Java 使用 gson 对 json 根据 key 键进行排序

引入Google的gson jar

        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
            <version>2.8.0</version>
        </dependency>

使用 

     /**
     * 定义比较规则
     *
     * @return
     */
    private static Comparator<String> getComparator() {
        return (s1, s2) -> s1.compareTo(s2);
    }

    /**
     * 排序
     *
     * @param e
     */
    public static void sort(JsonElement e) {
        if (e.isJsonNull() || e.isJsonPrimitive()) {
            return;
        }

        if (e.isJsonArray()) {
            JsonArray a = e.getAsJsonArray();
            Iterator<JsonElement> it = a.iterator();
            it.forEachRemaining(i -> sort(i));
            return;
        }

        if (e.isJsonObject()) {
            Map<String, JsonElement> tm = new TreeMap<>(getComparator());
            for (Map.Entry<String, JsonElement> en : e.getAsJsonObject().entrySet()) {
                tm.put(en.getKey(), en.getValue());
            }

            String key;
            JsonElement val;
            for (Map.Entry<String, JsonElement> en : tm.entrySet()) {
                key = en.getKey();
                val = en.getValue();
                e.getAsJsonObject().remove(key);
                e.getAsJsonObject().add(key, val);
                sort(val);
            }
        }
    }

    /**
     * 根据json key排序
     * @param json
     * @return
     */
    private static String sortJson(String json) {
        Gson g = new GsonBuilder().setPrettyPrinting().create();
        JsonParser p = new JsonParser();
        JsonElement e = p.parse(json);
        sort(e);
        return g.toJson(e);
    }

    public static void main(String[] args) {
        String json =
                    "{" +
                    "  \"aaa\":\"aaa\"," +
                    "  \"bbb\":\"bbb\"," +
                    "  \"abc\":\"abc\"," +
                    "  \"baa\":{" +
                    "    \"cab\":\"cab\"," +
                    "    \"abc\":\"abc\"," +
                    "    \"bac\":\"bac\"" +
                    "  }" +
                    "}";
        System.out.println(sortJson(json));;
    }