如何从java.io.IOException in java
获取HTTP状态代码（如果有的话）？
答案 0 :(得分：4)
我假设这是IOException抛出的URLConnection。
根据您的限制处理此问题的三种可能性。
1）将URLConnection投向HttpURLConnection并致电getResponseCode
如果您有权访问连接对象，则可以使用以下代码获取状态代码：
int statusCode = (HttpURLConnection)theConnection).getResponseCode();
2）首先使用HttpURLConnection代替URLConnection
如果你能做到这一点，那将是最好的解决方案，因为URLConnection不会抛出错误状态代码。您只需拨打getResponseCode并检查状态，而不会先获得任何异常。
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
所以你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，并抛出FileNotFoundException。我不确定是否还有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＆amp; 3：
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 1 to get status code
Status code from calling getResponseCode: 404
Trying method 2 to get status code
Got a FileNotFoundException
Status code from parsing exception message: 404
-------
Testing URL https://httpbin.org/status/403
Error!
Trying method 1 to get status code
Status code from calling getResponseCode: 403
Trying method 2 to get status code
Status code from parsing exception message: 403
-------
Testing URL http://nonexistingsite1111111.com
Error!
Trying method 1 to get status code
getResponseCode threw: java.net.UnknownHostException: nonexistingsite1111111.com
Status code from calling getResponseCode: 0
Trying method 2 to get status code
Exception (UnknownHostException) doesn't contain status code: java.net.UnknownHostException: nonexistingsite1111111.com
Status code from parsing exception message: 0
-------