问题
I want to make some API calls to a server using HttpURLConnection. But the requests are not successful, returning:
<error>
<http_status>400 Bad Request</http_status>
<message>Unexpected request Content-Type header ''. Expecting 'application/x-www-form-urlencoded'.</message>
</error>
So I want to check what the "real" content is that is being sent to the server. By real content I mean the exact HTTP request.
Any ideas how I can see this?
Edit: Based on the first answers here I should clarify my problem: I want to avoid using an external program like HTTP sniffer or anything and I was hoping that there is a function or a property or whatever that holds the information I am looking for.
If that is not the case, does someone know if this information can be manually rebuilt (for example by calling several functions like getRequestMethod(), etc.)
I am facing this problem kinda often so that it's worth the effort to build such functionality myself. Just need to know how :)
回答1:
You can put the HttpURLConnection in debug mode by enabling java.logging with
-Djava.util.logging.config.file=logging.properties
and put in logging.properties (by default in JRE_HOME\lib) the following property
sun.net.www.protocol.http.HttpURLConnection.level = ALL
回答2:
tcpdump will work, but it can be hard to make it do what you want. NetCat is more user-friendly (here's the project page: http://netcat.sourceforge.net/ - most Unix platforms already include it).
nc -l 9999
This will listen on TCP port 9999, and when an HTTP client connects, it'll print out the full text of the request.
回答3:
Use something like tcpdump, which can dump the actual network packets that are emitted or received by your computer.
来源：https://stackoverflow.com/questions/3428341/java-display-request-of-an-httpurlconnection-before-sending