276 lines
10 KiB
Java
276 lines
10 KiB
Java
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package org.json;
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import static net.lax1dude.eaglercraft.v1_8.HString.format;
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import java.io.UnsupportedEncodingException;
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import java.net.URLDecoder;
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import java.net.URLEncoder;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.List;
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/*
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Public Domain.
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*/
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/**
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* A JSON Pointer is a simple query language defined for JSON documents by
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* <a href="https://tools.ietf.org/html/rfc6901">RFC 6901</a>.
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*
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* In a nutshell, JSONPointer allows the user to navigate into a JSON document
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* using strings, and retrieve targeted objects, like a simple form of XPATH.
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* Path segments are separated by the '/' char, which signifies the root of
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* the document when it appears as the first char of the string. Array
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* elements are navigated using ordinals, counting from 0. JSONPointer strings
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* may be extended to any arbitrary number of segments. If the navigation
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* is successful, the matched item is returned. A matched item may be a
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* JSONObject, a JSONArray, or a JSON value. If the JSONPointer string building
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* fails, an appropriate exception is thrown. If the navigation fails to find
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* a match, a JSONPointerException is thrown.
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*
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* @author JSON.org
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* @version 2016-05-14
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*/
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public class JSONPointer {
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// used for URL encoding and decoding
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private static final String ENCODING = "utf-8";
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/**
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* This class allows the user to build a JSONPointer in steps, using
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* exactly one segment in each step.
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*/
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public static class Builder {
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// Segments for the eventual JSONPointer string
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private final List<String> refTokens = new ArrayList<String>();
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/**
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* Creates a {@code JSONPointer} instance using the tokens previously set using the
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* {@link #append(String)} method calls.
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* @return a JSONPointer object
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*/
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public JSONPointer build() {
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return new JSONPointer(this.refTokens);
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}
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/**
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* Adds an arbitrary token to the list of reference tokens. It can be any non-null value.
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*
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* Unlike in the case of JSON string or URI fragment representation of JSON pointers, the
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* argument of this method MUST NOT be escaped. If you want to query the property called
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* {@code "a~b"} then you should simply pass the {@code "a~b"} string as-is, there is no
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* need to escape it as {@code "a~0b"}.
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*
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* @param token the new token to be appended to the list
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* @return {@code this}
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* @throws NullPointerException if {@code token} is null
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*/
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public Builder append(String token) {
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if (token == null) {
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throw new NullPointerException("token cannot be null");
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}
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this.refTokens.add(token);
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return this;
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}
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/**
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* Adds an integer to the reference token list. Although not necessarily, mostly this token will
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* denote an array index.
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*
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* @param arrayIndex the array index to be added to the token list
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* @return {@code this}
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*/
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public Builder append(int arrayIndex) {
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this.refTokens.add(String.valueOf(arrayIndex));
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return this;
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}
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}
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/**
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* Static factory method for {@link Builder}. Example usage:
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*
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* <pre><code>
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* JSONPointer pointer = JSONPointer.builder()
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* .append("obj")
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* .append("other~key").append("another/key")
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* .append("\"")
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* .append(0)
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* .build();
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* </code></pre>
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*
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* @return a builder instance which can be used to construct a {@code JSONPointer} instance by chained
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* {@link Builder#append(String)} calls.
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*/
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public static Builder builder() {
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return new Builder();
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}
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// Segments for the JSONPointer string
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private final List<String> refTokens;
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/**
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* Pre-parses and initializes a new {@code JSONPointer} instance. If you want to
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* evaluate the same JSON Pointer on different JSON documents then it is recommended
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* to keep the {@code JSONPointer} instances due to performance considerations.
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*
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* @param pointer the JSON String or URI Fragment representation of the JSON pointer.
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* @throws IllegalArgumentException if {@code pointer} is not a valid JSON pointer
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*/
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public JSONPointer(final String pointer) {
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if (pointer == null) {
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throw new NullPointerException("pointer cannot be null");
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}
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if (pointer.isEmpty() || pointer.equals("#")) {
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this.refTokens = Collections.emptyList();
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return;
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}
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String refs;
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if (pointer.startsWith("#/")) {
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refs = pointer.substring(2);
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try {
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refs = URLDecoder.decode(refs, ENCODING);
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} catch (UnsupportedEncodingException e) {
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throw new RuntimeException(e);
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}
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} else if (pointer.startsWith("/")) {
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refs = pointer.substring(1);
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} else {
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throw new IllegalArgumentException("a JSON pointer should start with '/' or '#/'");
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}
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this.refTokens = new ArrayList<String>();
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int slashIdx = -1;
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int prevSlashIdx = 0;
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do {
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prevSlashIdx = slashIdx + 1;
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slashIdx = refs.indexOf('/', prevSlashIdx);
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if(prevSlashIdx == slashIdx || prevSlashIdx == refs.length()) {
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// found 2 slashes in a row ( obj//next )
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// or single slash at the end of a string ( obj/test/ )
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this.refTokens.add("");
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} else if (slashIdx >= 0) {
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final String token = refs.substring(prevSlashIdx, slashIdx);
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this.refTokens.add(unescape(token));
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} else {
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// last item after separator, or no separator at all.
