java - 非标准 HTTP 端口源的 URLConnection FileNotFoundException

Question

我尝试使用 Apache Ant Get task获取我们公司另一个团队生成的 WSDL 列表。他们将它们托管在 http://....com:7925/services/ 上的 weblogic 9.x 服务器上。 .我可以通过浏览器访问该页面，但是当尝试将页面复制到本地文件进行解析时，get 任务给了我一个 FileNotFoundException。我仍然能够(使用 ant 任务)获得一个没有用于 HTTP 的非标准端口 80 的 URL。

我查看了 Ant 源代码，并将错误缩小到 URLConnection。似乎 URLConnection 无法识别数据是 HTTP 流量，因为它不在标准端口上，即使协议(protocol)被指定为 HTTP。我使用 WireShark 嗅探了流量，页面通过网络正确加载，但仍然收到 FileNotFoundException。

这是一个您将看到错误的示例(更改了 URL 以保护无辜者)。 connection.getInputStream();

上抛出错误

import java.io.File;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;

    public class TestGet {
    private static URL source; 
    public static void main(String[] args) {
        doGet();
    }
    public static void doGet() {
            try {
            source = new URL("http", "test.com", 7925,
                    "/services/index.html");
            URLConnection connection = source.openConnection();
            connection.connect();
            InputStream is = connection.getInputStream();
        } catch (Exception e) {
            System.err.println(e.toString());
        }
    }

}

Answer 1

对我的 HTTP 请求的响应返回了状态代码 404，当我调用 getInputStream() 时，这导致了 FileNotFoundException。我仍然想阅读响应正文，所以我不得不使用不同的方法:HttpURLConnection#getErrorStream()。

这是 getErrorStream() 的 JavaDoc 片段:

Returns the error stream if the connection failed but the server sent useful data nonetheless. The typical example is when an HTTP server responds with a 404, which will cause a FileNotFoundException to be thrown in connect, but the server sent an HTML help page with suggestions as to what to do.

使用示例:

public static String httpGet(String url) {
    HttpURLConnection con = null;
    InputStream is = null;
    try {
        con = (HttpURLConnection) new URL(url).openConnection();
        con.connect();

        //4xx: client error, 5xx: server error. See: http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html.
        boolean isError = con.getResponseCode() >= 400;
        //In HTTP error cases, HttpURLConnection only gives you the input stream via #getErrorStream().
        is = isError ? con.getErrorStream() : con.getInputStream();

        String contentEncoding = con.getContentEncoding() != null ? con.getContentEncoding() : "UTF-8";
        return IOUtils.toString(is, contentEncoding); //Apache Commons IO
    } catch (Exception e) {
        throw new IllegalStateException(e);
    } finally {
        //Note: Closing the InputStream manually may be unnecessary, depending on the implementation of HttpURLConnection#disconnect(). Sun/Oracle's implementation does close it for you in said method.
        if (is != null) {
            try {
                is.close();
            } catch (IOException e) {
                throw new IllegalStateException(e);
            }
        }
        if (con != null) {
            con.disconnect();
        }
    }
}