一个服务访问另外一个服务的技术有很多种，比如feign, dubbo, activemq, ajax+jsonp等，httpclient是其中之一。本文将阐述如何通过httpclient去访问另外一个服务的api。

1、前提约束

• 已经创建了一个springmvc的项目，作者使用的是springboot
  https://www.jianshu.com/p/de979f53ad80
• 已经创建了一个普通的maven项目
  https://www.jianshu.com/p/1ad292812ab1

2、操作

• 1 启动第一个springboot项目，修改第二个普通maven项目
• 2 在第二个项目加入httpclient依赖【以下均为在第二个项目中操作】

<dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
            <version>4.5.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient-cache</artifactId>
            <version>4.5</version>
        </dependency>
        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpmime</artifactId>
            <version>4.3.2</version>
        </dependency>

• 3 新建一个类Test.java，完成get请求

import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;

public class TestGetReq {
    public static void main(String[] args) throws Exception{
        //创建httpClient对象
        CloseableHttpClient httpClient= HttpClients.createDefault();
        //创建get请求句柄，这里的URL就是第一个项目中提供的api，请读者根据实际情况设置
        HttpGet httpGet=new HttpGet("http://localhost:8080/user/queryjson");
        //发起请求
        CloseableHttpResponse httpResponse=httpClient.execute(httpGet);
        //获得请求状态并打印
        System.out.println(httpResponse.getStatusLine().getStatusCode());
        //获取响应实体
        HttpEntity entity=httpResponse.getEntity();
        //绑定响应实体到输入流
        InputStream inputStream=entity.getContent();
        //将输入流转换为缓冲流
        BufferedReader bufferedReader=new BufferedReader(new InputStreamReader(inputStream));
        String line="";
        /**
         * 一行一行打印
         */
        while ((line=bufferedReader.readLine())!=null){
            System.out.println(line);
        }
        /**
         * 关闭资源，后申请的先关闭
         */
        bufferedReader.close();
        inputStream.close();
        httpClient.close();
    }
}

• 4 创建一个Test1.java，完成post请求

package net.wanho.zaixian.cms;

import org.apache.http.HttpEntity;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
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 java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

public class Test1 {
    public static void main(String[] args) throws Exception {
        CloseableHttpClient httpClient = HttpClients.createDefault();
        List params = new ArrayList();
        params.add(new BasicNameValuePair("id", "123"));
        params.add(new BasicNameValuePair("name", "ali"));
        HttpEntity httpEntity = new UrlEncodedFormEntity(params, "UTF-8");
        HttpPost httpPost = new HttpPost("http://localhost:8080/user/postjson");
        httpPost.setEntity(httpEntity);
        CloseableHttpResponse httpResponse = httpClient.execute(httpPost);
        //获取响应实体
        HttpEntity entity = httpResponse.getEntity();
        //绑定响应实体到输入流
        InputStream inputStream = entity.getContent();
        //将输入流转换为缓冲流
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
        String line = "";
        /**
         * 一行一行打印
         */
        while ((line = bufferedReader.readLine()) != null) {
            System.out.println(line);
        }
        /**
         * 关闭资源，后申请的先关闭
         */
        bufferedReader.close();
        inputStream.close();
        httpClient.close();
    }

}

至此，我们完成了通过httpclient去访问另外一个服务中get和post的api之测试。