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tools.xor.util.JSONTransformer Maven / Gradle / Ivy
Empowering Model Driven Architecture in J2EE applications
/**
* XOR, empowering Model Driven Architecture in J2EE applications
*
* Copyright (c) 2012, Dilip Dalton
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
*
* See the License for the specific language governing permissions and limitations
* under the License.
*/
package tools.xor.util;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;
import java.util.Queue;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
/**
* A similar class will be provided for JavaScript code, so it can be used by clients that needs
* to communicate with this framework.
*
*/
public class JSONTransformer {
private static final Logger logger = LogManager.getLogger(new Exception().getStackTrace()[0].getClassName());
/**
* Do a BFS traversal
*
*/
public static class PackVisitor {
private Map marked = new HashMap();
private Queue unprocessed = new LinkedList();
private int currentID = 10000;
public PackVisitor(JSONObject obj)
{
this.unprocessed.add(obj);
}
/**
* We only need to inject Constants.XOR.ID to JSONObject instances
*/
public void process()
{
if(unprocessed.isEmpty())
{
throw new RuntimeException("Need to invoke IDVisitor with a JSONObject instance");
}
if(((JSONObject)unprocessed.peek()).has(Constants.XOR.ID)) {
logger.warn("JSONObject instance has already been packed");
return;
}
try {
while(!this.unprocessed.isEmpty())
{
Object element = unprocessed.poll();
if(marked.containsKey(element)) {
continue;
}
if(element instanceof JSONObject) {
JSONObject jsonObject = (JSONObject) element;
// Is this an entity?
if(jsonObject.length() > 0) {
jsonObject.put(Constants.XOR.ID, currentID++);
// TODO: If an ExcelVisitor is supplied then
// visit it. The logic in the visitor will store
// it by type and id, so it can build the necessary Excel sheets
}
for(String key: JSONObject.getNames(jsonObject))
{
Object obj = jsonObject.get(key);
if(obj instanceof JSONObject) {
JSONObject child = (JSONObject) obj;
if(!child.has(Constants.XOR.ID)) {
// this is the first time we are seeing it,
// so add it to unprocessed
unprocessed.add(child);
} else {
// We have seen this object before and it is being processed,
// so replace this reference with the id
int id = child.getInt(Constants.XOR.ID);
jsonObject.put(Constants.XOR.IDREF +key, id);
// Now remove the object link as we have recorded it
jsonObject.remove(key);
}
} else if(obj instanceof JSONArray) {
unprocessed.add(obj);
}
}
marked.put(element, Boolean.TRUE);
} else if(element instanceof JSONArray) {
// TODO: If ExcelVisitor is present then
// visit it, collections are handled in separate sheets in Excel
// The sheet will be named :
// Here targetType is not the polymorphic type, but the type where propertyName is
// defined
JSONArray jsonArray = (JSONArray) element;
for(int i = 0; i < jsonArray.length(); i++) {
Object obj = jsonArray.get(i);
if(obj instanceof JSONObject) {
JSONObject child = (JSONObject) obj;
if(!child.has(Constants.XOR.ID)) {
// this is the first time we are seeing it,
// so add it to unprocessed
unprocessed.add(child);
}
} else if(obj instanceof JSONArray) {
unprocessed.add(obj);
}
}
marked.put(element, Boolean.TRUE);
}
}
} catch (JSONException e) {
ClassUtil.wrapRun(e);
}
}
}
/**
* Do a BFS traversal, and do the reverse of pack,
* we replace the keys with prefix Constants.XOR.IDREF with the actual object
*
* We do 2 passes, first populate the id, object map.
