工具篇：apachehttpClient 和 jdk11HttpClient的使用

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HttpClient (apache)

apache HttpClient 是 java项目里 较为常用的组件之一；对接外部服务时，各个商家提供的接口是各式各样的，有自己的要求，因此要定制对应的请求客户端。httpClient是一个不错的选择

• apache HttpClient 实现了 HTTP 1.0 和 HTTP 1.1。支持 HTTP 全部的方法（GET, POST, PUT, DELETE, HEAD, OPTIONS, and TRACE）
  • GET, POST 的实现是继承 HttpRequestBase，HttpRequestBase 实现 HttpUriRequest，HttpUriRequest 继承 HttpRequest；GET, POST 方法对应 java 类的 HttpGet 和 HttpPost
• 支持 TLS，SSL 的 HTTPS。支持多线程操作
• 基于阻塞的 I/0 实现，也就是说使用 HttpClient 的线程会被阻塞
• 头部信息设置

HttpPost httpPost = new HttpPost("https://api.mch.weixin.qq.com/v3/pay/transactions/app");
httpPost.addHeader("Accept", "application/json");
httpPost.addHeader("Content-type","application/json; charset=utf-8");

• 证书信息设置

private static SSLContext getSslContext() throws Exception {
    //自身私钥
    KeyStore identityKeyStore = KeyStore.getInstance("jks");
    FileInputStream identityKeyStoreFile = new FileInputStream("/root/myServer.jks");
    identityKeyStore.load(identityKeyStoreFile, "password1".toCharArray());
    //服务端信任证书
    KeyStore trustKeyStore = KeyStore.getInstance("jks");
    FileInputStream trustKeyStoreFile = new FileInputStream("/root/trustKeyStore.jks");
    trustKeyStore.load(trustKeyStoreFile, "password".toCharArray());
    //构建SSLContexts
    return SSLContexts.custom()
            .loadKeyMaterial(identityKeyStore, "password1".toCharArray()) // load identity keystore
            .loadTrustMaterial(trustKeyStore, null) // load trust keystore
            .build();
}
public static void postWithSSL(String url, String jsonBody) throws Exception {
    SSLContext sslContext = getSslContext();
    SSLConnectionSocketFactory sslConnectionSocketFactory = new SSLConnectionSocketFactory(
            sslContext, new String[]{"TLSv1.2", "TLSv1.1", "TLSv1"}, null,
            SSLConnectionSocketFactory.getDefaultHostnameVerifier());
    CloseableHttpClient client = HttpClients.custom()
            .setSSLSocketFactory(sslConnectionSocketFactory)
            .build();
    /**
    // HttpClients 产生的 client 都共用相同的证书秘钥
    Registry<ConnectionSocketFactory> socketFactoryRegistry =  RegistryBuilder.<ConnectionSocketFactory>create()
                             .register("http", PlainConnectionSocketFactory.INSTANCE)
                             .register("https", new SSLConnectionSocketFactory(sslcontext))
                             .build(); 
    HttpClients.custom().setConnectionManager(connManager);
    */
    ....
}

• 缓存 cookie 设置

//自定义 cookie
CookieStore cookieStore = new BasicCookieStore();
BasicClientCookie cookie = new BasicClientCookie("csc", "lwl");
cookieStore.addCookie(cookie);
// 从上一次请求获取
HttpPost httppost = ...
DefaultHttpClient httpclient = new DefaultHttpClient();
HttpResponse response = httpclient.execute(httppost);
CookieStore cookiestore=httpclient.getCookieStore();
// DefaultHttpClient 使用 cookie
HttpPost httppost2 = ...
DefaultHttpClient httpclient2 = new DefaultHttpClient();
httpclient2.setCookieStore(cookiestore);
response = httpclient2.execute(httppost2);

• RequestConfig 的使用

RequestConfig defaultRequestConfig = RequestConfig.custom()
.setConnectTimeout(5000) 
.setSocketTimeout(5000)  
.setConnectionRequestTimeout(5000) 
.setRedirectsEnabled(true)
.build();
//使用
CloseableHttpClient httpclient = HttpClients.custom()
.setDefaultRequestConfig(defaultRequestConfig)
.build();

