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-2.14.0-sources.jar). You can download it at Jackson Maven Website.

You can also browse Jackson Core Source Code below:

⏎ com/fasterxml/jackson/core/util/DefaultPrettyPrinter.java

package com.fasterxml.jackson.core.util;

import java.io.*;

import com.fasterxml.jackson.core.*;
import com.fasterxml.jackson.core.io.SerializedString;

/**
 * Default {@link PrettyPrinter} implementation that uses 2-space
 * indentation with platform-default linefeeds.
 * Usually this class is not instantiated directly, but instead
 * method {@link JsonGenerator#useDefaultPrettyPrinter} is
 * used, which will use an instance of this class for operation.
 *
 * If you override this class, take note of {@link Instantiatable},
 * as subclasses will still create an instance of DefaultPrettyPrinter.
 */
@SuppressWarnings("serial")
public class DefaultPrettyPrinter
    implements PrettyPrinter, Instantiatable<DefaultPrettyPrinter>,
        java.io.Serializable
{
    private static final long serialVersionUID = 1;

    /**
     * Constant that specifies default "root-level" separator to use between
     * root values: a single space character.
     * 
     * @since 2.1
     */
    public final static SerializedString DEFAULT_ROOT_VALUE_SEPARATOR = new SerializedString(" ");

    /**
     * Interface that defines objects that can produce indentation used
     * to separate object entries and array values. Indentation in this
     * context just means insertion of white space, independent of whether
     * linefeeds are output.
     */
    public interface Indenter
    {
        void writeIndentation(JsonGenerator g, int level) throws IOException;

        /**
         * @return True if indenter is considered inline (does not add linefeeds),
         *   false otherwise
         */
        boolean isInline();
    }

    // // // Config, indentation

    /**
     * By default, let's use only spaces to separate array values.
     */
    protected Indenter _arrayIndenter = FixedSpaceIndenter.instance;

    /**
     * By default, let's use linefeed-adding indenter for separate
     * object entries. We'll further configure indenter to use
     * system-specific linefeeds, and 2 spaces per level (as opposed to,
     * say, single tabs)
     */
    protected Indenter _objectIndenter = DefaultIndenter.SYSTEM_LINEFEED_INSTANCE;

    /**
     * String printed between root-level values, if any.
     */
    protected final SerializableString _rootSeparator;

    // // // Config, other white space configuration

    /**
     * By default we will add spaces around colons used to
     * separate object fields and values.
     * If disabled, will not use spaces around colon.
     */
    protected boolean _spacesInObjectEntries = true;

    // // // State:

    /**
     * Number of open levels of nesting. Used to determine amount of
     * indentation to use.
     */
    protected transient int _nesting;

    /**
     * @since 2.9
     */
    protected Separators _separators;

    /**
     * @since 2.9
     */
    protected String _objectFieldValueSeparatorWithSpaces;

    /*
    /**********************************************************
    /* Life-cycle (construct, configure)
    /**********************************************************
    */

    public DefaultPrettyPrinter() {
        this(DEFAULT_ROOT_VALUE_SEPARATOR);
    }

    /**
     * Constructor that specifies separator String to use between root values;
     * if null, no separator is printed.
     *<p>
     * Note: simply constructs a {@link SerializedString} out of parameter,
     * calls {@link #DefaultPrettyPrinter(SerializableString)}
     *
     * @param rootSeparator String to use as root value separator
     */
    public DefaultPrettyPrinter(String rootSeparator) {
        this((rootSeparator == null) ? null : new SerializedString(rootSeparator));
    }

    /**
     * Constructor that specifies separator String to use between root values;
     * if null, no separator is printed.
     *
     * @param rootSeparator String to use as root value separator
     */
    public DefaultPrettyPrinter(SerializableString rootSeparator) {
        _rootSeparator = rootSeparator;
        withSeparators(DEFAULT_SEPARATORS);
    }
    
    public DefaultPrettyPrinter(DefaultPrettyPrinter base) {
        this(base, base._rootSeparator);
    }

    public DefaultPrettyPrinter(DefaultPrettyPrinter base,
            SerializableString rootSeparator)
    {
        _arrayIndenter = base._arrayIndenter;
        _objectIndenter = base._objectIndenter;
        _spacesInObjectEntries = base._spacesInObjectEntries;
        _nesting = base._nesting;

