httpclient的使用（java）

水深无声 2022-07-13 12:50 188阅读 0赞

httpclient主要用途，系统间的调用，一个系统使用http协议调用另一个系统的服务（web service），当然也可以做网页爬虫（爬虫推荐使用jsoup）

**0：添加maven依赖**

<dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
            <version>4.5.2</version>
        </dependency>

**1：使用httpclient执行get请求**

@Test
        public void doGet() throws Exception {
            //创建一个httpclient对象
            CloseableHttpClient httpClient = HttpClients.createDefault();
            //创建一个GET对象
            HttpGet get = new HttpGet("http://www.sogou.com");
            //执行请求
            CloseableHttpResponse response = httpClient.execute(get);
            //取响应的结果
            int statusCode = response.getStatusLine().getStatusCode();
            System.out.println(statusCode);
            HttpEntity entity = response.getEntity();
            String string = EntityUtils.toString(entity, "utf-8");
            System.out.println(string);
            //关闭httpclient
            response.close();
            httpClient.close();
        }

**2：执行get请求带参数**

@Test
        public void doGetWithParam() throws Exception{
            //创建一个httpclient对象
            CloseableHttpClient httpClient = HttpClients.createDefault();
            //创建一个uri对象
            URIBuilder uriBuilder = new URIBuilder("http://www.sogou.com/web");
            uriBuilder.addParameter("query", "花千骨");
            HttpGet get = new HttpGet(uriBuilder.build());
            //执行请求
            CloseableHttpResponse response = httpClient.execute(get);
            //取响应的结果
            int statusCode = response.getStatusLine().getStatusCode();
            System.out.println(statusCode);
            HttpEntity entity = response.getEntity();
            String string = EntityUtils.toString(entity, "utf-8");
            System.out.println(string);
            //关闭httpclient
            response.close();
            httpClient.close();
        }

**3：使用httpclient执行post请求**

@Test
        public void doPost() throws Exception {
            CloseableHttpClient httpClient = HttpClients.createDefault();
    
            //创建一个post对象
            HttpPost post = new HttpPost("http://localhost:8082/httpclient/post.html");
            //执行post请求
            CloseableHttpResponse response = httpClient.execute(post);
            String string = EntityUtils.toString(response.getEntity());
            System.out.println(string);
            response.close();
            httpClient.close();
    
        }

**4：带参数post请求**

@Test
        public void doPostWithParam() throws Exception{
            CloseableHttpClient httpClient = HttpClients.createDefault();
    
            //创建一个post对象
            HttpPost post = new HttpPost("http://localhost:8082/httpclient/post.html");
            //创建一个Entity。模拟一个表单
            List<NameValuePair> kvList = new ArrayList<>();
            kvList.add(new BasicNameValuePair("username", "zhangsan"));
            kvList.add(new BasicNameValuePair("password", "123"));
    
            //包装成一个Entity对象
            StringEntity entity = new UrlEncodedFormEntity(kvList, "utf-8");
            //设置请求的内容
            post.setEntity(entity);
    
            //执行post请求
            CloseableHttpResponse response = httpClient.execute(post);
            String string = EntityUtils.toString(response.getEntity());
            System.out.println(string);
            response.close();
            httpClient.close();
        }

**5：Httpclient封装成工具类**

package com.taotao.utils;
    
    import java.io.IOException;
    import java.net.URI;
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Map;
    
    import org.apache.http.NameValuePair;
    import org.apache.http.client.entity.UrlEncodedFormEntity;
    import org.apache.http.client.methods.CloseableHttpResponse;
    import org.apache.http.client.methods.HttpGet;
    import org.apache.http.client.methods.HttpPost;
    import org.apache.http.client.utils.URIBuilder;
    import org.apache.http.entity.ContentType;
    import org.apache.http.entity.StringEntity;
    import org.apache.http.impl.client.CloseableHttpClient;
    import org.apache.http.impl.client.HttpClients;
    import org.apache.http.message.BasicNameValuePair;
    import org.apache.http.util.EntityUtils;
    
    public class HttpClientUtil {
    
        public static String doGet(String url, Map<String, String> param) {
    
            // 创建Httpclient对象
            CloseableHttpClient httpclient = HttpClients.createDefault();
    
            String resultString = "";
            CloseableHttpResponse response = null;
            try {
                // 创建uri
                URIBuilder builder = new URIBuilder(url);
                if (param != null) {
                    for (String key : param.keySet()) {
                        builder.addParameter(key, param.get(key));
                    }
                }
                URI uri = builder.build();
    
                // 创建http GET请求
                HttpGet httpGet = new HttpGet(uri);
    
                // 执行请求
                response = httpclient.execute(httpGet);
                // 判断返回状态是否为200
                if (response.getStatusLine().getStatusCode() == 200) {
                    resultString = EntityUtils.toString(response.getEntity(), "UTF-8");
                }
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                try {
                    if (response != null) {
                        response.close();
                    }
                    httpclient.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return resultString;
        }
    
        public static String doGet(String url) {
            return doGet(url, null);
        }
    
        public static String doPost(String url, Map<String, String> param) {
            // 创建Httpclient对象
            CloseableHttpClient httpClient = HttpClients.createDefault();
            CloseableHttpResponse response = null;
            String resultString = "";
            try {
                // 创建Http Post请求
                HttpPost httpPost = new HttpPost(url);
                // 创建参数列表
                if (param != null) {
                    List<NameValuePair> paramList = new ArrayList<>();
                    for (String key : param.keySet()) {
                        paramList.add(new BasicNameValuePair(key, param.get(key)));
                    }
                    // 模拟表单
                    UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList);
                    httpPost.setEntity(entity);
                }
                // 执行http请求
                response = httpClient.execute(httpPost);
                resultString = EntityUtils.toString(response.getEntity(), "utf-8");
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                try {
                    response.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
    
            return resultString;
        }
    
        public static String doPost(String url) {
            return doPost(url, null);
        }
    
        public static String doPostJson(String url, String json) {
            // 创建Httpclient对象
            CloseableHttpClient httpClient = HttpClients.createDefault();
            CloseableHttpResponse response = null;
            String resultString = "";
            try {
                // 创建Http Post请求
                HttpPost httpPost = new HttpPost(url);
                // 创建请求内容
                StringEntity entity = new StringEntity(json, ContentType.APPLICATION_JSON);
                httpPost.setEntity(entity);
                // 执行http请求
                response = httpClient.execute(httpPost);
                resultString = EntityUtils.toString(response.getEntity(), "utf-8");
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                try {
                    response.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
    
            return resultString;
        }
    }