HTTP Components簡介

時間 2019-12-08

標籤 http components 簡介欄目 HTTP/TCP 简体版

原文原文鏈接

基於版本4.5.xhtml

簡介

組件

HttpClient，核心組件
HC Fluent，提供了流式操做接口
HttpMime，提供文件上傳時用到的一些工具類
HttpClient Cache，有待學習
HttpClient OSGi，有待學習

特性

基於標準、純淨的Java語言。實現了Http1.0和Http1.1
以可擴展的面向對象的結構實現了Http所有的方法（GET, POST, PUT, DELETE, HEAD, OPTIONS, and TRACE）。
支持HTTPS（基於SSL的HTTP）協議。
經過HTTP代理創建透明的鏈接。
利用CONNECT方法經過HTTP代理創建隧道的HTTPS鏈接。
Basic, Digest, NTLMv1, NTLMv2, NTLM2 Session, SNPNEGO, Kerberos認證方案。
插件式的自定義認證方案。
便攜可靠的套接字工廠使它更容易的使用第三方解決方案(Pluggable secure socket factories, making it easier to use third party solutions)。
支持多線程應用的鏈接管理器。支持設置最大鏈接數，同時支持設置每一個主機的最大鏈接數，發現並關閉過時的鏈接。
自動處理Set-Cookie中的Cookie。（Automatic Cookie handling for reading Set-Cookie: headers from the server and sending them back out in a Cookie: header when appropriate.）
插件式的自定義Cookie策略。
Request的輸出流能夠避免流中內容直接緩衝到socket服務器。（Request output streams to avoid buffering any content body by streaming directly to the socket to the server.）
Response的輸入流能夠有效的從socket服務器直接讀取相應內容。
在http1.0和http1.1中利用KeepAlive保持持久鏈接。
直接獲取服務器發送的response code和 headers。
可設置鏈接超時。
支持http1.1 response caching。
源代碼基於Apache License 可免費獲取。

Quick Start

HTTP Client

GET請求、POST請求及 response處理apache

CloseableHttpClient httpclient = HttpClients.createDefault();

//GET請求及response處理
HttpGet httpGet = new HttpGet("http://targethost/homepage");
CloseableHttpResponse response1 = httpclient.execute(httpGet);
// The underlying HTTP connection is still held by the response object
// to allow the response content to be streamed directly from the network socket.
// In order to ensure correct deallocation of system resources
// the user MUST call CloseableHttpResponse#close() from a finally clause.
// Please note that if response content is not fully consumed the underlying
// connection cannot be safely re-used and will be shut down and discarded
// by the connection manager. 
try {
    System.out.println(response1.getStatusLine());
    HttpEntity entity1 = response1.getEntity();
    // do something useful with the response body
    // and ensure it is fully consumed
    EntityUtils.consume(entity1);
} finally {
    response1.close();
}

//POST請求及response處理
HttpPost httpPost = new HttpPost("http://targethost/login");
List <NameValuePair> nvps = new ArrayList <NameValuePair>();
nvps.add(new BasicNameValuePair("username", "vip"));
nvps.add(new BasicNameValuePair("password", "secret"));
httpPost.setEntity(new UrlEncodedFormEntity(nvps));
CloseableHttpResponse response2 = httpclient.execute(httpPost);

try {
    System.out.println(response2.getStatusLine());
    HttpEntity entity2 = response2.getEntity();
    // do something useful with the response body
    // and ensure it is fully consumed
    EntityUtils.consume(entity2);
} finally {
    response2.close();
}

官網的例子註釋中有幾點是須要注意的：服務器

調用httpclient.execute(XXX)後，http鏈接會一直被response持有，須要調用CloseableHttpResponse#close()，固然也但是已使用jdk1.7的try-catch-resource。
若是response沒有充分的被消耗掉（好比：chunk模式下，只取了部分），會被connection manager丟棄而不能複用，使用EntityUtils.consume(entity)能夠確保response被充分消耗

HC Fluent 的流式接口

Request.Get("http://targethost/homepage")
    .execute().returnContent();
Request.Post("http://targethost/login")
    .bodyForm(Form.form().add("username",  "vip").add("password",  "secret").build())
    .execute().returnContent();

HttpMime 提交文件

multipart/form 類型的POST，下面例子中的FileBody、StringBody、MultipartEntityBuilder等都是HttpMine模塊中的類。多線程

public class ClientMultipartFormPost {

    public static void main(String[] args) throws Exception {
        if (args.length != 1)  {
            System.out.println("File path not given");
            System.exit(1);
        }
        CloseableHttpClient httpclient = HttpClients.createDefault();
        try {
            HttpPost httppost = new HttpPost("http://localhost:8080" +
                    "/fileUpload");

            FileBody bin = new FileBody(new File(args[0]));
            StringBody comment = new StringBody("A binary file of some kind", ContentType.TEXT_PLAIN);

            HttpEntity reqEntity = MultipartEntityBuilder.create()
                    .addPart("bin", bin)
                    .addPart("comment", comment)
                    .build();


            httppost.setEntity(reqEntity);

            System.out.println("executing request " + httppost.getRequestLine());
            CloseableHttpResponse response = httpclient.execute(httppost);
            try {
                System.out.println("----------------------------------------");
                System.out.println(response.getStatusLine());
                HttpEntity resEntity = response.getEntity();
                if (resEntity != null) {
                    System.out.println("Response content length: " + resEntity.getContentLength());
                }
                EntityUtils.consume(resEntity);
            } finally {
                response.close();
            }
        } finally {
            httpclient.close();
        }
    }

}