Java url tutorial

Gavin 155 Published: 10/29/2024

Java url tutorial

Here is a comprehensive Java URL tutorial:

Understanding URLs

A URL (Uniform Resource Locator) is an address of the internet that identifies the location of a resource on a particular web server. It is used to locate specific pages, images, and other resources on the World Wide Web.

Java URL Class

In Java, the URL class is used to represent a uniform resource locator. The URL class is part of the java.net package and is used to work with URLs in your Java applications.

Here are some key methods of the URL class:

public String getProtocol(): Returns the protocol name as a string. public String getHost(): Returns the hostname as a string. public int getPort(): Returns the port number. public String getPath(): Returns the path part of the URL as a string. public String getFile(): Returns the file name (everything after the last /) as a string. public String getQuery(): Returns the query string part of the URL as a string.

Creating a URL Object

To create a URL object, you need to pass the URL string to the URL(String url) constructor:

URL myUrl = new URL("http://www.example.com/myfile.html");

You can also use the URL(String protocol, String host, int port, String file) constructor to specify the protocol, hostname, port number, and file name separately.

Working with URLs

Here are some common tasks you may want to perform on a URL:

Getting the protocol: Use the getProtocol() method to get the protocol name.

String protocol = myUrl.getProtocol(); // returns "http"

Getting the hostname: Use the getHost() method to get the hostname.

String host = myUrl.getHost(); // returns "www.example.com"

Getting the port number: Use the getPort() method to get the port number.

int port = myUrl.getPort(); // returns 80 (default HTTP port)

Getting the path: Use the getPath() method to get the path part of the URL.

String path = myUrl.getPath(); // returns "/myfile.html"

Getting the file name: Use the getFile() method to get the file name.

String fileName = myUrl.getFile(); // returns "myfile.html"

Getting the query string: Use the getQuery() method to get the query string part of the URL.

String query = myUrl.getQuery(); // returns "?" (if there is no query string)

Resolving Relative URLs

The URL class also provides methods for resolving relative URLs. A relative URL is a URL that does not start with the protocol name, but is still relative to the current URL.

Here are some key methods for working with relative URLs:

public URL resolve(String relativeURL): Resolves a relative URL to an absolute URL.

URL resolvedUrl = myUrl.resolve("/mydir/subfile.html");

public boolean isAbsolute(): Checks if the URL is absolute (starts with a protocol name).

boolean isAbsolute = myUrl.isAbsolute(); // returns true

Conclusion

In this tutorial, we have covered the basics of working with URLs in Java using the URL class. We have seen how to create a URL object, get various parts of the URL, and work with relative URLs. With this knowledge, you should be able to perform common tasks involving URLs in your Java applications.

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