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Java Library to find / apply JSON Patches according to RFC 6902
/*
* Copyright 2016 flipkart.com zjsonpatch.
*
* 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 com.flipkart.zjsonpatch;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.JsonNodeFactory;
import com.fasterxml.jackson.databind.node.ObjectNode;
import org.apache.commons.collections4.ListUtils;
import java.util.*;
/**
* User: gopi.vishwakarma
* Date: 30/07/14
*/
public final class JsonDiff {
private final List diffs = new ArrayList();
private final EnumSet flags;
private JsonDiff(EnumSet flags) {
this.flags = flags.clone();
}
public static JsonNode asJson(final JsonNode source, final JsonNode target) {
return asJson(source, target, DiffFlags.defaults());
}
public static JsonNode asJson(final JsonNode source, final JsonNode target, EnumSet flags) {
JsonDiff diff = new JsonDiff(flags);
// generating diffs in the order of their occurrence
diff.generateDiffs(JsonPointer.ROOT, source, target);
if (!flags.contains(DiffFlags.OMIT_MOVE_OPERATION))
// Merging remove & add to move operation
diff.introduceMoveOperation();
if (!flags.contains(DiffFlags.OMIT_COPY_OPERATION))
// Introduce copy operation
diff.introduceCopyOperation(source, target);
return diff.getJsonNodes();
}
private static JsonPointer getMatchingValuePath(Map unchangedValues, JsonNode value) {
return unchangedValues.get(value);
}
private void introduceCopyOperation(JsonNode source, JsonNode target) {
Map unchangedValues = getUnchangedPart(source, target);
for (int i = 0; i < diffs.size(); i++) {
Diff diff = diffs.get(i);
if (Operation.ADD != diff.getOperation()) continue;
JsonPointer matchingValuePath = getMatchingValuePath(unchangedValues, diff.getValue());
if (matchingValuePath != null && isAllowed(matchingValuePath, diff.getPath())) {
// Matching value found; replace add with copy
if (flags.contains(DiffFlags.EMIT_TEST_OPERATIONS)) {
// Prepend test node
diffs.add(i, new Diff(Operation.TEST, matchingValuePath, diff.getValue()));
i++;
}
diffs.set(i, new Diff(Operation.COPY, matchingValuePath, diff.getPath()));
}
}
}
private static boolean isNumber(String str) {
int size = str.length();
for (int i = 0; i < size; i++) {
if (!Character.isDigit(str.charAt(i))) {
return false;
}
}
return size > 0;
}
// TODO this is quite unclear and needs some serious documentation
private static boolean isAllowed(JsonPointer source, JsonPointer destination) {
boolean isSame = source.equals(destination);
int i = 0;
int j = 0;
// Hack to fix broken COPY operation, need better handling here
while (i < source.size() && j < destination.size()) {
JsonPointer.RefToken srcValue = source.get(i);
JsonPointer.RefToken dstValue = destination.get(j);
String srcStr = srcValue.toString();
String dstStr = dstValue.toString();
if (isNumber(srcStr) && isNumber(dstStr)) {
if (srcStr.compareTo(dstStr) > 0) {
return false;
}
}
i++;
j++;
}
return !isSame;
}
private static Map getUnchangedPart(JsonNode source, JsonNode target) {
Map unchangedValues = new HashMap();
computeUnchangedValues(unchangedValues, JsonPointer.ROOT, source, target);
return unchangedValues;
}
private static void computeUnchangedValues(Map unchangedValues, JsonPointer path, JsonNode source, JsonNode target) {
if (source.equals(target)) {
if (!unchangedValues.containsKey(target)) {
unchangedValues.put(target, path);
}
return;
}
final NodeType firstType = NodeType.getNodeType(source);
final NodeType secondType = NodeType.getNodeType(target);
if (firstType == secondType) {
switch (firstType) {
case OBJECT:
computeObject(unchangedValues, path, source, target);
break;
case ARRAY:
computeArray(unchangedValues, path, source, target);
break;
default:
/* nothing */
}
}
}
private static void computeArray(Map unchangedValues, JsonPointer path, JsonNode source, JsonNode target) {
final int size = Math.min(source.size(), target.size());
for (int i = 0; i < size; i++) {
JsonPointer currPath = path.append(i);
computeUnchangedValues(unchangedValues, currPath, source.get(i), target.get(i));
}
}
private static void computeObject(Map unchangedValues, JsonPointer path, JsonNode source, JsonNode target) {
final Iterator firstFields = source.fieldNames();
while (firstFields.hasNext()) {
