Jackson Core Source Code

Jackson is "the Java JSON library" or "the best JSON parser for Java". Or simply as "JSON for Java".

Jackson Core Source Code files are provided in the source packge (jackson-core-2.12.4-sources.jar). You can download it at Jackson Maven Website.

You can also browse Jackson Core Source Code below:

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com/fasterxml/jackson/core/JsonStreamContext.java

/* Jackson JSON-processor.
 *
 * Copyright (c) 2007- Tatu Saloranta, tatu.saloranta@iki.fi
 */

package com.fasterxml.jackson.core;

import com.fasterxml.jackson.core.io.CharTypes;

/**
 * Shared base class for streaming processing contexts used during
 * reading and writing of Json content using Streaming API.
 * This context is also exposed to applications:
 * context object can be used by applications to get an idea of
 * relative position of the parser/generator within json content
 * being processed. This allows for some contextual processing: for
 * example, output within Array context can differ from that of
 * Object context.
 */
public abstract class JsonStreamContext
{
    // // // Type constants used internally
    // // // (but exposed publicly as of 2.12 as possibly needed)

    /**
     * Indicator for "Root Value" context (has not parent)
     */
    public final static int TYPE_ROOT = 0;

    /**
     * Indicator for "Array" context.
     */
    public final static int TYPE_ARRAY = 1;

    /**
     * Indicator for "Object" context.
     */
    public final static int TYPE_OBJECT = 2;

    /**
     * Indicates logical type of context as one of {@code TYPE_xxx} consants.
     */
    protected int _type;

    /**
     * Index of the currently processed entry. Starts with -1 to signal
     * that no entries have been started, and gets advanced each
     * time a new entry is started, either by encountering an expected
     * separator, or with new values if no separators are expected
     * (the case for root context).
     */
    protected int _index;

    /*
    /**********************************************************
    /* Life-cycle
    /**********************************************************
     */

    protected JsonStreamContext() { }

    /**
     * Copy constructor used by sub-classes for creating copies for
     * buffering.
     *
     * @param base Context instance to copy type and index from
     *
     * @since 2.9
     */
    protected JsonStreamContext(JsonStreamContext base) {
        _type = base._type;
        _index = base._index;
    }

    // @since 2.9
    protected JsonStreamContext(int type, int index) {
        _type = type;
        _index = index;
    }

    /*
    /**********************************************************
    /* Public API, accessors
    /**********************************************************
     */

    /**
     * Accessor for finding parent context of this context; will
     * return null for root context.
     *
     * @return Parent context of this context, if any; {@code null} for Root contexts
     */
    public abstract JsonStreamContext getParent();

    /**
     * Method that returns true if this context is an Array context;
     * that is, content is being read from or written to a JSON Array.
     *
     * @return {@code True} if this context represents an Array; {@code false} otherwise
     */
    public final boolean inArray() { return _type == TYPE_ARRAY; }

    /**
     * Method that returns true if this context is a Root context;
     * that is, content is being read from or written to without
     * enclosing array or object structure.
     *
     * @return {@code True} if this context represents a sequence of Root values; {@code false} otherwise
     */
    public final boolean inRoot() { return _type == TYPE_ROOT; }

    /**
     * Method that returns true if this context is an Object context;
     * that is, content is being read from or written to a JSON Object.
     *
     * @return {@code True} if this context represents an Object; {@code false} otherwise
     */
    public final boolean inObject() { return _type == TYPE_OBJECT; }

    /**
     * @return Type description String
     * 
     * @deprecated Since 2.8 use {@link #typeDesc} instead
     */
    @Deprecated // since 2.8
    public final String getTypeDesc() {
        switch (_type) {
        case TYPE_ROOT: return "ROOT";
        case TYPE_ARRAY: return "ARRAY";
        case TYPE_OBJECT: return "OBJECT";
        }
        return "?";
    }

    /**
     * Method for accessing simple type description of current context;
     * either ROOT (for root-level values), OBJECT (for field names and
     * values of JSON Objects) or ARRAY (for values of JSON Arrays)
     * 
     * @return Type description String
     *
     * @since 2.8
     */
    public String typeDesc() {
        switch (_type) {
        case TYPE_ROOT: return "root";
        case TYPE_ARRAY: return "Array";
        case TYPE_OBJECT: return "Object";
        }
        return "?";
    }

    /**
     * @return Number of entries that are complete and started.
     */
    public final int getEntryCount() { return _index + 1; }

    /**
     * @return Index of the currently processed entry, if any
     */
    public final int getCurrentIndex() { return (_index < 0) ? 0 : _index; }

    /**
     * Method that may be called to verify whether this context has valid index:
     * will return `false` before the first entry of Object context or before
     * first element of Array context; otherwise returns `true`.
     *
     * @return {@code True} if this context has value index to access, {@code false} otherwise
     *
     * @since 2.9
     */
    public boolean hasCurrentIndex() { return _index >= 0; }

