你可以像下面这样使用Gson

Gson gson = new GsonBuilder().setPrettyPrinting().create();
String jsonString = gson.toJson(object);

从post JSON漂亮打印使用Gson

或者，你可以像下面这样使用Jackson

ObjectMapper mapper = new ObjectMapper();
String perttyStr = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(object);

漂亮的Java JSON打印(Jackson)

希望这对你有所帮助!

GSON似乎支持这一点，尽管我不知道您是否想从正在使用的库切换。

来自用户指南:

Gson gson = new GsonBuilder().setPrettyPrinting().create();
String jsonOutput = gson.toJson(someObject);

我的情况是我的项目使用了不支持漂亮打印的遗留(非jsr) JSON解析器。然而，我需要生成漂亮的JSON样本;这是可能的，而不需要添加任何额外的库，只要你使用Java 7及以上:

ScriptEngineManager manager = new ScriptEngineManager();
ScriptEngine scriptEngine = manager.getEngineByName("JavaScript");
scriptEngine.put("jsonString", jsonStringNoWhitespace);
scriptEngine.eval("result = JSON.stringify(JSON.parse(jsonString), null, 2)");
String prettyPrintedJson = (String) scriptEngine.get("result");

I also use the org.json.simple package. I have simply coded the formatter, but since I don't have nulls, numbers or booleans in my JSON objects in the program that I wrote, I only coded for strings, objects and arrays. If anyone is interested, let this just be in the public domain. You are welcome to add the missing data types (where it says in the comment "it's a string"). Also, you can add the indentation as a parameter whereas mine is just two spaces. Please reshare after you've tested your improvements.

用法： printJsonObject（jsonObject， “”）;

功能:

    public static void printJsonObject(JSONObject object, String prefix) {
        boolean notFirst = false;
        System.out.println(prefix + "{");
        for (Object key : object.keySet()) {
            if (notFirst) {
                System.out.println(", ");
            }
            notFirst = true;
            Object value = object.get(key);
            System.out.print(prefix + "  " + "\"" + key + "\"" + ": ");
            if (value instanceof JSONObject) {
                printJsonObject((JSONObject) value, prefix + "  ");
            } else if (value instanceof JSONArray) {
                printJsonArray((JSONArray) value, prefix + "  ");
            } else {  // it's a string
                System.out.print("\"" + value + "\"");
            }
        }
        System.out.println("");
        System.out.print(prefix + "}");
    }

    public static void printJsonArray(JSONArray array, String prefix) {
        boolean notFirst = false;
        System.out.println("[");
        for (Object item : array) {
            if (notFirst) {
                System.out.println(", ");
            }
            notFirst = true;
            if (item instanceof JSONObject) {
                printJsonObject((JSONObject) item, prefix + "  ");
            } else if (item instanceof JSONArray) {
                printJsonArray((JSONArray) item, prefix + "  ");
            } else {
                System.out.print(prefix + "  " + "\"" + item + "\"");
            }
        }
        System.out.println("");
        System.out.print(prefix + "]");
    }

更新:new JsonParser().parse(…)已@弃用

基于Gson 2.8.6的javadoc:

不需要实例化这个类，而是使用静态方法。

JsonParser静态方法:

JsonParser.parseString​(jsonString);
JsonParser.parseReader​(reader);

包:

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonParser;

例子:

private Gson GSON = new GsonBuilder().setPrettyPrinting().create();
public static String getPerfectJSON(String unformattedJSON) {
    String perfectJSON = GSON.toJson(JsonParser.parseString(unformattedJSON));
    return perfectJSON;
}

使用Maven的Gson依赖:

<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.8.6</version>
</dependency>

参考:

JsonParser已弃用

你可以使用小的json库

String jsonstring = ....;
JsonValue json = JsonParser.parse(jsonstring);
String jsonIndendedByTwoSpaces = json.toPrettyString("  ");