帮我写一份关于httpclient的讲课课件

好的，下面是一份httpclient讲课课件：

# HttpClient讲课课件

## 什么是HttpClient？

HttpClient是Apache基金会的一个开源项目，它是一个用于处理HTTP请求和响应的Java库。HttpClient可以被用于客户端的HTTP通信。

## HttpClient的特点

- 支持HTTP、HTTPS、FTP等协议
- 支持连接池管理
- 支持自定义连接重试策略
- 支持自定义身份验证
- 支持代理服务器
- 支持Cookie管理
- 支持请求缓存
- 支持请求队列管理
- 支持HTTP/2协议

## HttpClient的版本

HttpClient有两个版本：HttpClient 3.x和HttpClient 4.x。

HttpClient 3.x是较早的版本，不再维护和更新。

HttpClient 4.x是目前使用最广泛的版本，它是基于Java5的并发框架构建的，支持HTTP协议的所有请求方法，包括GET、POST、PUT、DELETE等。使用HttpClient 4.x可以更加方便地进行HTTP通信。

## HttpClient的使用

### Maven依赖

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.13</version>
</dependency>

### 创建HttpClient对象

CloseableHttpClient httpclient = HttpClients.createDefault();

### 创建HttpGet对象

HttpGet httpGet = new HttpGet("http://www.baidu.com");

### 发送HttpGet请求

CloseableHttpResponse response = httpclient.execute(httpGet);

### 解析响应

HttpEntity entity = response.getEntity();
String result = EntityUtils.toString(entity, "UTF-8");

### 关闭连接

response.close();
httpclient.close();

## HttpClient的进阶使用

### 自定义请求头

httpGet.addHeader("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.3");

### 发送HttpPost请求

HttpPost httpPost = new HttpPost(url);
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("username", "admin"));
params.add(new BasicNameValuePair("password", "123456"));
httpPost.setEntity(new UrlEncodedFormEntity(params));
CloseableHttpResponse response = httpclient.execute(httpPost);

### 使用连接池

PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
cm.setMaxTotal(200);
cm.setDefaultMaxPerRoute(20);
CloseableHttpClient httpclient = HttpClients.custom()
        .setConnectionManager(cm)
        .build();

### 自定义连接重试策略

HttpRequestRetryHandler myRetryHandler = new HttpRequestRetryHandler() {
    @Override
    public boolean retryRequest(IOException exception, int executionCount, HttpContext context) {
        if (executionCount >= 5) {
            // Do not retry if over max retry count
            return false;
        }
        if (exception instanceof NoHttpResponseException) {
            // Retry if the server dropped connection on us
            return true;
        }
        if (exception instanceof SSLHandshakeException) {
            // Do not retry on SSL handshake exception
            return false;
        }
        if (exception instanceof InterruptedIOException) {
            // Timeout
            return false;
        }
        if (exception instanceof UnknownHostException) {
            // Unknown host
            return false;
        }
        if (exception instanceof ConnectTimeoutException) {
            // Connection refused
            return false;
        }
        if (exception instanceof SSLException) {
            // SSL handshake exception
            return false;
        }

        HttpClientContext clientContext = HttpClientContext.adapt(context);
        HttpRequest request = clientContext.getRequest();
        // Retry if the request is considered idempotent
        return !(request instanceof HttpEntityEnclosingRequest);
    }
};
CloseableHttpClient httpclient = HttpClients.custom()
        .setRetryHandler(myRetryHandler)
        .build();

### 使用代理服务器

HttpHost proxy = new HttpHost("localhost", 8888, "http");
RequestConfig config = RequestConfig.custom()
        .setProxy(proxy)
        .build();
HttpPost httpPost = new HttpPost(url);
httpPost.setConfig(config);
CloseableHttpResponse response = httpclient.execute(httpPost);

### Cookie管理

CookieStore cookieStore = new BasicCookieStore();
CloseableHttpClient httpclient = HttpClients.custom()
        .setDefaultCookieStore(cookieStore)
        .build();

### 请求缓存

HttpCacheStorage cacheStorage = new BasicHttpCacheStorage();
CacheConfig cacheConfig = CacheConfig.custom()
        .setMaxCacheEntries(1000)
        .setMaxObjectSize(8192)
        .build();
HttpClientContext context = HttpClientContext.create();
context.setCacheConfig(cacheConfig);
context.setHttpCacheStorage(cacheStorage);
HttpGet httpGet = new HttpGet("http://www.baidu.com");
CloseableHttpResponse response = httpclient.execute(httpGet, context);

### 请求队列管理

ExecutorService executorService = Executors.newFixedThreadPool(10);
HttpProcessor processor = HttpProcessorBuilder.create()
        .add(new RequestContent())
        .add(new RequestTargetHost())
        .add(new RequestConnControl())
        .add(new RequestUserAgent("MyAgent-HTTP/1.1"))
        .add(new RequestExpectContinue(true))
        .build();
HttpAsyncRequestExecutor requestExec = new HttpAsyncRequestExecutor();
HttpAsyncRequestProducer producer1 = HttpAsyncMethods.create(
        new HttpGet("http://localhost/"));
HttpAsyncRequestProducer producer2 = HttpAsyncMethods.create(
        new HttpGet("http://localhost/"));
Future<HttpResponse> future1 = requestExec.execute(
        new BasicAsyncRequestProducer(
                HttpHost.create("localhost"),
                producer1),
        new BasicAsyncResponseConsumer(),
        executorService,
        context,
        new FutureCallback<HttpResponse>() {
            @Override
            public void completed(HttpResponse result) {
                System.out.println("Response: " + result.getStatusLine());
            }
            @Override
            public void failed(Exception ex) {
                System.out.println("Exception: " + ex.getMessage());
            }
            @Override
            public void cancelled() {
                System.out.println("Cancelled");
            }
        });
Future<HttpResponse> future2 = requestExec.execute(
        new BasicAsyncRequestProducer(
                HttpHost.create("localhost"),
                producer2),
        new BasicAsyncResponseConsumer(),
        executorService,
        context,
        new FutureCallback<HttpResponse>() {
            @Override
            public void completed(HttpResponse result) {
                System.out.println("Response: " + result.getStatusLine());
            }
            @Override
            public void failed(Exception ex) {
                System.out.println("Exception: " + ex.getMessage());
            }
            @Override
            public void cancelled() {
                System.out.println("Cancelled");
            }
        });