java.net.ProtocolException: Cannot write output after reading input.

最新推荐文章于 2024-06-21 13:20:51 发布

andy_house

最新推荐文章于 2024-06-21 13:20:51 发布

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分类专栏： web Javaweb 文章标签： URLConnection链接问题网络连接

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本文探讨了在Java中使用HTTP请求时，getResponseCode()方法的正确使用方式。详细解释了该方法调用时机不当可能导致的问题，如在发送请求前调用会阻止后续数据发送，以及如何避免此类错误。

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用接口工具测试接口可以成功,但是在代码中调用就是一直报链接不上的错误,

java.net.ProtocolException: Cannot write output after reading input.

但是把conn.getResponseCode();这一行代码去掉之后,就可以正常访问,或者把这一样代码放到

outs = new OutputStreamWriter(conn.getOutputStream());这个链接的后面,这样也行

原因是:

The HTTP protocol is based on a request-response pattern: you send your request first and the server responds. Once the server responded, you can't send any more content, it wouldn't make sense. (How could the server give you a response code before it knows what is it you're trying to send?)

So when you call server.getResponseCode(), you effectively tell the server that your request has finished and it can process it. If you want to send more data, you have to start a new request.

Looking at your code you want to check whether the connection itself was successful, but there's no need for that: if the connection isn't successful, an Exception is thrown by server.connect(). But the outcome of a connection attempt isn't the same as the HTTP response code, which always comes after the server processed all your input

意思是说提前调用 getResponseCode()方法，表示该请求已经结束了，若要再写入数据，需要发起一个新的请求

注释:这一段英文摘自https://blog.youkuaiyun.com/bidewang_wolf/article/details/77164622,