HttpClient使用详解

作者: 上善若泪 | 来源:发表于2022-04-15 14:54 被阅读0次

1 HttpClient

1.1 简介

HttpClient是Apache Jakarta Common下的子项目，用来提供高效的、最新的、功能丰富的支持HTTP协议的客户端编程工具包，并且它支持HTTP协议最新的版本和建议。HttpClient已经应用在很多的项目中

HttpClient相比传统JDK自带的URLConnection，增加了易用性和灵活性（具体区别，日后我们再讨论），它不仅是客户端发送Http请求变得容易，而且也方便了开发人员测试接口（基于Http协议的），即提高了开发的效率，也方便提高代码的健壮性

1.2 HttpClient特性

HttpClient特性:

基于标准、纯净的java语言。实现了Http1.0和Http1.1
以可扩展的面向对象的结构实现了Http全部的方法(GET, POST, PUT, DELETE, HEAD, OPTIONS, and TRACE)
支持HTTPS协议
通过Http代理建立透明的连接
利用CONNECT方法通过Http代理建立隧道的`https连接
Basic, Digest, NTLMv1, NTLMv2, NTLM2 Session, SNPNEGO/Kerberos认证方案
插件式的自定义认证方案
便携可靠的套接字工厂使它更容易的使用第三方解决方案
连接管理器支持多线程应用。支持设置最大连接数，同时支持设置每个主机的最大连接数，发现并关闭过期的连接
自动处理Set-Cookie中的Cookie
插件式的自定义Cookie策略
Request的输出流可以避免流中内容直接缓冲到socket服务器
Response的输入流可以有效的从socket服务器直接读取相应内容
在http1.0和http1.1中利用KeepAlive保持持久连接
直接获取服务器发送的response code和 headers
设置连接超时的能力
实验性的支持`http1.1 response caching
源代码基于Apache License 可免费获取

1.3 使用方法

使用HttpClient发送请求、接收响应很简单，一般需要如下几步即可:

创建HttpClient对象
创建请求方法的实例，并指定请求URL。如果需要发送GET请求，创建HttpGet对象；如果需要发送POST请求，创建HttpPost对象。
如果需要发送请求参数，可调用HttpGet、HttpPost共同的setParams(HetpParams params)方法来添加请求参数；对于HttpPost对象而言，也可调用setEntity(HttpEntity entity)方法来设置请求参数，参数则必须用NameValuePair[]数组存储
调用HttpClient对象的execute(HttpUriRequest request)发送请求，该方法返回一个HttpResponse
调用HttpResponse的getAllHeaders()、getHeaders(String name)等方法可获取服务器的响应头；调用HttpResponse的getEntity()方法可获取HttpEntity对象，该对象包装了服务器的响应内容。程序可通过该对象获取服务器的响应内容
释放连接。无论执行方法是否成功，都必须释放连接