• HttpEntity 是对《请求或者响应》对象的封装，具体实现类有
  • BasicHttpEntity，InputStreamEntity：操作对象是数据流
  • BufferedHttpEntity：带缓冲区的 HttpEntity，其他HttpEntity的包装类，将内容存入一缓存区 可以重复读
  • FileEntity：文件对应的Entity FileEntity entity = new FileEntity(new File(""), "application/java-achive");
  • StringEntity：字符串 Entity。一般用 json ,text/plain,text/xml 类型的post请求
  • UrlEncodedFormEntity，一般用于 application/x-www-form-urlencoded 类型的post请求
• HttpContext：它是 Http 请求上下文类，如果是同一个上下文，则两次请求间可以共享这个上线文的信息。虽然 HttpClient 本身就具备维护cookies的功能，但 HttpContext 的好处是在于多个 HttpClient 实例之间可以共享 HttpContext

一些建议

• 1 释放资源：读取完响应后，我们需要尽快释放response本身和响应实体本身的流来对资源进行回收
• 2 有时可能需要多次读取返回的响应内容，将响应内容进行缓冲。最简单的方法是用BufferedHttpEntity 类包装原始实体。这会让原始实体的内容被读入内存缓冲区

CloseableHttpResponse response = ...
HttpEntity entity = new BufferedHttpEntity(response.getEntity());

• 3 HttpClient 的线程安全：使用同一个HttpClient的实例即可做到线程安全，因为 HttpClient 内部就有一个池化机制，支持多线程
• 4 EntityUtils.toString(entity) ： 把内容转成字符串

CloseableHttpClient 是 HttpClient 的子类。mvn 引入

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.5</version>
</dependency>
<dependency>
	<groupId>org.apache.httpcomponents</groupId>
	<artifactId>httpmime</artifactId>
	<version>4.5.5</version>
</dependency>

HttpClient 的API

HttpResponse execute(HttpUriRequest request)
HttpResponse execute(HttpUriRequest request, HttpContext context)
HttpResponse execute(HttpHost target, HttpRequest request)
HttpResponse execute(HttpHost target, HttpRequest request, HttpContext context)
<T> T execute(HttpUriRequest request, ResponseHandler<? extends T> responseHandler)
<T> T execute(HttpHost target,HttpRequest request, ResponseHandler<? extends T> responseHandler)
<T> T execute(HttpHost target, HttpRequest request,
            ResponseHandler<? extends T> responseHandler, HttpContext context)

get 请求

CloseableHttpClient httpclient = HttpClients.createDefault();
HttpGet httpGet = new HttpGet("http://localhost:8080/content/lwl");
CloseableHttpResponse  httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
System.out.println(EntityUtils.toString(httpEntity));// 输出请求结果
httpResponse.close();

post 请求

CloseableHttpClient httpclient = HttpClients.createDefault();
HttpPost httpPost = new HttpPost("https://www.baidu.com");
ArrayList<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("username", "csc"));
params.add(new BasicNameValuePair("password", "lwl"));
httpPost.setEntity(new UrlEncodedFormEntity(params));
CloseableHttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
System.out.println(EntityUtils.toString(httpEntity));// 输出请求结果
httpResponse.close();

文件上传

CloseableHttpClient httpClient = HttpClientBuilder.create().build();
HttpPost httpPost = new HttpPost("http://localhost:8080/lwl/upload");

MultipartEntityBuilder multipartEntityBuilder = MultipartEntityBuilder.create();
File file1 = new File("C:\\Users\\csc\\Desktop\\data.jpg"); // 第一个文件
multipartEntityBuilder.addBinaryBody("files", file1);
File file2 = new File("C:\\Users\\csc\\Desktop\\头像.jpg"); // 第二个文件
// 为避免中文乱码问题,可以对文件名 urlDecode
multipartEntityBuilder.addBinaryBody("files", file2, ContentType.DEFAULT_BINARY, URLEncoder.encode(file2.getName(), "utf-8"));

