[网络协议]java发送http请求

背景

在java体系的应用中，需要调用一些外部的接口，http协议是一种常用的协议。基于springboot体系的工程与普通工程都是有这种需求的，基于这种背景，研究一下java发http请求是非常有必要的。基本就是四种套路：java原生（URLConnection系列），独立低封装度jar包（okhttp，httpclient等），spring自带（resttemplate），高封装度jar包（forest）。对这四种套路进行一波整理。

参考资料

https://www.jb51.net/article/206762.htm JAVA发送HTTP请求的四种方式总结（主要是原生+依赖）
https://zhuanlan.zhihu.com/p/364017444 httpclient
https://blog.csdn.net/itguangit/article/details/78825505 resttemplate
http://forest.dtflyx.com/ forest官网
https://okhttps.ejlchina.com/ okhttp

案例与解决方案

java原生

使用JDK原生提供的net，无需其他jar包。HttpURLConnection是URLConnection的子类，提供更多的方法，使用更方便。

 package httpURLConnection;

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

import java.net.HttpURLConnection;
import java.net.URL;

public class HttpURLConnectionHelper {

 public static String sendRequest(String urlParam,String requestType) {

  HttpURLConnection con = null; 

  BufferedReader buffer = null; 
  StringBuffer resultBuffer = null; 

  try {
   URL url = new URL(urlParam); 
   //得到连接对象
   con = (HttpURLConnection) url.openConnection(); 
   //设置请求类型
   con.setRequestMethod(requestType); 
   //设置请求需要返回的数据类型和字符集类型
   con.setRequestProperty("Content-Type", "application/json;charset=GBK"); 
   //允许写出
   con.setDoOutput(true);
   //允许读入
   con.setDoInput(true);
   //不使用缓存
   con.setUseCaches(false);
   //得到响应码
   int responseCode = con.getResponseCode();

   if(responseCode == HttpURLConnection.HTTP_OK){
    //得到响应流
    InputStream inputStream = con.getInputStream();
    //将响应流转换成字符串
    resultBuffer = new StringBuffer();
    String line;
    buffer = new BufferedReader(new InputStreamReader(inputStream, "GBK"));
    while ((line = buffer.readLine()) != null) {
     resultBuffer.append(line);
    }
    return resultBuffer.toString();
   }

  }catch(Exception e) {
   e.printStackTrace();
  }
  return "";
 }
 public static void main(String[] args) {

  String url ="http://int.dpool.sina.com.cn/iplookup/iplookup.php?ip=120.79.75.96";
  System.out.println(sendRequest(url,"POST"));
 }
}

使用JDK原生提供的net，无需其他jar包。建议使用HttpURLConnection。

 package uRLConnection;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;

public class URLConnectionHelper {

 public static String sendRequest(String urlParam) {

  URLConnection con = null; 

  BufferedReader buffer = null; 
  StringBuffer resultBuffer = null; 

  try {
    URL url = new URL(urlParam); 
    con = url.openConnection(); 

   //设置请求需要返回的数据类型和字符集类型
   con.setRequestProperty("Content-Type", "application/json;charset=GBK"); 
   //允许写出
   con.setDoOutput(true);
   //允许读入
   con.setDoInput(true);
   //不使用缓存
   con.setUseCaches(false);
   //得到响应流
   InputStream inputStream = con.getInputStream();
   //将响应流转换成字符串
   resultBuffer = new StringBuffer();
   String line;
   buffer = new BufferedReader(new InputStreamReader(inputStream, "GBK"));
   while ((line = buffer.readLine()) != null) {
    resultBuffer.append(line);
   }
   return resultBuffer.toString();

  }catch(Exception e) {
   e.printStackTrace();
  }

  return "";
 }
 public static void main(String[] args) {
  String url ="http://int.dpool.sina.com.cn/iplookup/iplookup.php?ip=120.79.75.96";
  System.out.println(sendRequest(url));
 }
}

