java-HttpClient

1. apache HttpClient

用于替换jdk的httpclient,
官网文档 http://hc.apache.org/httpcomponents-client-4.5.x/tutorial/html/fundamentals.htm

2.基本套路

CloseableHttpClient httpclient = HttpClients.createDefault();
HttpGet httpget = new HttpGet("http://localhost/");
CloseableHttpResponse response = httpclient.execute(httpget);
try {
    <...>
} finally {
    response.close();
}

2.1 http请求

一个http请求对象，有HttpGet,HttpPost等，HttpGet接收一个uri作参数，可以用字符串比如 “http://localhost"， 注意加上http://， 也可以用URIBuilder来生成，如下:

URI uri = new URIBuilder()
        .setScheme("http")
        .setHost("www.google.com")
        .setPath("/search")
        .setParameter("q", "httpclient")
        .setParameter("btnG", "Google Search")
        .setParameter("aq", "f")
        .setParameter("oq", "")
        .build();
HttpGet httpget = new HttpGet(uri);
System.out.println(httpget.getURI());

如果想设置内容，可以用 httpPost.setEntity()方法，最简单的是用StringEntity声明一个，

String j1 = "xx"
StringEntity entity1 = new StringEntity(j1);
httpPost.setEntity(entity1);

也有setHeader这类实用的方法，

httpPost.setHeader("Content-Type","application/json-rpc");

2.2 http response回复

response一般是httpclient执行execute() HttpPost返回的对象。
可以用response.getStatusLine().toString()得到返回码。

2.3 http entity实体

一般用EntityUtils的toString(myEntity)将实体转换为字符串。

CloseableHttpClient httpclient = HttpClients.createDefault();
HttpGet httpget = new HttpGet("http://localhost/");
CloseableHttpResponse response = httpclient.execute(httpget);
try {
    HttpEntity entity = response.getEntity();
    if (entity != null) {
        long len = entity.getContentLength();
        if (len != -1 && len < 2048) {
            System.out.println(EntityUtils.toString(entity));
        } else {
            // Stream content out
        }
    }
} finally {
    response.close();
}

还能用低级的instream流来处理实体

CloseableHttpClient httpclient = HttpClients.createDefault();
HttpGet httpget = new HttpGet("http://localhost/");
CloseableHttpResponse response = httpclient.execute(httpget);
try {
    HttpEntity entity = response.getEntity();
    if (entity != null) {
        InputStream instream = entity.getContent();
        try {
            // do something useful
        } finally {
            instream.close();
        }
    }
} finally {
    response.close();
}

2.4 basic认证套路

CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
UsernamePasswordCredentials credentials =
new UsernamePasswordCredentials("admin","PASSWORD");
credentialsProvider.setCredentials(AuthScope.ANY, credentials);
CloseableHttpClient client = HttpClientBuilder.create()
                .setDefaultCredentialsProvider(credentialsProvider)
                .build();

创建CredentialsProvider对象，UsernamePasswordCredentials对象，然后用setCredentials方法将credentialsProvider设置。
之后使用HttpClientBuilder方法来构建一个添加过认证的client，之后的调用没有任何区别。