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package com.fasterxml.jackson.databind;

import java.io.IOException;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.*;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;
import com.fasterxml.jackson.core.TreeNode;

/**
 * Base class for all JSON nodes, which form the basis of JSON
 * Tree Model that Jackson implements.
 * One way to think of these nodes is to consider them
 * similar to DOM nodes in XML DOM trees.
 *

* As a general design rule, most accessors ("getters") are included * in this base class, to allow for traversing structure without * type casts. Most mutators, however, need to be accessed through * specific sub-classes (such as ObjectNode * and ArrayNode). * This seems sensible because proper type * information is generally available when building or modifying * trees, but less often when reading a tree (newly built from * parsed JSON content). *

* Actual concrete sub-classes can be found from package * {@link com.fasterxml.jackson.databind.node}. */ public abstract class JsonNode implements TreeNode, Iterable { protected final static List NO_NODES = Collections.emptyList(); protected final static List NO_STRINGS = Collections.emptyList(); /* /********************************************************** /* Construction, related /********************************************************** */ protected JsonNode() { } /** * Method that can be called to get a node that is guaranteed * not to allow changing of this node through mutators on * this node or any of its children. * This means it can either make a copy of this node (and all * mutable children and grand children nodes), or node itself * if it is immutable. *

* Note: return type is guaranteed to have same type as the * node method is called on; which is why method is declared * with local generic type. * * @since 2.0 * * @return Node that is either a copy of this node (and all non-leaf * children); or, for immutable leaf nodes, node itself. */ public abstract T deepCopy(); /* /********************************************************** /* Public API, type introspection /********************************************************** */ // // First high-level division between values, containers and "missing" /** * 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. */ public boolean isValueNode() { return false; } /** * 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. */ public boolean isContainerNode() { return false; } /** * 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. */ public boolean isMissingNode() { return false; } // // Then more specific type introspection // // (along with defaults to be overridden) /** * @return True if this node represents JSON Array */ public boolean isArray() { return false; } /** * @return True if this node represents JSON Object */ public boolean isObject() { return false; } /** * Method that can be used to check if the node is a wrapper * for a POJO ("Plain Old Java Object" aka "bean". * Returns true only for * instances of POJONode. * * @return True if this node wraps a POJO */ public boolean isPojo() { return false; } /** * @return True if this node represents a numeric JSON * value */ public boolean isNumber() { return false; } /** * * @return True if this node represents an integral (integer) * numeric JSON value */ public boolean isIntegralNumber() { return false; } /** * @return True if this node represents a non-integral * numeric JSON value */ public boolean isFloatingPointNumber() { return false; } /** * Method that can be used to check whether contained value * is a number represented as Java int. * Note, however, that even if this method returns false, it * is possible that conversion would be possible from other numeric * types -- to check if this is possible, use * {@link #canConvertToInt()} instead. * * @return True if the value contained by this node is stored as Java int */ public boolean isInt() { return false; } /** * Method that can be used to check whether contained value * is a number represented as Java long. * Note, however, that even if this method returns false, it * is possible that conversion would be possible from other numeric * types -- to check if this is possible, use * {@link #canConvertToInt()} instead. * * @return True if the value contained by this node is stored as Java long */ public boolean isLong() { return false; } public boolean isDouble() { return false; } public boolean isBigDecimal() { return false; } public boolean isBigInteger() { return false; } public boolean isTextual() { return false; } /** * Method that can be used to check if this node was created from * JSON boolean value (literals "true" and "false"). */ public boolean isBoolean() { return false; } /** * Method that can be used to check if this node was created from * JSON literal null value. */ public boolean isNull() { return false; } /** * Method that can be used to check if this node represents * binary data (Base64 encoded). Although this will be externally * written as JSON String value, {@link #isTextual} will * return false if this method returns true. * * @return True if this node represents base64 encoded binary data */ public boolean isBinary() { return false; } /** * 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) */ public abstract JsonToken asToken(); /** * If this node is a numeric type (as per {@link #isNumber}), * 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. */ public abstract JsonParser.NumberType numberType(); /** * Method that can be used to check whether this node is a numeric * node ({@link #isNumber} would return true) AND its value fits * within Java's 32-bit signed integer type, int. * Note that floating-point numbers are convertible if the integral * part fits without overflow (as per standard Java coercion rules) * * @since 2.0 */ public boolean canConvertToInt() { return false; } /** * Method that can be used to check whether this node is a numeric * node ({@link #isNumber} would return true) AND its value fits * within Java's 64-bit signed integer type, long. * Note that floating-point numbers are convertible if the integral * part fits without overflow (as per standard Java coercion rules) * * @since 2.0 */ public boolean canConvertToLong() { return false; } /* /********************************************************** /* Public API, straight value access /********************************************************** */ /** * Method to use for accessing String values. * Does NOT do any conversions for non-String value nodes; * for non-String values (ones for which {@link #isTextual} returns * false) null will be returned. * For String values, null is never returned (but empty Strings may be) * * @return Textual value this node contains, iff it is a textual * JSON node (comes from JSON String value entry) */ public String textValue() { return null; } /** * Method to use for accessing binary content of binary nodes (nodes * for which {@link #isBinary} returns true); or for Text Nodes * (ones for which {@link #textValue} returns non-null value), * to read decoded base64 data. * For other types of nodes, returns null. * * @return Binary data this node contains, iff it is a binary * node; null otherwise */ public byte[] binaryValue() throws IOException { return null; } /** * Method to use for accessing JSON boolean values (value * literals 'true' and 'false'). * For other types, always returns false. * * @return Textual value this node contains, iff it is a textual * json node (comes from JSON String value entry) */ public boolean booleanValue() { return false; } /** * Returns numeric value for this node, if and only if * this node is numeric ({@link #isNumber} returns true); otherwise * returns null * * @return Number value this node contains, if any (null for non-number * nodes). */ public Number numberValue() { return null; } /** * Returns integer value for this node, if and only if * this node is numeric ({@link #isNumber} returns true). For other * types returns 0. * For floating-point numbers, value is truncated using default * Java coercion, similar to how cast from double to int operates. * * @return Integer value this node contains, if any; 0 for non-number * nodes. */ public int intValue() { return 0; } public long longValue() { return 0L; } public double doubleValue() { return 0.0; } public BigDecimal decimalValue() { return BigDecimal.ZERO; } public BigInteger bigIntegerValue() { return BigInteger.ZERO; } /** * Method for accessing value of the specified element of * an array node. For other nodes, null is always 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. *

