Java 尝试从Json到字符串获取值时出现JSONException
我试图通过下一个API链接从Wikipedia获取2个值： 因为它是随机生成的，有时它不会返回我需要的一个值，但我稍后会解决这个问题，目前我在访问Json中需要的两个值“title”和“source”时遇到问题 返回的Json如下所示：Java 尝试从Json到字符串获取值时出现JSONException,java,json,Java,Json,我试图通过下一个API链接从Wikipedia获取2个值： 因为它是随机生成的，有时它不会返回我需要的一个值，但我稍后会解决这个问题，目前我在访问Json中需要的两个值“title”和“source”时遇到问题 返回的Json如下所示： {"batchcomplete":"","continue":{"grncontinue":"0.360395277951|0.360395626487|10429617|0","continue":"grncontinue||"},"query":{"pa
{"batchcomplete":"","continue":{"grncontinue":"0.360395277951|0.360395626487|10429617|0","continue":"grncontinue||"},"query":{"pages":{"38690716":{"pageid":38690716,"ns":0,"title":"Alaine Chartrand","thumbnail":{"source":"https://upload.wikimedia.org/wikipedia/commons/d/d4/Alaine_Chartrand.jpg","width":267,"height":400},"pageimage":"Alaine_Chartrand.jpg"}}}}
String API = "https://en.wikipedia.org/w/api.php?action=query&generator=random&grnnamespace=0&prop=pageimages&format=json&pithumbsize=500&utf8";
//open connection with wikipedia.
HttpURLConnection httpcon = (HttpURLConnection) new URL(API).openConnection();
//read all the input from wikipedia.
BufferedReader in = new BufferedReader(new InputStreamReader(httpcon.getInputStream()));
String responseSB = in.lines().collect(Collectors.joining());
in.close();
JSONObject incomingJSON = new JSONObject(responseSB);
//crashes here
String mTitle = incomingJSON.getString("title");
String mUrl = incomingJSON.getString("source");
您无法直接从JSON响应获取标题和源代码，因为它必须包含多个内部对象。下面是阅读标题和源代码的代码快照
// new code
JSONObject incomingJSON = new JSONObject(responseSB);
JSONObject innerObject = incomingJSON.getJsonObject("query").getJsonObject("pages").getJsonObject("38690716");
String mTitle= innerObject.getString("title");
String mUrl= innerObject.getJsonObject("thumbnail").getString("source");
//crashes here
String mTitle = incomingJSON.getString("title");
String mUrl = incomingJSON.getString("source");
您无法直接从JSON响应获取标题和源代码，因为它必须包含多个内部对象。下面是阅读标题和源代码的代码快照
// new code
JSONObject incomingJSON = new JSONObject(responseSB);
JSONObject innerObject = incomingJSON.getJsonObject("query").getJsonObject("pages").getJsonObject("38690716");
String mTitle= innerObject.getString("title");
String mUrl= innerObject.getJsonObject("thumbnail").getString("source");
//crashes here
String mTitle = incomingJSON.getString("title");
String mUrl = incomingJSON.getString("source");
如果您注意到JSON，它是随机生成的，但具有特定的格式 案例1
{
"batchcomplete": "",
"continue": {
"grncontinue": "0.720220803439|0.720221273467|12887566|0",
"continue": "grncontinue||"
},
"query": {
"pages": {
"4897672": {
"pageid": 4897672,
"ns": 0,
"title": "New Hope, Sunnyvale, Texas"
}
}
}
}
querypagesMapStringJSONObjecttitleString API = "https://en.wikipedia.org/w/api.php?action=query&generator=random&grnnamespace=0&prop=pageimages&format=json&pithumbsize=500&utf8";
//open connection with wikipedia.
HttpURLConnection httpcon = (HttpURLConnection) new URL(API).openConnection();
//read all the input from wikipedia.
BufferedReader in = new BufferedReader(new InputStreamReader(httpcon.getInputStream()));
String responseSB = in.lines().collect(Collectors.joining());
in.close();
JSONObject incomingJSON = new JSONObject(responseSB);
Map<String,JSONObject> map = (Map<String, JSONObject>) incomingJSON.getJSONObject("query").getJSONObject("pages");
map.forEach((k,v)->System.out.println(" The key is : "+k+" the title is : "+v.getString("title")));
sourceString API = "https://en.wikipedia.org/w/api.php?action=query&generator=random&grnnamespace=0&prop=pageimages&format=json&pithumbsize=500&utf8";
//open connection with wikipedia.