        _separators = base._separators;
        _objectFieldValueSeparatorWithSpaces = base._objectFieldValueSeparatorWithSpaces;

        _rootSeparator = rootSeparator;
    }

    public DefaultPrettyPrinter withRootSeparator(SerializableString rootSeparator)
    {
        if (_rootSeparator == rootSeparator ||
                (rootSeparator != null && rootSeparator.equals(_rootSeparator))) {
            return this;
        }
        return new DefaultPrettyPrinter(this, rootSeparator);
    }

    /**
     * @param rootSeparator Root-level value separator to use
     *
     * @return This pretty-printer instance (for call chaining)
     *
     * @since 2.6
     */
    public DefaultPrettyPrinter withRootSeparator(String rootSeparator) {
        return withRootSeparator((rootSeparator == null) ? null : new SerializedString(rootSeparator));
    }

    public void indentArraysWith(Indenter i) {
        _arrayIndenter = (i == null) ? NopIndenter.instance : i;
    }

    public void indentObjectsWith(Indenter i) {
        _objectIndenter = (i == null) ? NopIndenter.instance : i;
    }

    // @since 2.3
    public DefaultPrettyPrinter withArrayIndenter(Indenter i) {
        if (i == null) {
            i = NopIndenter.instance;
        }
        if (_arrayIndenter == i) {
            return this;
        }
        DefaultPrettyPrinter pp = new DefaultPrettyPrinter(this);
        pp._arrayIndenter = i;
        return pp;
    }

    // @since 2.3
    public DefaultPrettyPrinter withObjectIndenter(Indenter i) {
        if (i == null) {
            i = NopIndenter.instance;
        }
        if (_objectIndenter == i) {
            return this;
        }
        DefaultPrettyPrinter pp = new DefaultPrettyPrinter(this);
        pp._objectIndenter = i;
        return pp;
    }

    /**
     * "Mutant factory" method that will return a pretty printer instance
     * that does use spaces inside object entries; if 'this' instance already
     * does this, it is returned; if not, a new instance will be constructed
     * and returned.
     *
     * @return This pretty-printer instance (for call chaining)
     *
     * @since 2.3
     */
    public DefaultPrettyPrinter withSpacesInObjectEntries() {
        return _withSpaces(true);
    }

    /**
     * "Mutant factory" method that will return a pretty printer instance
     * that does not use spaces inside object entries; if 'this' instance already
     * does this, it is returned; if not, a new instance will be constructed
     * and returned.
     *
     * @return This pretty-printer instance (for call chaining)
     *
     * @since 2.3
     */
    public DefaultPrettyPrinter withoutSpacesInObjectEntries() {
        return _withSpaces(false);
    }

    protected DefaultPrettyPrinter _withSpaces(boolean state)
    {
        if (_spacesInObjectEntries == state) {
            return this;
        }
        DefaultPrettyPrinter pp = new DefaultPrettyPrinter(this);
        pp._spacesInObjectEntries = state;
        return pp;
    }

    /**
     * Method for configuring separators for this pretty-printer to use
     *
     * @param separators Separator definitions to use
     *
     * @return This pretty-printer instance (for call chaining)
     *
     * @since 2.9
     */
    public DefaultPrettyPrinter withSeparators(Separators separators) {
        _separators = separators;
        _objectFieldValueSeparatorWithSpaces = " " + separators.getObjectFieldValueSeparator() + " ";
        return this;
    }

    /*
    /**********************************************************
    /* Instantiatable impl
    /**********************************************************
     */

    @Override
    public DefaultPrettyPrinter createInstance() {
        if (getClass() != DefaultPrettyPrinter.class) { // since 2.10
            throw new IllegalStateException("Failed `createInstance()`: "+getClass().getName()
                    +" does not override method; it has to");
        }
        return new DefaultPrettyPrinter(this);
    }

    /*
    /**********************************************************
    /* PrettyPrinter impl
    /**********************************************************
     */

    @Override
    public void writeRootValueSeparator(JsonGenerator g) throws IOException
    {
        if (_rootSeparator != null) {
            g.writeRaw(_rootSeparator);
        }
    }

