString());
values.add(fieldValue);
params.put(fieldKey, values);
} else {
//key exists , it is a list already. Add more values
((ArrayList<String>) keyValueRetrieved).add(fieldValue);
}
} else {
params.put(fieldKey, fieldValue);
}
}
}
BeanUtils.populate(t, params);
} catch (Exception e) {
e.printStackTrace();
}
System.out.println("--------------------------------------------");
System.out.println(t.toString());
System.out.println("--------------------------------------------");
return t;
}
}
There are optimizations you can do , hopefully this gives you an idea

You can use as follows, you need to populate foodList (with values as [Steak,Pizza]) and then set to the bean using following method.
PropertyUtils.setProperty(studentBean, "foods", foodList);
or
BeanUtils.setProperty(studentBean, "foods", foodList);

Java Hibernate Transformer AliasToBeanNestedResultTransformer

i have a query like this. i pass the student ID i need some fields from Student as well as their parent as well some fields from the parent->Address[here is the main problem i am facing] i am using AliasToBeanNestedResultTransformer transformer by Sami Andoni
here is the implementation of it CODE
here is my code.
public List<Student>searchForStudent(Integer studentId)
{
Projection p=Projections.projectionList().create()
.add(Projections.property("name"),"name")//the student name it works O.K
.add(Projections.property("lastname"),"lastname")//the student name it works O.K
.add(Projections.property("age"),"age")//the student AGE it works O.K
.add(Projections.property("p.phone"),"parent.phone")//the parent phone it works O.K
.add(Projections.property("address.state").as("parent.Address.state")); // i need a field from address.state here is the problem...
Session session = ......
Criteria like = session.createCriteria(Student.class).add(prepareForSelect())//some filters..
.createAlias("parent","p")//the parent of the student. a student have one parent
.createAlias("parent.Address","address")//the address of the parent.... a parent have one address.
.setProjection(p)
.setResultTransformer(new AliasToBeanNestedResultTransformer(Student.class));
List<Student>results=like.list();
return results;
}
it throws
Exception in thread "main" org.hibernate.PropertyAccessException: IllegalArgumentException occurred while calling setter of com.generic.model.Parent.Address
FYI is some type mismatch i have done some tracing in SAMI code and i see this
[MyState]
[Address]
seems that Hibernate is returning a String State MyState in this case and the transformer is using a Address Object and this is the type Mismatch.
is any help is hugely needed it
thanks a lot.

