com.uprizer.sensearray.freetools.json.GsonPrettyPrinter.java Source code

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Here is the source code for com.uprizer.sensearray.freetools.json.GsonPrettyPrinter.java

Source

package com.uprizer.sensearray.freetools.json;

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

import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.*;
import java.util.Map.Entry;

/**
 * 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>
 * 
 */

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 static final int MAX_LEN_FOR_ONE_LINE = 70;

    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) {
        final StringWriter sw = new StringWriter();
        final PrintWriter pw = new PrintWriter(sw);
        ppJson(o, pw);
        return sw.toString();
    }

    public void ppJson(final Object o, final PrintWriter pw) {
        final JsonElement jsonTree = gson.toJsonTree(o);
        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));
        }
        // Can we fit the array on a single line?
        boolean oneLine = true;
        int approxLineLength = 0;
        for (final List<String> sl : sll) {
            if (sl.size() > 1) {
                oneLine = false;
                break;
            }
            approxLineLength += sl.get(0).length() + 2;
        }
        if (approxLineLength > MAX_LEN_FOR_ONE_LINE) {
            oneLine = false;
        }
        if (oneLine) {
            final StringBuffer sb = new StringBuffer(approxLineLength * 2 + 10);
            sb.append("[");
            boolean first = true;
            for (final List<String> sl : sll) {
                if (!first) {
                    sb.append(", ");
                }
                first = false;
                sb.append(sl.get(0));
            }
            sb.append("]");
            return Collections.singletonList(sb.toString());
        } else {
            final LinkedList<String> ret = new LinkedList<String>();
            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()));
        }
        // Can we fit the object on a single line?
        boolean oneLine = true;
        int approxLineLength = 0;
        for (final Entry<String, List<String>> e : slm.entrySet()) {
            if (e.getValue().size() > 1) {
                oneLine = false;
                break;
            }
            approxLineLength += e.getKey().length() + e.getValue().get(0).length() + 6;
        }
        if (approxLineLength > MAX_LEN_FOR_ONE_LINE) {
            oneLine = false;
        }
        if (oneLine) {
            final StringBuffer sb = new StringBuffer(approxLineLength * 2 + 10);
            sb.append("{");
            boolean first = true;
            for (final Entry<String, List<String>> e : orderEntrySet(slm.entrySet())) {
                if (!first) {
                    sb.append(", ");
                }
                first = false;
                sb.append("\"" + e.getKey() + "\" : " + e.getValue().get(0));
            }
            sb.append("}");
            return Collections.singletonList(sb.toString());
        } else {
            final LinkedList<String> ret = new LinkedList<String>();
            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.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);
        } else if (je.isJsonNull()) {
            return Collections.singletonList("null");
        } else {
            throw new RuntimeException("Unsupported Json element: " + je.getClass().getName());
        }
    }
}