In Java I have:
String params = "depCity=PAR&roomType=D&depCity=NYC";
I want to get values of depCity parameters (PAR,NYC).
So I created regex:
String regex = "depCity=([^&]+)";
Pattern p = Pattern.compile(regex);
Matcher m = p.matcher(params);
m.find() is returning false. m.groups() is returning IllegalArgumentException.
What am I doing wrong?
It doesn't have to be regex. Since I think there's no standard method to handle this thing, I'm using something that I copied from somewhere (and perhaps modified a bit):
public static Map<String, List<String>> getQueryParams(String url) {
try {
Map<String, List<String>> params = new HashMap<String, List<String>>();
String[] urlParts = url.split("\\?");
if (urlParts.length > 1) {
String query = urlParts[1];
for (String param : query.split("&")) {
String[] pair = param.split("=");
String key = URLDecoder.decode(pair[0], "UTF-8");
String value = "";
if (pair.length > 1) {
value = URLDecoder.decode(pair[1], "UTF-8");
}
List<String> values = params.get(key);
if (values == null) {
values = new ArrayList<String>();
params.put(key, values);
}
values.add(value);
}
}
return params;
} catch (UnsupportedEncodingException ex) {
throw new AssertionError(ex);
}
}
So, when you call it, you will get all parameters and their values. The method handles multi-valued params, hence the List<String> rather than String, and in your case you'll need to get the first list element.
Not sure how you used find and group, but this works fine:
String params = "depCity=PAR&roomType=D&depCity=NYC";
try {
Pattern p = Pattern.compile("depCity=([^&]+)");
Matcher m = p.matcher(params);
while (m.find()) {
System.out.println(m.group());
}
} catch (PatternSyntaxException ex) {
// error handling
}
However, If you only want the values, not the key depCity= then you can either use m.group(1) or use a regex with lookarounds:
Pattern p = Pattern.compile("(?<=depCity=).*?(?=&|$)");
It works in the same Java code as above. It tries to find a start position right after depCity=. Then matches anything but as little as possible until it reaches a point facing & or end of input.
I have three solutions, the third one is an improved version of Bozho's.
First, if you don't want to write stuff yourself and simply use a lib, then use Apache's httpcomponents lib's URIBuilder class: http://hc.apache.org/httpcomponents-client-ga/httpclient/apidocs/org/apache/http/client/utils/URIBuilder.html
new URIBuilder("http://...").getQueryParams()...
Second:
// overwrites duplicates
import org.apache.http.NameValuePair;
import org.apache.http.client.utils.URLEncodedUtils;
public static Map<String, String> readParamsIntoMap(String url, String charset) throws URISyntaxException {
Map<String, String> params = new HashMap<>();
List<NameValuePair> result = URLEncodedUtils.parse(new URI(url), charset);
for (NameValuePair nvp : result) {
params.put(nvp.getName(), nvp.getValue());
}
return params;
}
Third:
public static Map<String, List<String>> getQueryParams(String url) throws UnsupportedEncodingException {
Map<String, List<String>> params = new HashMap<String, List<String>>();
String[] urlParts = url.split("\\?");
if (urlParts.length < 2) {
return params;
}
String query = urlParts[1];
for (String param : query.split("&")) {
String[] pair = param.split("=");
String key = URLDecoder.decode(pair[0], "UTF-8");
String value = "";
if (pair.length > 1) {
value = URLDecoder.decode(pair[1], "UTF-8");
}
// skip ?& and &&
if ("".equals(key) && pair.length == 1) {
continue;
}
List<String> values = params.get(key);
if (values == null) {
values = new ArrayList<String>();
params.put(key, values);
}
values.add(value);
}
return params;
}
If you are developing an Android application, try this:
String yourParam = null;
Uri uri = Uri.parse(url);
try {
yourParam = URLDecoder.decode(uri.getQueryParameter(PARAM_NAME), "UTF-8");
} catch (UnsupportedEncodingException exception) {
exception.printStackTrace();
}
Uri class?
If spring-web is present on classpath, UriComponentsBuilder can be used.
MultiValueMap<String, String> queryParams =
UriComponentsBuilder.fromUriString(url).build().getQueryParams();
Simple Solution create the map out of all param name and values and use it :).
import org.apache.commons.lang3.StringUtils;
public String splitURL(String url, String parameter){
HashMap<String, String> urlMap=new HashMap<String, String>();
String queryString=StringUtils.substringAfter(url,"?");
for(String param : queryString.split("&")){
urlMap.put(StringUtils.substringBefore(param, "="),StringUtils.substringAfter(param, "="));
}
return urlMap.get(parameter);
}
Add String param = URLDecoder.decode(param , "UTF-8"); inside loopsame but with jsonobject:
public static JSONObject getQueryParams2(String url) {
JSONObject json = new JSONObject();
try {
String[] urlParts = url.split("\\?");
JSONArray array = new JSONArray();
if (urlParts.length > 1) {
String query = urlParts[1];
for (String param : query.split("&")) {
String[] pair = param.split("=");
String key = URLDecoder.decode(pair[0], "UTF-8");
String value = "";
if (pair.length > 1) {
value = URLDecoder.decode(pair[1], "UTF-8");
if(json.has(key)) {
array = json.getJSONArray(key);
array.put(value);
json.put(key, array);
array = new JSONArray();
} else {
array.put(value);
json.put(key, array);
array = new JSONArray();
}
}
}
}
return json;
} catch (Exception ex) {
throw new AssertionError(ex);
}
}