* NOTE: if the element value has been explicitly set as null * (which is different from removal!), * a {@link com.fasterxml.jackson.databind.node.NullNode} will be returned, * not null. * * @return Node that represent value of the specified element, * if this node is an array and has specified element. * Null otherwise. */ public JsonNode get(int index) { return null; } /** * 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: if the property value has been explicitly set as null * (which is different from removal!), * a {@link com.fasterxml.jackson.databind.node.NullNode} will be returned, * not null. * * @return Node that represent value of the specified field, * if this node is an object and has value for the specified * field. Null otherwise. */ public JsonNode get(String fieldName) { return null; } /* /********************************************************** /* Public API, value access with conversion(s)/coercion(s) /********************************************************** */ /** * Method that will return a valid String representation of * the container value, if the node is a value node * (method {@link #isValueNode} returns true), * otherwise empty String. */ public abstract String asText(); /** * Method that will try to convert value of this node to a Java int. * Numbers are coerced using default Java rules; booleans convert to 0 (false) * and 1 (true), and Strings are parsed using default Java language integer * parsing rules. *

* If representation can not be converted to an int (including structured types * like Objects and Arrays), * default value of 0 will be returned; no exceptions are thrown. */ public int asInt() { return asInt(0); } /** * Method that will try to convert value of this node to a Java int. * Numbers are coerced using default Java rules; booleans convert to 0 (false) * and 1 (true), and Strings are parsed using default Java language integer * parsing rules. *

* If representation can not be converted to an int (including structured types * like Objects and Arrays), * specified defaultValue will be returned; no exceptions are thrown. */ public int asInt(int defaultValue) { return defaultValue; } /** * Method that will try to convert value of this node to a Java long. * Numbers are coerced using default Java rules; booleans convert to 0 (false) * and 1 (true), and Strings are parsed using default Java language integer * parsing rules. *

* If representation can not be converted to an long (including structured types * like Objects and Arrays), * default value of 0 will be returned; no exceptions are thrown. */ public long asLong() { return asLong(0L); } /** * Method that will try to convert value of this node to a Java long. * Numbers are coerced using default Java rules; booleans convert to 0 (false) * and 1 (true), and Strings are parsed using default Java language integer * parsing rules. *

