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环境准备

引入maven依赖

  <!-- HttpClient -->    <dependency>      <groupId>org.apache.httpcomponents</groupId>      <artifactId>httpclient</artifactId>      <version>4.5.3</version>    </dependency>    <!-- 日志 -->    <dependency>      <groupId>org.slf4j</groupId>      <artifactId>slf4j-log4j12</artifactId>      <version>1.7.25</version>    </dependency>

加入日志配置文件

log4j.rootLogger=DEBUG,A1log4j.logger.cn.itcast = DEBUGlog4j.appender.A1=org.apache.log4j.ConsoleAppenderlog4j.appender.A1.layout=org.apache.log4j.PatternLayoutlog4j.appender.A1.layout.ConversionPattern=%-d{yyyy-MM-dd HH:mm:ss,SSS} [%t] [%c]-[%p] %m%n

http Get请求

代码如下：

public static void getTest()throws Exception{    CloseableHttpClient httpClient = HttpClients.createDefault();    HttpGet httpGet = new HttpGet("http://www.itcast.cn?pava=zhangxm");    CloseableHttpResponse response = httpClient.execute(httpGet);    if (response.getStatusLine().getStatusCode() == 200) {        String content = EntityUtils.toString(response.getEntity(), "UTF-8");        System.out.println(content);    }}

http POST请求

/**     * java 代码发送post请求并传递参数     * @throws Exception     */    public static void postTest () throws Exception{        //创建HttpClient对象        CloseableHttpClient httpClient = HttpClients.createDefault();        RequestConfig requestConfig = RequestConfig.custom()                .setConnectTimeout(1000)//设置创建连接的最长时间                .setConnectionRequestTimeout(500)//设置获取连接的最长时间                .setSocketTimeout(10 * 1000)//设置数据传输的最长时间                .build();        //创建HttpGet请求        HttpPost httpPost = new HttpPost("http://www.itcast.cn/");        httpPost.setConfig(requestConfig);        CloseableHttpResponse response = null;        try {            //声明存放参数的List集合            List<NameValuePair> params = new ArrayList<NameValuePair>();            params.add(new BasicNameValuePair("pava", "zhangxm"));            //创建表单数据Entity            UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(params, "UTF-8");            //设置表单Entity到httpPost请求对象中            httpPost.setEntity(formEntity);            //使用HttpClient发起请求            response = httpClient.execute(httpPost);            //判断响应状态码是否为200            if (response.getStatusLine().getStatusCode() == 200) {                //如果为200表示请求成功，获取返回数据                String content = EntityUtils.toString(response.getEntity(), "UTF-8");                //打印数据长度                System.out.println(content);            }        } catch (Exception e) {            e.printStackTrace();        } finally {            //释放连接            if (response == null) {                try {                    response.close();                } catch (IOException e) {                    e.printStackTrace();                }                httpClient.close();            }        }    }

httpClient 连接池

如果每次请求都要创建HttpClient，会有频繁创建和销毁的问题，可以使用连接池来解决这个问题。

/**

• 使用 httpClient 连接池 不用每次都新建销毁 client
• @throws IOException
  */
  public static void connPoolTest() throws IOException {
  PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
  //设置最大连接数
  cm.setMaxTotal(200);
  //设置每个主机的并发数
  cm.setDefaultMaxPerRoute(20);
  for(int i=0;i<10;i++){
  CloseableHttpClient httpClient = HttpClients.custom().setConnectionManager(cm).build();
  System.out.println(“httpClient:”+httpClient);
  httpClient.close();
  }
  }

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