使用JDK原生提供的net，无需其他jar包，使用起来有点麻烦。

 package socket;
import java.io.BufferedInputStream; 
import java.io.BufferedReader; 
import java.io.BufferedWriter; 
import java.io.IOException; 
import java.io.InputStreamReader; 
import java.io.OutputStreamWriter; 
import java.net.Socket; 
import java.net.URLEncoder; 

import javax.net.ssl.SSLSocket; 
import javax.net.ssl.SSLSocketFactory; 

public class SocketForHttpTest { 

 private int port; 
 private String host; 
 private Socket socket; 
 private BufferedReader bufferedReader; 
 private BufferedWriter bufferedWriter; 

 public SocketForHttpTest(String host,int port) throws Exception{ 

  this.host = host; 
  this.port = port; 

  /** 
   * http协议 
   */ 
  // socket = new Socket(this.host, this.port); 

  /** 
   * https协议 
   */ 
  socket = (SSLSocket)((SSLSocketFactory)SSLSocketFactory.getDefault()).createSocket(this.host, this.port); 


 } 

 public void sendGet() throws IOException{ 
  //String requestUrlPath = "/z69183787/article/details/17580325"; 
  String requestUrlPath = "/";   

  OutputStreamWriter streamWriter = new OutputStreamWriter(socket.getOutputStream()); 
  bufferedWriter = new BufferedWriter(streamWriter);    
  bufferedWriter.write("GET " + requestUrlPath + " HTTP/1.1\r\n"); 
  bufferedWriter.write("Host: " + this.host + "\r\n"); 
  bufferedWriter.write("\r\n"); 
  bufferedWriter.flush(); 

  BufferedInputStream streamReader = new BufferedInputStream(socket.getInputStream()); 
  bufferedReader = new BufferedReader(new InputStreamReader(streamReader, "utf-8")); 
  String line = null; 
  while((line = bufferedReader.readLine())!= null){ 
   System.out.println(line); 
  } 
  bufferedReader.close(); 
  bufferedWriter.close(); 
  socket.close(); 

 } 


 public void sendPost() throws IOException{ 
   String path = "/"; 
   String data = URLEncoder.encode("name", "utf-8") + "=" + URLEncoder.encode("张三", "utf-8") + "&" + 
      URLEncoder.encode("age", "utf-8") + "=" + URLEncoder.encode("32", "utf-8"); 
   // String data = "name=zhigang_jia"; 
   System.out.println(">>>>>>>>>>>>>>>>>>>>>"+data);    
   OutputStreamWriter streamWriter = new OutputStreamWriter(socket.getOutputStream(), "utf-8"); 
   bufferedWriter = new BufferedWriter(streamWriter);     
   bufferedWriter.write("POST " + path + " HTTP/1.1\r\n"); 
   bufferedWriter.write("Host: " + this.host + "\r\n"); 
   bufferedWriter.write("Content-Length: " + data.length() + "\r\n"); 
   bufferedWriter.write("Content-Type: application/x-www-form-urlencoded\r\n"); 
   bufferedWriter.write("\r\n"); 
   bufferedWriter.write(data); 

   bufferedWriter.write("\r\n"); 
   bufferedWriter.flush(); 

   BufferedInputStream streamReader = new BufferedInputStream(socket.getInputStream()); 
   bufferedReader = new BufferedReader(new InputStreamReader(streamReader, "utf-8")); 
   String line = null; 
   while((line = bufferedReader.readLine())!= null) 
   { 
    System.out.println(line); 
   } 
   bufferedReader.close(); 
   bufferedWriter.close(); 
   socket.close(); 
 } 

 public static void main(String[] args) throws Exception { 
  /** 
   * http协议测试 
   */ 
  //SocketForHttpTest forHttpTest = new SocketForHttpTest("www.baidu.com", 80); 
  /** 
   * https协议测试 
   */ 
  SocketForHttpTest forHttpTest = new SocketForHttpTest("www.baidu.com", 443); 
  try { 
   forHttpTest.sendGet(); 
  // forHttpTest.sendPost(); 
  } catch (IOException e) { 

   e.printStackTrace(); 
  } 
 } 

} 

独立jar包半原生

这部分主要针对的是httpclient，okhttp这种封装的还可以的jar包。

httpclient

导入依赖文件

<!-- https://mvnrepository.com/artifact/commons-httpclient/commons-httpclient -->
<dependency>
 <groupId>commons-httpclient</groupId>
 <artifactId>commons-httpclient</artifactId>
 <version>3.1</version>
</dependency>

