网络编程之URL和URLConnection

Love The Way You Lie 2022-09-23 12:58 23阅读 0赞

# 网络编程之URL和URLConnection #

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## 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).

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## 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();

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## 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 superclass
    of all classes that represent a communications link between the
    application and a URL. Instances of this class can be used both to
    read from and to write to the resource referenced by the URL.

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**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][http_blog.csdn.net_nicewuranran_article_details_51756122]

## 参考 ##

1、[http://tutorials.jenkov.com/java-networking/url-urlconnection.html][http_tutorials.jenkov.com_java-networking_url-urlconnection.html]  
2、[https://en.wikipedia.org/wiki/Uniform\_Resource\_Locator][https_en.wikipedia.org_wiki_Uniform_Resource_Locator]  
3、[http://blog.csdn.net/nicewuranran/article/details/51756122][http_blog.csdn.net_nicewuranran_article_details_51756122]

[http_blog.csdn.net_nicewuranran_article_details_51756122]: http://blog.csdn.net/nicewuranran/article/details/51756122
[http_tutorials.jenkov.com_java-networking_url-urlconnection.html]: http://tutorials.jenkov.com/java-networking/url-urlconnection.html
[https_en.wikipedia.org_wiki_Uniform_Resource_Locator]: https://en.wikipedia.org/wiki/Uniform_Resource_Locator