URLConnection发送HTTP请求的方法_动力节点Java学院整理

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。

运用原生java api发送简单的get请求、post请求

http请求粗分为两种，一种是get请求，一种是post请求。使用java发送这两种请求的代码大同小异，只是一些参数设置的不同。步骤如下：

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

简单的get请求示例如下：

package com.bjpowernode.httprequestdemo;

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 httpgetrequest {

  /**
   * main
   * @param args
   * @throws exception 
   */
  public static void main(string[] args) throws exception {
    system.out.println(doget());
  }
  
  /**
   * get request
   * @return
   * @throws exception
   */
  public static string doget() throws exception {
    url localurl = new url("http://localhost:8080/onehttpserver/");
    urlconnection connection = localurl.openconnection();
    httpurlconnection httpurlconnection = (httpurlconnection)connection;
    
    httpurlconnection.setrequestproperty("accept-charset", "utf-8");
    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;
    
    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();
  }
  
}

 简单的post请求示例如下：

package com.bjpowernode.httprequestdemo;

import java.io.bufferedreader;
import java.io.inputstream;
import java.io.inputstreamreader;
import java.io.outputstream;
import java.io.outputstreamwriter;
import java.net.httpurlconnection;
import java.net.url;
import java.net.urlconnection;

public class httppostrequest {

  /**
   * main
   * @param args
   * @throws exception 
   */
  public static void main(string[] args) throws exception {
    system.out.println(dopost());
  }
  
  /**
   * post request
   * @return
   * @throws exception
   */
  public static string dopost() throws exception {
    string parameterdata = "username=nickhuang&blog=http://www.cnblogs.com/nick-huang/";
    
    url localurl = new url("http://localhost:8080/onehttpserver/");
    urlconnection connection = localurl.openconnection();
    httpurlconnection httpurlconnection = (httpurlconnection)connection;
    
    httpurlconnection.setdooutput(true);
    httpurlconnection.setrequestmethod("post");
    httpurlconnection.setrequestproperty("accept-charset", "utf-8");
    httpurlconnection.setrequestproperty("content-type", "application/x-www-form-urlencoded");
    httpurlconnection.setrequestproperty("content-length", string.valueof(parameterdata.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(parameterdata.tostring());
      outputstreamwriter.flush();
      
      if (httpurlconnection.getresponsecode() >= 300) {
        throw new exception("http request is not success, response code is " + httpurlconnection.getresponsecode());
      }
      
      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();
  }

}

简单封装

如果项目中有多处地方使用http请求，我们适当对其进行封装，

1. 可以大大减少代码量（不需每次都写一大段原生的请求source code）
2. 也可以使配置更灵活、方便（全局设置一些项目特有的配置，比如已商榷的time out时间、已确定的proxy server，避免以后改动繁琐）

 以下简单封装成httprequestor，以便使用：

package com.bjpowernode.util.httprequestor;

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 = 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;
    
    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 = 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();
      
      if (httpurlconnection.getresponsecode() >= 300) {
        throw new exception("http request is not success, response code is " + httpurlconnection.getresponsecode());
      }
      
      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;
  }
  
}

写一个调用的测试类：

package com.bjpowernode.util.httprequestor;

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

public class call {

  public static void main(string[] args) throws exception {
    
    /* post request */
    map datamap = new hashmap();
    datamap.put("username", "nick huang");
    datamap.put("blog", "it");
    system.out.println(new httprequestor().dopost("http://localhost:8080/onehttpserver/", datamap));
    
    /* get request */
    system.out.println(new httprequestor().doget("http://localhost:8080/onehttpserver/"));
  }

}

ok，完成！！

简单测试

以上的请求地址都是http://localhost:8080/onehttpserver/

这是自己的一个用于测试的web application，就一个简单的servlet和web.xml。毕竟需要测试请求参数是否能正常接收，处理超时的情况。

loginservlet

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

public class loginservlet extends httpservlet {
  private static final long serialversionuid = 1l;
    
  public loginservlet() {
    super();
  }

  protected void doget(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
    this.dopost(request, response);
  }

  protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
    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");
    response.getwriter().write("it is ok!");
  }

}

 web.xml

<?xml version="1.0" encoding="utf-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/xmlschema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemalocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="webapp_id" version="2.5">
 <display-name>onehttpserver</display-name>
 <welcome-file-list>
  <welcome-file>loginservlet</welcome-file>
 </welcome-file-list>
 
 <servlet>
  <description></description>
  <display-name>loginservlet</display-name>
  <servlet-name>loginservlet</servlet-name>
  <servlet-class>loginservlet</servlet-class>
 </servlet>
 <servlet-mapping>
  <servlet-name>loginservlet</servlet-name>
  <url-pattern>/loginservlet</url-pattern>
 </servlet-mapping>
 
</web-app>