* then replace the object ids with the actual object reference
*
*/
public static class UnPackVisitor {
private Map idMap = new HashMap();
private JSONObject json;
public UnPackVisitor(JSONObject obj)
{
this.json = obj;
}
private void collectIds()
{
Queue unprocessed = new LinkedList();
// marked data structure is not really needed, since an object should having only
// one incoming edge
unprocessed.add(json);
if(!((JSONObject)unprocessed.peek()).has(Constants.XOR.ID)) {
logger.warn("JSONObject instance has not been packed");
return;
}
try {
while(!unprocessed.isEmpty())
{
Object element = unprocessed.poll();
if(element instanceof JSONObject) {
JSONObject jsonObject = (JSONObject) element;
if(!jsonObject.has(Constants.XOR.ID))
{
throw new RuntimeException("XOR Id not found, object has not be fully packed");
}
if(idMap.containsKey(jsonObject.getInt(Constants.XOR.ID))) {
throw new RuntimeException("Multiple objects found with same id, or object was modified after being packed");
}
idMap.put(jsonObject.getInt(Constants.XOR.ID), jsonObject);
// Remove the XOR id from the object
jsonObject.remove(Constants.XOR.ID);
for(String key: JSONObject.getNames(jsonObject))
{
Object obj = jsonObject.get(key);
if(obj instanceof JSONObject ||
obj instanceof JSONArray) {
unprocessed.add(obj);
}
}
} else if(element instanceof JSONArray) {
JSONArray jsonArray = (JSONArray) element;
for(int i = 0; i < jsonArray.length(); i++) {
Object obj = jsonArray.get(i);
if(obj instanceof JSONObject ||
obj instanceof JSONArray) {
unprocessed.add(obj);
}
}
}
}
} catch (JSONException e) {
ClassUtil.wrapRun(e);
}
}
/**
* We only need to inject Constants.XOR.ID to JSONObject instances
*/
public void process()
{
collectIds();
Map marked = new HashMap();
Queue unprocessed = new LinkedList();
unprocessed.add(json);
try {
while(!unprocessed.isEmpty())
{
Object element = unprocessed.poll();
if(marked.containsKey(element)) {
continue;
}
if(element instanceof JSONObject) {
JSONObject jsonObject = (JSONObject) element;
for(String key: JSONObject.getNames(jsonObject))
{
if(key.startsWith(Constants.XOR.IDREF)) {
// replace the id ref with the actual object
Object ref = idMap.get(jsonObject.get(key));
String newKey = key.substring(Constants.XOR.IDREF.length());
jsonObject.put(newKey, ref);
jsonObject.remove(key);
} else {
Object obj = jsonObject.get(key);
if(obj instanceof JSONObject ||
obj instanceof JSONArray) {
unprocessed.add(obj);
}
}
}
marked.put(element, Boolean.TRUE);
} else if(element instanceof JSONArray) {
JSONArray jsonArray = (JSONArray) element;
for(int i = 0; i < jsonArray.length(); i++) {
Object obj = jsonArray.get(i);
if(obj instanceof JSONObject ||
obj instanceof JSONArray) {
unprocessed.add(obj);
}
}
marked.put(element, Boolean.TRUE);
}
}
} catch (JSONException e) {
ClassUtil.wrapRun(e);
}
}
}
/**
* Pack a JSONObject instance so that it can be serialized over the network
* Do a DFS and add an id value for each object. Create an object and id map as traversing through the graph,
* when accessing a new node, if it has already been visited then we replace it with an id and
* mark the attribute name (e.g., prefix) This object id can use System.identityHashCode or be based
* on a sequence
* @param input object graph
*/
public static void pack(JSONObject input)
{
PackVisitor visitor = new PackVisitor(input);
visitor.process();
}
/**
* Retrieve a JSONObject instance and fix all the broken links thus restoring loops in the object graph
* 1. Traverse the object graph and populate the map between an object's id and the object instance
* 2. Fix all references to the id (using a special attribute prefix e.g., |XOR|) with the help of this map
* during a second scan
* @param input object tree
*/
public static void unpack(JSONObject input)
{
UnPackVisitor visitor = new UnPackVisitor(input);
visitor.process();
}
}