1.4 实例

1.4.1 HttpClient连接SSL

public class HttpClientTest {  
  
    @Test  
    public void jUnitTest() {  
        get();  
    }  
  
    /** 
     * HttpClient连接SSL 
     */  
    public void ssl() {  
        CloseableHttpClient httpclient = null;  
        try {  
            KeyStore trustStore = KeyStore.getInstance(KeyStore.getDefaultType());  
            FileInputStream instream = new FileInputStream(new File("d:\\tomcat.keystore"));  
            try {  
                // 加载keyStore d:\\tomcat.keystore    
                trustStore.load(instream, "123456".toCharArray());  
            } catch (CertificateException e) {  
                e.printStackTrace();  
            } finally {  
                try {  
                    instream.close();  
                } catch (Exception ignore) {  
                }  
            }  
            // 相信自己的CA和所有自签名的证书  
            SSLContext sslcontext = SSLContexts.custom().loadTrustMaterial(trustStore, new TrustSelfSignedStrategy()).build();  
            // 只允许使用TLSv1协议  
            SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(sslcontext, new String[] { "TLSv1" }, null,  
            SSLConnectionSocketFactory.BROWSER_COMPATIBLE_HOSTNAME_VERIFIER);  
            httpclient = HttpClients.custom().setSSLSocketFactory(sslsf).build();  
            // 创建http请求(get方式)  
            HttpGet httpget = new HttpGet("https://localhost:8080/xxx");  
            System.out.println("executing request" + httpget.getRequestLine());  
            CloseableHttpResponse response = httpclient.execute(httpget);  
            try {  
                HttpEntity entity = response.getEntity();  
                System.out.println("----------------------------------------");  
                System.out.println(response.getStatusLine());  
                if (entity != null) {  
                    System.out.println("Response content length: " + entity.getContentLength());  
                    System.out.println(EntityUtils.toString(entity));  
                    EntityUtils.consume(entity);  
                }  
            } finally {  
                response.close();  
            }  
        } catch (ParseException e) {  
            e.printStackTrace();  
        } catch (IOException e) {  
            e.printStackTrace();  
        } catch (KeyManagementException e) {  
            e.printStackTrace();  
        } catch (NoSuchAlgorithmException e) {  
            e.printStackTrace();  
        } catch (KeyStoreException e) {  
            e.printStackTrace();  
        } finally {  
            if (httpclient != null) {  
                try {  
                    httpclient.close();  
                } catch (IOException e) {  
                    e.printStackTrace();  
                }  
            }  
        }  
    }

1.4.2 POST提交

    /** 
     * post方式提交表单（模拟用户登录请求） 
     */  
    public void postForm() {  
        // 创建默认的httpClient实例.    
        CloseableHttpClient httpclient = HttpClients.createDefault();  
        // 创建httppost    
        HttpPost httppost = new HttpPost("http://localhost:8080/xxxxxx");  
        // 创建参数队列    
        List<NameValuePair> formparams = new ArrayList<NameValuePair>();  
        formparams.add(new BasicNameValuePair("username", "admin"));  
        formparams.add(new BasicNameValuePair("password", "123456"));  
        UrlEncodedFormEntity uefEntity;  
        try {  
            uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8");  
            httppost.setEntity(uefEntity);  
            System.out.println("executing request " + httppost.getURI());  
            CloseableHttpResponse response = httpclient.execute(httppost);  
            try {  
                HttpEntity entity = response.getEntity();  
                if (entity != null) {  
                    System.out.println("--------------------------------------");  
                    System.out.println("Response content: " + EntityUtils.toString(entity, "UTF-8"));  
                    System.out.println("--------------------------------------");  
                }  
            } finally {  
                response.close();  
            }  
        } catch (ClientProtocolException e) {  
            e.printStackTrace();  
        } catch (UnsupportedEncodingException e1) {  
            e1.printStackTrace();  
        } catch (IOException e) {  
            e.printStackTrace();  
        } finally {  
            // 关闭连接,释放资源    
            try {  
                httpclient.close();  
            } catch (IOException e) {  
                e.printStackTrace();  
            }  
        }  
    }

public String doPost()  
    {  
        String uriAPI = "http://XXXXXX";//Post方式没有参数在这里  
        String result = "";  
        HttpPost httpRequst = new HttpPost(uriAPI);//创建HttpPost对象  
          
        List <NameValuePair> params = new ArrayList<NameValuePair>();  
        params.add(new BasicNameValuePair("str", "I am Post String"));  
          
        try {  
            httpRequst.setEntity(new UrlEncodedFormEntity(params,HTTP.UTF_8));  
            HttpResponse httpResponse = new DefaultHttpClient().execute(httpRequst);  
            if(httpResponse.getStatusLine().getStatusCode() == 200)  
            {  
                HttpEntity httpEntity = httpResponse.getEntity();  
                result = EntityUtils.toString(httpEntity);//取出应答字符串  
            }  
        } catch (UnsupportedEncodingException e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
            result = e.getMessage().toString();  
        }  
        catch (ClientProtocolException e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
            result = e.getMessage().toString();  
        }  
        catch (IOException e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
            result = e.getMessage().toString();  
        }  
        return result;  
    }

