如何（如果有的话）从java.io.IOException in java
获取 HTTP 状态代码？
【问题讨论】：
IOException 子类吗？
标签： java http ioexception http-status-codes
我假设这是关于由 URLConnection 抛出的 IOException。
三种可能的处理方式，取决于您的限制。
1) 将您的 URLConnection 转换为 HttpURLConnection 并调用 getResponseCode
如果您有权访问连接对象，则可以使用此代码获取状态代码：
int statusCode = (HttpURLConnection)theConnection).getResponseCode();
2) 首先使用HttpURLConnection 而不是URLConnection
如果你能做到这一点，那将是最好的解决方案，因为URLConnection 不会引发错误状态代码。您可以直接调用getResponseCode 并检查状态，而不会先得到任何异常。
3) 解析异常消息本身
IOException 的消息通常如下所示：
Server returned HTTP response code: 403 for URL: http://something
所以您可以使用正则表达式（或简单的字符串操作）来获取响应代码。
请注意，对于状态 404，消息看起来不像这样，并且会抛出 FileNotFoundException。我不确定是否有任何其他状态代码会抛出这样的“特殊”异常，但请注意这一点。
演示方法 2 和 3 的示例代码：
import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.util.regex.Pattern;
import java.util.regex.Matcher;
public class HelloWorld {
public static void testUrl(String urlString) throws MalformedURLException {
URLConnection conn = null;
System.out.println("Testing URL " + urlString);
try {
URL url = new URL(urlString);
conn = url.openConnection();
// Just to make the exception happen
conn.getInputStream();
System.out.println("Success!");
} catch(IOException ex) {
System.out.println("Error!");
System.out.println();
// Method 2 with access to the URLConnection object
// (Method 1 would have been having the connection as HttpURLConnection from the beginning.)
int responseCode = 0;
System.out.println("Trying method 2 to get status code");
try {
if(conn != null) {
// Casting to HttpURLConnection allows calling getResponseCode
responseCode = ((HttpURLConnection)conn).getResponseCode();
} else {
System.out.println("conn variable not set");
}
} catch(IOException ex2) {
System.out.println("getResponseCode threw: " + ex2);
}
System.out.println("Status code from calling getResponseCode: " + responseCode);
System.out.println();
// Method 3 without access to the URLConnection object
responseCode = 0;
System.out.println("Trying method 3 to get status code");
// First we try parsing the exception message to see if it contains the response code
Matcher exMsgStatusCodeMatcher = Pattern.compile("^Server returned HTTP response code: (\\d+)").matcher(ex.getMessage());
if(exMsgStatusCodeMatcher.find()) {
responseCode = Integer.parseInt(exMsgStatusCodeMatcher.group(1));
} else if(ex.getClass().getSimpleName().equals("FileNotFoundException")) {
// 404 is a special case because it will throw a FileNotFoundException instead of having "404" in the message
System.out.println("Got a FileNotFoundException");
responseCode = 404;
} else {
// There can be other types of exceptions not handled here
System.out.println("Exception (" + ex.getClass().getSimpleName() + ") doesn't contain status code: " + ex);
}
System.out.println("Status code from parsing exception message: " + responseCode);
System.out.println();
}
System.out.println("-------");
System.out.println();
}
public static void main(String []args) throws MalformedURLException {
testUrl("https://httpbin.org/status/200");
testUrl("https://httpbin.org/status/404");
testUrl("https://httpbin.org/status/403");
testUrl("http://nonexistingsite1111111.com");
}
}
示例代码的输出：
Testing URL https://httpbin.org/status/200
Success!
-------
Testing URL https://httpbin.org/status/404
Error!
Trying method 2 to get status code
Status code from calling getResponseCode: 404
Trying method 3 to get status code
Got a FileNotFoundException
Status code from parsing exception message: 404
-------
Testing URL https://httpbin.org/status/403
Error!
Trying method 2 to get status code
Status code from calling getResponseCode: 403
Trying method 3 to get status code
Status code from parsing exception message: 403
-------
Testing URL http://nonexistingsite1111111.com
Error!
Trying method 2 to get status code
getResponseCode threw: java.net.UnknownHostException: nonexistingsite1111111.com
Status code from calling getResponseCode: 0
Trying method 3 to get status code
Exception (UnknownHostException) doesn't contain status code: java.net.UnknownHostException: nonexistingsite1111111.com
Status code from parsing exception message: 0
-------
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