工具篇：apache-httpClient 和 jdk11-HttpClient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 socketFactoryRegistry =  RegistryBuilder.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

    org.apache.httpcomponents
    httpclient
    4.5.5


	org.apache.httpcomponents
	httpmime
	4.5.5

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 execute(HttpUriRequest request, ResponseHandler responseHandler)
 T execute(HttpHost target,HttpRequest request, ResponseHandler responseHandler)
 T execute(HttpHost target, HttpRequest request,
            ResponseHandler 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 params = new ArrayList();
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() // 获取 CookieHandler
public abstract Optional connectTimeout()
public abstract Redirect followRedirects()
public abstract Optional proxy()
public abstract SSLContext sslContext()
public abstract Optional 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
 HttpResponse send(HttpRequest request, HttpResponse.BodyHandler responseBodyHandler)
//相当于使用了多路复用I/O
 CompletableFuture> sendAsync(HttpRequest request, BodyHandler responseBodyHandler)
abstract  CompletableFuture> sendAsync(HttpRequest request, 
	BodyHandler responseBodyHandler, PushPromiseHandler 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 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 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)