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

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");

这将是一个公共方法，用于打印对象的漂亮版本(你需要安装Gson依赖项:

import com.google.gson.GsonBuilder;
...

public void printMe(){
    Gson gson = new GsonBuilder().setPrettyPrinting().create();
    String prettyJSON = gson.toJson(this);
    System.out.println(printable);
}

我用的是org。Json内置方法来漂亮地打印数据。

import org.json.JSONObject;
JSONObject json = new JSONObject(jsonString); // Convert text to object
System.out.println(json.toString(4)); // Print it with specified indentation

JSON中每个定义的字段顺序是随机的。具体的顺序取决于解析器的实现。

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 + "]");
    }

如果您正在使用用于JSON处理(JSR-353)实现的Java API，那么您可以指定JsonGenerator。当您创建JsonGeneratorFactory时，PRETTY_PRINTING属性。

下面的例子最初发表在我的博客文章中。

import java.util.*;
import javax.json.Json;
import javax.json.stream.*;

Map<String, Object> properties = new HashMap<String, Object>(1);
properties.put(JsonGenerator.PRETTY_PRINTING, true);
JsonGeneratorFactory jgf = Json.createGeneratorFactory(properties);
JsonGenerator jg = jgf.createGenerator(System.out);

jg.writeStartObject()                    // {
    .write("name", "Jane Doe")           //    "name":"Jane Doe",
    .writeStartObject("address")         //    "address":{
        .write("type", 1)                //        "type":1,
        .write("street", "1 A Street")   //        "street":"1 A Street",
        .writeNull("city")               //        "city":null,
        .write("verified", false)        //        "verified":false
    .writeEnd()                          //    },
    .writeStartArray("phone-numbers")    //    "phone-numbers":[
        .writeStartObject()              //        {
            .write("number", "555-1111") //            "number":"555-1111",
            .write("extension", "123")   //            "extension":"123"
        .writeEnd()                      //        },
        .writeStartObject()              //        {
            .write("number", "555-2222") //            "number":"555-2222",
            .writeNull("extension")      //            "extension":null
        .writeEnd()                      //        }
    .writeEnd()                          //    ]
.writeEnd()                              // }
.close();