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使用URLConnection获取网页信息的基本流程

發(fā)布時間：2024/1/23 编程问答 28 豆豆

生活随笔收集整理的這篇文章主要介紹了使用URLConnection获取网页信息的基本流程小編覺得挺不錯的,現(xiàn)在分享給大家,幫大家做個參考.

? 參考自core java v2, chapter3 Networking.

注：URLConnection的子類HttpURLConnection被廣泛用于Android網(wǎng)絡(luò)客戶端編程，它與apache HttpClient是兩種主要的客戶端實(shí)現(xiàn)方式，google官方推薦使用HttpURLConnection.

使用URL類可以簡單獲取網(wǎng)頁信息，

URL url = new URL("http://www.baidu.com"); InputStream is = url.openStream(); Scanner sc = new Scanner(is); 但URLConnection提供了更為強(qiáng)大的功能，其基本步驟如下：

1. Call the openConnection method of the URL class to obtain the URLConnection object:
URLConnection connection = url.openConnection();

2. Set any request properties, using the methods
setDoInput
setDoOutput
setIfModifiedSince
setUseCaches
setAllowUserInteraction
setRequestProperty
setConnectTimeout
setReadTimeout
We discuss these methods later in this section and in the API notes.

3. Connect to the remote resource by calling the connect method.
connection.connect();
Besides making a socket connection to the server, this method also queries the server for header information.

4. After connecting to the server, you can query the header information. Two methods, getHeaderFieldKey and
getHeaderField, enumerate all fields of the header. The method getHeaderFields gets a standard Map object
containing the header fields. For your convenience, the following methods query standard fields:
getContentType
getContentLength
getContentEncoding
getDate
getExpiration
getLastModified

5. Finally, you can access the resource data. Use the getInputStream method to obtain an input stream for reading the
information. (This is the same input stream that the openStream method of the URL class returns.) The other method,
getContent, isn’t very useful in practice. The objects that are returned by standard content types such as
text/plain and image/gif require classes in the com.sun hierarchy for processing. You could register your own
content handlers, but we do not discuss that technique in this book.

package com.ljh.corejava;import java.io.IOException; import java.io.InputStream; import java.net.URL; import java.net.URLConnection; import java.util.List; import java.util.Map; import java.util.Scanner;public class URLConnectionTest {public static void main(String[] args) {try{//1、創(chuàng)建URLConnction. URL url = new URL("http://www.baidu.com");URLConnection connection = url.openConnection();//2、設(shè)置connection的屬性connection.setConnectTimeout(10000);connection.setReadTimeout(10000);//3.連接connection.connect();//4.獲取頭部信息之一：獲取所有頭部信息后再遍歷Map<String, List<String>> headers = connection.getHeaderFields();for(Map.Entry<String,List<String>> entry : headers.entrySet()){System.out.println(entry.getKey()+" : ");for(String value : entry.getValue()){System.out.println(value+" , ");}}//4.獲取頭部信息之二：使用簡便方法System.out.println("----------");System.out.println("getContentType: " + connection.getContentType());System.out.println("getContentLength: " + connection.getContentLength());System.out.println("getContentEncoding: " + connection.getContentEncoding());System.out.println("getDate: " + connection.getDate());System.out.println("getExpiration: " + connection.getExpiration());System.out.println("getLastModifed: " + connection.getLastModified());System.out.println("----------");//5.獲取內(nèi)容InputStream is = connection.getInputStream();Scanner sc = new Scanner(is);while(sc.hasNextLine()){System.out.println(sc.nextLine());}sc.close();is.close();}catch(IOException e){e.printStackTrace();}} } 輸出結(jié)果如下：

