如果使用复杂对象，应该应用enableComplexMapKeySerialization()，如https://stackoverflow.com/a/24635655/2914140和https://stackoverflow.com/a/26374888/2914140中所述。

Gson gson = new GsonBuilder().enableComplexMapKeySerialization().create();
Map<Point, String> original = new LinkedHashMap<Point, String>();
original.put(new Point(5, 6), "a");
original.put(new Point(8, 8), "b");
System.out.println(gson.toJson(original));

输出将是:

{
 "(5,6)": "a",
 "(8,8)": "b"
}

您可以使用Jackson将Map转换为JSON，如下所示:

Map<String,Object> map = new HashMap<>();
//You can convert any Object.
String[] value1 = new String[] { "value11", "value12", "value13" };
String[] value2 = new String[] { "value21", "value22", "value23" };
map.put("key1", value1);
map.put("key2", value2);
map.put("key3","string1");
map.put("key4","string2");

String json = new ObjectMapper().writeValueAsString(map);
System.out.println(json);

Jackson的Maven依赖:

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-core</artifactId>
    <version>2.5.3</version>
    <scope>compile</scope>
</dependency>

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.5.3</version>
    <scope>compile</scope>
</dependency>

If you are using `JSONObject` library, you can convert map to `JSON` as follows: JSONObject Library: import org.json.JSONObject; Map<String, Object> map = new HashMap<>(); // Convert a map having list of values. String[] value1 = new String[] { "value11", "value12", "value13" }; String[] value2 = new String[] { "value21", "value22", "value23" }; map.put("key1", value1); map.put("key2", value2); JSONObject json = new JSONObject(map); System.out.println(json); Maven Dependencies for `JSONObject` : <dependency> <groupId>org.json</groupId> <artifactId>json</artifactId> <version>20140107</version> </dependency> Hope this will help. Happy coding.

您只需枚举映射并将键-值对添加到JSONObject

方法:

private JSONObject getJsonFromMap(Map<String, Object> map) throws JSONException {
    JSONObject jsonData = new JSONObject();
    for (String key : map.keySet()) {
        Object value = map.get(key);
        if (value instanceof Map<?, ?>) {
            value = getJsonFromMap((Map<String, Object>) value);
        }
        jsonData.put(key, value);
    }
    return jsonData;
}

这通常是Json库的工作，你不应该尝试自己做。所有json库都应该实现您所要求的内容，而且您可以做到 在页面底部的json.org上找到Java Json库的列表。

    import org.json.JSONObject;

    HashMap<Object, Object> map = new HashMap<>();
    String[] list={"Grader","Participant"};
    String[] list1={"Assistant","intern"};
    map.put("TeachingAssistant",list);
    map.put("Writer",list1);
    JSONObject jsonObject = new JSONObject(map);
    System.out.printf(jsonObject.toString());

    // Result: {"TeachingAssistant":["Grader","Participant"],"Writer":["Assistant","intern"]}

如果你真的不需要HashMap，你可以这样做:

String jsonString = new JSONObject() {{
  put("firstName", user.firstName);
  put("lastName", user.lastName);
}}.toString();

输出:

{
  "firstName": "John",
  "lastName": "Doe"
}