JsonNode
* base class in mapper package.
*
* Note that in Jackson 1.x JsonNode itself
* was part of core package: Jackson 2.x refactored this
* since conceptually Tree Model is part of mapper package,
* and so part visible to core package should
* be minimized.
*
* NOTE: starting with Jackson 2.2, there is more functionality * available via this class, and the intent is that this should * form actual base for multiple alternative tree representations; * for example, immutable trees could use different implementation * than mutable trees. It should also be possible to move actual * Tree Model implementation out of databind package eventually * (Jackson 3?). * * @since 2.2 */ public interface TreeNode { /* /********************************************************** /* Minimal introspection methods /********************************************************** */ /** * Method that can be used for efficient type detection * when using stream abstraction for traversing nodes. * Will return the first {@link JsonToken} that equivalent * stream event would produce (for most nodes there is just * one token but for structured/container types multiple) */ JsonToken asToken(); /** * If this node is a numeric type (as per {@link JsonToken#isNumeric}), * returns native type that node uses to store the numeric value; * otherwise returns null. * * @return Type of number contained, if any; or null if node does not * contain numeric value. */ JsonParser.NumberType numberType(); /** * Method that returns number of child nodes this node contains: * for Array nodes, number of child elements, for Object nodes, * number of fields, and for all other nodes 0. * * @return For non-container nodes returns 0; for arrays number of * contained elements, and for objects number of fields. * * @since 2.2 */ int size(); /** * Method that returns true for all value nodes: ones that * are not containers, and that do not represent "missing" nodes * in the path. Such value nodes represent String, Number, Boolean * and null values from JSON. *
* Note: one and only one of methods {@link #isValueNode}, * {@link #isContainerNode} and {@link #isMissingNode} ever * returns true for any given node. * * @since 2.2 */ boolean isValueNode(); /** * Method that returns true for container nodes: Arrays and Objects. *
* Note: one and only one of methods {@link #isValueNode}, * {@link #isContainerNode} and {@link #isMissingNode} ever * returns true for any given node. * * @since 2.2 */ boolean isContainerNode(); /** * Method that returns true for "virtual" nodes which represent * missing entries constructed by path accessor methods when * there is no actual node matching given criteria. *
* Note: one and only one of methods {@link #isValueNode}, * {@link #isContainerNode} and {@link #isMissingNode} ever * returns true for any given node. * * @since 2.2 */ boolean isMissingNode(); /** * Method that returns true if this node is an Array node, false * otherwise. * Note that if true is returned, {@link #isContainerNode} * must also return true. * * @since 2.2 */ boolean isArray(); /** * Method that returns true if this node is an Object node, false * otherwise. * Note that if true is returned, {@link #isContainerNode} * must also return true. * * @since 2.2 */ boolean isObject(); /* /********************************************************** /* Basic traversal through structured entries (Arrays, Objects) /********************************************************** */ /** * Method for accessing value of the specified field of * an object node. If this node is not an object (or it * does not have a value for specified field name), or * if there is no field with such name, null is returned. *
* NOTE: handling of explicit null values may vary between * implementations; some trees may retain explicit nulls, others * not. * * @return Node that represent value of the specified field, * if this node is an object and has value for the specified * field. Null otherwise. * * @since 2.2 */ TreeNode get(String fieldName); /** * Method for accessing value of the specified element of * an array node. For other nodes, null is returned. *
* For array nodes, index specifies
* exact location within array and allows for efficient iteration
* over child elements (underlying storage is guaranteed to
* be efficiently indexable, i.e. has random-access to elements).
* If index is less than 0, or equal-or-greater than
* node.size(), null is returned; no exception is
* thrown for any index.
*
* @return Node that represent value of the specified element,
* if this node is an array and has specified element.
* Null otherwise.
*
* @since 2.2
*/
TreeNode get(int index);
/**
* Method for accessing value of the specified field of
* an object node.
* For other nodes, a "missing node" (virtual node
* for which {@link #isMissingNode} returns true) is returned.
*
* @return Node that represent value of the specified field,
* if this node is an object and has value for the specified field;
* otherwise "missing node" is returned.
*
* @since 2.2
*/
TreeNode path(String fieldName);
/**
* Method for accessing value of the specified element of
* an array node.
* For other nodes, a "missing node" (virtual node
* for which {@link #isMissingNode} returns true) is returned.
*
* For array nodes, index specifies
* exact location within array and allows for efficient iteration
* over child elements (underlying storage is guaranteed to
* be efficiently indexable, i.e. has random-access to elements).
* If index is less than 0, or equal-or-greater than
*
* Note that if the same expression is used often, it is preferable to construct
* {@link JsonPointer} instance once and reuse it: this method will not perform
* any caching of compiled expressions.
*
* @param jsonPointerExpression Expression to compile as a {@link JsonPointer}
* instance
*
* @return Node that matches given JSON Pointer: if no match exists,
* will return a node for which {@link TreeNode#isMissingNode()} returns true.
*
* @since 2.3
*/
TreeNode at(String jsonPointerExpression) throws IllegalArgumentException;
/*
/**********************************************************
/* Converting to/from Streaming API
/**********************************************************
*/
/**
* Method for constructing a {@link JsonParser} instance for
* iterating over contents of the tree that this node is root of.
* Functionally equivalent to first serializing tree using
* {@link ObjectCodec} and then re-parsing but
* more efficient.
*
* NOTE: constructed parser instance will NOT initially point to a token,
* so before passing it to deserializers, it is typically necessary to
* advance it to the first available token by calling {@link JsonParser#nextToken()}.
*
* Also note that calling this method will NOT pass {@link ObjectCodec}
* reference, so data-binding callback methods like {@link JsonParser#readValueAs(Class)}
* will not work with calling {@link JsonParser#setCodec}).
* It is often better to call {@link #traverse(ObjectCodec)} to pass the codec explicitly.
*/
JsonParser traverse();
/**
* Same as {@link #traverse()}, but additionally passes {@link com.fasterxml.jackson.core.ObjectCodec}
* to use if {@link JsonParser#readValueAs(Class)} is used (otherwise caller must call
* {@link JsonParser#setCodec} on response explicitly).
*
* NOTE: constructed parser instance will NOT initially point to a token,
* so before passing it to deserializers, it is typically necessary to
* advance it to the first available token by calling {@link JsonParser#nextToken()}.
*
* @since 2.1
*/
JsonParser traverse(ObjectCodec codec);
}
node.size(), "missing node" is returned; no exception is
* thrown for any index.
*
* @return Node that represent value of the specified element,
* if this node is an array and has specified element;
* otherwise "missing node" is returned.
*
* @since 2.2
*/
TreeNode path(int index);
/**
* Method for accessing names of all fields for this node, iff
* this node is an Object node. Number of field names accessible
* will be {@link #size}.
*
* @since 2.2
*/
Iterator
* return at(JsonPointer.valueOf(jsonPointerExpression));
*
*