HttpClient发送请求时动态替换目标ip

看HttpClient的源代码可以发现URI是个线索，在execute方法中会判断URI中设置的是否是绝对路径还是相对路径，如果是相对路径时httpclient会将defaulthost+uri拼接为完整的请求地址。如果URI中设置了scheme并且URI配置了host就会用URI完整的绝对路径作为请求地址。判断逻辑如下

public final HttPResponse execute(HttpUriRequest request,                                  HttpContext context)    throws IOException, ClientProtocolException {    if (request == null) {        throw new IllegalArgumentException            ("Request must not be null.");    }    return execute(determineTarget(request), request, context);}private static HttpHost determineTarget(HttpUriRequest request) throws ClientProtocolException {    // A null target may be acceptable if there is a default target.    // Otherwise, the null target is detected in the director.    HttpHost target = null;    URI requestURI = request.getURI();    if (requestURI.isAbsolute()) {        target = URIUtils.extractHost(requestURI);        if (target == null) {            throw new ClientProtocolException(                    "URI does not specify a valid host name: " + requestURI);        }    }    return target;}分析完就找到了方法解决问题了，在请求时设置URI即可，要注意的是build URI的时候要配置scheme参数才能生效。