java利用java.net.URLConnection发送HTTP请求的方法详解

一、前言

如何通过java发送http请求，通俗点讲，如何通过java（模拟浏览器）发送http请求。

java有原生的api可用于发送http请求，即java.net.url、java.net.urlconnection，这些api很好用、很常用，但不够简便；

所以，也流行有许多java http请求的framework，如，apache的httpclient。

目前项目主要用到java原生的方式，所以，这里主要介绍此方式。

二、运用原生java api发送简单的get请求、post请求步骤

       1.通过统一资源定位器（java.net.url）获取连接器（java.net.urlconnection）

       2.设置请求的参数

       3.发送请求

       4.以输入流的形式获取返回内容

       5.关闭输入流

三、发送请求与接收响应流类 httprequestor

package me.http;

import java.io.bufferedreader;
import java.io.ioexception;
import java.io.inputstream;
import java.io.inputstreamreader;
import java.io.outputstream;
import java.io.outputstreamwriter;
import java.net.httpurlconnection;
import java.net.inetsocketaddress;
import java.net.proxy;
import java.net.url;
import java.net.urlconnection;
import java.util.iterator;
import java.util.map;

public class httprequestor {
 
 private string charset = "utf-8";
 private integer connecttimeout = null;
 private integer sockettimeout = null;
 private string proxyhost = null;
 private integer proxyport = null;
 
 /**
  * do get request
  * @param url
  * @return
  * @throws exception
  * @throws ioexception
  */
 public string doget(string url) throws exception {
  
  url localurl = new url(url);
  
  urlconnection connection = this.openconnection(localurl);
  httpurlconnection httpurlconnection = (httpurlconnection)connection;
  
  httpurlconnection.setrequestproperty("accept-charset", charset);
  httpurlconnection.setrequestproperty("content-type", "application/x-www-form-urlencoded");
  
  inputstream inputstream = null;
  inputstreamreader inputstreamreader = null;
  bufferedreader reader = null;
  stringbuffer resultbuffer = new stringbuffer();
  string templine = null;
  //响应失败
  if (httpurlconnection.getresponsecode() >= 300) {
   throw new exception("http request is not success, response code is " + httpurlconnection.getresponsecode());
  }
  
  try {
   inputstream = httpurlconnection.getinputstream();
   inputstreamreader = new inputstreamreader(inputstream);
   reader = new bufferedreader(inputstreamreader);
   
   while ((templine = reader.readline()) != null) {
    resultbuffer.append(templine);
   }
   
  } finally {
   
   if (reader != null) {
    reader.close();
   }
   
   if (inputstreamreader != null) {
    inputstreamreader.close();
   }
   
   if (inputstream != null) {
    inputstream.close();
   }
   
  }

  return resultbuffer.tostring();
 }
 
 /**
  * do post request
  * @param url
  * @param parametermap
  * @return
  * @throws exception 
  */
 public string dopost(string url, map parametermap) throws exception {
  
  /* translate parameter map to parameter date string */
  stringbuffer parameterbuffer = new stringbuffer();
  if (parametermap != null) {
   iterator iterator = parametermap.keyset().iterator();
   string key = null;
   string value = null;
   while (iterator.hasnext()) {
    key = (string)iterator.next();
    if (parametermap.get(key) != null) {
     value = (string)parametermap.get(key);
    } else {
     value = "";
    }
    
    parameterbuffer.append(key).append("=").append(value);
    if (iterator.hasnext()) {
     parameterbuffer.append("&");
    }
   }
  }
  
  system.out.println("post parameter : " + parameterbuffer.tostring());
  
  url localurl = new url(url);
  
  urlconnection connection = this.openconnection(localurl);
  httpurlconnection httpurlconnection = (httpurlconnection)connection;
  
  httpurlconnection.setdooutput(true);
  httpurlconnection.setrequestmethod("post");
  httpurlconnection.setrequestproperty("accept-charset", charset);
  httpurlconnection.setrequestproperty("content-type", "application/x-www-form-urlencoded");
  httpurlconnection.setrequestproperty("content-length", string.valueof(parameterbuffer.length()));
  
  outputstream outputstream = null;
  outputstreamwriter outputstreamwriter = null;
  inputstream inputstream = null;
  inputstreamreader inputstreamreader = null;
  bufferedreader reader = null;
  stringbuffer resultbuffer = new stringbuffer();
  string templine = null;
  
  try {
   outputstream = httpurlconnection.getoutputstream();
   outputstreamwriter = new outputstreamwriter(outputstream);
   
   outputstreamwriter.write(parameterbuffer.tostring());
   outputstreamwriter.flush();
   //响应失败
   if (httpurlconnection.getresponsecode() >= 300) {
    throw new exception("http request is not success, response code is " + httpurlconnection.getresponsecode());
   }
   //接收响应流
   inputstream = httpurlconnection.getinputstream();
   inputstreamreader = new inputstreamreader(inputstream);
   reader = new bufferedreader(inputstreamreader);
   
   while ((templine = reader.readline()) != null) {
    resultbuffer.append(templine);
   }
   