以发送连接请求时，需要设置链接超时和请求超时等参数，否则会长期停止或者崩溃。

HttpParams httpParameters = new BasicHttpParams();  
HttpConnectionParams.setConnectionTimeout(httpParameters, 10*1000);//设置请求超时10秒  
HttpConnectionParams.setSoTimeout(httpParameters, 10*1000); //设置等待数据超时10秒  
HttpConnectionParams.setSocketBufferSize(params, 8192);  
HttpClient httpclient = new DefaultHttpClient(httpParameters); //此时构造DefaultHttpClient时将参数传入

1.4.3 GET请求

    /** 
     * 发送 get请求 
     */  
    public void get() {  
        CloseableHttpClient httpclient = HttpClients.createDefault();  
        try {  
            // 创建httpget.    
            HttpGet httpget = new HttpGet("http://www.xxxx.com/");  
            System.out.println("executing request " + httpget.getURI());  
            // 执行get请求.    
            CloseableHttpResponse response = httpclient.execute(httpget);  
            try {  
                // 获取响应实体    
                HttpEntity entity = response.getEntity();  
                System.out.println("--------------------------------------");  
                // 打印响应状态    
                System.out.println(response.getStatusLine());  
                if (entity != null) {  
                    // 打印响应内容长度    
                    System.out.println("Response content length: " + entity.getContentLength());  
                    // 打印响应内容    
                    System.out.println("Response content: " + EntityUtils.toString(entity));  
                }  
                System.out.println("------------------------------------");  
            } finally {  
                response.close();  
            }  
        } catch (ClientProtocolException e) {  
            e.printStackTrace();  
        } catch (ParseException e) {  
            e.printStackTrace();  
        } catch (IOException e) {  
            e.printStackTrace();  
        } finally {  
            // 关闭连接,释放资源    
            try {  
                httpclient.close();  
            } catch (IOException e) {  
                e.printStackTrace();  
            }  
        }  
    }

 public String doGet()  
    {  
        String uriAPI = "http://XXXXX?str=I+am+get+String";  
        String result= "";  
//      HttpGet httpRequst = new HttpGet(URI uri);  
//      HttpGet httpRequst = new HttpGet(String uri);  
//      创建HttpGet或HttpPost对象，将要请求的URL通过构造方法传入HttpGet或HttpPost对象。  
        HttpGet httpRequst = new HttpGet(uriAPI);  
  
//      new DefaultHttpClient().execute(HttpUriRequst requst);  
        try {  
   //使用DefaultHttpClient类的execute方法发送HTTP GET请求，并返回HttpResponse对象。  
            HttpResponse httpResponse = new DefaultHttpClient().execute(httpRequst);//其中HttpGet是HttpUriRequst的子类  
            if(httpResponse.getStatusLine().getStatusCode() == 200)  
            {  
                HttpEntity httpEntity = httpResponse.getEntity();  
                result = EntityUtils.toString(httpEntity);//取出应答字符串  
            // 一般来说都要删除多余的字符   
                result.replaceAll("\r", "");//去掉返回结果中的"\r"字符，否则会在结果字符串后面显示一个小方格    
            }  
                   else   
                        httpRequst.abort();  
           } catch (ClientProtocolException e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
            result = e.getMessage().toString();  
        } catch (IOException e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
            result = e.getMessage().toString();  
        }  
        return result;  
    }

1.4.4 上传文件

    /** 
     * 上传文件 
     */  
    public void upload() {  
        CloseableHttpClient httpclient = HttpClients.createDefault();  
        try {  
            HttpPost httppost = new HttpPost("http://localhost:8080/xxxx");  
  
            FileBody bin = new FileBody(new File("F:\\image\\sendpix0.jpg"));  
            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();  
            }  
        } catch (ClientProtocolException e) {  
            e.printStackTrace();  
        } catch (IOException e) {  
            e.printStackTrace();  
        } finally {  
            try {  
                httpclient.close();  
            } catch (IOException e) {  
                e.printStackTrace();  
            }  
        }  
    }  
}

HttpClient使用详解

1 HttpClient

1.1 简介

1.2 HttpClient特性

1.3 使用方法

1.4 实例

1.4.1 HttpClient连接SSL

1.4.2 POST提交

1.4.3 GET请求

1.4.4 上传文件

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