1 URL

程式來源:
Java URL处理

練習程式1:

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;

class Main {
 public static void main(String[] args) {
  try {
   URL url = new URL("https://www.google.com/webhp?hl=zh-TW&ictx=2&sa=X&ved=0ahUKEwjq5562tNTkAhVsyosBHUcmBx0QPQgH");
   System.out.println("URL：" + url.toString());
   System.out.println("協議：" + url.getProtocol());
   System.out.println("驗證信息：" + url.getAuthority());
   System.out.println("文件名及請求參數：" + url.getFile());
   System.out.println("主機名：" + url.getHost());
   System.out.println("路徑：" + url.getPath());
   System.out.println("端口：" + url.getPort());
   System.out.println("默認端口：" + url.getDefaultPort());
   System.out.println("請求參數：" + url.getQuery());
   System.out.println("定位位置：" + url.getRef());
  } catch (IOException e) {
   e.printStackTrace();
  }
 }
}

URL：https://www.google.com/webhp?hl=zh-TW&ictx=2&sa=X&ved=0ahUKEwjq5562tNTkAhVsyosBHUcmBx0QPQgH
協議：https
驗證信息：www.google.com
文件名及請求參數：/webhp?hl=zh-TW&ictx=2&sa=X&ved=0ahUKEwjq5562tNTkAhVsyosBHUcmBx0QPQgH
主機名：www.google.com
路徑：/webhp
端口：-1
默認端口：443
請求參數：hl=zh-TW&ictx=2&sa=X&ved=0ahUKEwjq5562tNTkAhVsyosBHUcmBx0QPQgH
定位位置：null

練習程式2:用jsp把網頁全部複製過來

<%@ page import="java.io.*" %>
<%@ page import="java.net.HttpURLConnection" %>
<%@ page import="java.net.URL" %>

<% 
URL obj = new URL("https://www.google.com");
HttpURLConnection con = (HttpURLConnection) obj.openConnection();
BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream(), "UTF-8"));
String inputLine;
String urlString="";

while ((inputLine = in.readLine()) != null) {
      urlString += inputLine;
}

in.close();
%>
<% out.println(urlString); %>

2 path

詳談java中File類getPath()、getAbsolutePath()、getCanonical的區別

3

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HttpURLConnection java.io.FileNotFoundException

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Convert array of strings into a string in Java
整理:

1
Receive JSON POST with PHP 要用:

$_POST = json_decode(file_get_contents('php://input'), true);

不能用

$_POST['param']

2 (Output 類似 寫 ， 所以如果false，就不能 寫資料 到 server)
如果

connection.setDoOutput(false);

就不能

OutputStream out = connection.getOutputStream();

會有

java.net.ProtocolException: cannot write to a URLConnection if doOutput=false - call setDoOutput(true)

3
如果 (Input 類似 讀 ， 所以如果false，就代表不能讀server回傳的資料)

connection.setDoInput(false);

就不能

BufferedReader reader = new BufferedReader(new InputStreamReader(
                    connection.getInputStream(),"UTF-8"));

會有

java.net.ProtocolException: Cannot read from URLConnection if doInput=false (call setDoInput(true))