HttpURLConnection httpcon = (HttpURLConnection) new URL(API).openConnection();
//read all the input from wikipedia.
BufferedReader in = new BufferedReader(new InputStreamReader(httpcon.getInputStream()));
String responseSB = in.lines().collect(Collectors.joining());
in.close();
JSONObject incomingJSON = new JSONObject(responseSB);
Map<String,JSONObject> map = (Map<String, JSONObject>) incomingJSON.getJSONObject("query").getJSONObject("pages");
map.forEach((k,v)->{
System.out.println(" The key is : "+k+" the title is : "+v.getString("title"));
//use try catch to get source because you will not get the same response every time
String source = v.getJSONObject("thumbnail").getString("source");
});
}
stringapi=”https://en.wikipedia.org/w/api.php?action=query&generator=random&grnnamespace=0&prop=pageimages&format=json&pithumbsize=500&utf8";
//打开与维基百科的连接。
HttpURLConnection httpcon=（HttpURLConnection）新URL（API）.openConnection（）；
//阅读维基百科的所有输入。
BufferedReader in=新的BufferedReader（新的InputStreamReader（httpcon.getInputStream（））；
字符串responseb=in.lines（）.collect（collector.joining（））；
in.close（）；
JSONObject incomingJSON=新的JSONObject（responseB）；
Map Map=（Map）incomingJSON.getJSONObject（“查询”）.getJSONObject（“页面”）；
图.forEach（（k，v）->{
System.out.println（“键为：+k+”，标题为：+v.getString（“标题”）；
//使用try-catch获取源代码，因为您不会每次都得到相同的响应
字符串源=v.getJSONObject（“缩略图”）.getString（“源”）；
});
}
{
"batchcomplete": "",
"continue": {
"grncontinue": "0.720220803439|0.720221273467|12887566|0",
"continue": "grncontinue||"
},
"query": {
"pages": {
"4897672": {
"pageid": 4897672,
"ns": 0,
"title": "New Hope, Sunnyvale, Texas"
}
}
}
}
querypagesMapStringJSONObjecttitleString API = "https://en.wikipedia.org/w/api.php?action=query&generator=random&grnnamespace=0&prop=pageimages&format=json&pithumbsize=500&utf8";
//open connection with wikipedia.
HttpURLConnection httpcon = (HttpURLConnection) new URL(API).openConnection();
//read all the input from wikipedia.
BufferedReader in = new BufferedReader(new InputStreamReader(httpcon.getInputStream()));
String responseSB = in.lines().collect(Collectors.joining());
in.close();
JSONObject incomingJSON = new JSONObject(responseSB);
Map<String,JSONObject> map = (Map<String, JSONObject>) incomingJSON.getJSONObject("query").getJSONObject("pages");
map.forEach((k,v)->System.out.println(" The key is : "+k+" the title is : "+v.getString("title")));
sourceString API = "https://en.wikipedia.org/w/api.php?action=query&generator=random&grnnamespace=0&prop=pageimages&format=json&pithumbsize=500&utf8";
//open connection with wikipedia.
HttpURLConnection httpcon = (HttpURLConnection) new URL(API).openConnection();
//read all the input from wikipedia.
