អាយធីជនបទ: Java

ឧទាហរណ៍នៃការប្រើប្រាស់ Java JSON ជាមួយ Gson library

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Gson គឹជា json library សំរាប់ java,ដែលបង្កើតឡើងដោយgoogle, សំរាប់បង្កើតជា json. យើងអាចប្រើប្រាស Gson, សំរប់បង្កើតជាjson និងបំលែងjson ទៅជាjava objects.
 
<pre style="background: #f0f0f0; border: 1px dashed #cccccc; color: black; font-family: "arial"; font-size: 12px; height: auto; line-height: 20px; overflow: auto; padding: 0px; text-align: left; width: 99%;"><code style="color: black; word-wrap: normal;"> //Direct Initialization 
 Gson gson = new Gson(); 
 //or 
 //we can set our formatting options 
 Gson gson = new GsonBuilder() 
 .disableHtmlEscaping() 
 .setFieldNamingPolicy(FieldNamingPolicy.UPPER_CAMEL_CASE) 
 .setPrettyPrinting() 
 .serializeNulls() 
 .create(); 
</code></pre>
 
យើងអាចបោះតំលៃរបស់អថេរដោយផ្ទាល់(អាចជាobject or primitives),ដែលនឹងត្រូវបំលែងទៅជាjson format.តែវាជាបញ្ហាា គឹដោយសារវាមិនមែនជាkey value pair.
 
<pre style="background: #f0f0f0; border: 1px dashed #cccccc; color: black; font-family: "arial"; font-size: 12px; height: auto; line-height: 20px; overflow: auto; padding: 0px; text-align: left; width: 99%;"><code style="color: black; word-wrap: normal;"> import com.google.gson.Gson; 
 public class GsonExample { 
 public static void main(String[] args) { 
 // TODO Auto-generated method stub 
 Gson gson=new Gson(); 
 String name="itjontot"; 
 System.out.println(gson.toJson(name)); 
 } 
 } 
 output: 
 "itjontot" //expected format is {"name":"itjontot"} 
</code></pre>
 
តោះបង្កើត Employee class ដែលមាន name និង age ដែលជា data members ហើយបង្កើត setters និង getters method។ បន្ទាប់មក បង្កើត employee object ហើយ pass ទៅgson ដើម្បីបបំលែងពីjava objectទៅជា json format។
 
Employee class
 
<pre style="background: #f0f0f0; border: 1px dashed #cccccc; color: black; font-family: "arial"; font-size: 12px; height: auto; line-height: 20px; overflow: auto; padding: 0px; text-align: left; width: 99%;"><code style="color: black; word-wrap: normal;"> public class Emp { 
 String name; 
 int age; 
 public String getName() { 
 return name; 
 } 
 public void setName(String name) { 
 this.name = name; 
 } 
 public int getAge() { 
 return age; 
 } 
 public Emp(String name, int age) { 
 super(); 
 this.name = name; 
 this.age = age; 
 } 
 public Emp() { 
 super(); 
 } 
 public void setAge(int age) { 
 this.age = age; 
 } 
 } 
</code></pre>
<pre style="background: #f0f0f0; border: 1px dashed #cccccc; color: black; font-family: "arial"; font-size: 12px; height: auto; line-height: 20px; overflow: auto; padding: 0px; text-align: left; width: 99%;"><code style="color: black; word-wrap: normal;"> import com.google.gson.Gson; 
 public class GsonExample { 
 public static void main(String[] args) { 
 // TODO Auto-generated method stub 
 Gson gson=new Gson(); 
 Emp emp=new Emp("Sok",25); 
 System.out.println(gson.toJson(emp)); 
 } 
 } 
 output: 
 {"name":"Sok","age":25} 
</code></pre>
 
ខាងក្រោមជាការបំលែងទិន្នន័យពី JSON format ទៅជា Java Object វិញ។ជាជំហានដំបូងបង្កើត gson objectរួចហើយ fromJson method របស់ gson oject ដោយ បោះjson data និង matching class របស់ data ហ្នឹង។
 
