com.fasterxml.jackson.core.JsonPointer Maven / Gradle / Ivy
package com.fasterxml.jackson.core;
import com.fasterxml.jackson.core.io.NumberInput;
/**
* Implementation of
* JSON Pointer
* specification.
* Pointer instances can be used to locate logical JSON nodes for things like
* tree traversal (see {@link TreeNode#at}).
* It may be used in future for filtering of streaming JSON content
* as well (not implemented yet for 2.3).
*
* Instances are fully immutable and can be cached, shared between threads.
*
* @author Tatu Saloranta
*
* @since 2.3
*/
public class JsonPointer
{
/**
* Character used to separate segments.
*
* @since 2.9
*/
public final static char SEPARATOR = '/';
/**
* Marker instance used to represent segment that matches current
* node or position (that is, returns true for
* {@link #matches()}).
*/
protected final static JsonPointer EMPTY = new JsonPointer();
/**
* Reference to rest of the pointer beyond currently matching
* segment (if any); null if this pointer refers to the matching
* segment.
*/
protected final JsonPointer _nextSegment;
/**
* Reference from currently matching segment (if any) to node
* before leaf.
* Lazily constructed if/as needed.
*
* NOTE: we'll use `volatile` here assuming that this is unlikely to
* become a performance bottleneck. If it becomes one we can probably
* just drop it and things still should work (despite warnings as per JMM
* regarding visibility (and lack thereof) of unguarded changes).
*
* @since 2.5
*/
protected volatile JsonPointer _head;
/**
* We will retain representation of the pointer, as a String,
* so that {@link #toString} should be as efficient as possible.
*/
protected final String _asString;
protected final String _matchingPropertyName;
protected final int _matchingElementIndex;
/*
/**********************************************************
/* Construction
/**********************************************************
*/
/**
* Constructor used for creating "empty" instance, used to represent
* state that matches current node.
*/
protected JsonPointer() {
_nextSegment = null;
_matchingPropertyName = "";
_matchingElementIndex = -1;
_asString = "";
}
// Constructor used for creating non-empty Segments
protected JsonPointer(String fullString, String segment, JsonPointer next) {
_asString = fullString;
_nextSegment = next;
// Ok; may always be a property
_matchingPropertyName = segment;
// but could be an index, if parsable
_matchingElementIndex = _parseIndex(segment);
}
// @since 2.5
protected JsonPointer(String fullString, String segment, int matchIndex, JsonPointer next) {
_asString = fullString;
_nextSegment = next;
_matchingPropertyName = segment;
_matchingElementIndex = matchIndex;
}
/*
/**********************************************************
/* Factory methods
/**********************************************************
*/
/**
* Factory method that parses given input and construct matching pointer
* instance, if it represents a valid JSON Pointer: if not, a
* {@link IllegalArgumentException} is thrown.
*
* @param expr Pointer expression to compile
*
* @return Compiled {@link JsonPointer} path expression
*
* @throws IllegalArgumentException Thrown if the input does not present a valid JSON Pointer
* expression: currently the only such expression is one that does NOT start with
* a slash ('/').
*/
public static JsonPointer compile(String expr) throws IllegalArgumentException
{
// First quick checks for well-known 'empty' pointer
if ((expr == null) || expr.length() == 0) {
return EMPTY;
}
// And then quick validity check:
if (expr.charAt(0) != '/') {
throw new IllegalArgumentException("Invalid input: JSON Pointer expression must start with '/': "+"\""+expr+"\"");
}
return _parseTail(expr);
}
/**
* Alias for {@link #compile}; added to make instances automatically
* deserializable by Jackson databind.
*
* @param expr Pointer expression to compile
*
* @return Compiled {@link JsonPointer} path expression
*/
public static JsonPointer valueOf(String expr) { return compile(expr); }
/**
* Accessor for an "empty" expression, that is, one you can get by
* calling {@link #compile} with "" (empty String).
