How to solve Java network connection redirection failure exception (RedirectFailureException)

Title: How to solve Java network connection redirection failure exception (RedirectFailureException)

Introduction:
In Java network programming, the redirection function is often used , that is, the specified URL will automatically jump to other URLs. However, sometimes due to some special circumstances, we may encounter an exception in which network connection redirection fails, that is, RedirectFailureException. This article will introduce how to solve this exception and give sample code.

1. What is RedirectFailureException?
RedirectFailureException is one of the exceptions that Java network connection libraries (such as HttpURLConnection or HttpClient) will encounter when connecting to the network. It usually occurs under the following circumstances:

1. The redirected URL is illegal or inaccessible;
2. The number of redirections is too many and exceeds the preset maximum limit;
3. The redirection status code returned by the server is incorrect;
4. Connection timeout or network error.

2. Methods to solve RedirectFailureException:

1. Check the legality of the URL:
   When encountering a RedirectFailureException, first check whether the redirected URL is legal. . You can check the validity of a URL by using the isValid() method of the java.net.URL class. The sample code is as follows:

public static boolean isValidURL(String url) {
    try {
        new URL(url).toURI();
        return true;
    } catch (MalformedURLException | URISyntaxException e) {
        return false;
    }
}

2. Increase the limit on the number of redirects:
   Sometimes, the number of redirects on the server may exceed the preset maximum limit, resulting in an exception. You can increase the redirection limit by setting the setMaxRedirects() method of HttpURLConnection or HttpClient. The sample code is as follows:

HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setInstanceFoll
owRedirects(false);
connection.setMaxRedirects(10); // 设置重定向次数限制为10次

3. Handling the redirected URL:
   When redirecting, the server will return a "Location" header field, which contains the redirected URL. We can redirect the connection to a new URL by getting this field. The sample code is as follows:

HttpURLConnection connection = (HttpURLConnection) url.openConnection();
String redirectUrl = connection.getHeaderField("Location");
URL newUrl = new URL(redirectUrl);
HttpURLConnection newConnection = (HttpURLConnection) newUrl.openConnection();

4. Increase the network connection timeout setting:
   Sometimes the network connection timeout will cause an exception that the redirection fails. Timeout settings can be increased by setting the connection timeout and read timeout. The sample code is as follows:

HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setConnectTimeout(5000); // 连接超时设置为5秒
connection.setReadTimeout(5000); // 读取超时设置为5秒

3. Summary:
This article introduces how to solve the Java network connection redirection failure exception (RedirectFailureException). We can effectively solve this anomaly by checking the legitimacy of the URL, increasing the limit on the number of redirects, handling redirected URLs, and increasing the network connection timeout settings. I hope the content of this article will be helpful to readers when they encounter similar problems in Java network programming.

However, the above are just some common methods to solve RedirectFailureException exceptions. Specific solutions need to be adjusted and modified according to the actual situation. When encountering this exception, you should debug and troubleshoot based on the specific problem to find the root cause of the problem and take appropriate solutions.

References:
[1] Java SE 11 API Specification: https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/net /HttpURLConnection.html
[2] Java SE 11 API Specification: https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/net/URL.html

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