<pre style="background: #f0f0f0; border: 1px dashed #cccccc; color: black; font-family: "arial"; font-size: 12px; height: auto; line-height: 20px; overflow: auto; padding: 0px; text-align: left; width: 99%;"><code style="color: black; word-wrap: normal;"> import com.google.gson.Gson; 
 public class ReverseJson { 
 public static void main(String[] args) 
 { 
 Gson gson = new Gson(); 
 Emp emp=gson.fromJson("{'name':'Dara','age':25}", 
 Emp.class); 
 System.out.println(emp.getName()); 
 } 
 } 
 output: 
 Dara 
</code></pre>

ឧទាហរណ៍នៃការប្រើប្រាស់ Java JSON ជាមួយ Gson library

Gson គឹជា json library សំរាប់ java,ដែលបង្កើតឡើងដោយgoogle, សំរាប់បង្កើតជា json. យើងអាចប្រើប្រាស Gson, សំរប់បង្កើតជាjson និងបំលែងjson ទៅជា...

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ប្រើប្រាស់ Apache Common File Upload APIជាមួយ File Upload Servlet

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នៅក្នុងមេរៀននេះ អ្នកនឹងបានសិក្សាអំពីការបង្កើត Java Servlet ដើម្បីអាចឲ្យ client អាចupload fileបាន ហើយនៅក្នុងនេះ យើងនឹងលើកយកចំនុចដូចខាងក្រោម៖
 
១. បង្កើត Form Upload ដែលអាចឲ្យclient ជ្រើសរើស file សំរាប់Upload
 
២. បង្កើត Java Servlet ដែលជាអ្នកធ្វើការងារនៅពេលដែល client បានបញ្ជូន file តាមរយៈ Form Upload ខាងលើ
 
៣. បង្កើតជា message page មួយសំរាប់បង្ហាញថា ការ upload file បានសម្រេច ឬ បរាជ័យ
 
ជាដំបូង សូមបង្កើត Dynamic Web Project មួយថ្មី (ប្រើប្រាស់ Eclipse) ដោយកំណត់ឈ្មោះរបស់ Project ថា UploadServletApp។ បន្ទាប់មកទៀត នៅក្នុង folder src សូមបង្កើតនូវ java package មួយថ្មី (ដែលយើងនឹងសរសេរកូដនៅក្នុងហ្នឹង) ហើយកំណត់ឈ្មោះវា (ឧទាហរណ៍៖ tk.itjonbot.tutorial.java.upload) ។
 
ដើម្បីអាចប្រើប្រាស់ Apache Common file upload api បាន អ្នកត្រូវdownload យក library ជាមិនសិន ហើយcopy-paste វាទៅក្នុង folder WebContent\WEB-INF\lib។ Library ទាំងនោះរួមមាន 
១. commons-fileupload.-1.2.2.jar
 
២. commons-io-2.3.jar
 
ជំហានបន្ទាប់នេះ អ្នកត្រូវបង្កើតជា Form Upload សំរាប់អាចឲ្យclient ជ្រើសរើស file សំរាប់ upload ទៅកាន់ web server របស់អ្នកបាន។ ខាងក្រោមនេះ ជាកូដសំរាប់ បង្កើត Form Upload (index.jsp) 
<pre style="background: #f0f0f0; border: 1px dashed #cccccc; color: black; font-family: "arial"; font-size: 12px; height: auto; line-height: 20px; overflow: auto; padding: 0px; text-align: left; width: 99%;"><code style="color: black; word-wrap: normal;"> <%@ page language="java" contentType="text/html; charset=UTF-8" 
 pageEncoding="UTF-8"%> 
 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" 
 "http://www.w3.org/TR/html4/loose.dtd"> 
 <html> 
 <head> 
 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 
 <title>File Upload</title> 
 </head> 
 <body> 
 <center> 
 <form method="post" action="upload" enctype="multipart/form-data"> 
 Select file to upload: <input type="file" name="uploadFile" /> 
 
 <input type="submit" value="Upload" /> 
 </form> 
 </center> 
 </body> 
 </html> 
</code></pre>
 
ចំណាំ៖
 
១. method =”post” នៅពេលដែលclient ចុចលើbutton submit។ វាគឺចាំបាច់ព្រោះថា file’s content អាចបញ្ជូនបានតាមតែរយៈ HTTP POST method
 
២. action=”upload” កំណត់នូវទីតាំង ឬ url របស់ servlet ដែលនឹងhandle ការងារកាលណា client បញ្ជូន fileទៅ
 
