How to Extract Name-Value Pairs from a URI Query String in Java?

Extract Embedded Data from URIs Using Java

Parsing a URI string into its corresponding name-value pairs is a common task in many web development scenarios. In Java, you can achieve this operation without relying on external libraries by applying a straightforward approach.

Step-by-Step Guide:

1. Split the URI Query String:
   Using the URL.getQuery() method, obtain the query string portion of the URI. The query string is the part after the question mark (?) and contains key-value pairs separated by the ampersand (&) character.
2. Separate Key-Value Pairs:
   Split the query string into individual key-value pairs using the String.split("&") method.
3. Parse Key-Value Pairs:
   For each key-value pair, locate the equals sign (=) to separate the key from the value. Decode both the key and value using a suitable encoding, such as URLDecoder.decode().
4. Construct Name-Value Collection:
   Create a map data structure to store the parsed key-value pairs.

Sample Implementation:

The following Java code demonstrates how to implement the above steps:

import java.net.URL;
import java.net.URLDecoder;
import java.util.LinkedHashMap;
import java.util.Map;

public class ParseUriQuery {

    public static Map<string string> splitQuery(URL url) throws UnsupportedEncodingException {
        Map<string string> queryPairs = new LinkedHashMap();
        String query = url.getQuery();
        String[] pairs = query.split("&");
        for (String pair : pairs) {
            int idx = pair.indexOf("=");
            queryPairs.put(URLDecoder.decode(pair.substring(0, idx), "UTF-8"), URLDecoder.decode(pair.substring(idx + 1), "UTF-8"));
        }
        return queryPairs;
    }

}</string></string>

Example Usage:

To parse the URI provided in your question, you can use the following code:

URL url = new URL("https://google.com.ua/oauth/authorize?client_id=SS&response_type=code&scope=N_FULL&access_type=offline&redirect_uri=http://localhost/Callback");
Map<string string> queryPairs = ParseUriQuery.splitQuery(url);

// Access parsed elements
String clientId = queryPairs.get("client_id"); // Returns "SS"</string>

This approach provides a convenient and versatile way to extract information embedded in URI query strings in Java.

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