BufferedReader in = new BufferedReader(new InputStreamReader(httpcon.getInputStream()));
String responseSB = in.lines().collect(Collectors.joining());
in.close();
JSONObject incomingJSON = new JSONObject(responseSB);
Map<String,JSONObject> map = (Map<String, JSONObject>) incomingJSON.getJSONObject("query").getJSONObject("pages");
map.forEach((k,v)->{
System.out.println(" The key is : "+k+" the title is : "+v.getString("title"));
//use try catch to get source because you will not get the same response every time
String source = v.getJSONObject("thumbnail").getString("source");
});
}
stringapi=”https://en.wikipedia.org/w/api.php?action=query&generator=random&grnnamespace=0&prop=pageimages&format=json&pithumbsize=500&utf8";
//打开与维基百科的连接。
HttpURLConnection httpcon=（HttpURLConnection）新URL（API）.openConnection（）；
//阅读维基百科的所有输入。
BufferedReader in=新的BufferedReader（新的InputStreamReader（httpcon.getInputStream（））；
字符串responseb=in.lines（）.collect（collector.joining（））；
in.close（）；
JSONObject incomingJSON=新的JSONObject（responseB）；
Map Map=（Map）incomingJSON.getJSONObject（“查询”）.getJSONObject（“页面”）；
图.forEach（（k，v）->{
System.out.println（“键为：+k+”，标题为：+v.getString（“标题”）；
//使用try-catch获取源代码，因为您不会每次都得到相同的响应
字符串源=v.getJSONObject（“缩略图”）.getString（“源”）；
});
}
您应该知道页面id将更改，缩略图是可选的
// new code
JSONObject incomingJSON = new JSONObject(responseSB);
JSONObject pages = incomingJSON.getJSONObject("query").getJSONObject("pages");
Iterator<String> it = pages.keys();
while(it.hasNext()) {
JSONObject page = pages.getJSONObject(it.next());
String mTitle= page.getString("title");
if(page.keySet().contains("thumbnail")) {
String mUrl= page.getJSONObject("thumbnail").getString("source");
}
}
//新代码
JSONObject incomingJSON=新的JSONObject（responseB）；
JSONObject pages=incomingJSON.getJSONObject（“查询”）.getJSONObject（“页面”）；
迭代器it=pages.keys（）；
while（it.hasNext（））{
JSONObject page=pages.getJSONObject（it.next（））；
String mTitle=page.getString（“title”）；
如果（page.keySet（）包含（“缩略图”））{
String mUrl=page.getJSONObject（“缩略图”）.getString（“源”）；
}
}
// new code
JSONObject incomingJSON = new JSONObject(responseSB);
JSONObject pages = incomingJSON.getJSONObject("query").getJSONObject("pages");
Iterator<String> it = pages.keys();
while(it.hasNext()) {
JSONObject page = pages.getJSONObject(it.next());
String mTitle= page.getString("title");
if(page.keySet().contains("thumbnail")) {
String mUrl= page.getJSONObject("thumbnail").getString("source");
}
}
//新代码
JSONObject incomingJSON=新的JSONObject（responseB）；
JSONObject pages=incomingJSON.getJSONObject（“查询”）.getJSONObject（“页面”）；
迭代器it=pages.keys（）；
while（it.hasNext（））{
JSONObject page=pages.getJSONObject（it.next（））；
String mTitle=page.getString（“title”）；
如果（page.keySet（）包含（“缩略图”））{
String mUrl=page.getJSONObject（“缩略图”）.getString（“源”）；
}
}
Pattern p = Pattern.compile("\"source\":\"(.*?)\",\"width");
Matcher m = p.matcher(responseSB);
if (m.find()) {
url = m.group(1);
}
p = Pattern.compile("\"title\":(.*?)\",\"thumbnail");
m = p.matcher(responseSB);
if (m.find()) {
description = m.group(1);
}
因此，由于ID不断变化，我决定采用另一种方法。 我使用了以下代码：
Pattern p = Pattern.compile("\"source\":\"(.*?)\",\"width");
Matcher m = p.matcher(responseSB);
if (m.find()) {
url = m.group(1);
}
p = Pattern.compile("\"title\":(.*?)\",\"thumbnail");
m = p.matcher(responseSB);
if (m.find()) {
description = m.group(1);
}
但它并不总是38690716 OK，尝试使用索引而不是对象名。但它并不总是38690716 OK，尝试使用索引而不是对象名。它不总是38690716它不总是38690716嗨，我得到了错误“语言级别7不支持lambda表达式”，因为我理解它给出这个错误是因为map.forEach行。我不确定什么是lambda表达式。还有其他方法吗？您使用的是jdk 7，lambda表达式来自jdk-8，所以只需使用for循环来迭代mapNo，我在这里发布了另一个解决方案。您好，我收到了错误“lambda表达式在语言级别7不受支持”，因为我知道它会因为map.forEach行而给出此错误。我不确定什么是lambda表达式。还有其他方法吗？您使用的是jdk 7，lambda表达式来自jdk-8，所以只需使用for循环来迭代mapNo，我已经提出了另一个解决方案，我在这里发布了。