*
* NOTE: this is different from expression for {@code "/"} which would
* instead match Object node property with empty String ("") as name.
*
* @return "Empty" pointer expression instance that matches given root value
*
* @since 2.10
*/
public static JsonPointer empty() { return EMPTY; }
/**
* Factory method that will construct a pointer instance that describes
* path to location given {@link JsonStreamContext} points to.
*
* @param context Context to build pointer expression for
* @param includeRoot Whether to include number offset for virtual "root context"
* or not.
*
* @return {@link JsonPointer} path to location of given context
*
* @since 2.9
*/
public static JsonPointer forPath(JsonStreamContext context,
boolean includeRoot)
{
// First things first: last segment may be for START_ARRAY/START_OBJECT,
// in which case it does not yet point to anything, and should be skipped
if (context == null) {
return EMPTY;
}
if (!context.hasPathSegment()) {
// one special case; do not prune root if we need it
if (!(includeRoot && context.inRoot() && context.hasCurrentIndex())) {
context = context.getParent();
}
}
JsonPointer tail = null;
for (; context != null; context = context.getParent()) {
if (context.inObject()) {
String seg = context.getCurrentName();
if (seg == null) { // is this legal?
seg = "";
}
tail = new JsonPointer(_fullPath(tail, seg), seg, tail);
} else if (context.inArray() || includeRoot) {
int ix = context.getCurrentIndex();
String ixStr = String.valueOf(ix);
tail = new JsonPointer(_fullPath(tail, ixStr), ixStr, ix, tail);
}
// NOTE: this effectively drops ROOT node(s); should have 1 such node,
// as the last one, but we don't have to care (probably some paths have
// no root, for example)
}
if (tail == null) {
return EMPTY;
}
return tail;
}
private static String _fullPath(JsonPointer tail, String segment)
{
if (tail == null) {
StringBuilder sb = new StringBuilder(segment.length()+1);
sb.append('/');
_appendEscaped(sb, segment);
return sb.toString();
}
String tailDesc = tail._asString;
StringBuilder sb = new StringBuilder(segment.length() + 1 + tailDesc.length());
sb.append('/');
_appendEscaped(sb, segment);
sb.append(tailDesc);
return sb.toString();
}
private static void _appendEscaped(StringBuilder sb, String segment)
{
for (int i = 0, end = segment.length(); i < end; ++i) {
char c = segment.charAt(i);
if (c == '/') {
sb.append("~1");
continue;
}
if (c == '~') {
sb.append("~0");
continue;
}
sb.append(c);
}
}
/* Factory method that composes a pointer instance, given a set
* of 'raw' segments: raw meaning that no processing will be done,
* no escaping may is present.
*
* @param segments
*
* @return Constructed path instance
*/
/* TODO!
public static JsonPointer fromSegment(String... segments)
{
if (segments.length == 0) {
return EMPTY;
}
JsonPointer prev = null;
for (String segment : segments) {
JsonPointer next = new JsonPointer()
}
}
*/
/*
/**********************************************************
/* Public API
/**********************************************************
*/
public boolean matches() { return _nextSegment == null; }
public String getMatchingProperty() { return _matchingPropertyName; }
public int getMatchingIndex() { return _matchingElementIndex; }
/**
* @return True if the root selector matches property name (that is, could
* match field value of JSON Object node)
*/
public boolean mayMatchProperty() { return _matchingPropertyName != null; }
/**
* @return True if the root selector matches element index (that is, could
* match an element of JSON Array node)
*/
public boolean mayMatchElement() { return _matchingElementIndex >= 0; }
/**
* @return the leaf of current JSON Pointer expression: leaf is the last
* non-null segment of current JSON Pointer.
