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java网络编程-HTTP编程_Stillsings的博客-CSDN博客HTTP编程Java HTTP编程支持模拟成浏览器的方式去访问网页URL, Uniform Resource Locator，代表一个资源URLConnection获取资源连接器根据URL的openConnection（）方法获得URLConnectionconnect方法，建立和资源的联系通道getInputStream方法，获取资源的内容示例代码：Get获取网页h...https://blog.csdn.net/Listen_heart/article/details/104448012

【1】HTTP编程

Java HTTP编程

支持模拟成浏览器的方式去访问网页
    URL, Uniform Resource Locator，代表一个资源
    URLConnection
        获取资源连接器
        根据URL的openConnection（）方法获得URLConnection
        connect方法，建立和资源的联系通道
        getInputStream方法，获取资源的内容

【2】URLConnection

示例代码1：Get获取网页html-使用URLConnection

package com.lihuan.network.demo03;import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.nio.charset.StandardCharsets;
import java.util.List;
import java.util.Map;public class URLConnectionGetTest {public static void main(String[] args) {try {String urlName = "http://www.baidu.com";URL url = new URL(urlName);URLConnection connection = url.openConnection();//建立联系通道connection.connect();//打印http的头部信息Map<String, List<String>> headers = connection.getHeaderFields();for (Map.Entry<String, List<String>> entry : headers.entrySet()){String key = entry.getKey();for (String value : entry.getValue()){System.out.println(key + ":" + value);}}//输出将要收到的内容属性信息System.out.println("-------------");System.out.println("getContentType: " + connection.getContentType());System.out.println("getContentLength: " + connection.getContentLength());System.out.println("getContentEncoding: " + connection.getContentEncoding());System.out.println("getDate: " + connection.getDate());System.out.println("getExpiration: " + connection.getExpiration());System.out.println("getLastModified:" + connection.getLastModified());System.out.println("-------------");BufferedReader br = new BufferedReader(new InputStreamReader(connection.getInputStream(), StandardCharsets.UTF_8));// 输出收到的内容String line = "";while ((line = br.readLine()) != null){System.out.println(line);}br.close();} catch (IOException e) {e.printStackTrace();}}
}

实例代码2： Post提交表单-使用 HttpURLConnection

package com.lihuan.network.demo03;import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.net.*;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;public class URLConnectionPostTest {public static void main(String[] args) throws IOException {String urlString = "https://tools.usps.com/zip-code-lookup.htm?byaddress";Object userAgent = "HTTPie/0.9.2";Object redirects = "1";CookieHandler.setDefault(new CookieManager(null, CookiePolicy.ACCEPT_ALL));Map<String, String> params = new HashMap<String, String>();params.put("tAddress", "1 Market Street");params.put("tCity", "san Francisco");params.put("sState", "CA");String result = doPost(new URL(urlString), params,userAgent == null ? null : userAgent.toString(),redirects == null ? -1 : Integer.parseInt(redirects.toString()));System.out.println(result);}public static String doPost(URL url, Map<String, String> nameValuePairs, String userAgent, int redirects) throws IOException {HttpURLConnection connection = (HttpURLConnection) url.openConnection();//设置请求头if(userAgent != null){connection.setRequestProperty("User-Agent", userAgent);}//设为不自动重定向if(redirects >= 0){connection.setInstanceFollowRedirects(false);}//设置可以使用conn.getOutputStream().printconnection.setDoOutput(true);//输出请求的参数try (PrintWriter out = new PrintWriter(connection.getOutputStream())){boolean first = true;for (Map.Entry<String, String> pair : nameValuePairs.entrySet()){//参数拼接if(first){first = false;}else{out.print('&');}String name = pair.getKey();String value = pair.getValue();out.print(name);out.print("=");out.print(URLEncoder.encode(value, "UTF-8"));}}String encoding = connection.getContentEncoding();if(encoding == null){encoding = "UTF-8";}if(redirects > 0){int responseCode = connection.getResponseCode();System.out.println("responseCode: " + responseCode);if(responseCode == HttpURLConnection.HTTP_MOVED_PERM|| responseCode == HttpURLConnection.HTTP_MOVED_TEMP|| responseCode == HttpURLConnection.HTTP_SEE_OTHER){String location = connection.getHeaderField("Location");if(location != null){URL base = connection.getURL();connection.disconnect();return doPost(new URL(base, location), nameValuePairs, userAgent, redirects - 1);}}}else if(redirects == 0){throw new IOException("Too many redirects");}//接下来获取html内容StringBuilder response = new StringBuilder();try (Scanner in = new Scanner(connection.getInputStream(), encoding)){while (in.hasNextLine()){response.append(in.nextLine());response.append("\n");}}catch (IOException e){InputStream err = connection.getErrorStream();if(err == null) throw e;try (Scanner in = new Scanner(err)){response.append(in.nextLine());response.append("\n");}}return response.toString();}
}

