java发http请求

下面介绍两种方式 
1.使用jdk提供的URLConnection 
2.使用apache提供的HttpClient（封装了jdk）

一、使用URLConnect进行http请求

  1 public class HttpUtil {
  2 
  3     /**
  4      * 向指定URL发送GET方法的请求
  5      *
  6      * @param url
  7      *            发送请求的URL
  8      * @param param
  9      *            请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
 10      * @return URL 所代表远程资源的响应结果
 11      */
 12     public static String sendGet(String url, String param) {
 13         String result = "";
 14         BufferedReader in = null;
 15         try {
 16             String urlNameString = url + "?" + param;
 17             URL realUrl = new URL(urlNameString);
 18             // 打开和URL之间的连接
 19             URLConnection connection = realUrl.openConnection();
 20             // 设置通用的请求属性
 21             connection.setRequestProperty("accept", "*/*");
 22             connection.setRequestProperty("connection", "Keep-Alive");
 23             connection.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
 24             // 建立实际的连接
 25             connection.connect();
 26             // 获取所有响应头字段
 27             Map<String, List<String>> map = connection.getHeaderFields();
 28             // 遍历所有的响应头字段
 29             for (String key : map.keySet()) {
 30                 System.out.println(key + "--->" + map.get(key));
 31             }
 32             // 定义 BufferedReader输入流来读取URL的响应
 33             in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
 34             String line;
 35             while ((line = in.readLine()) != null) {
 36                 result += line;
 37             }
 38         } catch (Exception e) {
 39             System.out.println("发送GET请求出现异常！" + e);
 40             e.printStackTrace();
 41         }
 42         // 使用finally块来关闭输入流
 43         finally {
 44             try {
 45                 if (in != null) {
 46                     in.close();
 47                 }
 48             } catch (Exception e2) {
 49                 e2.printStackTrace();
 50             }
 51         }
 52         return result;
 53     }
 54 
 55     /**
 56      * 向指定 URL 发送POST方法的请求
 57      *
 58      * @param url
 59      *            发送请求的 URL
 60      * @param param
 61      *            请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
 62      * @return 所代表远程资源的响应结果
 63      */
 64     public static String sendPost(String url, String param) {
 65         PrintWriter out = null;
 66         BufferedReader in = null;
 67         String result = "";
 68         try {
 69             URL realUrl = new URL(url);
 70             // 打开和URL之间的连接
 71             URLConnection conn = realUrl.openConnection();
 72             // 设置通用的请求属性
 73             conn.setRequestProperty("accept", "*/*");
 74             conn.setRequestProperty("connection", "Keep-Alive");
 75             conn.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
 76             // 发送POST请求必须设置如下两行
 77             conn.setDoOutput(true);
 78             conn.setDoInput(true);
 79             // 获取URLConnection对象对应的输出流
 80             out = new PrintWriter(conn.getOutputStream());
 81             // 发送请求参数
 82             out.print(param);
 83             // flush输出流的缓冲
 84             out.flush();
 85             // 定义BufferedReader输入流来读取URL的响应
 86             in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
 87             String line;
 88             while ((line = in.readLine()) != null) {
 89                 result += line;
 90             }
 91         } catch (Exception e) {
 92             System.out.println("发送 POST 请求出现异常！" + e);
 93             e.printStackTrace();
 94         }
 95         // 使用finally块来关闭输出流、输入流
 96         finally {
 97             try {
 98                 if (out != null) {
 99                     out.close();
100                 }
101                 if (in != null) {
102                     in.close();
103                 }
104             } catch (IOException ex) {
105                 ex.printStackTrace();
106             }
107         }
108         return result;
109     }
110 
111     public static void main(String[] args) {
112         // 发送 GET 请求
113         String result = HttpUtil.sendGet("http://baidu.com", "key=123&v=456");
114         System.out.println("result: " + result);
115         System.out.println("-----------------------------------------------------");
116         // 发送 POST 请求
117         String sr = HttpUtil.sendPost("http://baidu.com", "key=123&v=456");
118         System.out.println("sr: " + sr);
119     }
120 }

二、使用HttpClient进行http请求

maven依赖：

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.3</version>
</dependency>

代码：

public class HttpClientUtil {
    public static void get() {
        /**
         * client和response需要关闭资源
         */
        // 创建client,放入try()中自动释放,不需要finally
        try (CloseableHttpClient client = HttpClientBuilder.create().build()) {

            // 执行得到response
            try (CloseableHttpResponse response = client.execute(new HttpGet("http://www.baidu.com"))) {
                // 获取statusCode
                Integer statusCode = response.getStatusLine().getStatusCode();
                HttpEntity entity = response.getEntity();
                if (entity != null) {
                    // body
                    String bodyAsString = EntityUtils.toString(entity);
                    // Media Type
                    String contentMimeType = ContentType.getOrDefault(entity).getMimeType();
                    // head
                    Header[] headers = response.getHeaders(HttpHeaders.CONTENT_TYPE);
                    // 输出
                    System.out.println("statusCode:" + statusCode);
                    System.out.println("contentMinmeType:" + contentMimeType);
                    System.out.println("body:" + bodyAsString);
                    System.out.println("head" + headers);
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void post() {
        // 创建client
        try (CloseableHttpClient client = HttpClientBuilder.create().build()) {
            HttpPost postRequest = new HttpPost("http://www.baidu.com");
            // 添加请求参数
            List<NameValuePair> params = new ArrayList<>();
            params.add(new BasicNameValuePair("key1", "value1"));
            params.add(new BasicNameValuePair("key2", "value2"));
            postRequest.setEntity(new UrlEncodedFormEntity(params, Consts.UTF_8));
            // 执行并获取返回结果到response
            try (CloseableHttpResponse response = client.execute(postRequest)) {
                // 获取statusCode
                Integer statusCode = response.getStatusLine().getStatusCode();
                // Media Type
                String contentMimeType = ContentType.getOrDefault(response.getEntity()).getMimeType();
                // body
                String bodyAsString = EntityUtils.toString(response.getEntity());
                // head
                Header[] headers = response.getHeaders(HttpHeaders.CONTENT_TYPE);
                System.out.println("statusCode:" + statusCode);
                System.out.println("contentMinmeType:" + contentMimeType);
                System.out.println("body:" + bodyAsString);
                System.out.println("head" + headers);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        get();
        System.out.println("------------------------------------");
        post();
    }
}

转载：

https://blog.csdn.net/ludonglue/article/details/78038643

posted on 2018-07-21 23:27  ajax取个名字真难  阅读(1372)  评论(0)  编辑  收藏  举报

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