HttpClient异常：java.lang.IllegalArgumentException：host参数为null

Question

I have next code

    URL targetUrl = ...
    HttpClient client = new HttpClient(connectionManager);
    GetMethod getMethod = new GetMethod();
    getMethod.setPath(targetUrl.getPath());

    HostConfiguration hostConfiguration = getConfiguration(targetUrl) //unknown lib code

    client.executeMethod(hostConfiguration, getMethod);

In some cases(on some hosts) I get

java.lang.IllegalArgumentException: host parameter is null"

on client.executeMethod call.

Why may this happen?

Answer 1

The error message is misleading...

You must add the protocol in front of the host, something like HTTP:// or whatever you want to use. There may be other circumstances in which this happens, according to this blog article , but setHostConfiguration has been deprecated so this only applies to legacy code.

The client code should catch it earlier instead of failing so deep in the system, how can incorrect data go that far?

Answer 2

这是一个代理的书面例子http://svn.apache.org/viewvc/httpcomponents/oac.hc3x/trunk/src/examples/ProxyTunnelDemo.java?view=co在我的情况下问题是在hostConfiguration创建中

Answer 3

This error means that you are using incomplete url or without protocol. For example String url ="google.com" . Change it to String url="http://google.com" . It will work now