    /**
     * Method that may be called to check if this context is either:
     *<ul>
     * <li>Object, with at least one entry written (partially or completely)
     *  </li>
     * <li>Array, with at least one entry written (partially or completely)
     *  </li>
     *</ul>
     * and if so, return `true`; otherwise return `false`. Latter case includes
     * Root context (always), and Object/Array contexts before any entries/elements
     * have been read or written.
     *<p>
     * Method is mostly used to determine whether this context should be used for
     * constructing {@link JsonPointer}
     *
     * @return {@code True} if this context has value path segment to access, {@code false} otherwise
     *
     * @since 2.9
     */
    public boolean hasPathSegment() {
        if (_type == TYPE_OBJECT) {
            return hasCurrentName();
        } else if (_type == TYPE_ARRAY) {
            return hasCurrentIndex();
        }
        return false;
    }
    
    /**
     * Method for accessing name associated with the current location.
     * Non-null for <code>FIELD_NAME</code> and value events that directly
     * follow field names; null for root level and array values.
     *
     * @return Current field name within context, if any; {@code null} if none
     */
    public abstract String getCurrentName();

    /**
     * @return {@code True} if a call to {@link #getCurrentName()} would return non-{@code null}
     *    name; {@code false} otherwise
     *
     * @since 2.9
     */
    public boolean hasCurrentName() { return getCurrentName() != null; }

    /**
     * Method for accessing currently active value being used by data-binding
     * (as the source of streaming data to write, or destination of data being
     * read), at this level in hierarchy.
     *<p>
     * Note that "current value" is NOT populated (or used) by Streaming parser or generator;
     * it is only used by higher-level data-binding functionality.
     * The reason it is included here is that it can be stored and accessed hierarchically,
     * and gets passed through data-binding.
     * 
     * @return Currently active value, if one has been assigned.
     * 
     * @since 2.5
     */
    public Object getCurrentValue() {
        return null;
    }

    /**
     * Method to call to pass value to be returned via {@link #getCurrentValue}; typically
     * called indirectly through {@link JsonParser#setCurrentValue}
     * or {@link JsonGenerator#setCurrentValue}).
     *
     * @param v Current value to assign to this context
     *
     * @since 2.5
     */
    public void setCurrentValue(Object v) { }

    /**
     * Factory method for constructing a {@link JsonPointer} that points to the current
     * location within the stream that this context is for, excluding information about
     * "root context" (only relevant for multi-root-value cases)
     *
     * @return Pointer instance constructed
     *
     * @since 2.9
     */
    public JsonPointer pathAsPointer() {
        return JsonPointer.forPath(this, false);
    }

    /**
     * Factory method for constructing a {@link JsonPointer} that points to the current
     * location within the stream that this context is for, optionally including
     * "root value index"
     *
     * @param includeRoot Whether root-value offset is included as the first segment or not;
     *
     * @return Pointer instance constructed
     *
     * @since 2.9
     */
    public JsonPointer pathAsPointer(boolean includeRoot) {
        return JsonPointer.forPath(this, includeRoot);
    }

    /**
     * Optional method that may be used to access starting location of this context:
     * for example, in case of JSON `Object` context, offset at which `[` token was
     * read or written. Often used for error reporting purposes.
     * Implementations that do not keep track of such location are expected to return
     * {@link JsonLocation#NA}; this is what the default implementation does.
     *<p>
     * NOTE: demoted from <code>JsonReadContext</code> in 2.9, to allow use for
     * "non-standard" read contexts.
     *
     * @param srcRef Source reference needed to construct location instance
     *
     * @return Location pointing to the point where the context
     *   start marker was found (or written); never `null`.
     *
     * @since 2.9
     */
    public JsonLocation getStartLocation(Object srcRef) {
        return JsonLocation.NA;
    }

    /**
     * Overridden to provide developer readable "JsonPath" representation
     * of the context.
     *
     * @return Simple developer-readable description this context layer
     *   (note: NOT constructed with parents, unlike {@link #pathAsPointer})
     * 
     * @since 2.9
     */
    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder(64);
        switch (_type) {
        case TYPE_ROOT:
            sb.append("/");
            break;
        case TYPE_ARRAY:
            sb.append('[');
            sb.append(getCurrentIndex());
            sb.append(']');
            break;
        case TYPE_OBJECT:
        default:
            sb.append('{');
            String currentName = getCurrentName();
            if (currentName != null) {
                sb.append('"');
                CharTypes.appendQuoted(sb, currentName);
                sb.append('"');
            } else {
                sb.append('?');
            }
            sb.append('}');
            break;
        }
        return sb.toString();
    }
}

com/fasterxml/jackson/core/JsonStreamContext.java

 

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