// 其它参数 
multipartEntityBuilder.addTextBody("name", "lwl", ContentType.create("text/plain", Charset.forName("UTF-8"))); 
   
HttpEntity httpEntity = multipartEntityBuilder.build();
httpPost.setEntity(httpEntity);
CloseableHttpResponse response = httpClient.execute(httpPost);
HttpEntity responseEntity = response.getEntity();
System.out.println(response.getStatusLine()); 
response.close();

HttpClient (jdk11)

java.net.http.HttpClient 是 jdk11 中正式启用的一个 http 工具类(在 jdk9 的时候就已经存在)，官方想要取代 HttpURLConnection 和 Apache HttpClient 等比较古老的开发工具

HttpClient 的API

//创建一个 HttpClient
public static Builder newBuilder()
public static HttpClient newHttpClient() //  HttpClient.newBuilder().build()
//webSocket协议的请求客户端的构建者
public WebSocket.Builder newWebSocketBuilder()
public abstract Optional<CookieHandler> cookieHandler() // 获取 CookieHandler
public abstract Optional<Duration> connectTimeout()
public abstract Redirect followRedirects()
public abstract Optional<ProxySelector> proxy()
public abstract SSLContext sslContext()
public abstract Optional<Executor> executor()

• HttpClient.Builder 的 API

//缓存cookie设置
public Builder cookieHandler(CookieHandler cookieHandler);
//连接超时时间
public Builder connectTimeout(Duration duration);
// 证书信息设置
public Builder sslContext(SSLContext sslContext);
// SSL / TLS / DTLS连接的参数 设置
public Builder sslParameters(SSLParameters sslParameters);
//涉及到异步操作用到的 线程池
public Builder executor(Executor executor);
// 是否支持重定向 Redirect.SAME_PROTOCOL
public Builder followRedirects(Redirect policy);
// 协议版本，HTTP/1.1 还是 HTTP/2
public Builder version(HttpClient.Version version);
public Builder priority(int priority);
//配置代理 
public Builder proxy(ProxySelector proxySelector);
//认证 Authenticator.getDefault()
public Builder authenticator(Authenticator authenticator);

• HttpClient 调用 API

//阻塞调用
<T> HttpResponse<T> send(HttpRequest request, HttpResponse.BodyHandler<T> responseBodyHandler)
//相当于使用了多路复用I/O
<T> CompletableFuture<HttpResponse<T>> sendAsync(HttpRequest request, BodyHandler<T> responseBodyHandler)
abstract <T> CompletableFuture<HttpResponse<T>> sendAsync(HttpRequest request, 
	BodyHandler<T> responseBodyHandler, PushPromiseHandler<T> pushPromiseHandler)

HttpRequest 构建的 API

对于请求内容可以使用 BodyPublishers 封装的函数生成

HttpResponse 的API

对于响应的解析读取可以使用 BodyHandlers 或者 BodySubscribers 封装的函数处理

get 请求

HttpRequest request = HttpRequest.newBuilder(URI.create("http://localhost:8080/content/lwl"))
        .GET()
        .timeout(Duration.ofSeconds(10)) // 设置响应超时时间
        .build();
HttpClient httpClient = HttpClient.newHttpClient();
HttpResponse<String> response = httpClient.send(request, HttpResponse.BodyHandlers.ofString());
System.out.println(response.body());

post 请求

String data = .....// json 请求数据
HttpRequest request = HttpRequest.newBuilder(URI.create("https://www.baidu.com"))
        .POST(HttpRequest.BodyPublishers.ofString(data, Charset.defaultCharset()))
        .header("Content-Type", "application/json") //设置头部信息
        .timeout(Duration.ofSeconds(10)) // 设置响应超时时间
        .build();
HttpClient httpClient = HttpClient.newHttpClient();
HttpResponse<String> response = httpClient.send(request, HttpResponse.BodyHandlers.ofString());
System.out.println(response.body());

欢迎指正文中错误

参考文章

• HttpClient用法--这一篇全了解
• HttpClient详细使用示例
• Java9之HttpClientAPI实战详解
• JDK 之 HttpClient(jdk11)