How to read the parameters and value from the query-string using java?

Question

I am using Ciui from google code and all the requests are only GET requests and not POST. The calls are made by the ajax (I am not sure). I need to know how to read the "searchstring" parameter from this URL. When I read this in my Servlet using the getQueryString() method I am not able to properly form the actual text. This unicode (when % replaced by /) like text is actually in Chinese. Please let me how to decode search string and create the string.

http://xxxx.com?searchString=%u8BF7%u5728%u6B64%u5904%u8F93%u5165%u4EA7%u54C1%u7F16%u53F7%u6216%u540D%u79F0&button=%E6%90%9C%E7%B4%A2

The other parameter is in proper percentage encoding an I am able to decode using the URL decode. Thanks in advance.

Solution 1

Your encoding scheme for those chinese characters actually violates web standards (namely RFC 3986): the percent sign is a reserved character that may not be used except for the standard percent encoding.

I'd strongly advise you to use the standard encoding scheme (UTF-8 bytes and percent encoding); then you can simply use the standard getParameter() method. If you insist on violating the standard, it may well be impossible to solve your problem within a standards-compliant servlet container.

Solution 2

Ok in my case I had the querystring from another source so you maybe need this:

    public static Map<String, String> getQueryMap(String query)  
{  
    String[] params = query.split("&");  
    Map<String, String> map = new HashMap<String, String>();  
    for (String param : params)  
    {  String [] p=param.split("=");
        String name = p[0];  
      if(p.length>1)  {String value = p[1];  
        map.put(name, value);
      }  
    }  
    return map;  
} 

So then you can use:

 Map params=getQueryMap(querystring);
 String id=(String)params.get("id");
 String anotherparam=(String)params.get("anotherparam");

Solution 3

A solution with Java 8.

This piece of code transform the query string in a key/value list:

List<AbstractMap.SimpleEntry<String, String>> list = 
        asList(queryString.split("&")).stream()
        .map(s -> copyOf(s.split("="), 2))
        .map(o -> new AbstractMap.SimpleEntry<String, String>(o[0], o[1]) )
        .collect(toList());

the comment of @Tuno inspired me to write a new answer, this alternative (and shorter) solution use groupingBy method:

Map<String, List<String>> llist = 
       asList(queryString.split("&")).stream()
       .map(s -> copyOf(s.split("="), 2))
       .collect(groupingBy(s -> s[0], mapping(s -> s[1], toList())));

I suggest to decode the values with URLDecoder.decode(String s, String enc)

Both the solutions prints collection content with this line:

list.stream().forEach(s -> System.out.println(s.getKey() + " = " + s.getValue()));

Solution 4

public void doGet(HttpServletRequest request, HttpServletResponse response) {
    String searchString = request.getParameter("searchString");
    // process searchString
}

Decoding the parameter is done automatically.

View more solutions

Comments

[BalusC]

What does System.out.println(Collections.list(request.getParameterName‌​s())) say? Is the searchString there? (note that it is case sensitive).

[Tuno]

Nice one. I have used .collect(Collectors.toMap(o -> o[0], o -> o[1])) to get a Map and retrieve by key.

[freedev]

@Tuno Your solution does not work when there are multiple values associated to a single field (e.g. field1=value1&field1=value2&field1=value3).

[freedev]

This solution does not handle the case when there are multiple values associated to a single field (e.g. field1=value1&field1=value2&field1=value3).