elemental.json.impl.JsonVisitor Maven / Gradle / Ivy
/*
* Copyright 2010 Google Inc.
*
* 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 elemental.json.impl;
import elemental.json.JsonArray;
import elemental.json.JsonObject;
import elemental.json.JsonValue;
import elemental.json.impl.JsonContext;
/**
* A visitor for JSON objects. For each unique JSON datatype, a callback is
* invoked with a {@link elemental.json.impl.JsonContext}
* that can be used to replace a value or remove it. For Object and Array
* types, the {@link #visitKey} and {@link #visitIndex} methods are invoked
* respectively for each contained value to determine if they should be
* processed or not. Finally, the visit methods for Object and Array types
* returns a boolean that determines whether or not to process its contained
* values.
*/
class JsonVisitor {
private class ImmutableJsonContext extends JsonContext {
public ImmutableJsonContext(JsonValue node) {
super(node);
}
@Override
public void removeMe() {
immutableError();
}
@Override
public void replaceMe(double d) {
immutableError();
}
@Override
public void replaceMe(String d) {
immutableError();
}
@Override
public void replaceMe(boolean d) {
immutableError();
}
@Override
public void replaceMe(JsonValue value) {
immutableError();
}
private void immutableError() {
throw new UnsupportedOperationException("Immutable context");
}
}
public void accept(JsonValue node) {
accept(node, new ImmutableJsonContext(node));
}
/**
* Accept array or object type and visit its members.
*/
public void accept(JsonValue node, JsonContext ctx) {
if (node == null) {
return;
}
((JreJsonValue) node).traverse(this, ctx);
}
/**
* Called after every element of array has been visited.
*/
public void endVisit(JsonArray array, JsonContext ctx) {
}
/**
* Called after every field of an object has been visited.
* @param object
* @param ctx
*/
public void endVisit(JsonObject object, JsonContext ctx) {
}
/**
* Called for JS numbers present in a JSON object.
*/
public void visit(double number, JsonContext ctx) {
}
/**
* Called for JS strings present in a JSON object.
*/
public void visit(String string, JsonContext ctx) {
}
/**
* Called for JS boolean present in a JSON object.
*/
public void visit(boolean bool, elemental.json.impl.JsonContext ctx) {
}
/**
* Called for JS arrays present in a JSON object. Return true if array
* elements should be visited.
* @param array a JS array
* @param ctx a context to replace or delete the array
* @return true if the array elements should be visited
*/
public boolean visit(JsonArray array, JsonContext ctx) {
return true;
}
/**
* Called for JS objects present in a JSON object. Return true if object
* fields should be visited.
* @param object a Json object
* @param ctx a context to replace or delete the object
* @return true if object fields should be visited
*/
public boolean visit(JsonObject object, JsonContext ctx) {
return true;
}
/**
* Return true if the value for a given array index should be visited.
* @param index an index in a JSON array
* @param ctx a context object used to delete or replace values
* @return true if the value associated with the index should be visited
*/
public boolean visitIndex(int index, JsonContext ctx) {
return true;
}
/**
* Return true if the value for a given object key should be visited.
* @param key a key in a JSON object
* @param ctx a context object used to delete or replace values
* @return true if the value associated with the key should be visited
*/
public boolean visitKey(String key, JsonContext ctx) {
return true;
}
/**
* Called for nulls present in a JSON object.
*/
public void visitNull(JsonContext ctx) {
}
}