HttpClient

HttpClient 是Apache Jakarta Common 下的子项目，可以用来提供高效的、最新的、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。

1、需要的依赖

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.12</version>
</dependency>

2、测试类

package com.qianfeng;

import org.apache.http.Header;
import org.apache.http.HttpEntity;
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.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.message.BufferedHeader;
import org.apache.http.util.EntityUtils;
import org.junit.Test;

import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class HttpClientTest {
    @Test
    public void testGetString() throws IOException {
        //创建HttpClient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();
        //创建HttpGet
        HttpGet httpGet = new HttpGet("https://www.baidu.com");
        //请求配置
        RequestConfig config = RequestConfig.custom()
                .setConnectTimeout(5000)//建立连接的时间
                .setSocketTimeout(5000)//
                .setConnectionRequestTimeout(5000)
                .build();
        //设置配置
        httpGet.setConfig(config);
        //执行请求，返回响应
        CloseableHttpResponse response = httpClient.execute(httpGet);
        //判断响应状态码，如果时200继续操作
        if(response.getStatusLine().getStatusCode()==200){
            HttpEntity entity = response.getEntity();
            //获取响应头
            BufferedHeader header = (BufferedHeader) entity.getContentType();
            //header.getValue()获取的是contentType的类型，比如application/json
            if("application/json".equals(header.getValue())||"text/html".equals(header.getValue())){
                String s = EntityUtils.toString(entity, "UTF-8");
                System.out.println(s);
            }
            //如果是图片类型就存起来
            else if("image/jpeg".equals(header.getValue())){
                //EntityUtils这个工具类可以很方便的帮我们转换entity为字符串或者字节数组
                byte[] bytes = EntityUtils.toByteArray(entity);
                FileOutputStream fos = new FileOutputStream("test.jpg");
                fos.write(bytes);
                fos.close();
            }
        }
        //最后关闭response与httpClient
        response.close();
        httpClient.close();
    }

    @Test
    public void testGetByte() throws IOException {
        CloseableHttpClient httpClient = HttpClients.createDefault();
        HttpGet httpGet = new HttpGet("https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=3984473917,238095211&fm=26&gp=0.jpg");
        RequestConfig config = RequestConfig.custom()
                .setConnectTimeout(5000)
                .setSocketTimeout(5000)
                .setConnectionRequestTimeout(5000)
                .build();
        httpGet.setConfig(config);
        CloseableHttpResponse response = httpClient.execute(httpGet);
        if(response.getStatusLine().getStatusCode()==200){
            HttpEntity entity = response.getEntity();
            byte[] bytes = EntityUtils.toByteArray(entity);
            FileOutputStream fos = new FileOutputStream("test.jpg");
            fos.write(bytes);
            fos.close();
        }
        response.close();
        httpClient.close();
    }

    @Test
    public void testPostString() throws IOException {
        CloseableHttpClient httpClient = HttpClients.createDefault();
        HttpPost httpPost = new HttpPost("http://www.httpbin.org/post");
        RequestConfig config = RequestConfig.custom()
                .setConnectTimeout(5000)
                .setSocketTimeout(5000)
                .setConnectionRequestTimeout(5000)
                .build();
        httpPost.setConfig(config);
        httpPost.addHeader("User-Agent","Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36");
        List<NameValuePair> parameters = new ArrayList<NameValuePair>(0);
        parameters.add(new BasicNameValuePair("name","zhangsan"));
        parameters.add(new BasicNameValuePair("password","zhangsan123"));
        UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(parameters,"UTF-8");
        httpPost.setEntity(formEntity);
        CloseableHttpResponse response = httpClient.execute(httpPost);
        if(response.getStatusLine().getStatusCode()==200){
            HttpEntity entity = response.getEntity();
            String s = EntityUtils.toString(entity, "UTF-8");
            //byte[] bytes = EntityUtils.toByteArray(entity);
            System.out.println(s);
        }
        response.close();
        httpClient.close();
    }
}

这三个方法分别模拟了get方式请求普通网页，get方式请求图片、post方式添加参数请求的三种方式