com.ludo.efialtes.util.GsonPrettyPrinter.java Source code

Introduction

Here is the source code for com.ludo.efialtes.util.GsonPrettyPrinter.java

Source

package com.ludo.efialtes.util;

import java.io.PrintWriter;
import java.io.StringWriter;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;
import java.util.Map.Entry;

import com.google.gson.Gson;
import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;

/**
 * A decent pretty-printer for Gson. Features include:
 * 
 * <ul>
 * <li>Will try to use a single line where possible</li>
 * <li>Configurable indent string</li>
 * </ul>
 * 
 * This file is (c) Copyright 2009 Uprizer Labs LLC It is released to the public under the Lesser GNU Public License
 * v3.0 See http://www.gnu.org/licenses/lgpl.html for details.
 * 
 * @author Ian Clarke <ian@uprizer.com>, minor additions by Eric Poggel (NuOrbit Media, nuorbit.com)
 * @see http://gist.github.com/212791, http://blog.locut.us/main/2009/10/18/a-good-pretty-printer-for-google-gson.html
 * 
 * @example
 * new GsonPrettyPrinter(gb.create()).ppJson(some_object);
 */

public class GsonPrettyPrinter {

    private static <V> SortedSet<Entry<String, V>> orderEntrySet(final Set<Entry<String, V>> es) {
        final TreeSet<Entry<String, V>> ret = new TreeSet<Entry<String, V>>(new Comparator<Entry<String, V>>() {

            public int compare(final Entry<String, V> o1, final Entry<String, V> o2) {
                return o1.getKey().compareTo(o2.getKey());
            }
        });
        ret.addAll(es);
        return ret;
    }

    private final Gson gson;

    private final String indent;

    public GsonPrettyPrinter(final Gson gson) {
        this(gson, " ");
    }

    public GsonPrettyPrinter(final Gson gson, final String indent) {
        this.gson = gson;
        this.indent = indent;
    }

    public String ppJson(final Object o) {
        return ppJson(o, null);
    }

    public String ppJson(final Object o, Type t) {
        if (t == null)
            t = o.getClass();
        final StringWriter sw = new StringWriter();
        final PrintWriter pw = new PrintWriter(sw);
        ppJson(o, pw, t);
        return sw.toString();
    }

    public void ppJson(final Object o, final PrintWriter pw, Type t) {
        final JsonElement jsonTree = gson.toJsonTree(o, t);
        final List<String> stringList = toStringList(jsonTree);
        for (final String s : stringList) {
            pw.println(s);
        }
    }

    private List<String> arrayToStringList(final JsonArray jsonArray) {
        final List<List<String>> sll = new LinkedList<List<String>>();
        for (final JsonElement arrayElement : jsonArray) {
            sll.add(toStringList(arrayElement));
        }

        final LinkedList<String> ret = new LinkedList<String>();
        ret.add("");
        ret.add("[");
        int oPos = 0;
        for (final List<String> sl : sll) {
            oPos++;
            final int slLen = sl.size();
            int pos = 0;
            for (final String s : sl) {
                pos++;
                final boolean needComma = (pos == slLen && oPos < sll.size());
                ret.add(indent + s + (needComma ? ", " : ""));
            }
        }
        ret.add("]");
        return ret;

    }

    private List<String> objectToStringList(final JsonObject jsonObject) {
        final Map<String, List<String>> slm = new HashMap<String, List<String>>();
        for (final Entry<String, JsonElement> e : jsonObject.entrySet()) {
            slm.put(e.getKey(), toStringList(e.getValue()));
        }

        final LinkedList<String> ret = new LinkedList<String>();
        ret.add("");
        ret.add("{");
        int oPos = 0;
        for (final Entry<String, List<String>> e : orderEntrySet(slm.entrySet())) {
            oPos++;
            final int slLen = e.getValue().size();
            int pos = 0;
            for (final String s : e.getValue()) {
                pos++;
                final boolean needComma = (pos == slLen && oPos < slm.size());
                if (pos == 1) {
                    ret.add(indent + "\"" + e.getKey() + "\" : " + s + (needComma ? ", " : ""));
                } else {
                    ret.add(indent + s + (needComma ? ", " : ""));
                }
            }
        }
        ret.add("}");
        return ret;
    }

    private List<String> toStringList(final JsonElement je) {
        if (je == null || je.isJsonNull())
            return new ArrayList<String>(Arrays.asList(new String[] { "null" }));
        if (je.isJsonPrimitive())
            return Collections.singletonList(je.getAsJsonPrimitive().toString());
        if (je.isJsonArray()) {
            final JsonArray jsonArray = je.getAsJsonArray();
            return arrayToStringList(jsonArray);
        } else if (je.isJsonObject()) {
            final JsonObject jsonObject = je.getAsJsonObject();
            return objectToStringList(jsonObject);
        }
        throw new RuntimeException("Unsupported Json element: " + je.getClass().getName());
    }
}