使用jar的功能。

 package httpClient;

import java.io.IOException;

import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.HttpException;
import org.apache.commons.httpclient.methods.GetMethod;
import org.apache.commons.httpclient.methods.PostMethod;
import org.apache.commons.httpclient.params.HttpMethodParams;

public class HttpClientHelper {
 public static String sendPost(String urlParam) throws HttpException, IOException {
  // 创建httpClient实例对象
  HttpClient httpClient = new HttpClient();
  // 设置httpClient连接主机服务器超时时间：15000毫秒
  httpClient.getHttpConnectionManager().getParams().setConnectionTimeout(15000);
  // 创建post请求方法实例对象
  PostMethod postMethod = new PostMethod(urlParam);
  // 设置post请求超时时间
  postMethod.getParams().setParameter(HttpMethodParams.SO_TIMEOUT, 60000);
  postMethod.addRequestHeader("Content-Type", "application/json");

  httpClient.executeMethod(postMethod);

  String result = postMethod.getResponseBodyAsString();
  postMethod.releaseConnection();
  return result;
 }
 public static String sendGet(String urlParam) throws HttpException, IOException {
  // 创建httpClient实例对象
  HttpClient httpClient = new HttpClient();
  // 设置httpClient连接主机服务器超时时间：15000毫秒
  httpClient.getHttpConnectionManager().getParams().setConnectionTimeout(15000);
  // 创建GET请求方法实例对象
  GetMethod getMethod = new GetMethod(urlParam);
  // 设置post请求超时时间
  getMethod.getParams().setParameter(HttpMethodParams.SO_TIMEOUT, 60000);
  getMethod.addRequestHeader("Content-Type", "application/json");

  httpClient.executeMethod(getMethod);

  String result = getMethod.getResponseBodyAsString();
  getMethod.releaseConnection();
  return result;
 }
 public static void main(String[] args) throws HttpException, IOException {
  String url ="http://int.dpool.sina.com.cn/iplookup/iplookup.php?ip=120.79.75.96";
  System.out.println(sendPost(url));
  System.out.println(sendGet(url));
 }
}

okhttp

案例代码，直接看官网最好，使用过程十分优雅。

// 构建实例
HTTP http = HTTP.builder()
        .baseUrl("http://api.example.com")
        .addMsgConvertor(new GsonMsgConvertor());
        .build();

// 同步 HTTP
List<User> users = http.sync("/users") 
        .get()                          // GET请求
        .getBody()                      // 响应报文体
        .toList(User.class);            // 自动反序列化 List 

// 异步 HTTP
http.async("/users/1")
        .setOnResponse((HttpResult res) -> {
            // // 自动反序列化 Bean 
            User user = res.getBody().toBean(User.class);
        })
        .get();                         // GET请求

独立jar包高度封装

这里指的是forest，官网地址，只需要声明接口，就可以使用。具体的使用方式看官网，案例十分详细，项目中我是采用这种方式的。

public interface MyClient {

    @Request(url = "http://localhost:8080/hello")
    String helloForest();

}

spring体系自带RestTemplate

 //有参数的 getForObject 请求
    @RequestMapping("get2/{id}")
    public UserEntity getById(@PathVariable(name = "id") String id) {

        UserEntity userEntity = restTemplate.getForObject("http://localhost/get/{id}", UserEntity.class, id);

        return userEntity;
    }
  //有参数的 getForEntity 请求,参数列表
    @RequestMapping("getForEntity/{id}")
    public UserEntity getById2(@PathVariable(name = "id") String id) {

        ResponseEntity<UserEntity> responseEntity = restTemplate.getForEntity("http://localhost/get/{id}", UserEntity.class, id);
        UserEntity userEntity = responseEntity.getBody();
        return userEntity;
    }

这里只是举了两个例子，具体的学习，参看参考资料中的博客即可。