Java URL对象初始化以及通过URL或者URLConnection读取内容

摘要: 最近在读《Java语言程序设计第二版》，关于网络编程。Java 提供两种层次的网络支持，第一种，是URL层次，第二种是Socket层次。

一、URL层次。

URL对象的创建。

1、public URL（String spec）;

URL urlbase=new URL("http://my.oschina.net/u/2308739/admin/new-blog.html");

2、public URL（URL context,String spec）;

URL urlbase=new URL("http://my.oschina.net/u/2308739/admin/");

URL indexUrl=new URL(urlbase,"new-blog.html");

3、public URL（String protocol,String host,String file）;

通过协议名、主机名、文件名构造一个URL对象。

new URL("http","http://my.oschina.net","/u/2308739/admin/new-blog.html");

4、public URL（String protocol,String host,int port,String file）;

通过协议名、主机名、端口号，文件名构造一个URL对象。

new URL("http","http://my.oschina.net",80,"/u/2308739/admin/new-blog.html");

二、通过URL读取内容

通过URL的openstream()方法，得到Java.io.inputstream类的对象，从该输入流中读取URL地址的内容。

这个方法的定义是：

public final Inputstream openstream() throws IOException;

三、实例通过访问URL获取内容

package com.yuan.test;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;

public class TestUrl {

public static void main(String[] args) {
// TODO Auto-generated method stub
try {
//String accessurlString=URLEncoder.encode("http://www.ifeng.com/", "utf-8");

URL ifeng=new URL("http://www.ifeng.com/");

BufferedReader bReader=new
BufferedReader(new InputStreamReader(ifeng.openStream()));//通过URL的openstrea//m()将数据转换为inputstream
String inputlineString;
while((inputlineString=bReader.readLine())!=null){
System.out.println(inputlineString);
}
bReader.close();
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}

}

四、实例通过访问URLConnection读取内容

通过对一个指定的URL之间建立一个连接，然后对该资源进行读写操作。

URLConnection重要的获取连接的输入/输出流的方法。

Inputstream getInputstream()

Outputstream getOutputStream()

package com.yuan.test;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLEncoder;

public class TestUrl {

public static void main(String[] args) {
// TODO Auto-generated method stub
try {
//String accessurlString=URLEncoder.encode("http://www.ifeng.com/", "utf-8");

URL ifeng=new URL("http://www.ifeng.com/");
URLConnection urlConnection=ifeng.openConnection();
BufferedReader bReader=new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
String inputlineString;
while((inputlineString=bReader.readLine())!=null){
System.out.println(inputlineString);
}
bReader.close();
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}

}

五、实例通过URLConnection写内容

package com.yuan.test;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.util.logging.Level;
import java.util.logging.Logger;

import org.apache.commons.io.IOUtils;

public class TestUrlConnetion {
public static void main(String[] args){
try{
// Configure and open a connection to the site you will send the request
URL url = new URL("http://wx.tclha.com/login.do");
URLConnection urlConnection = url.openConnection();

// 设置doOutput属性为true表示将使用此urlConnection写入数据
urlConnection.setDoOutput(true);
// 定义待写入数据的内容类型，我们设置为application/x-www-form-urlencoded类型
urlConnection.setRequestProperty("content-type", "application/x-www-form-urlencoded");
HttpURLConnection httpURLConnection = (HttpURLConnection)urlConnection;//httpurlconection 有可以获得返回状态值的方法。
/****httpurlconnetion一些配置属性*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()));****/
// 得到请求的输出流对象
OutputStreamWriter out = new OutputStreamWriter(httpURLConnection.getOutputStream());
// 把数据写入请求的Body
out.write("userName=yuanw&passWord=121212");
out.flush();
out.close();
System.out.println("ResponseCode:"+httpURLConnection.getResponseCode());
if (httpURLConnection.getResponseCode() >= 300) {
System.out.println("HTTP Request is not success, Response code is " + httpURLConnection.getResponseCode());
}
// 从服务器读取响应
InputStream inputStream = urlConnection.getInputStream();
String encoding = urlConnection.getContentEncoding();
System.out.println("encoding:"+encoding);
String body = IOUtils.toString(inputStream, "utf-8");
System.out.println(body);
}catch(IOException e){
Logger.getLogger(TestUrlConnetion.class.getName()).log(Level.SEVERE, null, e);
}
}
}

更多内容参考博文：

参考博文：http://www.cnblogs.com/nick-huang/p/3859353.html