在java中从一个json字符串创建一个hashmap？
我有像 {"phonetype":"N95","cat":"WP"} 这样的 json 字符串，想转换成标准的 Hashmap。
我该怎么做？
【问题讨论】：
JsonNode）
解析 JSONObject 并创建 HashMap
public static void jsonToMap(String t) throws JSONException {
HashMap<String, String> map = new HashMap<String, String>();
JSONObject jObject = new JSONObject(t);
Iterator<?> keys = jObject.keys();
while( keys.hasNext() ){
String key = (String)keys.next();
String value = jObject.getString(key);
map.put(key, value);
}
System.out.println("json : "+jObject);
System.out.println("map : "+map);
}
测试输出：
json : {"phonetype":"N95","cat":"WP"}
map : {cat=WP, phonetype=N95}
【讨论】：
keys() 或 getString()
您可以使用 Google 的 Gson 库将 json 转换为 Hashmap。试试下面的代码
String jsonString = "Your JSON string";
HashMap<String,String> map = new Gson().fromJson(jsonString, new TypeToken<HashMap<String, String>>(){}.getType());
【讨论】：
TypeToken<HashMap<String, String>>(){}.getType()
public class JsonMapExample {
public static void main(String[] args) {
String json = "{\"phonetype\":\"N95\",\"cat\":\"WP\"}";
Map<String, String> map = new HashMap<String, String>();
ObjectMapper mapper = new ObjectMapper();
try {
//convert JSON string to Map
map = mapper.readValue(json, new TypeReference<HashMap<String, String>>() {});
System.out.println(map);
} catch (Exception e) {
e.printStackTrace();
}
}
}
输出：
{phonetype=N95, cat=WP}
你可以看到这个链接很有帮助http://www.mkyong.com/java/how-to-convert-java-map-to-from-json-jackson/
【讨论】：
org.codehaus.jackson?还在使用 Jackson 1.9.x？ ;)
你可以使用Gson库
Type type = new TypeToken<HashMap<String, String>>() {}.getType();
new Gson().fromJson(jsonString, type);
【讨论】：
这个操作很简单，不需要使用任何外部库。
你可以改用这个类:)（处理偶数列表、嵌套列表和json）
public class Utility {
public static Map<String, Object> jsonToMap(Object json) throws JSONException {
if(json instanceof JSONObject)
return _jsonToMap_((JSONObject)json) ;
else if (json instanceof String)
{
JSONObject jsonObject = new JSONObject((String)json) ;
return _jsonToMap_(jsonObject) ;
}
return null ;
}
private static Map<String, Object> _jsonToMap_(JSONObject json) throws JSONException {
Map<String, Object> retMap = new HashMap<String, Object>();
if(json != JSONObject.NULL) {
retMap = toMap(json);
}
return retMap;
}
private static Map<String, Object> toMap(JSONObject object) throws JSONException {
Map<String, Object> map = new HashMap<String, Object>();
Iterator<String> keysItr = object.keys();
while(keysItr.hasNext()) {
String key = keysItr.next();
Object value = object.get(key);
if(value instanceof JSONArray) {
value = toList((JSONArray) value);
}
else if(value instanceof JSONObject) {
value = toMap((JSONObject) value);
}
map.put(key, value);
}
return map;
}
public static List<Object> toList(JSONArray array) throws JSONException {
List<Object> list = new ArrayList<Object>();
for(int i = 0; i < array.length(); i++) {
Object value = array.get(i);
if(value instanceof JSONArray) {
value = toList((JSONArray) value);
}
else if(value instanceof JSONObject) {
value = toMap((JSONObject) value);
}
list.add(value);
}
return list;
}
}
要将您的 JSON 字符串转换为 hashmap，请使用：
HashMap<String, Object> hashMap = new HashMap<>(Utility.jsonToMap(response)) ;
【讨论】：
HashMap<String, Object> map = new Gson().fromJson(jsonString, HashMap.class);
试试这个
【讨论】：
HashMap<String, String> hashMap = new HashMap<String, String>();
String string = "{\"phonetype\":\"N95\",\"cat\":\"WP\"}";
try {
JSONObject json = new JSONObject(string);
hashMap.put("phonetype", json.getString("phonetype"));
hashMap.put("cat", json.getString("cat"));
} catch (JSONException e) {
// TODO Handle expection!
