com.fasterxml.jackson.core

Interface TreeNode



  • public interface TreeNode
    Marker interface used to denote JSON Tree nodes, as far as the core package knows them (which is very little): mostly needed to allow ObjectCodec to have some level of interoperability. Most functionality is within 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?).

    • Method Summary

      Methods 
      Modifier and Type Method and Description
      JsonToken asToken()
      Method that can be used for efficient type detection when using stream abstraction for traversing nodes.
      Iterator<String> fieldNames()
      Method for accessing names of all fields for this node, iff this node is an Object node.
      TreeNode get(int index)
      Method for accessing value of the specified element of an array node.
      TreeNode get(String fieldName)
      Method for accessing value of the specified field of an object node.
      boolean isArray()
      Method that returns true if this node is an Array node, false otherwise.
      boolean isContainerNode()
      Method that returns true for container nodes: Arrays and Objects.
      boolean isMissingNode()
      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.
      boolean isObject()
      Method that returns true if this node is an Object node, false otherwise.
      boolean isValueNode()
      Method that returns true for all value nodes: ones that are not containers, and that do not represent "missing" nodes in the path.
      JsonParser.NumberType numberType()
      If this node is a numeric type (as per JsonToken.isNumeric()), returns native type that node uses to store the numeric value; otherwise returns null.
      TreeNode path(int index)
      Method for accessing value of the specified element of an array node.
      TreeNode path(String fieldName)
      Method for accessing value of the specified field of an object node.
      int size()
      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.
      JsonParser traverse()
      Method for constructing a JsonParser instance for iterating over contents of the tree that this node is root of.
      JsonParser traverse(ObjectCodec codec)
      Same as traverse(), but additionally passes ObjectCodec to use if JsonParser.readValueAs(Class) is used (otherwise caller must call JsonParser.setCodec(com.fasterxml.jackson.core.ObjectCodec) on response explicitly).
    • Method Detail

      • asToken

        JsonToken asToken()
        Method that can be used for efficient type detection when using stream abstraction for traversing nodes. Will return the first JsonToken that equivalent stream event would produce (for most nodes there is just one token but for structured/container types multiple)
      • numberType

        JsonParser.NumberType numberType()
        If this node is a numeric type (as per JsonToken.isNumeric()), returns native type that node uses to store the numeric value; otherwise returns null.
        Returns:
        Type of number contained, if any; or null if node does not contain numeric value.
      • size

        int size()
        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.
        Returns:
        For non-container nodes returns 0; for arrays number of contained elements, and for objects number of fields.
        Since:
        2.2
      • isValueNode

        boolean isValueNode()
        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 isValueNode(), isContainerNode() and isMissingNode() ever returns true for any given node.

        Since:
        2.2
      • isContainerNode

        boolean isContainerNode()
        Method that returns true for container nodes: Arrays and Objects.

        Note: one and only one of methods isValueNode(), isContainerNode() and isMissingNode() ever returns true for any given node.

        Since:
        2.2
      • isMissingNode

        boolean isMissingNode()
        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 isValueNode(), isContainerNode() and isMissingNode() ever returns true for any given node.

        Since:
        2.2
      • isArray

        boolean isArray()
        Method that returns true if this node is an Array node, false otherwise. Note that if true is returned, isContainerNode() must also return true.
        Since:
        2.2
      • isObject

        boolean isObject()
        Method that returns true if this node is an Object node, false otherwise. Note that if true is returned, isContainerNode() must also return true.
        Since:
        2.2
      • get

        TreeNode get(String fieldName)
        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.

        Returns:
        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
      • get

        TreeNode get(int index)
        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.

        Returns:
        Node that represent value of the specified element, if this node is an array and has specified element. Null otherwise.
        Since:
        2.2
      • path

        TreeNode path(String fieldName)
        Method for accessing value of the specified field of an object node. For other nodes, a "missing node" (virtual node for which isMissingNode() returns true) is returned.
        Returns:
        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
      • path

        TreeNode path(int index)
        Method for accessing value of the specified element of an array node. For other nodes, a "missing node" (virtual node for which 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 node.size(), "missing node" is returned; no exception is thrown for any index.

        Returns:
        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
      • fieldNames

        Iterator<String> fieldNames()
        Method for accessing names of all fields for this node, iff this node is an Object node. Number of field names accessible will be size().
        Since:
        2.2
      • traverse

        JsonParser traverse()
        Method for constructing a JsonParser instance for iterating over contents of the tree that this node is root of. Functionally equivalent to first serializing tree using ObjectCodec and then re-parsing but more efficient.

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