    @Override
    public void writeStartObject(JsonGenerator g) throws IOException
    {
        g.writeRaw('{');
        if (!_objectIndenter.isInline()) {
            ++_nesting;
        }
    }

    @Override
    public void beforeObjectEntries(JsonGenerator g) throws IOException
    {
        _objectIndenter.writeIndentation(g, _nesting);
    }

    /**
     * Method called after an object field has been output, but
     * before the value is output.
     *<p>
     * Default handling (without pretty-printing) will output a single
     * colon to separate the two. Pretty-printer is
     * to output a colon as well, but can surround that with other
     * (white-space) decoration.
     */
    @Override
    public void writeObjectFieldValueSeparator(JsonGenerator g) throws IOException
    {
        if (_spacesInObjectEntries) {
            g.writeRaw(_objectFieldValueSeparatorWithSpaces);
        } else {
            g.writeRaw(_separators.getObjectFieldValueSeparator());
        }
    }

    /**
     * Method called after an object entry (field:value) has been completely
     * output, and before another value is to be output.
     *<p>
     * Default handling (without pretty-printing) will output a single
     * comma to separate the two. Pretty-printer is
     * to output a comma as well, but can surround that with other
     * (white-space) decoration.
     */
    @Override
    public void writeObjectEntrySeparator(JsonGenerator g) throws IOException
    {
        g.writeRaw(_separators.getObjectEntrySeparator());
        _objectIndenter.writeIndentation(g, _nesting);
    }

    @Override
    public void writeEndObject(JsonGenerator g, int nrOfEntries) throws IOException
    {
        if (!_objectIndenter.isInline()) {
            --_nesting;
        }
        if (nrOfEntries > 0) {
            _objectIndenter.writeIndentation(g, _nesting);
        } else {
            g.writeRaw(' ');
        }
        g.writeRaw('}');
    }

    @Override
    public void writeStartArray(JsonGenerator g) throws IOException
    {
        if (!_arrayIndenter.isInline()) {
            ++_nesting;
        }
        g.writeRaw('[');
    }

    @Override
    public void beforeArrayValues(JsonGenerator g) throws IOException {
        _arrayIndenter.writeIndentation(g, _nesting);
    }

    /**
     * Method called after an array value has been completely
     * output, and before another value is to be output.
     *<p>
     * Default handling (without pretty-printing) will output a single
     * comma to separate the two. Pretty-printer is
     * to output a comma as well, but can surround that with other
     * (white-space) decoration.
     */
    @Override
    public void writeArrayValueSeparator(JsonGenerator g) throws IOException
    {
        g.writeRaw(_separators.getArrayValueSeparator());
        _arrayIndenter.writeIndentation(g, _nesting);
    }

    @Override
    public void writeEndArray(JsonGenerator g, int nrOfValues) throws IOException
    {
        if (!_arrayIndenter.isInline()) {
            --_nesting;
        }
        if (nrOfValues > 0) {
            _arrayIndenter.writeIndentation(g, _nesting);
        } else {
            g.writeRaw(' ');
        }
        g.writeRaw(']');
    }

    /*
    /**********************************************************
    /* Helper classes
    /**********************************************************
     */

    /**
     * Dummy implementation that adds no indentation whatsoever
     */
    public static class NopIndenter
        implements Indenter, java.io.Serializable
    {
        public static final NopIndenter instance = new NopIndenter();

        @Override
        public void writeIndentation(JsonGenerator g, int level) throws IOException { }

        @Override
        public boolean isInline() { return true; }
    }

    /**
     * This is a very simple indenter that only adds a
     * single space for indentation. It is used as the default
     * indenter for array values.
     */
    public static class FixedSpaceIndenter extends NopIndenter
    {
        public static final FixedSpaceIndenter instance = new FixedSpaceIndenter();

        @Override
        public void writeIndentation(JsonGenerator g, int level) throws IOException
        {
            g.writeRaw(' ');
        }

        @Override
        public boolean isInline() { return true; }
    }
}

⏎ com/fasterxml/jackson/core/util/DefaultPrettyPrinter.java

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File name: jackson-core-2.14.0-sources.jar
File size: 497693 bytes
Release date: 2022-11-05
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