  } finally {
   
   if (outputstreamwriter != null) {
    outputstreamwriter.close();
   }
   
   if (outputstream != null) {
    outputstream.close();
   }
   
   if (reader != null) {
    reader.close();
   }
   
   if (inputstreamreader != null) {
    inputstreamreader.close();
   }
   
   if (inputstream != null) {
    inputstream.close();
   }
   
  }

  return resultbuffer.tostring();
 }

 private urlconnection openconnection(url localurl) throws ioexception {
  urlconnection connection;
  if (proxyhost != null && proxyport != null) {
   proxy proxy = new proxy(proxy.type.http, new inetsocketaddress(proxyhost, proxyport));
   connection = localurl.openconnection(proxy);
  } else {
   connection = localurl.openconnection();
  }
  return connection;
 }
 
 /**
  * render request according setting
  * @param request
  */
 private void renderrequest(urlconnection connection) {
  
  if (connecttimeout != null) {
   connection.setconnecttimeout(connecttimeout);
  }
  
  if (sockettimeout != null) {
   connection.setreadtimeout(sockettimeout);
  }
  
 }

 /*
  * getter & setter
  */
 public integer getconnecttimeout() {
  return connecttimeout;
 }

 public void setconnecttimeout(integer connecttimeout) {
  this.connecttimeout = connecttimeout;
 }

 public integer getsockettimeout() {
  return sockettimeout;
 }

 public void setsockettimeout(integer sockettimeout) {
  this.sockettimeout = sockettimeout;
 }

 public string getproxyhost() {
  return proxyhost;
 }

 public void setproxyhost(string proxyhost) {
  this.proxyhost = proxyhost;
 }

 public integer getproxyport() {
  return proxyport;
 }

 public void setproxyport(integer proxyport) {
  this.proxyport = proxyport;
 }

 public string getcharset() {
  return charset;
 }

 public void setcharset(string charset) {
  this.charset = charset;
 }
 
}

四、为测试方便,新建一个项目,并新建一个servlet,接收post请求并对httprequestor请求响应,发出响应流

loginservlet.java代码:此处使用了

注解: @webservlet("/loginservlet") ,也可以在web.xml配置servlet

package me.loginservlet;

import java.io.ioexception;
import javax.servlet.servletexception;
import javax.servlet.annotation.webservlet;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;

/**
 * servlet implementation class loginservlet
 */
@webservlet("/loginservlet")
public class loginservlet extends httpservlet {
 private static final long serialversionuid = 1l;
  
 /**
  * @see httpservlet#httpservlet()
  */
 public loginservlet() {
  super();
  // todo auto-generated constructor stub
 }

 /**
  * @see httpservlet#doget(httpservletrequest request, httpservletresponse response)
  */
 protected void doget(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
  // todo auto-generated method stub
  system.out.println("111");
 }

 /**
  * @see httpservlet#dopost(httpservletrequest request, httpservletresponse response)
  */
 protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
  // todo auto-generated method stub
   string username = request.getparameter("username");
   string blog = request.getparameter("blog");
   
   system.out.println(username);
   system.out.println(blog);
   
   response.setcontenttype("text/plain; charset=utf-8");
   response.setcharacterencoding("utf-8");
//响应流
   response.getwriter().write("it is ok!");
  
 }

}

五.测试类test.java

package me.http;

import java.util.hashmap;
import java.util.map;

public class test {
public static void main(string[] args) {
  /* post request */
 map datamap = new hashmap();
 datamap.put("username", "nick huang");
 datamap.put("blog", "it");
 try {
  system.out.println(new httprequestor().dopost("http://localhost:8081/testprogect2/loginservlet", datamap));
  //system.out.println(new httprequestor().doget("http://localhost:8081/testprogect2/loginservlet"));
 } catch (exception e) {
  // todo auto-generated catch block
  e.printstacktrace();
 }
 
 /* get request */
 
}
}

1.接收post请求类loginservlet,控制台测试结果

2.httprequestor接收loginservlet返回的流

ok,完成

六.对于接收testprogect2项目中loginservlet.java类返回的流,在真实环境中可能是异步接收返回的流的,当一台机器a向另外一台机器b发送请求,b接收到a的信息,将信息处理后,需要将处理结果返回即响应返回给a,a会接收到b返回的信息

可以另外建一个servlet类httplistenerservlet.java来专门异步接收返回的信息

package me.http;

import java.io.bufferedreader;
import java.io.ioexception;
import java.io.inputstream;
import java.io.inputstreamreader;

import javax.servlet.servletexception;
import javax.servlet.annotation.webservlet;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;

/**
 * servlet implementation class httplistenerservlet
 */
@webservlet("/httplistenerservlet")
public class httplistenerservlet extends httpservlet {
 private static final long serialversionuid = 1l;
  
 /**
  * @see httpservlet#httpservlet()
  */
 public httplistenerservlet() {
  super();
  // todo auto-generated constructor stub
 }

 /**
  * @see httpservlet#doget(httpservletrequest request, httpservletresponse response)
  */
 protected void doget(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
  // todo auto-generated method stub
 }

 /**
  * @see httpservlet#dopost(httpservletrequest request, httpservletresponse response)
  */
 protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
  // todo auto-generated method stub
   inputstream inputstream = null;
   inputstream = request.getinputstream();
   inputstreamreader inputstreamreader = new inputstreamreader(inputstream);
   bufferedreader reader = new bufferedreader(inputstreamreader);
   string templine = null;
   stringbuffer resultbuffer=new stringbuffer();
   while ((templine = reader.readline()) != null) {
    resultbuffer.append(templine);
   }
   
   system.out.println(resultbuffer.tostring());
 }

}

总结

以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作能带来一定的帮助，如果有疑问大家可以留言交流，谢谢大家对的支持。