I have improved the SamiAndoni class, maybe it solve your issue
package com.alutiiq.develop.promanagesys.core.util;
import java.lang.reflect.Field;
import java.lang.reflect.ParameterizedType;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.hibernate.HibernateException;
import org.hibernate.property.PropertyAccessor;
import org.hibernate.property.PropertyAccessorFactory;
import org.hibernate.property.Setter;
import org.hibernate.transform.AliasToBeanResultTransformer;
import org.hibernate.transform.AliasedTupleSubsetResultTransformer;
import org.hibernate.transform.ResultTransformer;
/**
* Help to transform alises with nested alises
*
* #author Miguel Resendiz
*
*/
public class AliasToBeanNestedResultTransformer extends
AliasedTupleSubsetResultTransformer {
private static final long serialVersionUID = -8047276133980128266L;
private static final int TUPE_INDEX = 0;
private static final int ALISES_INDEX = 1;
private static final int FIELDNAME_INDEX = 2;
private static final PropertyAccessor accessor = PropertyAccessorFactory
.getPropertyAccessor("property");
private final Class<?> resultClass;
private Object[] entityTuples;
private String[] entityAliases;
private Map<String, Class<?>> fieldToClass = new HashMap<String, Class<?>>();
private Map<String, List<?>> subEntities = new HashMap<String, List<?>>();
private List<String> nestedAliases = new ArrayList<String>();
private Map<String, Class<?>> listFields = new HashMap<String, Class<?>>();
public boolean isTransformedValueATupleElement(String[] aliases,
int tupleLength) {
return false;
}
public AliasToBeanNestedResultTransformer(Class<?> resultClass) {
this.resultClass = resultClass;
}
public Object transformTuple(Object[] tuple, String[] aliases) {
handleSubEntities(tuple, aliases);
cleanParams(tuple, aliases);
ResultTransformer rootTransformer = new AliasToBeanResultTransformer(
resultClass);
Object root = rootTransformer.transformTuple(entityTuples,
entityAliases);
loadSubEntities(root);
cleanMaps();
return root;
}
private void handleSubEntities(Object[] tuple, String[] aliases)
throws HibernateException {
String fieldName = "";
String aliasName = "";
try {
for (int i = 0; i < aliases.length; i++) {
String alias = aliases[i];
if (alias.contains(".")) {
String[] sp = alias.split("\\.");
StringBuilder aliasBuilder = new StringBuilder();
for (int j = 0; j < sp.length; j++) {
if (j == 0) {
fieldName = sp[j];
} else {
aliasBuilder.append(sp[j]);
aliasBuilder.append(".");
}
}
aliasName = aliasBuilder.substring(0,
aliasBuilder.length() - 1);
nestedAliases.add(alias);
manageEntities(fieldName, aliasName, tuple[i]);
}
}
} catch (NoSuchFieldException e) {
throw new HibernateException("Could not instantiate resultclass: "
+ resultClass.getName() + " for field name: " + fieldName
+ " and alias name:" + aliasName);
}
}
private Class<?> findClass(String fieldName) throws NoSuchFieldException,
SecurityException {
if (fieldToClass.containsKey(fieldName)) {
return fieldToClass.get(fieldName);
} else {
Class<?> subclass = resultClass.getDeclaredField(fieldName)
.getType();
if (subclass.equals(List.class) || subclass.equals(Set.class)) {
if (subclass.equals(List.class)) {
listFields.put(fieldName, LinkedList.class);
} else {
listFields.put(fieldName, HashSet.class);
}
Field field = resultClass.getDeclaredField(fieldName);
ParameterizedType genericType = (ParameterizedType) field
.getGenericType();
subclass = (Class<?>) genericType.getActualTypeArguments()[0];
}
fieldToClass.put(fieldName, subclass);
return subclass;
}
}
#SuppressWarnings("unchecked")
private void manageEntities(String fieldName, String aliasName,
Object tupleValue) throws NoSuchFieldException, SecurityException {
Class<?> subclass = findClass(fieldName);
if (!subEntities.containsKey(fieldName)) {
List<Object> list = new ArrayList<Object>();
list.add(new ArrayList<Object>());
list.add(new ArrayList<String>());
list.add(FIELDNAME_INDEX, subclass);
subEntities.put(fieldName, list);
}
((List<Object>) subEntities.get(fieldName).get(TUPE_INDEX))
.add(tupleValue);
((List<String>) subEntities.get(fieldName).get(ALISES_INDEX))
.add(aliasName);
}
private void cleanParams(Object[] tuple, String[] aliases) {
entityTuples = new Object[aliases.length - nestedAliases.size()];
entityAliases = new String[aliases.length - nestedAliases.size()];
for (int j = 0, i = 0; j < aliases.length; j++) {
if (!nestedAliases.contains(aliases[j])) {
entityTuples[i] = tuple[j];
entityAliases[i] = aliases[j];
++i;
}
}
}
#SuppressWarnings({ "unchecked", "rawtypes" })
