I am trying to create a simple HttpServer in Java to handle GET requests, but when I try to get the GET parameters for a request I noticed the HttpExchange class does not have a
This answer, contrary to annon01's, properly decodes the keys and values. It does not use String.split
, but scans the string using indexOf
, which is faster.
public static Map<String, String> parseQueryString(String qs) {
Map<String, String> result = new HashMap<>();
if (qs == null)
return result;
int last = 0, next, l = qs.length();
while (last < l) {
next = qs.indexOf('&', last);
if (next == -1)
next = l;
if (next > last) {
int eqPos = qs.indexOf('=', last);
try {
if (eqPos < 0 || eqPos > next)
result.put(URLDecoder.decode(qs.substring(last, next), "utf-8"), "");
else
result.put(URLDecoder.decode(qs.substring(last, eqPos), "utf-8"), URLDecoder.decode(qs.substring(eqPos + 1, next), "utf-8"));
} catch (UnsupportedEncodingException e) {
throw new RuntimeException(e); // will never happen, utf-8 support is mandatory for java
}
}
last = next + 1;
}
return result;
}
The following: httpExchange.getRequestURI().getQuery()
will return string in format similar to this: "field1=value1&field2=value2&field3=value3..."
so you could simply parse string yourself, this is how function for parsing could look like:
public Map<String, String> queryToMap(String query) {
Map<String, String> result = new HashMap<>();
for (String param : query.split("&")) {
String[] entry = param.split("=");
if (entry.length > 1) {
result.put(entry[0], entry[1]);
}else{
result.put(entry[0], "");
}
}
return result;
}
And this is how you could use it:
Map<String, String> params = queryToMap(httpExchange.getRequestURI().getQuery());
System.out.println("param A=" + params.get("A"));
Stumbled across this, and figured I'd toss a Java 8 / Streams implementation out here, whilst adding a few extra bits (not in previous answers).
Extra 1: I've added a filter to avoid processing any empty params. Something that should not happen, but it allows a cleaner implementation vs. not handling the issue (and sending an empty response). An example of this would look like ?param1=value1¶m2=
Extra 2: I've leveraged String.split(String regex, int limit) for the second split operation. This allows a query parameter such as ?param1=it_has=in-it&other=something
to be passed.
public static Map<String, String> getParamMap(String query) {
// query is null if not provided (e.g. localhost/path )
// query is empty if '?' is supplied (e.g. localhost/path? )
if (query == null || query.isEmpty()) return Collections.emptyMap();
return Stream.of(query.split("&"))
.filter(s -> !s.isEmpty())
.map(kv -> kv.split("=", 2))
.collect(Collectors.toMap(x -> x[0], x-> x[1]));
}
Imports
import java.util.Map;
import java.util.Collections;
import java.util.stream.Stream;
import java.util.stream.Collectors;
Building on the answer by @anon01, this is how to do it in Groovy:
Map<String,String> getQueryParameters( HttpExchange httpExchange )
{
def query = httpExchange.getRequestURI().getQuery()
return query.split( '&' )
.collectEntries {
String[] pair = it.split( '=' )
if (pair.length > 1)
{
return [(pair[0]): pair[1]]
}
else
{
return [(pair[0]): ""]
}
}
}
And this is how to use it:
def queryParameters = getQueryParameters( httpExchange )
def parameterA = queryParameters['A']