The URISyntaxException is an exception that occurs when constructing, parsing, or manipulating URIs with incorrect syntax. In this article, we will discuss some best practices for dealing with URISyntaxException in Java.

This exception is usually thrown during the creation of a new URI using the URI class or when parsing and manipulating existing URIs that are not properly formatted according to RFC standards.

How to deal with URISyntaxException?

Constructing valid URI

When creating URIs, please make sure that components (scheme, authority, path, query, etc.) are properly formatted. You can use the URI class’s constructors to create URIs, which perform syntax validation before object creation.

try {
    URI uri = new URI("http://example.com");
    // Use the valid URI
} catch (URISyntaxException e) {
    // Handle the exception
}

Validate the user input

If you are receiving the URI as an input from the user, validate and sanitize the input to ensure it adheres to proper URI syntax before constructing or parsing. There are several libraries or regular expressions available for URI validations.

String userInput = getUserInput();
if (isValidUri(userInput)) {
    try {
        URI uri = new URI(userInput);
        // Use the valid URI
    } catch (URISyntaxException e) {
        // Handle the exception
    }
} else {
    // Handle invalid input
}

Handling exception

It is a best practice to handle the URISyntaxException when you are processing the URI’s. You can show meaningful feedback to the users or log detailed error information for debugging.

try {
    URI uri = new URI("invalid uri");
    // Use the valid URI
} catch (URISyntaxException e) {
    System.err.println("Invalid URI syntax: " + e.getInput());
    e.printStackTrace();
    // Handle the exception gracefully
}

Fallback Mechanisms

You should have a fallback mechanism in place to handle when things go wrong. This can prevent application crashes and ensure continued functionality.

try {
    URI uri = new URI("invalid uri");
    // Use the valid URI
} catch (URISyntaxException e) {
    // Use fallback URI or perform alternative action
}

References:

https://docs.oracle.com/javase/8/docs/api/java/net/URI.html

https://tools.ietf.org/html/rfc3986

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