}
【讨论】：
{"phonetype":"N95","cat":"WP"}，应该是通用的。
我建议不要自己这样做。
使用图书馆，例如来自 Google 的 Gson 库。
【讨论】：
考虑这个json字符串
{
"12": [
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/12/12_960x540_200k.mp4/manifest.mpd",
"video_bitrate": "200k",
"audio_bitrate": "32k",
"video_width": 960,
"video_height": 540,
"file_size": 125465600
},
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/12/12_960x540_80k.mp4/manifest.mpd",
"video_bitrate": "80k",
"audio_bitrate": "32k",
"video_width": 960,
"video_height": 540,
"file_size": 50186240
},
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/12/12_640x360_201k.mp4/manifest.mpd",
"video_bitrate": "201k",
"audio_bitrate": "32k",
"video_width": 640,
"video_height": 360,
"file_size": 145934731
},
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/12/12_640x360_199k.mp4/manifest.mpd",
"video_bitrate": "199k",
"audio_bitrate": "32k",
"video_width": 640,
"video_height": 360,
"file_size": 145800030
},
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/12/12_640x360_79k.mp4/manifest.mpd",
"video_bitrate": "79k",
"audio_bitrate": "32k",
"video_width": 640,
"video_height": 360,
"file_size": 71709477
}
],
"13": [
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/13/13_960x540_200k.mp4/manifest.mpd",
"video_bitrate": "200k",
"audio_bitrate": "32k",
"video_width": 960,
"video_height": 540,
"file_size": 172902400
},
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/13/13_960x540_80k.mp4/manifest.mpd",
"video_bitrate": "80k",
"audio_bitrate": "32k",
"video_width": 960,
"video_height": 540,
"file_size": 69160960
},
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/13/13_640x360_201k.mp4/manifest.mpd",
"video_bitrate": "201k",
"audio_bitrate": "32k",
"video_width": 640,
"video_height": 360,
"file_size": 199932081
},
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/13/13_640x360_199k.mp4/manifest.mpd",
"video_bitrate": "199k",
"audio_bitrate": "32k",
"video_width": 640,
"video_height": 360,
"file_size": 199630781
},
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/13/13_640x360_79k.mp4/manifest.mpd",
"video_bitrate": "79k",
"audio_bitrate": "32k",
"video_width": 640,
"video_height": 360,
"file_size": 98303415
}
],
"14": [
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/14/14_960x540_200k.mp4/manifest.mpd",
"video_bitrate": "200k",
"audio_bitrate": "32k",
"video_width": 960,
"video_height": 540,
"file_size": 205747200
},
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/14/14_960x540_80k.mp4/manifest.mpd",
"video_bitrate": "80k",
"audio_bitrate": "32k",
"video_width": 960,
"video_height": 540,
"file_size": 82298880
},
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/14/14_640x360_201k.mp4/manifest.mpd",
"video_bitrate": "201k",
"audio_bitrate": "32k",
"video_width": 640,
"video_height": 360,
"file_size": 237769546
},
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/14/14_640x360_199k.mp4/manifest.mpd",
"video_bitrate": "199k",
"audio_bitrate": "32k",
"video_width": 640,
"video_height": 360,
"file_size": 237395552
},
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/14/14_640x360_79k.mp4/manifest.mpd",
"video_bitrate": "79k",
"audio_bitrate": "32k",
"video_width": 640,
"video_height": 360,
"file_size": 116885686
}
],
"15": [
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/15/15_960x540_200k.mp4/manifest.mpd",
"video_bitrate": "200k",
"audio_bitrate": "32k",
"video_width": 960,
