I'm reasonably confident in my first generics container, but stuck on how to word the casting on the client side. This is what was working before I got involved in learning <T> stuff:
CommonNounContainer typeContainer = new Json().fromJson(CommonNounContainer.class, result);
I was looking at having to create a different container for each class, and that doesn't seem like good design. Below is my updated, non-working attempt to read in my new generics container:
JSONContainer<CommonNoun> typeContainer = new Json().fromJson(JSONContainer.class, result);
My IDE doesn't care for this phrasing, noting:
Type safety: The expression of type JSONContainer needs unchecked conversion to conform to JSONContainer
When executed, my err log reads:
result = {"myObject":{"cid":{"oid":129},"name":"technology","form":1},"children":[]}
com.badlogic.gdx.utils.SerializationException: Field not found: cid (java.lang.Object)
Serialization trace:
{}.myObject.cid
myObject (semanticWeb.rep.concept.JSONContainer)
at com.badlogic.gdx.utils.Json.readFields(Json.java:854)
at com.badlogic.gdx.utils.Json.readValue(Json.java:1011)
at com.badlogic.gdx.utils.Json.readFields(Json.java:863)
at com.badlogic.gdx.utils.Json.readValue(Json.java:1011)
at com.badlogic.gdx.utils.Json.fromJson(Json.java:789)
at com.b2tclient.net.Communicator$2.handleHttpResponse(Communicator.java:95)
at com.badlogic.gdx.net.NetJavaImpl$2.run(NetJavaImpl.java:224)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:830)
I'm sure there's some way I'm supposed to include a reference to the CommonNoun type to the right of the equals sign, but I haven't been able to figure it out. How do I do it? There's lots of applicable posts concerning generics, casting, JSON, and stripping away of class information. One of them I tried to follow that wasn't about the casting above regarded adding the T class as a private variable within the container during construction:
How do I get a class instance of generic type T?
but I ran into similar syntax issues trying to refer to the class correctly, just in a different spot along the process. I have my doubts, too, that I can read this class variable from the JSON file before telling JSON how to classify the information in the file.
Javadoc for the fromJson(Class<T>, String) method:
Type Parameters:
<T>
Parameters:
type May be null if the type is unknown.
json
Returns:
May be null.
I may already have a viable answer submitted by deduper, but, as requested, here are the CommonNounContainer and JSONContainer classes:
import java.util.ArrayList;
public class CommonNounContainer {
private CommonNoun myCommonNoun;
private ArrayList<CommonNounContainer> children;
public CommonNounContainer(CommonNoun concept) {
myCommonNoun = concept;
children = new ArrayList<CommonNounContainer>();
}
//Creates an empty shell. This would be for categories you want to group by, but not display/select in the select box.
public CommonNounContainer() {
children = new ArrayList<CommonNounContainer>();
}
public void addChildren(ArrayList<CommonNounContainer> newChildren) {
children.addAll(newChildren);
}
public void addChild(CommonNoun concept) {
children.add(new CommonNounContainer(concept));
}
public ArrayList<CommonNounContainer> getChildren() {
return children;
}
public CommonNoun getValue() {
return myCommonNoun;
}
public boolean hasChildren() {
if (children.size() > 0) return true;
else return false;
}
public String toString() {
return myCommonNoun.toString();
}
}
public class JSONContainer<T> {
private T myObject;
private ArrayList<JSONContainer<T>> children;
// public Class<T> typeParameterClass;
public JSONContainer() {
}
public JSONContainer(T anObject) {
myObject = anObject;
children = new ArrayList<JSONContainer<T>>();
}
/* public JSONContainer(T anObject, Class<T> typeParameterClass) {
myObject = anObject;
children = new ArrayList<JSONContainer<T>>();
this.typeParameterClass = typeParameterClass;
}
*/
public void addChildren(ArrayList<JSONContainer<T>> newChildren) {
children.addAll(newChildren);
}
public void addChild(T concept) {
children.add(new JSONContainer<T>(concept));
}
public ArrayList<JSONContainer<T>> getChildren() {
return children;
}
public T getValue() {
return myObject;
}
public boolean hasChildren() {
if (children.size() > 0) return true;
else return false;
}
public String toString() {
return myObject.toString();
}
}
Additional classes requested:
public class CommonNoun extends Concept {
/**
*
*/
private static final long serialVersionUID = 6444629581712454049L;
public CommonNoun() {
super();
}
public CommonNoun(String name, ConceptID cidIn) {
super(name, cidIn);
this.form = ConceptDefs.COMMON_NOUN;
}
}
public class Concept implements Serializable {
/**
*
*/
private static final long serialVersionUID = 2561549161503772431L;
private ConceptID cid = null;
private final String name;
Integer form = 0;
// ArrayList<ProperRelationship> myRelationships = null;
/* @Deprecated
public Concept(String name) {
this.name = name;
}*/
public Concept() {
name = "";
}
public Concept(String name, ConceptID cidIn) {
// this(name);
this.name = name;
cid = cidIn;
}
/*
* This should be over-ridden by any subclasses
*/
public Integer getForm() {
return form;
}
public ConceptID getID() {
return cid;
}
public void setID(ConceptID cidIn) {
cid = cidIn;
}
//this doesn't make any sense. Throw exception?
public String getName() {
return name;
}
public boolean isCommon() {
return true;
}
/**
*
* @return
*/
@Override
public String toString() {
return getName() + "(" + cid.toString() + ")";
}
public boolean equals(Concept other) {
return ((getID().equals(other.getID())));
}
}
public class ConceptID implements Serializable {
long oid;
public ConceptID() {
oid = -1;
}
public ConceptID(long oid) {
this.oid = oid;
}
public long getValue() {
return oid;
}
/**
*
* @return
*/
@Override
public String toString() {
return Long.toString(oid);
}
public Long toLong() {
return Long.valueOf(oid);
}
public boolean equals(ConceptID other) {
return (oid == other.getValue());
}
/**
* Factory model for generating ConceptIDs
*
* This one is here as a convenience as many IDs come in as a String from web POSTs
* @param idAsString
* @return
*/
static public ConceptID parseIntoID(String idAsString) {
ConceptID returnID = null;
try {
returnID = new ConceptID( Long.parseLong(idAsString) );
} catch (Exception e) {
System.err.println("Expected the string, " + idAsString + ", to be Long parsable.");
e.printStackTrace();
}
return returnID;
}
