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"]}

迟到的派对，但这里是我的GSON adhoc作家序列化hashmap。我必须写映射的键值对作为json字符串属性，期望一个特定的整数类型。我不想为这个简单的用例创建自定义JavaBean包装器。

GSON JsonWriter类是一个易于使用的序列化器类，它包含少量强类型writer.value()函数。

// write Map as JSON document to http servlet response
Map<String,String> sd = DAO.getSD(123);
res.setContentType("application/json; charset=UTF-8");
res.setCharacterEncoding("UTF-8");
JsonWriter writer = new JsonWriter(new OutputStreamWriter(res.getOutputStream(), "UTF-8"));
writer.beginObject();
for(String key : sd.keySet()) {
    String val = sd.get(key);
    writer.name(key);
    if (key.equals("UniqueID") && val!=null)
        writer.value(Long.parseLong(val));
    else
        writer.value(val);
}
writer.endObject();
writer.close();

如果不需要任何自定义类型，我可以只使用toJson()函数。jar库只有不到190KB，没有任何残酷的依赖关系。易于在任何自定义servlet应用程序或独立应用程序上使用，无需大型框架集成。

Gson gson = new Gson(); 
String json = gson.toJson(myMap); 

java库可以将哈希映射或数组列表转换为json，反之亦然。

import com.github.underscore.U;
import java.util.*;

public class Main {

    public static void main(String[] args) {

        Map<String, Object> map = new LinkedHashMap<>();
        map.put("1", "a");
        map.put("2", "b");

        System.out.println(U.toJson(map));
        // {
        //    "1": "a",
        //    "2": "b"
        // }
    }
}

你可以使用XStream——它真的很方便。请看这里的例子

package com.thoughtworks.xstream.json.test;

import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.io.json.JettisonMappedXmlDriver;

public class WriteTest {

    public static void main(String[] args) {

      HashMap<String,String> map = new HashMap<String,String>();
      map.add("1", "a");
      map.add("2", "b");
      XStream xstream = new XStream(new JettisonMappedXmlDriver());

      System.out.println(xstream.toXML(map));       

    }

}

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.

如果你需要在代码中使用它。

Gson gsone = new Gson();
JsonObject res = gsone.toJsonTree(sqlParams).getAsJsonObject();