String name = firstFields.next();
if (target.has(name)) {
JsonPointer currPath = path.append(name);
computeUnchangedValues(unchangedValues, currPath, source.get(name), target.get(name));
}
}
}
/**
* This method merge 2 diffs ( remove then add, or vice versa ) with same value into one Move operation,
* all the core logic resides here only
*/
private void introduceMoveOperation() {
for (int i = 0; i < diffs.size(); i++) {
Diff diff1 = diffs.get(i);
// if not remove OR add, move to next diff
if (!(Operation.REMOVE == diff1.getOperation() ||
Operation.ADD == diff1.getOperation())) {
continue;
}
for (int j = i + 1; j < diffs.size(); j++) {
Diff diff2 = diffs.get(j);
if (!diff1.getValue().equals(diff2.getValue())) {
continue;
}
Diff moveDiff = null;
if (Operation.REMOVE == diff1.getOperation() &&
Operation.ADD == diff2.getOperation()) {
JsonPointer relativePath = computeRelativePath(diff2.getPath(), i + 1, j - 1, diffs);
moveDiff = new Diff(Operation.MOVE, diff1.getPath(), relativePath);
} else if (Operation.ADD == diff1.getOperation() &&
Operation.REMOVE == diff2.getOperation()) {
JsonPointer relativePath = computeRelativePath(diff2.getPath(), i, j - 1, diffs); // diff1's add should also be considered
moveDiff = new Diff(Operation.MOVE, relativePath, diff1.getPath());
}
if (moveDiff != null) {
diffs.remove(j);
diffs.set(i, moveDiff);
break;
}
}
}
}
//Note : only to be used for arrays
//Finds the longest common Ancestor ending at Array
private static JsonPointer computeRelativePath(JsonPointer path, int startIdx, int endIdx, List diffs) {
List counters = new ArrayList(path.size());
for (int i = 0; i < path.size(); i++) {
counters.add(0);
}
for (int i = startIdx; i <= endIdx; i++) {
Diff diff = diffs.get(i);
//Adjust relative path according to #ADD and #Remove
if (Operation.ADD == diff.getOperation() || Operation.REMOVE == diff.getOperation()) {
updatePath(path, diff, counters);
}
}
return updatePathWithCounters(counters, path);
}
private static JsonPointer updatePathWithCounters(List counters, JsonPointer path) {
List tokens = path.decompose();
for (int i = 0; i < counters.size(); i++) {
int value = counters.get(i);
if (value != 0) {
int currValue = tokens.get(i).getIndex();
tokens.set(i, new JsonPointer.RefToken(Integer.toString(currValue + value)));
}
}
return new JsonPointer(tokens);
}
private static void updatePath(JsonPointer path, Diff pseudo, List counters) {
//find longest common prefix of both the paths
if (pseudo.getPath().size() <= path.size()) {
int idx = -1;
for (int i = 0; i < pseudo.getPath().size() - 1; i++) {
if (pseudo.getPath().get(i).equals(path.get(i))) {
idx = i;
} else {
break;
}
}
if (idx == pseudo.getPath().size() - 2) {
if (pseudo.getPath().get(pseudo.getPath().size() - 1).isArrayIndex()) {
updateCounters(pseudo, pseudo.getPath().size() - 1, counters);
}
}
}
}
private static void updateCounters(Diff pseudo, int idx, List counters) {
if (Operation.ADD == pseudo.getOperation()) {
counters.set(idx, counters.get(idx) - 1);
} else {
if (Operation.REMOVE == pseudo.getOperation()) {
counters.set(idx, counters.get(idx) + 1);
}
}
}
private ArrayNode getJsonNodes() {
JsonNodeFactory FACTORY = JsonNodeFactory.instance;
final ArrayNode patch = FACTORY.arrayNode();
for (Diff diff : diffs) {
ObjectNode jsonNode = getJsonNode(FACTORY, diff, flags);
patch.add(jsonNode);
}
return patch;
}
private static ObjectNode getJsonNode(JsonNodeFactory FACTORY, Diff diff, EnumSet flags) {
ObjectNode jsonNode = FACTORY.objectNode();
jsonNode.put(Constants.OP, diff.getOperation().rfcName());
switch (diff.getOperation()) {
case MOVE:
case COPY:
jsonNode.put(Constants.FROM, diff.getPath().toString()); // required {from} only in case of Move Operation
jsonNode.put(Constants.PATH, diff.getToPath().toString()); // destination Path
break;
case REMOVE:
jsonNode.put(Constants.PATH, diff.getPath().toString());
if (!flags.contains(DiffFlags.OMIT_VALUE_ON_REMOVE))
jsonNode.set(Constants.VALUE, diff.getValue());
break;
case REPLACE:
if (flags.contains(DiffFlags.ADD_ORIGINAL_VALUE_ON_REPLACE)) {
jsonNode.set(Constants.FROM_VALUE, diff.getSrcValue());
}
case ADD:
case TEST:
jsonNode.put(Constants.PATH, diff.getPath().toString());
jsonNode.set(Constants.VALUE, diff.getValue());
break;
default:
// Safety net
