2.8. HttpClient代理配置

即使HttpClient意识到路由方案和代理连接的复杂性，它也只支持简单直连或单跳代理连接的开箱即用。

通知HttpClient连接到目标主机，最简单的方法是通过设置默认参数的代理:

HttpHost proxy = new HttpHost("someproxy", 8080);
DefaultProxyRoutePlanner routePlanner = new DefaultProxyRoutePlanner(proxy);
CloseableHttpClient httpclient = HttpClients.custom()
        .setRoutePlanner(routePlanner)
        .build();

还可以指示HttpClient使用标准的JRE代理选择器来获取代理信息:

SystemDefaultRoutePlanner routePlanner = new SystemDefaultRoutePlanner(
        ProxySelector.getDefault());
CloseableHttpClient httpclient = HttpClients.custom()
        .setRoutePlanner(routePlanner)
        .build();

或者，可以利用customRoutePlanner接口的实现类来完全控制HTTP路由计算的过程：

HttpRoutePlanner routePlanner = new HttpRoutePlanner() {

    public HttpRoute determineRoute(
            HttpHost target,
            HttpRequest request,
            HttpContext context) throws HttpException {
        return new HttpRoute(target, null,  new HttpHost("someproxy", 8080),
                "https".equalsIgnoreCase(target.getSchemeName()));
    }

};
CloseableHttpClient httpclient = HttpClients.custom()
        .setRoutePlanner(routePlanner)
        .build();
    }
}