HttpClient基础

简介： HttpClient是Apache的一个子项目，可以提供高效的、功能丰富的支持HTTP协议的客户端编程工具包，并且它支持HTTP协议最新的版本和建议。
作用：

• 发送HTTP请求
• 接收响应数据

使用

导入maven坐标：

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.13</version>
</dependency>

核心API：

• HttpClient：使用它发送http请求；
• HttpClients：它相当于一个构建器，用它可以创建HttpClient对象；
• CloseableHttpClient：它是一个实现类，该实现类实现了HttpClient接口；
• HttpGet：代表http的Get请求方式；
• HttpPost：代表http的Post的请求方式；

发送请求的步骤：

• 创建HttpClient对象
• 创建Http请求对象（例如HttpGet，HttpPost等）
• 调用HttpClient的execute方法发送请求

测试

导入maven坐标，如果项目中已经导入aliyun-oss依赖，那么可以不用导入了，因为aliyun-oss依赖于httpcomponents，通过依赖传递，httpcomponents已经被导入到项目中了，如图所示：

显示导入：

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.13</version>
</dependency>

测试：
Get请求测试：

    /**
     * 测试 通过HttpCLient发送Get方式的请求
     */
    @Test
    public void TestGet() throws Exception{
        //创建HttpClient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();

        // 创建请求对象
        HttpGet httpGet = new HttpGet("http://localhost:8080/user/shop/status");

        //发送请求
        CloseableHttpResponse response = httpClient.execute(httpGet);

        //获取服务端返回的状态码
        int statusCode = response.getStatusLine().getStatusCode();
        System.out.println("服务端返回的状态码为："+statusCode);
		
		//解析返回结果
        HttpEntity entity = response.getEntity();
        String body = EntityUtils.toString(entity);
        System.out.println("服务端返回的数据为："+ body);

        // 关闭资源
        response.close();
        httpClient.close();
    }

输出：

服务端返回的状态码为：200
服务端返回的数据为：{"code":1,"msg":null,"data":1}

Post请求测试：

	/**
     * 测试 通过HttpCLient发送Post方式的请求
     */
    @Test
    public void TestPost() throws Exception{
        //创建HttpClient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();

        // 创建请求对象
        HttpPost httpPost = new HttpPost("http://localhost:8080/admin/employee/login");
        // 设置Post请求体
        //StringEntity entity = new StringEntity("{username:'',password:''}");
        JSONObject jsonObject = new JSONObject();
        jsonObject.put("username","aaa");
        jsonObject.put("password","bbb");
        StringEntity entity = new StringEntity(jsonObject.toString());
        // 指定请求编码方式
        entity.setContentEncoding("utf-8");
        // 设置数据格式
        entity.setContentType("application/json");
        httpPost.setEntity(entity);

        //发送请求
        CloseableHttpResponse response = httpClient.execute(httpPost);

        //获取服务端返回的状态码
        int statusCode = response.getStatusLine().getStatusCode();
        System.out.println("服务端返回的状态码为："+statusCode);

        //解析返回结果
        HttpEntity entity1 = response.getEntity();
        String body = EntityUtils.toString(entity1);
        System.out.println("服务端返回的数据为："+ body);

        // 关闭资源
        response.close();
        httpClient.close();
    }

输出：

服务端返回的状态码为：200
服务端返回的数据为：{"code":1,"msg":null,"data":{"id":1,"userName":"aaa","name":"管理员","token":"***************************************o"}}

应用举例

封装HttpClient工具类：

import com.alibaba.fastjson.JSONObject;
import org.apache.http.NameValuePair;
import org.apache.http.client.config.RequestConfig;
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.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;

import java.io.IOException;
import java.net.URI;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

/**
 * Http工具类
 */
public class HttpClientUtil {

    static final  int TIMEOUT_MSEC = 5 * 1000;

    /**
     * 发送GET方式请求
     * @param url
     * @param paramMap
     * @return
     */
    public static String doGet(String url,Map<String,String> paramMap){
        // 创建Httpclient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();

        String result = "";
        CloseableHttpResponse response = null;
		
		// 构造请求地址，并处理请求参数
        try{
            URIBuilder builder = new URIBuilder(url);
            if(paramMap != null){
                for (String key : paramMap.keySet()) {
                    builder.addParameter(key,paramMap.get(key));
                }
            }
            URI uri = builder.build();

            //创建GET请求
            HttpGet httpGet = new HttpGet(uri);

            //发送请求
            response = httpClient.execute(httpGet);

            //判断响应状态
            if(response.getStatusLine().getStatusCode() == 200){
                result = EntityUtils.toString(response.getEntity(),"UTF-8");
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            try {
                response.close();
                httpClient.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        return result;
    }

    /**
     * 发送POST方式请求
     * @param url
     * @param paramMap
     * @return
     * @throws IOException
     */
    public static String doPost(String url, Map<String, String> paramMap) throws IOException {
        // 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 (paramMap != null) {
                List<NameValuePair> paramList = new ArrayList();
                for (Map.Entry<String, String> param : paramMap.entrySet()) {
                    paramList.add(new BasicNameValuePair(param.getKey(), param.getValue()));
                }
                // 模拟表单
                UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList);
                httpPost.setEntity(entity);
            }

            httpPost.setConfig(builderRequestConfig());

            // 执行http请求
            response = httpClient.execute(httpPost);

            resultString = EntityUtils.toString(response.getEntity(), "UTF-8");
        } catch (Exception e) {
            throw e;
        } finally {
            try {
                response.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        return resultString;
    }

    /**
     * 发送POST方式请求
     * @param url
     * @param paramMap
     * @return
     * @throws IOException
     */
    public static String doPost4Json(String url, Map<String, String> paramMap) throws IOException {
        // 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);

            if (paramMap != null) {
                //构造json格式数据
                JSONObject jsonObject = new JSONObject();
                for (Map.Entry<String, String> param : paramMap.entrySet()) {
                    jsonObject.put(param.getKey(),param.getValue());
                }
                StringEntity entity = new StringEntity(jsonObject.toString(),"utf-8");
                //设置请求编码
                entity.setContentEncoding("utf-8");
                //设置数据类型
                entity.setContentType("application/json");
                httpPost.setEntity(entity);
            }

            httpPost.setConfig(builderRequestConfig());

            // 执行http请求
            response = httpClient.execute(httpPost);

            resultString = EntityUtils.toString(response.getEntity(), "UTF-8");
        } catch (Exception e) {
            throw e;
        } finally {
            try {
                response.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        return resultString;
    }
    private static RequestConfig builderRequestConfig() {
        return RequestConfig.custom()
                .setConnectTimeout(TIMEOUT_MSEC)
                .setConnectionRequestTimeout(TIMEOUT_MSEC)
                .setSocketTimeout(TIMEOUT_MSEC).build();
    }

}