【3】JDK HttpClient

JDK 9新增，JDK10更新，JDK11正式发
    java.net.http包
    取代URLConnection
    支持HTTP/1.1和HTTP/2
    实现大部分HTTP方法
    主要类
        HttpClient
        HttpRequest
        HttpResponse

HttpComponents

是一个集成的Java HTTP工具包
    实现所有HTTP方法: get/post/put/delete
    支持自动转向
    支持https协议
    支持代理服务器等

HttpComponent示例代码3：Get获取网页html

package com.lihuan.network.demo04;import org.apache.http.HttpResponse;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;import java.io.IOException;public class HttpComponentGetTest {public static void main(String[] args) {CloseableHttpClient httpClient = HttpClients.createDefault();RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(5000).setConnectionRequestTimeout(5000).setSocketTimeout(5000).setRedirectsEnabled(true).build();HttpGet httpGet = new HttpGet("http://www.baidu.com");httpGet.setConfig(requestConfig);String strResult = "";try {HttpResponse httpResponse = httpClient.execute(httpGet);if(httpResponse.getStatusLine().getStatusCode() == 200){strResult = EntityUtils.toString(httpResponse.getEntity(), "UTF-8");System.out.println(strResult);}else{}} catch (IOException e) {e.printStackTrace();}finally {try {httpClient.close();} catch (IOException e) {e.printStackTrace();}}}
}

HttpComponent实例代码4：Post提交表单

package com.lihuan.network.demo04;import org.apache.http.HttpResponse;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.client.LaxRedirectStrategy;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.util.ArrayList;
import java.util.List;public class HttpComponentsPostTest {public static void main(String[] args) throws UnsupportedEncodingException {//获取可关闭的 httpClientCloseableHttpClient httpClient = HttpClientBuilder.create().setRedirectStrategy(new LaxRedirectStrategy()).build();//配置超时时间RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(10000).setConnectionRequestTimeout(10000).setSocketTimeout(10000).setRedirectsEnabled(false).build();HttpPost httpPost = new HttpPost("https://tools.usps.com/zip-code-lookup.htm?byaddress");//设置超时时间httpPost.setConfig(requestConfig);List<BasicNameValuePair> list = new ArrayList<>();list.add(new BasicNameValuePair("tAddress", URLEncoder.encode("1 Market Street", "UTF-8")));list.add(new BasicNameValuePair("tCity", URLEncoder.encode("san Francisco", "UTF-8")));list.add(new BasicNameValuePair("sState", "CA"));try {UrlEncodedFormEntity entity = new UrlEncodedFormEntity(list, "UTF-8");//设置post请求参数httpPost.setEntity(entity);httpPost.setHeader("User-Agent", "HTTPie/0.9.2");HttpResponse httpResponse = httpClient.execute(httpPost);String strResult = "";if(httpResponse != null){System.out.println(httpResponse.getStatusLine().getStatusCode());if(httpResponse.getStatusLine().getStatusCode() == 200){strResult = EntityUtils.toString(httpResponse.getEntity());}else{strResult = "Error Response：" + httpResponse.getStatusLine().toString();}}else{}System.out.println(strResult);} catch (IOException e) {e.printStackTrace();} finally {if(httpClient != null){try {httpClient.close();} catch (IOException e) {e.printStackTrace();}}}}
}

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