HTTPCLIENT总结
1、httpclient总结：
一、基本知识准备
(1)构建URI工具类，URIBuilder
(2)HttpResponse类，可以添加Header信息
获取所有Header信息的方法，调用HeaderIterator接口
HeaderIterator it = response.headerIterator("Set-Cookie");while (it.hasNext()) {
System.out.println(it.next());
}
(3)HttpEntity内容实体 可以被装入Request和Response中..
只有独立的entity才可以被重复调用.
当请求需要entity HttpEntity.writeTo(OutputStream)
从响应中解析entity HttpEntity.getContent()
HttpEntity.getContentType()
HttpEntity.getContentLength()
HttpEntity.getContentEncoding()
对entity进行解析可采用流的方式或者调用EntityUtils，但后者有长度的限制2048
利用 BufferedEntity可以将entity缓存到本地磁盘，用来进行多次读取.
创建entity信息时需要指定meta信息，包括contentType
(4)可以调用ResponseHandler写入响应统一处理
二、常用策略
keep-Alieve策略:自定义ConnectionKeepAliveStrategy
重定向策略:LaxRedirectStrategy
三、资源分配
当CloseableHttpClient不再需要，并且不再连接管理的范围，需要调用CloseableHttpClient.close()方法将其关闭..
四、HttpClient状态管理
1、在HTTP上下文中，很多有逻辑关系的请求都可以放入到同一个session中..
HttpClient本身线程HttpContext 包含任意的键值对，因此线程不安全..通常建议每个线程拥有自己的上下文
2、自动恢复机制---->HttpRequestRetryHandler
HttpRequestRetryHandler myRetryHandler = new HttpRequestRetryHandler() {public boolean retryRequest(IOException exception,int executionCount,HttpContext context) {if (executionCount >= 5) {// Do not retry if over max retry countreturn false;
}if (exception instanceof InterruptedIOException) {// Timeoutreturn false;
}if (exception instanceof UnknownHostException) {// Unknown hostreturn false;
}if (exception instanceof ConnectTimeoutException) {// Connection refusedreturn false;
}if (exception instanceof SSLException) {// SSL handshake exceptionreturn false;
}
HttpClientContext clientContext = HttpClientContext.adapt(context);
HttpRequest request = clientContext.getRequest();boolean idempotent = !(request instanceof HttpEntityEnclosingRequest);if (idempotent) {// Retry if the request is considered idempotentreturn true;
}return false;
}
};
CloseableHttpClient httpclient = HttpClients.custom()
.setRetryHandler(myRetryHandler)
.build();
4、多线程中的应用AtomicInteger，，，，待研究...
从连接管理器中获取连接
(1)通过HttpClientConnectionManager来管理一个连接
HttpClientContext context = HttpClientContext.create();
HttpClientConnectionManager connMrg = new BasicHttpClientConnectionManager();
HttpRoute route = new HttpRoute(new HttpHost("www.yeetrack.com", 80));// 获取新的连接. 这里可能耗费很多时间ConnectionRequest connRequest = connMrg.requestConnection(route, null);// 10秒超时HttpClientConnection conn = connRequest.get(10, TimeUnit.SECONDS);try {// 如果创建连接失败if (!conn.isOpen()) {// establish connection based on its route infoconnMrg.connect(conn, route, 1000, context);// and mark it as route completeconnMrg.routeComplete(conn, route, context);
}// 进行自己的操作.} finally {
connMrg.releaseConnection(conn, null, 1, TimeUnit.MINUTES);
}
通过更复杂的PoolingHttpClientConnectionManager来管理多个连接，适合多线程中的请求
PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();// 将最大连接数增加到200cm.setMaxTotal(200);// 将每个路由基础的连接增加到20cm.setDefaultMaxPerRoute(20);//将目标主机的最大连接数增加到50HttpHost localhost = new HttpHost("www.yeetrack.com", 80);
cm.setMaxPerRoute(new HttpRoute(localhost), 50);
CloseableHttpClient httpClient = HttpClients.custom()
.setConnectionManager(cm)
.build();
示例1---------------------------------PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
CloseableHttpClient httpClient = HttpClients.custom()
.setConnectionManager(cm)
.build();// URL列表数组String[] urisToGet = {"http://www.domain1.com/","http://www.domain2.com/","http://www.domain3.com/","http://www.domain4.com/"};// 为每个url创建一个线程，GetThread是自定义的类GetThread[] threads = new GetThread[urisToGet.length];for (int i = 0; i < threads.length; i++) {
HttpGet httpget = new HttpGet(urisToGet[i]);
threads[i] = new GetThread(httpClient, httpget);
}// 启动线程for (int j = 0; j < threads.length; j++) {
threads[j].start();
}// join the threadsfor (int j = 0; j < threads.length; j++) {
threads[j].join();
}
自定义类GetThreadstatic class GetThread extends Thread {private final CloseableHttpClient httpClient;private final HttpContext context;private final HttpGet httpget;public GetThread(CloseableHttpClient httpClient, HttpGet httpget) {this.httpClient = httpClient;this.context = HttpClientContext.create();this.httpget = httpget;
}
@Overridepublic void run() {try {
CloseableHttpResponse response = httpClient.execute(
httpget, context);try {
HttpEntity entity = response.getEntity();
} finally {
response.close();
}
} catch (ClientProtocolException ex) {// Handle protocol errors} catch (IOException ex) {// Handle I/O errors}
}
}
注意：即使httpclient可以被多线程访问，仍建议每个httpclient采用自己的context
5、 public static class IdleConnectionMonitorThread extends Thread {private final HttpClientConnectionManager connMgr;private volatile boolean shutdown;public IdleConnectionMonitorThread(HttpClientConnectionManager connMgr) {super();this.connMgr = connMgr;
}
@Overridepublic void run() {try {while (!shutdown) {synchronized (this) {
wait(5000);// 关闭失效的连接connMgr.closeExpiredConnections();// 可选的, 关闭30秒内不活动的连接connMgr.closeIdleConnections(30, TimeUnit.SECONDS);
}
}
} catch (InterruptedException ex) {// terminate}
}public void shutdown() {
shutdown = true;synchronized (this) {
notifyAll();
}
}
}