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使用JSON字符串创建哈希表

javaandroidjsonhashmap
69
在Java中从JSON字符串创建哈希映射？
我有一个JSON字符串，如{"phonetype":"N95","cat":"WP"}，想要将其转换为标准哈希映射。
我该怎么做？
1
使用 JSON 库，例如 Jackson（参见 JsonNode）。 - fge
请看这个链接.. https://dev59.com/Umkv5IYBdhLWcg3wwjgI - Vinay Veluri
处理嵌套和复杂对象：https://dev59.com/QWEh5IYBdhLWcg3wyGHy#51121461 - Natesh bhat
16个回答
0
public Map<String, String> parseJSON(JSONObject json, Map<String, String> dataFields) throws JSONException {
        Iterator<String> keys = json.keys();
        while (keys.hasNext()) {
            String key = keys.next();
            String val = null;
            try {
                JSONObject value = json.getJSONObject(key);
                parseJSON(value, dataFields);
            } catch (Exception e) {
                if (json.isNull(key)) {
                    val = "";
                } else {
                    try {
                        val = json.getString(key);
                    } catch (Exception ex) {
                        System.out.println(ex.getMessage());
                    }
                }
            }

            if (val != null) {
                dataFields.put(key, val);
            }
        }
        return dataFields;
    }
0
将Json解析为HashMap最佳方法
public static HashMap<String, String> jsonToMap(JSONObject json) throws JSONException {
            HashMap<String, String> map = new HashMap<>();
            try {
                Iterator<String> iterator = json.keys();

                while (iterator.hasNext()) {
                    String key = iterator.next();
                    String value = json.getString(key);
                    map.put(key, value);
                }

                return map;
            } catch (JSONException e) {
                e.printStackTrace();
            }
            return null;
        }
0
这对我有用：
JSONObject jsonObj = new JSONObject();
jsonObj.put("phonetype","N95");
jsonObj.put("cat","WP");

使用Gson将jsonObj转换为以下的Hashmap 
HashMap<String, Object> hashmap = new Gson().fromJson(jsonObj.toString(), HashMap.class);

使用的包

<dependencies>
    <dependency>
        <groupId>org.json</groupId>
        <artifactId>json</artifactId>
        <version>20180813</version>
    </dependency>
    <dependency>
        <groupId>com.google.code.gson</groupId>
        <artifactId>gson</artifactId>
        <version>2.8.6</version>
    </dependency>
</dependencies>
0
这是一个简单易懂的示例，演示如何仅使用JSON simple库从JSON字符串创建一个Hashmap：

{"Collection":{"Item_Type":"Any","Name":"A","Item_ID":"000014"},"Object_Name":"System"}

import java.io.FileReader;
import java.util.HashMap;
import java.util.Iterator; 
import java.util.Map;  
import org.json.simple.JSONObject; 
import org.json.simple.parser.*;

public class JSONRead {

public static void main(String[] args) throws Exception {
    
    Object obj = new JSONParser().parse(new FileReader("D:\\other.json"));
    
    HashMap<String,String> map =new HashMap<String,String>();
    
    // typecasting obj to JSONObject 
    JSONObject jo = (JSONObject) obj;
    
    Map Item_Id = ((Map)jo.get("Collection"));
            
    Iterator<Map.Entry> itr1 = Item_Id.entrySet().iterator(); 
    while (itr1.hasNext()) { 
        Map.Entry pair = itr1.next(); 
        String key = (String) pair.getKey();
        String value = (String) pair.getValue();
        System.out.println( pair.getKey() + " : " + pair.getValue()); 
        map.put(key, value);
    }
    
    System.out.println(map)
    System.out.println(map.get("Item"));        
}
0
-1
你可以使用Jackson来实现这个功能。我还没有找到一个简单的Gson解决方案。
其中，`data_map.json`是一个JSON（对象）资源文件，而`data_list.json`是一个JSON（数组）资源文件。
import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URISyntaxException;
import java.net.URL;
import java.util.List;
import java.util.Map;
import java.util.Scanner;

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

/**
 * Based on:
 * 
 * http://www.mkyong.com/java/how-to-convert-java-map-to-from-json-jackson/
 */
public class JsonLoader {
    private static final ObjectMapper OBJ_MAPPER;
    private static final TypeReference<Map<String,Object>> OBJ_MAP;
    private static final TypeReference<List<Map<String,Object>>> OBJ_LIST;

    static {
        OBJ_MAPPER = new ObjectMapper();
        OBJ_MAP = new TypeReference<Map<String,Object>>(){};
        OBJ_LIST = new TypeReference<List<Map<String,Object>>>(){};
    }

    public static void main(String[] args) {
        try {
            System.out.println(jsonToString(parseJsonString(read("data_map.json", true))));
            System.out.println(jsonToString(parseJsonString(read("data_array.json", true))));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static final Object parseJsonString(String jsonString) {
        try {
            if (jsonString.startsWith("{")) {
                return readJsonObject(jsonString);
            } else if (jsonString.startsWith("[")) {
                return readJsonArray(jsonString);
            }
        } catch (JsonGenerationException e) {
            e.printStackTrace();
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return null;
    }