private void loadSubEntities(Object root) throws HibernateException {
try {
for (String fieldName : subEntities.keySet()) {
Class<?> subclass = (Class<?>) subEntities.get(fieldName).get(
FIELDNAME_INDEX);
ResultTransformer subclassTransformer = new AliasToBeanNestedResultTransformer(
subclass);
Object subObject = subclassTransformer.transformTuple(
((List<Object>) subEntities.get(fieldName).get(0))
.toArray(),
((List<Object>) subEntities.get(fieldName).get(1))
.toArray(new String[0]));
Setter setter = accessor.getSetter(resultClass, fieldName);
if (listFields.containsKey(fieldName)) {
Class<?> collectionClass = listFields.get(fieldName);
Collection subObjectList = (Collection) collectionClass
.newInstance();
subObjectList.add(subObject);
setter.set(root, subObjectList, null);
} else {
setter.set(root, subObject, null);
}
}
} catch (Exception e) {
throw new HibernateException(e);
}
}
private void cleanMaps() {
fieldToClass = new HashMap<String, Class<?>>();
subEntities = new HashMap<String, List<?>>();
nestedAliases = new ArrayList<String>();
listFields = new HashMap<String, Class<?>>();
}
}
I hope it help you.
--------------edit 07/25/15---------------
To group nested list.
public List<? extends Entity<?>> cleanList(
List<? extends Entity<?>> resultList) throws DataException {
List<Entity<?>> entities = new ArrayList<Entity<?>>();
Entity<?> current = null;
try {
for (Entity<?> entity : resultList) {
if (entity.getId() == null) {
continue;
}
if (current == null) {
current = entity;
continue;
}
if (current.getId().equals(entity.getId())) {
append(current, entity);
} else {
entities.add(current);
current = entity;
}
}
if (current != null) {
entities.add(current);
}
cleanSubList(entities);
return entities;
} catch (Exception e) {
throw new DataException(e);
}
}
#SuppressWarnings({ "rawtypes", "unchecked" })
public Set<? extends Entity<?>> cleanList(
Set<? extends Entity<?>> resultList) throws DataException {
List listToClean = new LinkedList();
listToClean.addAll(resultList);
listToClean = cleanList(listToClean);
resultList.clear();
resultList.addAll(listToClean);
return resultList;
}
#SuppressWarnings({ "unchecked", "rawtypes" })
private void append(Entity<?> current, Entity<?> next)
throws IllegalArgumentException, IllegalAccessException {
Field[] fields = current.getClass().getDeclaredFields();
for (Field field : fields) {
if (field.getType().equals(List.class)) {
field.setAccessible(true);
List valueNext = (List) field.get(next);
List valueCurrent = (List) field.get(current);
if (valueNext != null) {
if (valueCurrent != null) {
valueCurrent.addAll(valueNext);
field.set(current, valueCurrent);
} else {
field.set(current, valueNext);
}
}
} else if (field.getType().equals(Set.class)) {
field.setAccessible(true);
Set valueNext = (Set) field.get(next);
Set valueCurrent = (Set) field.get(current);
if (valueNext != null) {
if (valueCurrent != null) {
valueCurrent.addAll(valueNext);
field.set(current, valueCurrent);
} else {
field.set(current, valueNext);
}
}
}
}
}
#SuppressWarnings({ "rawtypes", "unchecked" })
private void cleanSubList(List<? extends Entity<?>> listToClean)
throws IllegalArgumentException, IllegalAccessException,
DataException {
for (Entity<?> entity : listToClean) {
Field[] fields = entity.getClass().getDeclaredFields();
for (Field field : fields) {
if (field.getType().equals(List.class)) {
field.setAccessible(true);
List valueToClean = (List) field.get(entity);
// Throw a thread
if (valueToClean != null) {
valueToClean = cleanList(valueToClean);
field.set(entity, valueToClean);
}
} else if (field.getType().equals(Set.class)) {
field.setAccessible(true);
Set valueToClean = (Set) field.get(entity);
// Throw a thread
if (valueToClean != null) {
valueToClean = cleanList(valueToClean);
field.set(entity, valueToClean);
}
}
}
}
}
To speed up the process I´m suggesting throw a thread in the main process.
This is my Entity interface:
package com.alutiiq.develop.promanagesys.common.entity;
import java.io.Serializable;
/**
* Entity for Hibernate comunications
*
* #author Miguel Resendiz
*
* #param <I>
* Primary key type
*/
public interface Entity<I extends Serializable> extends Serializable {
/**
* Enable poissibility to write generic queries using primary key
*
* #return primary key value for entity
*/
I getId();
void setId(I id);
void setId(String id);
}
Usage example:
criteria.setResultTransformer(new AliasToBeanNestedResultTransformer(
entityClass));
List<Project> projects = criteria.list();
projects = (List<Project>) cleanList(projects);