"video_height": 540,
"file_size": 176128000
},
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/15/15_960x540_80k.mp4/manifest.mpd",
"video_bitrate": "80k",
"audio_bitrate": "32k",
"video_width": 960,
"video_height": 540,
"file_size": 70451200
},
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/15/15_640x360_201k.mp4/manifest.mpd",
"video_bitrate": "201k",
"audio_bitrate": "32k",
"video_width": 640,
"video_height": 360,
"file_size": 204263286
},
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/15/15_640x360_199k.mp4/manifest.mpd",
"video_bitrate": "199k",
"audio_bitrate": "32k",
"video_width": 640,
"video_height": 360,
"file_size": 204144447
},
{
"dash_url": "http://mediaserver.superprofs.com:1935/vods3/_definst_/mp4:amazons3/superprofs-media/private/lectures/15/15_640x360_79k.mp4/manifest.mpd",
"video_bitrate": "79k",
"audio_bitrate": "32k",
"video_width": 640,
"video_height": 360,
"file_size": 100454382
}
]
}
使用杰克逊解析器
private static ObjectMapper underScoreToCamelCaseMapper;
static {
final DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
underScoreToCamelCaseMapper = new ObjectMapper();
underScoreToCamelCaseMapper.setDateFormat(df);
underScoreToCamelCaseMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
underScoreToCamelCaseMapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);
underScoreToCamelCaseMapper.setPropertyNamingStrategy(
PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES);
}
public static <T> T parseUnderScoredResponse(String json, Class<T> classOfT) {
try {
if (json == null) {
return null;
}
return underScoreToCamelCaseMapper.readValue(json, classOfT);
} catch (JsonParseException e) {
} catch (JsonMappingException e) {
} catch (IOException e) {
}
return null;
}
使用以下代码解析
HashMap<String, ArrayList<Video>> integerArrayListHashMap =
JsonHandler.parseUnderScoredResponse(test, MyHashMap.class);
MyHashMap 在哪里
private static class MyHashMap extends HashMap<String,ArrayList<Video>>{
}
【讨论】：
没有 JSON 库，只有 String 和 HashMap。
保持简单！
希望它适合所有人。
// JSON 转换为基于 String 的 HashMap 示例
String tempJson = "{\"incomePhone\":\"213121122\",\"clientId\":\"1001\",\"clientAccountManager\":\"Gestor de Conta 1\",\"clientRetailBranch\":\"100\",\"phoneAccountManager\":\"7800100\"}";
System.out.println(tempJson);
String[] parts = tempJson.split(",");
HashMap<String,String> jsonHash = new HashMap<String,String>();
for(int i=0;i<parts.length;i++){
parts[i] = parts[i].replace("\"", "");
parts[i] = parts[i].replace("{", "");
parts[i] = parts[i].replace("}", "");
String[] subparts = parts[i].split(":");
jsonHash.put(subparts[0],subparts[1]);
}
【讨论】：
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;
}
【讨论】：
将 Json 解析为 HashMap 的最佳方法
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;
}
【讨论】：
在 Java 中，我们可以使用以下语句来实现。我们需要使用 Jackson ObjectMapper 并提供 HashMap.class 作为映射类。最后将结果存储为 HashMap 对象。
HashMap<String,String> hashMap = new ObjectMapper().readValue(jsonString, HashMap.class);
【讨论】：
这对我有用：
JSONObject jsonObj = new JSONObject();
jsonObj.put("phonetype","N95");
jsonObj.put("cat","WP");
jsonObj 到 Hashmap 如下使用 gson
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>
【讨论】：
下面是一个简单的例子，它可以通过仅使用 JSON 简单库从 JSON 字符串创建 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"));
}
【讨论】：
您可以使用 Jackson 来执行此操作。我还没有找到一个简单的 Gson 解决方案。
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();
}
}
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));
}
}
【讨论】：