*
* @since 2.5
*/
public JsonPointer last() {
JsonPointer current = this;
if (current == EMPTY) {
return null;
}
JsonPointer next;
while ((next = current._nextSegment) != JsonPointer.EMPTY) {
current = next;
}
return current;
}
/**
* Mutant factory method that will return
*
* - `tail` if `this` instance is "empty" pointer, OR
*
* - `this` instance if `tail` is "empty" pointer, OR
*
* - Newly constructed {@link JsonPointer} instance that starts with all segments
* of `this`, followed by all segments of `tail`.
*
*
*
* @param tail {@link JsonPointer} instance to append to this one, to create a new pointer instance
*
* @return Either `this` instance, `tail`, or a newly created combination, as per description above.
*/
public JsonPointer append(JsonPointer tail) {
if (this == EMPTY) {
return tail;
}
if (tail == EMPTY) {
return this;
}
// 21-Mar-2017, tatu: Not superbly efficient; could probably improve by not concatenating,
// re-decoding -- by stitching together segments -- but for now should be fine.
String currentJsonPointer = _asString;
if (currentJsonPointer.endsWith("/")) {
//removes final slash
currentJsonPointer = currentJsonPointer.substring(0, currentJsonPointer.length()-1);
}
return compile(currentJsonPointer + tail._asString);
}
/**
* Method that may be called to see if the pointer head (first segment)
* would match property (of a JSON Object) with given name.
*
* @param name Name of Object property to match
*
* @return {@code True} if the pointer head matches specified property name
*
* @since 2.5
*/
public boolean matchesProperty(String name) {
return (_nextSegment != null) && _matchingPropertyName.equals(name);
}
/**
* Method that may be called to check whether the pointer head (first segment)
* matches specified Object property (by name) and if so, return
* {@link JsonPointer} that represents rest of the path after match.
* If there is no match, {@code null} is returned.
*
* @param name Name of Object property to match
*
* @return Remaining path after matching specified property, if there is match;
* {@code null} otherwise
*/
public JsonPointer matchProperty(String name) {
if ((_nextSegment != null) && _matchingPropertyName.equals(name)) {
return _nextSegment;
}
return null;
}
/**
* Method that may be called to see if the pointer would match
* Array element (of a JSON Array) with given index.
*
* @param index Index of Array element to match
*
* @return {@code True} if the pointer head matches specified Array index
*
* @since 2.5
*/
public boolean matchesElement(int index) {
return (index == _matchingElementIndex) && (index >= 0);
}
/**
* Method that may be called to check whether the pointer head (first segment)
* matches specified Array index and if so, return
* {@link JsonPointer} that represents rest of the path after match.
* If there is no match, {@code null} is returned.
*
* @param index Index of Array element to match
*
* @return Remaining path after matching specified index, if there is match;
* {@code null} otherwise
*
* @since 2.6
*/
public JsonPointer matchElement(int index) {
if ((index != _matchingElementIndex) || (index < 0)) {
return null;
}
return _nextSegment;
}
/**
* Accessor for getting a "sub-pointer" (or sub-path), instance where current segment
* has been removed and pointer includes rest of the segments.
* For example, for JSON Pointer "/root/branch/leaf", this method would
* return pointer "/branch/leaf".
* For matching state (last segment), will return {@code null}.
*
* Note that this is a very cheap method to call as it simply returns "next" segment
* (which has been constructed when pointer instance was constructed).
*
* @return Tail of this pointer, if it has any; {@code null} if this pointer only
* has the current segment
*/
public JsonPointer tail() {
return _nextSegment;
}
/**
* Accessor for getting a pointer instance that is identical to this
* instance except that the last segment has been dropped.
* For example, for JSON Pointer "/root/branch/leaf", this method would
* return pointer "/root/branch" (compared to {@link #tail()} that
* would return "/branch/leaf").
*
* Note that whereas {@link #tail} is a very cheap operation to call (as "tail" already
* exists for single-linked forward direction), this method has to fully
* construct a new instance by traversing the chain of segments.
*
* @return Pointer expression that contains same segments as this one, except for
* the last segment.
