网络编程之URL和URLConnection

---

介绍

URL和URLConnection类是完成http网络请求时所用到的两个对象The java.net package contains two interesting classes: The URL class and the URLConnection class. these classes can be used to create client connections to web servers (HTTP servers).

---

URL

java中URL类代表了日常所使用的url(统一资源定位符),我们当然也可以使用字符串来代替url,不过java是面向对象编程语言因此使用URL对象来表示。Class URL represents a Uniform Resource Locator, a pointer to a "resource" on the World Wide Web.A resource can be something as simple as a file or a directory, or it can be a reference to a more complicated object,such as a query to a database or to a search engine.

核心方法

    /**     * URL类中定义了很多方法,能够操作大部分url里面的内容,URL类定义和url语法格式一致。所以操作起来也很方便。     *      * 最常用的两个方法     *     URL(String url);构造方法 URLConnection     *     openConnection();获得URLConnection连接对象     */    // 初始化URL对象    URL url = new URL("url 地址");    // 根据URL对象获得连接对象    URLConnection connection = url.openConnection();

---

URLConnection

URLConnection表示一个连接对象,通过这个对象我们可以做很多事情(获得响应信息)。URLConnection其实是一个抽象类,其主要实现有HttpURLConnection和JarURLConnection类,绝大多数情况下我们是使用HttpURLConnection类的。The abstract class URLConnection is the superclassof all classes that represent a communications link between theapplication and a URL. Instances of this class can be used both toread from and to write to the resource referenced by the URL. 

---

核心方法

abstract public class HttpURLConnection extends URLConnection {    public void setRequestMethod(String method) throws ProtocolException {}//重点掌握    public int getResponseCode() throws IOException {}//重点掌握    //Returns an input stream that reads from this open connection.    //设置输入流就是为了获得请求体里的数据    public InputStream getInputStream() throws IOException {}//重点掌握    //Returns an output stream that writes to this connection.    //获得这个输出流其实就是为了向请求体里增加数据    public OutputStream getOutputStream() throws IOException {}//重点掌握    //设置从HttpURLConnection对象能否获得输入和输出流    public void setDoInput(boolean doinput) {}//默认为true(因为很常用所以设置为true),重点掌握    //如果是post方法时,就一定要设置为true    public void setDoOutput(boolean dooutput) {}//默认为false,重点掌握    //Sets the general request property. If a property with the key already    //exists, overwrite its value with the new value.    //就是设置请求头信息    public void setRequestProperty(String key, String value) {}    public Map<String,List<String>> getRequestProperties() {}}我们可以使用URL和URLConnection来完成http请求组件工具,具体参考之前写的一篇文章

http://blog.csdn.net/nicewuranran/article/details/51756122

参考

1、http://tutorials.jenkov.com/java-networking/url-urlconnection.html
2、https://en.wikipedia.org/wiki/Uniform_Resource_Locator
3、http://blog.csdn.net/nicewuranran/article/details/51756122