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final String token = refs.substring(prevSlashIdx);
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this.refTokens.add(unescape(token));
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}
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} while (slashIdx >= 0);
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// using split does not take into account consecutive separators or "ending nulls"
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//for (String token : refs.split("/")) {
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// this.refTokens.add(unescape(token));
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//}
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}
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public JSONPointer(List<String> refTokens) {
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this.refTokens = new ArrayList<String>(refTokens);
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}
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/**
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* @see <a href="https://tools.ietf.org/html/rfc6901#section-3">rfc6901 section 3</a>
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*/
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private static String unescape(String token) {
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return token.replace("~1", "/").replace("~0", "~");
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}
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/**
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* Evaluates this JSON Pointer on the given {@code document}. The {@code document}
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* is usually a {@link JSONObject} or a {@link JSONArray} instance, but the empty
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* JSON Pointer ({@code ""}) can be evaluated on any JSON values and in such case the
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* returned value will be {@code document} itself.
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*
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* @param document the JSON document which should be the subject of querying.
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* @return the result of the evaluation
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* @throws JSONPointerException if an error occurs during evaluation
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*/
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public Object queryFrom(Object document) throws JSONPointerException {
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if (this.refTokens.isEmpty()) {
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return document;
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}
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Object current = document;
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for (String token : this.refTokens) {
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if (current instanceof JSONObject) {
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current = ((JSONObject) current).opt(unescape(token));
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} else if (current instanceof JSONArray) {
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current = readByIndexToken(current, token);
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} else {
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throw new JSONPointerException(format(
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"value [%s] is not an array or object therefore its key %s cannot be resolved", current,
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token));
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}
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}
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return current;
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}
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/**
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* Matches a JSONArray element by ordinal position
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* @param current the JSONArray to be evaluated
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* @param indexToken the array index in string form
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* @return the matched object. If no matching item is found a
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* @throws JSONPointerException is thrown if the index is out of bounds
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*/
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private static Object readByIndexToken(Object current, String indexToken) throws JSONPointerException {
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try {
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int index = Integer.parseInt(indexToken);
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JSONArray currentArr = (JSONArray) current;
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if (index >= currentArr.length()) {
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throw new JSONPointerException(format("index %s is out of bounds - the array has %d elements", indexToken,
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Integer.valueOf(currentArr.length())));
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}
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try {
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return currentArr.get(index);
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} catch (JSONException e) {
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throw new JSONPointerException("Error reading value at index position " + index, e);
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}
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} catch (NumberFormatException e) {
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throw new JSONPointerException(format("%s is not an array index", indexToken), e);
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}
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}
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/**
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* Returns a string representing the JSONPointer path value using string
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* representation
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*/
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@Override
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public String toString() {
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StringBuilder rval = new StringBuilder("");
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for (String token: this.refTokens) {
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rval.append('/').append(escape(token));
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}
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return rval.toString();
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}
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/**
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* Escapes path segment values to an unambiguous form.
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* The escape char to be inserted is '~'. The chars to be escaped
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* are ~, which maps to ~0, and /, which maps to ~1.
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* @param token the JSONPointer segment value to be escaped
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* @return the escaped value for the token
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*
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* @see <a href="https://tools.ietf.org/html/rfc6901#section-3">rfc6901 section 3</a>
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*/
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private static String escape(String token) {
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return token.replace("~", "~0")
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.replace("/", "~1");
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}
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/**
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* Returns a string representing the JSONPointer path value using URI
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* fragment identifier representation
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* @return a uri fragment string
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*/
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public String toURIFragment() {
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try {
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StringBuilder rval = new StringBuilder("#");
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for (String token : this.refTokens) {
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rval.append('/').append(URLEncoder.encode(token, ENCODING));
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}
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return rval.toString();
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} catch (UnsupportedEncodingException e) {
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throw new RuntimeException(e);
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}
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}
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}
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