*
* @since 2.5
*/
public JsonPointer head() {
JsonPointer h = _head;
if (h == null) {
if (this != EMPTY) {
h = _constructHead();
}
_head = h;
}
return h;
}
/*
/**********************************************************
/* Standard method overrides
/**********************************************************
*/
@Override public String toString() { return _asString; }
@Override public int hashCode() { return _asString.hashCode(); }
@Override public boolean equals(Object o) {
if (o == this) return true;
if (o == null) return false;
if (!(o instanceof JsonPointer)) return false;
return _asString.equals(((JsonPointer) o)._asString);
}
/*
/**********************************************************
/* Internal methods
/**********************************************************
*/
private final static int _parseIndex(String str) {
final int len = str.length();
// [core#133]: beware of super long indexes; assume we never
// have arrays over 2 billion entries so ints are fine.
if (len == 0 || len > 10) {
return -1;
}
// [core#176]: no leading zeroes allowed
char c = str.charAt(0);
if (c <= '0') {
return (len == 1 && c == '0') ? 0 : -1;
}
if (c > '9') {
return -1;
}
for (int i = 1; i < len; ++i) {
c = str.charAt(i);
if (c > '9' || c < '0') {
return -1;
}
}
if (len == 10) {
long l = NumberInput.parseLong(str);
if (l > Integer.MAX_VALUE) {
return -1;
}
}
return NumberInput.parseInt(str);
}
protected static JsonPointer _parseTail(String input) {
final int end = input.length();
// first char is the contextual slash, skip
for (int i = 1; i < end; ) {
char c = input.charAt(i);
if (c == '/') { // common case, got a segment
return new JsonPointer(input, input.substring(1, i),
_parseTail(input.substring(i)));
}
++i;
// quoting is different; offline this case
if (c == '~' && i < end) { // possibly, quote
return _parseQuotedTail(input, i);
}
// otherwise, loop on
}
// end of the road, no escapes
return new JsonPointer(input, input.substring(1), EMPTY);
}
/**
* Method called to parse tail of pointer path, when a potentially
* escaped character has been seen.
*
* @param input Full input for the tail being parsed
* @param i Offset to character after tilde
*
* @return Pointer instance constructed
*/
protected static JsonPointer _parseQuotedTail(String input, int i) {
final int end = input.length();
StringBuilder sb = new StringBuilder(Math.max(16, end));
if (i > 2) {
sb.append(input, 1, i-1);
}
_appendEscape(sb, input.charAt(i++));
while (i < end) {
char c = input.charAt(i);
if (c == '/') { // end is nigh!
return new JsonPointer(input, sb.toString(),
_parseTail(input.substring(i)));
}
++i;
if (c == '~' && i < end) {
_appendEscape(sb, input.charAt(i++));
continue;
}
sb.append(c);
}
// end of the road, last segment
return new JsonPointer(input, sb.toString(), EMPTY);
}
protected JsonPointer _constructHead()
{
// ok; find out who we are to drop
JsonPointer last = last();
if (last == this) {
return EMPTY;
}
// and from that, length of suffix to drop
int suffixLength = last._asString.length();
JsonPointer next = _nextSegment;
return new JsonPointer(_asString.substring(0, _asString.length() - suffixLength), _matchingPropertyName,
_matchingElementIndex, next._constructHead(suffixLength, last));
}
protected JsonPointer _constructHead(int suffixLength, JsonPointer last)
{
if (this == last) {
return EMPTY;
}
JsonPointer next = _nextSegment;
String str = _asString;
return new JsonPointer(str.substring(0, str.length() - suffixLength), _matchingPropertyName,
_matchingElementIndex, next._constructHead(suffixLength, last));
}
private static void _appendEscape(StringBuilder sb, char c) {
if (c == '0') {
c = '~';
} else if (c == '1') {
c = '/';
} else {
sb.append('~');
}
sb.append(c);
}
}