null :?
HTTP/1.1 200 OK ,?
Expires :?
Sat, 12 Oct 2013 16:16:20 GMT ,?
Set-Cookie :?
H_PS_PSSID=; path=/; domain=.baidu.com ,?
BDSVRTM=0; path=/ ,?
BAIDUID=2CD6C90F50267C4DD25F1DA90D209AB5:FG=1; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com ,?
Connection :?
Keep-Alive ,?
Server :?
BWS/1.0 ,?
Cache-Control :?
private ,?
Date :?
Sat, 12 Oct 2013 16:16:51 GMT ,?
BDQID :?
0xad03b06b916405ea ,?
Vary :?
Accept-Encoding ,?
Transfer-Encoding :?
chunked ,?
P3P :?
CP=" OTI DSP COR IVA OUR IND COM " ,?
BDPAGETYPE :?
1 ,?
Content-Type :?
text/html;charset=utf-8 ,?
BDUSERID :?
0 ,?
----------
getContentType: text/html;charset=utf-8
getContentLength: -1
getContentEncoding: null
getDate: 1381594611000
getExpiration: 1381594580000
getLastModifed: 0
----------
<!DOCTYPE html><html><head><meta http-equiv="content-type" content="text/html;charset=utf-8"><title>百度一下，你就知道</title><style >html,body{height:100%}html{overflow-y:auto}#wrapper{position:relative;_position:;min-height:100%}#content{padding-bottom:100px;text-align:center}#ftCon{height:100px;position:absolute;bottom:44px;text-align:center;width:100%;margin:0 auto;z-index:0;overflow:hidden}#ftConw{width:720px;margin:0 auto}body{font:12px arial;text-align:;background:#fff}body,p,form,ul,li{margin:0;padding:0;list-style:none}body,form,#fm{position:relative}td{text-align:left}img{border:0}a{color:#00c}a:active{color:#f60}.bg{background-image:url(http://s1.bdstatic.com/r/www/cache/static/global/img/icons_db1b0e67.png);background-repeat:no-repeat;_background-image:url(http://s1.bdstatic.com/r/www/cache/static/global/img/icons_190dda05.gif)}.c-icon{display:inline-block;width:14px;height:14px;vertical-align:text-bottom;font-style normal;overflow:hidden;background:url(http://s1.bdstatic.com/r/www/cache/static/global/img/icons_db1b0e67.png) no-repeat 0 0;_background-image:url(http://s1.bdstatic.com/r/www/cache/static/global/img/icons_190dda05.gif)}.c-icon-triangle-down-blue{background-position:-480px -24px}.c-icon-chevron-unfold2{background-position:-504px -24px}#u{color:#999;padding:4px 10px 5px 0;text-align:right}#u a{margin:0 5px}#u .reg{margin:0}#m{width:720px;margin:0 auto}#nv a,#nv b,.btn,#lk{font-size:14px}#fm{padding-left:110px;text-align:left;z-index:1}input{border:0;padding:0}#nv{height:19px;font-size:16px;margin:0 0 4px;text-align:left;text-indent:137px}.s_ipt_wr{width:418px;height:30px;display:inline-block;margin-right:5px;background-position:0 -288px;border:1px solid #b6b6b6;border-color:#9a9a9a #cdcdcd #cdcdcd #9a9a9a;vertical-align:top}.s_ipt{width:405px;height:22px;font:16px/22px arial;margin:5px 0 0 7px;background:#fff;outline:0;-webkit-appearance:none}.s_btn{width:95px;height:32px;padding-top:2px\9;font-size:14px;background-color:#ddd;background-position:0 -240px;cursor:pointer}.s_btn_h{background-position:-240px -240px}.s_btn_wr{width:97px;height:34px;display:inline-block;background-position:-120px -240px;*position:relative;z-index:0;vertical-align:top}#lg img{vertical-align:top;margin-bottom:3px}#lk{margin:33px 0}#lk span{font:14px "宋體"}#lm{height:60px}#lh{margin:16px 0 5px;word-spacing:3px}.tools{position:absolute;top:-4px;*top:10px;right:7px}#mHolder{width:62px;position:relative;z-index:296;display:none}#mCon{height:18px;line-height:18px;position:absolute;cursor:pointer}#mCon span{color:#00c;cursor:default;display:block}#mCon .hw{text-decoration:underline;cursor:pointer;display:inline-block}#mCon .pinyin{display:inline-block}#mCon .c-icon-chevron-unfold2{margin-left:5px}#mMenu a{width:100%;height:100%;display:block;line-height:22px;text-indent:6px;text-decoration:none;filter:none\9}#mMenu,#user ul{box-shadow:1px 1px 2px #ccc;-moz-box-shadow:1px 1px 2px #ccc;-webkit-box-shadow:1px 1px 2px #ccc;filter:progid:DXImageTransform.Microsoft.Shadow(Strength=2,Direction=135,Color="#cccccc")\9}#mMenu{width:56px;border:1px solid #9b9b9b;list-style:none;position:absolute;right:27px;top:28px;display:none;background:#fff}#mMenu a:hover{background:#ebebeb}#mMenu .ln{height:1px;background:#ebebeb;overflow:hidden;font-size:1px;line-height:1px;margin-top:-1px}#cp,#cp a{color:#666}#seth{display:none;behavior:url(#default#homepage)}#setf{display:none}#sekj{margin-left:14px}#shouji{margin-right:14px}</style><script >function h(obj){obj.style.behavior='url(#default#homepage)';var a = obj.setHomePage('http://www.baidu.com/');}</script></head><body><div id="wrapper"><div id="content"><div id="u"><a href="http://www.baidu.com/gaoji/preferences.html" name="tj_setting">搜索設(shè)置</a>|<a href="https://passport.baidu.com/v2/?login&tpl=mn&u=http%3A%2F%2Fwww.baidu.com%2F" name="tj_login" id="lb" οnclick="return false;">登錄</a><a href="https://passport.baidu.com/v2/?reg&regType=1&tpl=mn&u=http%3A%2F%2Fwww.baidu.com%2F" target="_blank" name="tj_reg" class="reg">注冊</a></div><div id="m"><p id="lg"><img src="http://www.baidu.com/img/270%EF%BC%8F129_f01c4e74c976a9e3baf6cfa8a3f97c8f.gif" width="270" height="129" usemap="#mp"><map name="mp"><area shape="rect" coords="0,1,270,129" href="http://www.baidu.com/s?wd=%E9%87%8D%E9%98%B3%E8%8A%82" target="_blank" title="九九重陽，關(guān)愛老人"οnmοusedοwn="return ns_c({'fm':'behs','tab':'bdlogo'})"></map></p><p id="nv"><a href="http://news.baidu.com">新 聞</a>　<b>網(wǎng) 頁</b>　<a href="http://tieba.baidu.com">貼 吧</a>　<a href="http://zhidao.baidu.com">知 道</a>　<a href="http://music.baidu.com">音 樂</a>　<a href="http://image.baidu.com">圖 片</a>　<a href="http://v.baidu.com">視 頻</a>　<a href="http://map.baidu.com">地 圖</a></p><div id="fm"><form name="f" action="/s"><span class="bg s_ipt_wr"><input type="text" name="wd" id="kw" maxlength="100" class="s_ipt"></span><input type="hidden" name="rsv_bp" value="0"><input type="hidden" name="rsv_spt" value="3"><input type="hidden" name="ie" value="utf-8"><span class="bg s_btn_wr"><input type="submit" value="百度一下" id="su" class="bg s_btn" οnmοusedοwn="this.className='bg s_btn s_btn_h'" οnmοuseοut="this.className='bg s_btn'"></span></form><span class="tools"><span id="mHolder"><div id="mCon"><span>輸入法</span></div></span></span><ul id="mMenu"><li><a href="#" name="ime_hw">手寫</a></li><li><a href="#" name="ime_py">拼音</a></li><li class="ln"></li><li><a href="#" name="ime_cl">關(guān)閉</a></li></ul></div><p id="lk"><a href="http://baike.baidu.com">百科</a>　<a href="http://wenku.baidu.com">文庫</a>　<a href="http://www.hao123.com">hao123</a><span> | <a href="http://www.baidu.com/more/">更多>></a></span></p><p id="lm"></p></div></div><div id="ftCon"><div id="ftConw"><p ><a id="seth" onClick="h(this)" href="/" οnmοusedοwn="return ns_c({'fm':'behs','tab':'homepage','pos':0})">把百度設(shè)為主頁</a><a id="setf" href="http://www.baidu.com/cache/sethelp/index.html" οnmοusedοwn="return ns_c({'fm':'behs','tab':'favorites','pos':0})" target="_blank">把百度設(shè)為主頁</a><span id="sekj"><a href="http://weishi.baidu.com/?shouye" target="_blank" οnmοusedοwn="return ns_c({'fm':'behs','tab':'bdbrwlk','pos':1})">安裝百度衛(wèi)士</a></span></p><p id="lh"><a href="http://e.baidu.com/?refer=888" οnmοusedοwn="return ns_c({'fm':'behs','tab':'btlink','pos':2})">加入百度推廣</a> | <a οnmοusedοwn="return ns_c({'fm':'behs','tab':'tj_bang'})" href="http://top.baidu.com">搜索風(fēng)云榜</a> | <a οnmοusedοwn="return ns_c({'fm':'behs','tab':'tj_about'})" href="http://home.baidu.com">關(guān)于百度</a> | <a οnmοusedοwn="return ns_c({'fm':'behs','tab':'tj_about_en'})" href="http://ir.baidu.com">About