Simple-XML: Overriding an element name at runtime

I am using simple-xml to perform XML serialization/deserialization in my Java application. I have a class as follows:
#Root(name="config")
public class Config{
#Element(name="update_interval")
private int updateInterval;
#Element(name="timestamp")
private long timestamp;
//...
//...
}
Now, this would produce XML like the following:
<config>
<update_interval>2000</update_interval>
<timestamp>1234567890</timestamp>
</config>
Question:
How can I override the element name at runtime, so that in some cases, the XML reads as follows?
<config>
<updt_int>2000</updt_int>
<ts>1234567890</ts>
</config>
Edit:
To clarify, I want to override the element names only in some cases. So basically,
if(condition){
//Override Element Names
} else {
//Serialize Normally
}

I found an easy way to achieve serialization in this case, thanks to this comment.
However, I haven't been able to de-serialize such an XML document. Here's my partial solution:
/*
* Config.java
*/
#Root(name="config", strict = false)
public class Config {
#Element(name="timestamp", required = false)
private long timestamp;
#Element(name = "update_interval", required = false)
private int updateInterval;
public Config() {
}
public int getUpdateInterval() {
return updateInterval;
}
public void setUpdateInterval(int updateInterval) {
this.updateInterval = updateInterval;
}
public long getTimestamp() {
return timestamp;
}
public void setTimestamp(long timestamp) {
this.timestamp = timestamp;
}
#Override
public String toString() {
return "Config{" +
"timestamp=" + timestamp +
", updateInterval=" + updateInterval +
'}';
}
}
/*
* Custom Visitor implementation
*/
public class MyInterceptor implements Visitor {
private static int sReadCount = 0;
private static int sWriteCount = 0;
#Override
public void read(Type field, NodeMap<InputNode> node) throws Exception {
/*
* This is where I need help!
*
*
* This method is only called once: for the <config> node
* It is not called for the other nodes since they are not "recognized"
* i.e., there are no annotations for the nodes <ts> and <updt_int>
*/
System.out.println("Read Count : "+ (++sReadCount));
System.out.println(node.getName());
System.out.println(node.getNode());
}
#Override
public void write(Type field, NodeMap<OutputNode> node) throws Exception {
/*
* This works like a charm.
*/
System.out.println("Write Count : "+ (++sWriteCount));
OutputNode opNode = node.getNode();
if("timestamp".equals(opNode.getName())){
opNode.setName("ts");
}
if("update_interval".equals(opNode.getName())){
opNode.setName("updt_int");
}
}
}
/*
*
*/ Main class
public class Bootstrap {
static final Random RANDOM = new Random();
public static void main(String [] args){
Config cfg = new Config();
cfg.setTimestamp(RANDOM.nextLong());
cfg.setUpdateInterval(1000);
Serializer serializer = new Persister(new VisitorStrategy(new MyInterceptor()));
StringWriter writer = new StringWriter();
try {
serializer.write(cfg, writer);
} catch (Exception e) {
e.printStackTrace();
}
String serialized = writer.toString();
System.out.println(serialized);
Config desCfg = null;
try {
desCfg = serializer.read(Config.class, serialized);
} catch (Exception e) {
e.printStackTrace();
}
if(desCfg != null){
System.out.println(desCfg.toString());
}
}
}