throw new IllegalArgumentException("Unknown operation specified:" + diff.getOperation());
}
return jsonNode;
}
private void generateDiffs(JsonPointer path, JsonNode source, JsonNode target) {
if (!source.equals(target)) {
final NodeType sourceType = NodeType.getNodeType(source);
final NodeType targetType = NodeType.getNodeType(target);
if (sourceType == NodeType.ARRAY && targetType == NodeType.ARRAY) {
//both are arrays
compareArray(path, source, target);
} else if (sourceType == NodeType.OBJECT && targetType == NodeType.OBJECT) {
//both are json
compareObjects(path, source, target);
} else {
//can be replaced
if (flags.contains(DiffFlags.EMIT_TEST_OPERATIONS))
diffs.add(new Diff(Operation.TEST, path, source));
diffs.add(Diff.generateDiff(Operation.REPLACE, path, source, target));
}
}
}
private void compareArray(JsonPointer path, JsonNode source, JsonNode target) {
List lcs = getLCS(source, target);
int srcIdx = 0;
int targetIdx = 0;
int lcsIdx = 0;
int srcSize = source.size();
int targetSize = target.size();
int lcsSize = lcs.size();
int pos = 0;
while (lcsIdx < lcsSize) {
JsonNode lcsNode = lcs.get(lcsIdx);
JsonNode srcNode = source.get(srcIdx);
JsonNode targetNode = target.get(targetIdx);
if (lcsNode.equals(srcNode) && lcsNode.equals(targetNode)) { // Both are same as lcs node, nothing to do here
srcIdx++;
targetIdx++;
lcsIdx++;
pos++;
} else {
if (lcsNode.equals(srcNode)) { // src node is same as lcs, but not targetNode
//addition
JsonPointer currPath = path.append(pos);
diffs.add(Diff.generateDiff(Operation.ADD, currPath, targetNode));
pos++;
targetIdx++;
} else if (lcsNode.equals(targetNode)) { //targetNode node is same as lcs, but not src
//removal,
JsonPointer currPath = path.append(pos);
if (flags.contains(DiffFlags.EMIT_TEST_OPERATIONS))
diffs.add(new Diff(Operation.TEST, currPath, srcNode));
diffs.add(Diff.generateDiff(Operation.REMOVE, currPath, srcNode));
srcIdx++;
} else {
JsonPointer currPath = path.append(pos);
//both are unequal to lcs node
generateDiffs(currPath, srcNode, targetNode);
srcIdx++;
targetIdx++;
pos++;
}
}
}
while ((srcIdx < srcSize) && (targetIdx < targetSize)) {
JsonNode srcNode = source.get(srcIdx);
JsonNode targetNode = target.get(targetIdx);
JsonPointer currPath = path.append(pos);
generateDiffs(currPath, srcNode, targetNode);
srcIdx++;
targetIdx++;
pos++;
}
pos = addRemaining(path, target, pos, targetIdx, targetSize);
removeRemaining(path, pos, srcIdx, srcSize, source);
}
private void removeRemaining(JsonPointer path, int pos, int srcIdx, int srcSize, JsonNode source) {
while (srcIdx < srcSize) {
JsonPointer currPath = path.append(pos);
if (flags.contains(DiffFlags.EMIT_TEST_OPERATIONS))
diffs.add(new Diff(Operation.TEST, currPath, source.get(srcIdx)));
diffs.add(Diff.generateDiff(Operation.REMOVE, currPath, source.get(srcIdx)));
srcIdx++;
}
}
private int addRemaining(JsonPointer path, JsonNode target, int pos, int targetIdx, int targetSize) {
while (targetIdx < targetSize) {
JsonNode jsonNode = target.get(targetIdx);
JsonPointer currPath = path.append(pos);
diffs.add(Diff.generateDiff(Operation.ADD, currPath, jsonNode.deepCopy()));
pos++;
targetIdx++;
}
return pos;
}
private void compareObjects(JsonPointer path, JsonNode source, JsonNode target) {
Iterator keysFromSrc = source.fieldNames();
while (keysFromSrc.hasNext()) {
String key = keysFromSrc.next();
if (!target.has(key)) {
//remove case
JsonPointer currPath = path.append(key);
if (flags.contains(DiffFlags.EMIT_TEST_OPERATIONS))
diffs.add(new Diff(Operation.TEST, currPath, source.get(key)));
diffs.add(Diff.generateDiff(Operation.REMOVE, currPath, source.get(key)));
continue;
}
JsonPointer currPath = path.append(key);
generateDiffs(currPath, source.get(key), target.get(key));
}
Iterator keysFromTarget = target.fieldNames();
while (keysFromTarget.hasNext()) {
String key = keysFromTarget.next();
if (!source.has(key)) {
//add case
JsonPointer currPath = path.append(key);
diffs.add(Diff.generateDiff(Operation.ADD, currPath, target.get(key)));
}
}
}
private static List getLCS(final JsonNode first, final JsonNode second) {
return ListUtils.longestCommonSubsequence(InternalUtils.toList((ArrayNode) first), InternalUtils.toList((ArrayNode) second));
}
}
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