Baidu</a></p><p id="cp">©2013 Baidu <a href="/duty/" name="tj_duty">使用百度前必讀</a> 京ICP證030173號 <img src="http://www.baidu.com/cache/global/img/gs.gif"></p></div></div></div></body><script>var bds={se:{},comm : {ishome : 1,sid : "",user : "",username : "",sugHost : "http://suggestion.baidu.com/su",loginAction : []}}</script><script type="text/javascript" src="http://s1.bdstatic.com/r/www/cache/static/global/js/home_f813a739.js" charset="utf-8"></script><script>var bdUser = null;var w=window,d=document,n=navigator,k=d.f.wd,a=d.getElementById("nv").getElementsByTagName("a"),isIE=n.userAgent.indexOf("MSIE")!=-1&&!window.opera;(function(){if(/q=([^&]+)/.test(location.search)){k.value=decodeURIComponent(RegExp["\x241"])}})();if(n.cookieEnabled){bds.se.sug();};function addEV(o, e, f){if(w.attachEvent){o.attachEvent("on" + e, f);}else if(w.addEventListener){ o.addEventListener(e, f, false);}}function G(id){return d.getElementById(id);}function ns_c(q){var p = encodeURIComponent(window.document.location.href), sQ = '', sV = '', mu='', img = window["BD_PS_C" + (new Date()).getTime()] = new 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"" : bds.comm.user;function _addTJ(obj){addEV(obj, "mousedown", function(e){var e = e || window.event;var target = e.target || e.srcElement;ns_c({'fm':'behs','tab':target.name||'tj_user','un':encodeURIComponent(un)});});}for(var i = 0; i < u.length; i++){_addTJ(u[i]);}for(var i = 0; i < nv.length; i++){nv[i].name = 'tj_' + tj_nv[i];}for(var i = 0; i < lk.length; i++){lk[i].name = 'tj_' + tj_lk[i];}})();(function() {var links = {'tj_news': ['word', 'http://news.baidu.com/ns?tn=news&cl=2&rn=20&ct=1&ie=utf-8'],'tj_tieba': ['kw', 'http://tieba.baidu.com/f?ie=utf-8'],'tj_zhidao': ['word', 'http://zhidao.baidu.com/search?pn=0&rn=10&lm=0'],'tj_mp3': ['key', 'http://music.baidu.com/search?fr=ps&ie=utf-8'],'tj_img': ['word', 'http://image.baidu.com/i?ct=201326592&cl=2&nc=1&lm=-1&st=-1&tn=baiduimage&istype=2&fm=&pv=&z=0&ie=utf-8'],'tj_video': ['word', 'http://video.baidu.com/v?ct=301989888&s=25&ie=utf-8'],'tj_map': ['wd', 'http://map.baidu.com/?newmap=1&ie=utf-8&s=s'],'tj_baike': ['word', 'http://baike.baidu.com/search/word?pic=1&sug=1&enc=utf8'],'tj_wenku': ['word', 'http://wenku.baidu.com/search?ie=utf-8']};var domArr = [G('nv'), G('lk'),G('cp')],kw = G('kw');for (var i = 0, l = domArr.length; i < l; i++) {domArr[i].onmousedown = function(e) {e = e || window.event;var target = e.target || e.srcElement,name = target.getAttribute('name'),items = links[name],reg = new RegExp('^\\s+|\\s+\x24'),key = kw.value.replace(reg, '');if (items) {if (key.length > 0) {var wd = items[0], url = items[1],url = url + ( name === 'tj_map' ? encodeURIComponent('&' + wd + '=' + key) : ( ( url.indexOf('?') > 0 ? '&' : '?' ) + wd + '=' + encodeURIComponent(key) ) );target.href = url;} else {target.href = target.href.match(new RegExp('^http:\/\/.+\.baidu\.com'))[0];}}name && ns_c({'fm': 'behs','tab': name,'query': encodeURIComponent(key),'un': encodeURIComponent(bds.comm.user || '') });};}})();addEV(w,"load",function(){k.focus()});w.οnunlοad=function(){};</script><script type="text/javascript" src="http://s1.bdstatic.com/r/www/cache/static/global/js/tangram-1.3.4c1.0_07038476.js"></script><script type="text/javascript" src="http://s1.bdstatic.com/r/www/cache/static/user/js/u_ec0ebfe1.js" charset="utf-8"></script><script>try{document.cookie="WWW_ST=;expires=Sat, 01 Jan 2000 00:00:00 GMT";baidu.on(document.forms[0],"submit",function(){var _t=new Date().getTime();document.cookie = "WWW_ST=" + _t +";expires=" + new Date(_t + 10000).toGMTString()})}catch(e){}</script></html>
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