* If representation can not be converted to an long (including structured types * like Objects and Arrays), * specified defaultValue will be returned; no exceptions are thrown. */ public long asLong(long defaultValue) { return defaultValue; } /** * Method that will try to convert value of this node to a Java double. * Numbers are coerced using default Java rules; booleans convert to 0.0 (false) * and 1.0 (true), and Strings are parsed using default Java language integer * parsing rules. *

* If representation can not be converted to an int (including structured types * like Objects and Arrays), * default value of 0.0 will be returned; no exceptions are thrown. */ public double asDouble() { return asDouble(0.0); } /** * Method that will try to convert value of this node to a Java double. * Numbers are coerced using default Java rules; booleans convert to 0.0 (false) * and 1.0 (true), and Strings are parsed using default Java language integer * parsing rules. *

* If representation can not be converted to an int (including structured types * like Objects and Arrays), * specified defaultValue will be returned; no exceptions are thrown. */ public double asDouble(double defaultValue) { return defaultValue; } /** * Method that will try to convert value of this node to a Java boolean. * JSON booleans map naturally; integer numbers other than 0 map to true, and * 0 maps to false * and Strings 'true' and 'false' map to corresponding values. *

* If representation can not be converted to a boolean value (including structured types * like Objects and Arrays), * default value of false will be returned; no exceptions are thrown. */ public boolean asBoolean() { return asBoolean(false); } /** * Method that will try to convert value of this node to a Java boolean. * JSON booleans map naturally; integer numbers other than 0 map to true, and * 0 maps to false * and Strings 'true' and 'false' map to corresponding values. *

* If representation can not be converted to a boolean value (including structured types * like Objects and Arrays), * specified defaultValue will be returned; no exceptions are thrown. */ public boolean asBoolean(boolean defaultValue) { return defaultValue; } /* /********************************************************** /* Public API, value find / existence check methods /********************************************************** */ /** * Method that allows checking whether this node is JSON Object node * and contains value for specified property. If this is the case * (including properties with explicit null values), returns true; * otherwise returns false. *

* This method is equivalent to: *

     *   node.get(fieldName) != null
     *
* (since return value of get() is node, not value node contains) *

* NOTE: when explicit null values are added, this * method will return true for such properties. * * @param fieldName Name of element to check * * @return True if this node is a JSON Object node, and has a property * entry with specified name (with any value, including null value) */ public boolean has(String fieldName) { return get(fieldName) != null; } /** * Method that allows checking whether this node is JSON Array node * and contains a value for specified index * If this is the case * (including case of specified indexing having null as value), returns true; * otherwise returns false. *

* Note: array element indexes are 0-based. *

* This method is equivalent to: *

     *   node.get(index) != null
     *
*

* NOTE: this method will return true for explicitly added * null values. * * @param index Index to check * * @return True if this node is a JSON Object node, and has a property * entry with specified name (with any value, including null value) */ public boolean has(int index) { return get(index) != null; } /** * Method that is similar to {@link #has(String)}, but that will * return false for explicitly added nulls. *

* This method is functionally equivalent to: *

     *   node.get(fieldName) != null && !node.get(fieldName).isNull()
     *
* * @since 2.1 */ public boolean hasNonNull(String fieldName) { JsonNode n = get(fieldName); return (n != null) && !n.isNull(); } /** * Method that is similar to {@link #has(int)}, but that will * return false for explicitly added nulls. *