    public static String jsonToString(Object json) throws JsonProcessingException {
        return OBJ_MAPPER.writerWithDefaultPrettyPrinter().writeValueAsString(json);
    }

    private static final Map<String,Object> readJsonObject(String jsonObjectString) throws JsonParseException, JsonMappingException, IOException {
        return OBJ_MAPPER.readValue(jsonObjectString, OBJ_MAP);
    }

    private static final List<Map<String,Object>> readJsonArray(String jsonArrayString) throws JsonParseException, JsonMappingException, IOException {
        return OBJ_MAPPER.readValue(jsonArrayString, OBJ_LIST);
    }

    public static final Map<String,Object> loadJsonObject(String path, boolean isResource) throws JsonParseException, JsonMappingException, MalformedURLException, IOException {
        return OBJ_MAPPER.readValue(load(path, isResource), OBJ_MAP);
    }

    public static final List<Map<String,Object>> loadJsonArray(String path, boolean isResource) throws JsonParseException, JsonMappingException, MalformedURLException, IOException {
        return OBJ_MAPPER.readValue(load(path, isResource), OBJ_LIST);
    }

    private static final URL pathToUrl(String path, boolean isResource) throws MalformedURLException {
        if (isResource) {
            return JsonLoader.class.getClassLoader().getResource(path);
        }

        return new URL("file:/" + path);
    }

    protected static File load(String path, boolean isResource) throws MalformedURLException {
        return load(pathToUrl(path, isResource));
    }

    protected static File load(URL url) {
        try {
            return new File(url.toURI());
        } catch (URISyntaxException e) {
            return new File(url.getPath());
        }
    }

    public static String read(String path, boolean isResource) throws IOException {
        return read(path, "UTF-8", isResource);
    }

    public static String read(String path, String charset, boolean isResource) throws IOException {
        return read(pathToUrl(path, isResource), charset);
    }

    @SuppressWarnings("resource")
    public static String read(URL url, String charset) throws IOException {
        return new Scanner(url.openStream(), charset).useDelimiter("\\A").next();
    }
}

额外

这是Dheeraj Sachan示例的完整代码。

import java.io.File;
import java.io.IOException;
import java.io.Serializable;
import java.net.MalformedURLException;
import java.net.URISyntaxException;
import java.net.URL;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map.Entry;
import java.util.Scanner;

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.PropertyNamingStrategy;

public class JsonHandler {
    private static ObjectMapper propertyMapper;

    static {
        final DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

        propertyMapper = new ObjectMapper();
        propertyMapper.setDateFormat(df);
        propertyMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        propertyMapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);
        propertyMapper.setPropertyNamingStrategy(PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES);
    }

    private static class MyHashMap extends HashMap<String, List<Video>>{
        private static final long serialVersionUID = 7023107716981734468L;
    }

    private static class Video implements Serializable {
        private static final long serialVersionUID = -446275421030765463L;

        private String dashUrl;
        private String videoBitrate;
        private String audioBitrate;
        private int videoWidth;
        private int videoHeight;
        private long fileSize;

        @Override
        public String toString() {
            return "Video [url=" + dashUrl + ", video=" + videoBitrate + ", audio=" + audioBitrate
                    + ", width=" + videoWidth + ", height=" + videoHeight + ", size=" + fileSize + "]";
        }
    }

    public static void main(String[] args) {
        try {
            HashMap<String, List<Video>> map = loadJson("sample.json", true);
            Iterator<Entry<String, List<Video>>> lectures = map.entrySet().iterator();

            while (lectures.hasNext()) {
                Entry<String, List<Video>> lecture = lectures.next();

                System.out.printf("Lecture #%s%n", lecture.getKey());

                for (Video video : lecture.getValue()) {
                    System.out.println(video);
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static <T> T parseUnderScoredResponse(String json, Class<T> classOfT) {
        try {
            if (json == null) {
                return null;
            }
            return propertyMapper.readValue(json, classOfT);

        } catch (JsonParseException e) {
            e.printStackTrace();
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    public static URL pathToUrl(String path, boolean isResource) throws MalformedURLException {
        if (isResource) {
            return JsonHandler.class.getClassLoader().getResource(path);
        }

        return new URL("file:/" + path);
    }

    public static File load(String path, boolean isResource) throws MalformedURLException {
        return load(pathToUrl(path, isResource));
    }

    public static File load(URL url) {
        try {
            return new File(url.toURI());
        } catch (URISyntaxException e) {
            return new File(url.getPath());
        }
    }

    @SuppressWarnings("resource")
    public static String readFile(URL url, String charset) throws IOException {
        return new Scanner(url.openStream(), charset).useDelimiter("\\A").next();
    }

    public static String loadJsonString(String path, boolean isResource) throws IOException {
        return readFile(path, isResource, "UTF-8");
    }

    public static String readFile(String path, boolean isResource, String charset) throws IOException {
        return readFile(pathToUrl(path, isResource), charset);
    }

    public static HashMap<String, List<Video>> loadJson(String jsonString) throws IOException {
        return JsonHandler.parseUnderScoredResponse(jsonString, MyHashMap.class);
    }

    public static HashMap<String, List<Video>> loadJson(String path, boolean isResource) throws IOException {
        return loadJson(loadJsonString(path, isResource));
    }
}
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