Question

json = [{"a":"555","b":"ee"},{"a":"556","b":"rr"}]

我试过了：

ObjectMapper mapper = new ObjectMapper();
TypeReference<Map<String,String>> typeRef = new TypeReference<Map<String,String>>() {};
HashMap<String, String> result = mapper.readValue(json, typeRef);

但它不起作用。我想这就是因为json是一个列表而不是一个对象。

事实上，如果json是{"a":"555","b":"ee"}，那就有效。

Answer 1

为了解决这个问题，我将使用Jackson SDK。请从以下网址下载最新版本：http://wiki.fasterxml.com/JacksonDownload

JSON TO MAP示例：

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import com.fasterxml.jackson.core.JsonGenerationException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JsonMapExample {

    public static void main(String[] args) {

        try {

            ObjectMapper mapper = new ObjectMapper();
            String json = "{\"name\":\"mkyong\", \"age\":29}";

            Map<String, Object> map = new HashMap<String, Object>();

            // convert JSON string to Map
            map = mapper.readValue(json, new TypeReference<Map<String, String>>(){});

            System.out.println(map);

        } catch (JsonGenerationException e) {
            e.printStackTrace();
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

映射到JSON示例：

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import com.fasterxml.jackson.core.JsonGenerationException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class MapJsonExample{

    public static void main(String[] args) {

        try {

            ObjectMapper mapper = new ObjectMapper();
            String json = "";

            Map<String, Object> map = new HashMap<String, Object>();
            map.put("name", "mkyong");
            map.put("age", 29);

            // convert map to JSON string
            json = mapper.writeValueAsString(map);

            System.out.println(json);

            json = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(map);

            // pretty print
            System.out.println(json);

        } catch (JsonGenerationException e) {
            e.printStackTrace();
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

JSONArray to HashMaps：

HashMap<String, String> pairs = new HashMap<String, String>();
for (int i = 0; i < myArray.length(); i++) {
   JSONObject j = myArray.optJSONObject(i);
   Iterator it = j.keys();
   while (it.hasNext()) {
      String n = it.next();
      pairs.put(n, j.getString(n));
   }
}

将JSON哈希映射到Java哈希映射

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