你可以使用小的json库

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

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 + "]");
    }

所以我也很喜欢json-simple lib，并研究了如何打印它的输出。不幸的是，虽然这是一个悬而未决的问题，但我找不到它的任何代码。所以我想我应该试一试，这是我想出的(使用他们自己的来源)..

public class JsonPrinter {
  
  
  
  public static String toJson(Map<?,?> map) {
    StringBuilder out = new StringBuilder(32);
    new JsonPrinter(out).print(map);
    return out.toString();
  }
  
  
  public static String toJson(List<?> list) {
    StringBuilder out = new StringBuilder(32);
    new JsonPrinter(out).print(list);
    return out.toString();
  }
  
  
  
  
  
  
  
  private final Appendable out;
  private final String indentUnit;
  private final String newLine;
  
  
  private int indents;
  
  public JsonPrinter(Appendable out) {
    this(out, "  ", System.lineSeparator());
  }

  /**
   * 
   */
  public JsonPrinter(Appendable out, String indentUnit, String newLine) {
    this.out = Objects.requireNonNull(out, "null out");
    this.indentUnit = Objects.requireNonNull(indentUnit, "null indentUnit");
    this.newLine = Objects.requireNonNull(newLine, "null newLine");
    
    if (!indentUnit.isBlank())
      throw new IllegalArgumentException(
          "indentUnit must be a blank sequence (quoted): '" + indentUnit + "'");
    if (!"\r\n".equals(newLine) && ! "\n".equals(newLine))
      throw new IllegalArgumentException(
          "unrecognized newLine (quoted): '" + newLine + "'");
  }
  
  
  public void print(List<?> list) throws UncheckedIOException {
    try {
      assert indents == 0;
      printImpl(list);
      assert indents == 0;
    } catch (IOException iox) {
      throw new UncheckedIOException("on print(List): " + list, iox);
    }
  }
  
  
  public void print(Map<?,?> map) throws UncheckedIOException {
    try {
      assert indents == 0;
      printImpl(map);
      assert indents == 0;
    } catch (IOException iox) {
      throw new UncheckedIOException("on print(Map): " + map, iox);
    }
  }
  
  
  protected void printImpl(List<?> list) throws IOException {
    if (list == null) {
      out.append("null");
      return;
    }
    
    
    boolean first = true;
    var iter = list.iterator();
    
    open('[');
    while (iter.hasNext()) {
      if (first)
        first = false;
      else
        out.append(',');
      
      out.append(newLine);
      appendIndents();
      
      appendValue(iter.next());
    }
    close(']');
  }
  
  
  protected void printImpl(Map<?, ?> map) throws IOException {
    if (map == null) {
      out.append("null");
      return;
    }
    
    
    boolean first = true;
    var iter = map.entrySet().iterator();
    
    open('{');
    while (iter.hasNext()) {
      if (first)
        first = false;
      else
        out.append(',');
      
      out.append(newLine);
      appendIndents();
      
      var entry = iter.next();
      print(entry.getKey().toString(), entry.getValue());
    }
    close('}');
  }
  
  
  private void open(char c) throws IOException {
    out.append(c);
    ++indents;
  }
  
  private void close(char c) throws IOException {
    --indents;
    out.append(newLine);
    appendIndents();
    out.append(c);
  }
  
  private void appendIndents() throws IOException {
    for (int count = indents; count-- > 0; )
      out.append(indentUnit);
  }
  
  
  
  private void print(String key, Object value) throws IOException {
    out.append('"');
    appendString(key);
    out.append('"').append(':').append(' ');
    appendValue(value);
  }
  
  
  
  private void appendString(String s) throws IOException {
    for (int i = 0; i < s.length(); i++) {
      char ch = s.charAt(i);
      switch(ch){
      case '"':
        out.append("\\\"");
        break;
      case '\\':
        out.append("\\\\");
        break;
      case '\b':
        out.append("\\b");
        break;
      case '\f':
        out.append("\\f");
        break;
      case '\n':
        out.append("\\n");
        break;
      case '\r':
        out.append("\\r");
        break;
      case '\t':
        out.append("\\t");
        break;
      case '/':
        out.append("\\/");
        break;
      default:
                //Reference: http://www.unicode.org/versions/Unicode5.1.0/
        if ((ch>='\u0000' && ch<='\u001F') || (ch>='\u007F' && ch<='\u009F') || (ch>='\u2000' && ch<='\u20FF')) {
          String ss = Integer.toHexString(ch);
          out.append("\\u");
          for (int k=0; k < 4-ss.length(); k++) {
            out.append('0');
          }
          out.append(ss.toUpperCase());
        }
        else{
          out.append(ch);
        }
      }
    }//for
  }
  
  
  private void appendValue(Object value) throws IOException {
    if (value == null) {
      out.append("null");
      
    } else if (value instanceof String) {
      out.append('"');
      appendString(value.toString());
      out.append('"');
      
    } else if (value instanceof Double) {
      var num = (Double) value;
      if (num.isInfinite() || num.isNaN())
        out.append("null");
      else
        out.append(value.toString());
      
    } else if (value instanceof Float) {
      var num = (Float) value;
      if (num.isInfinite() || num.isNaN())
        out.append("null");
      else
        out.append(value.toString());
      
    } else if (value instanceof Map) {
      printImpl((Map<?,?>) value);
      
    } else if (value instanceof List) {
      printImpl((List<?>) value);
      
//    } else if (value instanceof Number || value instanceof Boolean) {
//      out.append(value.toString());
      
    } else {
      out.append(value.toString());
      
    }
  }

}

它适用于JSONObject和JSONArray，即使它没有依赖于他们..因为这些是常规的Map和List对象。(事实代码是从同一个库中提取的)。

https://github.com/crums-io/io-util/blob/master/src/main/java/io/crums/util/json/JsonPrinter.java

使用org json。参考链接

JSONObject jsonObject = new JSONObject(obj);
String prettyJson = jsonObject.toString(4);

使用Gson。参考链接

Gson gson = new GsonBuilder().setPrettyPrinting().create();
String json = gson.toJson(obj);

使用杰克逊。参考链接

ObjectMapper mapper = new ObjectMapper();
mapper.enable(SerializationFeature.INDENT_OUTPUT);
String json = mapper.writeValueAsString(obj);

使用Genson的律师。参考链接。

Genson prettyGenson = new GensonBuilder().useIndentation(true).create();
String prettyJson = prettyGenson.serialize(obj);

使用javax.json。参考链接。

Map<String, Boolean> config = new HashMap<>();

config.put(JsonGenerator.PRETTY_PRINTING, true);

JsonWriterFactory writerFactory = Json.createWriterFactory(config);
Writer writer = new StringWriter();

writerFactory.createWriter(writer).write(jsonObject);

String json = writer.toString();

使用Moshi库。参考链接。

String json = jsonAdapter.indent("  ").toJson(emp1);

(OR)

Buffer buffer = new Buffer();
JsonWriter jsonWriter = JsonWriter.of(buffer);
jsonWriter.setIndent("   ");

jsonAdapter.toJson(jsonWriter, emp1);

json = buffer.readUtf8();

这招对我很管用，用了杰克逊的话:

mapper.writerWithDefaultPrettyPrinter().writeValueAsString(JSONString)

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);