* This method is equivalent to: *

     *   node.get(index) != null && !node.get(index).isNull()
     *
* * @since 2.1 */ public boolean hasNonNull(int index) { JsonNode n = get(index); return (n != null) && !n.isNull(); } /** * Method for finding a JSON Object field with specified name in this * node or its child nodes, and returning value it has. * If no matching field is found in this node or its descendants, returns null. * * @param fieldName Name of field to look for * * @return Value of first matching node found, if any; null if none */ public abstract JsonNode findValue(String fieldName); /** * Method for finding JSON Object fields with specified name, and returning * found ones as a List. Note that sub-tree search ends if a field is found, * so possible children of result nodes are not included. * If no matching fields are found in this node or its descendants, returns * an empty List. * * @param fieldName Name of field to look for */ public final List findValues(String fieldName) { List result = findValues(fieldName, null); if (result == null) { return Collections.emptyList(); } return result; } /** * Similar to {@link #findValues}, but will additionally convert * values into Strings, calling {@link #asText}. */ public final List findValuesAsText(String fieldName) { List result = findValuesAsText(fieldName, null); if (result == null) { return Collections.emptyList(); } return result; } /** * Method similar to {@link #findValue}, but that will return a * "missing node" instead of null if no field is found. Missing node * is a specific kind of node for which {@link #isMissingNode} * returns true; and all value access methods return empty or * missing value. * * @param fieldName Name of field to look for * * @return Value of first matching node found; or if not found, a * "missing node" (non-null instance that has no value) */ public abstract JsonNode findPath(String fieldName); /** * Method for finding a JSON Object that contains specified field, * within this node or its descendants. * If no matching field is found in this node or its descendants, returns null. * * @param fieldName Name of field to look for * * @return Value of first matching node found, if any; null if none */ public abstract JsonNode findParent(String fieldName); /** * Method for finding a JSON Object that contains specified field, * within this node or its descendants. * If no matching field is found in this node or its descendants, returns null. * * @param fieldName Name of field to look for * * @return Value of first matching node found, if any; null if none */ public final List findParents(String fieldName) { List result = findParents(fieldName, null); if (result == null) { return Collections.emptyList(); } return result; } public abstract List findValues(String fieldName, List foundSoFar); public abstract List findValuesAsText(String fieldName, List foundSoFar); public abstract List findParents(String fieldName, List foundSoFar); /* /********************************************************** /* Public API, container access /********************************************************** */ /** * 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. */ public int size() { return 0; } /** * Same as calling {@link #elements}; implemented so that * convenience "for-each" loop can be used for looping over elements * of JSON Array constructs. */ // @Override public final Iterator iterator() { return elements(); } /** * Method for accessing all value nodes of this Node, iff * this node is a JSON Array or Object node. In case of Object node, * field names (keys) are not included, only values. * For other types of nodes, returns empty iterator. */ public Iterator elements() { return NO_NODES.iterator(); } /** * Method for accessing names of all fields for this Node, iff * this node is a JSON Object node. */ public Iterator fieldNames() { return NO_STRINGS.iterator(); } /** * @return Iterator that can be used to traverse all key/value pairs for * object nodes; empty iterator (no contents) for other types */ public Iterator> fields() { Collection> coll = Collections.emptyList(); return coll.iterator(); } /* /********************************************************** /* Public API, path handling /********************************************************** */ /** * This method is similar to {@link #get(String)}, except * that instead of returning null if no such value exists (due * to this node not being an object, or object not having value * for the specified field), * a "missing node" (node that returns true for * {@link #isMissingNode}) will be returned. This allows for * convenient and safe chained access via path calls. */ public abstract JsonNode path(String fieldName); /** * This method is similar to {@link #get(int)}, except * that instead of returning null if no such element exists (due * to index being out of range, or this node not being an array), * a "missing node" (node that returns true for * {@link #isMissingNode}) will be returned. This allows for * convenient and safe chained access via path calls. */ public abstract JsonNode path(int index); /** * Method that can be called on Object nodes, to access a property * that has Object value; or if no such property exists, to create, * add and return such Object node. * If the node method is called on is not Object node, * or if property exists and has value that is not Object node, * {@link UnsupportedOperationException} is thrown */ public JsonNode with(String propertyName) { throw new UnsupportedOperationException("JsonNode not of type ObjectNode (but " +getClass().getName()+"), can not call with() on it"); } /** * Method that can be called on Object nodes, to access a property * that has Array value; or if no such property exists, to create, * add and return such Array node. * If the node method is called on is not Object node, * or if property exists and has value that is not Array node, * {@link UnsupportedOperationException} is thrown */ public JsonNode withArray(String propertyName) { throw new UnsupportedOperationException("JsonNode not of type ObjectNode (but " +getClass().getName()+"), can not call withArray() on it"); } /* /********************************************************** /* Public API: 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 com.fasterxml.jackson.core.ObjectCodec} and then re-parsing but * more efficient. */ public abstract JsonParser traverse(); /* /********************************************************** /* Overridden standard methods /********************************************************** */ /** *

* Note: marked as abstract to ensure all implementation * classes define it properly. */ @Override public abstract String toString(); /** * Equality for node objects is defined as full (deep) value * equality. This means that it is possible to compare complete * JSON trees for equality by comparing equality of root nodes. *

* Note: marked as abstract to ensure all implementation * classes define it properly and not rely on definition * from {@link java.lang.Object}. */ @Override public abstract boolean equals(Object o); }





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