HttpClient

Get请求

@Test
public void testHttpGet() throws Exception {
    // 第一步：把HttpClient使用的jar包添加到工程中。
    // 第二步：创建一个HttpClient的测试类
    // 第三步：创建测试方法。
    // 第四步：创建一个HttpClient对象
    CloseableHttpClient httpClient = HttpClients.createDefault();
    // 第五步：创建一个HttpGet对象，需要指定一个请求的url
    HttpGet get = new HttpGet("http://www.baidu.com");
    // 第六步：执行请求。
    CloseableHttpResponse response = httpClient.execute(get);
    // 第七步：接收返回结果。HttpEntity对象。
    HttpEntity entity = response.getEntity();
    // 第八步：取响应的内容。
    String html = EntityUtils.toString(entity);
    System.out.println(html);
    // 第九步：关闭response、HttpClient。
    response.close();
    httpClient.close();
}

Post请求

@Test
public void testHttpPost() throws Exception {
    // 第一步：创建一个httpClient对象
    CloseableHttpClient httpClient = HttpClients.createDefault();
    // 第二步：创建一个HttpPost对象。需要指定一个url
    HttpPost post = new HttpPost("http://localhost:8080/posttest.do");
    // 第三步：创建一个list模拟表单，list中每个元素是一个NameValuePair对象
    List<NameValuePair> formList = new ArrayList<>();
    formList.add(new BasicNameValuePair("name", "张三"));
    formList.add(new BasicNameValuePair("pass", "1243"));
    // 第四步：需要把表单包装到Entity对象中。StringEntity
    StringEntity entity = new UrlEncodedFormEntity(formList, "utf-8");
    post.setEntity(entity);
    // 第五步：执行请求。
    CloseableHttpResponse response = httpClient.execute(post);
    // 第六步：接收返回结果
    HttpEntity httpEntity = response.getEntity();
    String result = EntityUtils.toString(httpEntity);
    System.out.println(result);
    // 第七步：关闭流。
    response.close();
    httpClient.close();
}

HttpClientUtil

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;
    }
}