៣. enctype=”multipart/form-date” បញ្ជាក់ថា form នេះមានផ្ទុកទិន្នន័យសំរាប់ upload 
 
បន្ទាប់មក យើងត្រូវបង្កើតនូវ Servletមួយសំរាប់ handle ការងារខាងលើ ហើយសូមអនុវត្តដូចខាងក្រោម៖
 
១. បង្កើត Java Class មួយនៅក្នុង package ដែលយើងបានបង្កើតខាងលើ (tk.itjonbot.tutorial.java.upload) ហើយ class នេះត្រូវតែ extends ពី Class HttpServlet ហើយ override នូវmethod doPost ដូចខាងក្រោម៖

<pre style="background: #f0f0f0; border: 1px dashed #cccccc; color: black; font-family: "arial"; font-size: 12px; height: auto; line-height: 20px; overflow: auto; padding: 0px; text-align: left; width: 99%;"><code style="color: black; word-wrap: normal;"> import java.io.File; 
 import java.io.IOException; 
 import java.io.PrintWriter; 
 import java.util.Iterator; 
 import java.util.List; 
 import javax.servlet.ServletException; 
 import javax.servlet.http.HttpServlet; 
 import javax.servlet.http.HttpServletRequest; 
 import javax.servlet.http.HttpServletResponse; 
 import org.apache.commons.fileupload.FileItem; 
 import org.apache.commons.fileupload.disk.DiskFileItemFactory; 
 import org.apache.commons.fileupload.servlet.ServletFileUpload;

public class UploadServlet extends HttpServlet {  
   private static final long serialVersionUID = 1L;  
   private static final String UPLOAD_DIRECTORY = "upload";  
   private static final int THRESHOLD_SIZE   = 1024 * 1024 * 3; // 3MB  
   private static final int MAX_FILE_SIZE   = 1024 * 1024 * 40; // 40MB  
   private static final int MAX_REQUEST_SIZE  = 1024 * 1024 * 50; // 50MB  
   /**  
    * ដោះស្រាយការងារ file upload តាមរយៈ HTTP POST method  
    */  
   protected void doPost(HttpServletRequest request,  
       HttpServletResponse response) throws ServletException, IOException {  
     // ពិនិត្យមើលថាតើវាមាន file ដែរឬអត់? 
     if (!ServletFileUpload.isMultipartContent(request)) {  
       PrintWriter writer = response.getWriter();  
       writer.println("Request does not contain upload data");  
       writer.flush();  
       return;  
     }  
     // កំណត់ upload setting 
     DiskFileItemFactory factory = new DiskFileItemFactory();  
     factory.setSizeThreshold(THRESHOLD_SIZE);  
     factory.setRepository(new File(System.getProperty("java.io.tmpdir")));  
     ServletFileUpload upload = new ServletFileUpload(factory);  
     upload.setFileSizeMax(MAX_FILE_SIZE);  
     upload.setSizeMax(MAX_REQUEST_SIZE);

String uploadPath = getServletContext().getRealPath("")  
       + File.separator + UPLOAD_DIRECTORY;  
     // បង្កើតជា directory ប្រសិនបើគ្មាន
     File uploadDir = new File(uploadPath);  
     if (!uploadDir.exists()) {  
       uploadDir.mkdir();  
     }  
     try {  
       // ទាញយក file data  ដែលបានupload
       List formItems = upload.parseRequest(request);  
       Iterator iter = formItems.iterator();

while (iter.hasNext()) {  
         FileItem item = (FileItem) iter.next();

if (!item.isFormField()) { 
 String fileName = new File(item.getName()).getName(); 
 String filePath = uploadPath + File.separator + fileName; 
 File storeFile = new File(filePath); 
 // រក្សាទុក file ដែលបាន upload 
 item.write(storeFile); 
 } 
 } 
 request.setAttribute("message", "Upload has been done successfully!"); 
 } catch (Exception ex) { 
 request.setAttribute("message", "There was an error: " + ex.getMessage()); 
 } 
 getServletContext().getRequestDispatcher("/message.jsp").forward(request, response); 
 } 
 } 
</code></pre>
 
យើងត្រូវបង្កើតនូវ jsp pageមួយទៀតសំរាប់បង្ហាញmessage ថាតើclient បានupload fileបានជោគជ័យ ឬ មិនបានជោគជ័យ។ខាងក្រោមនេះជាកូដ (message.jsp)
 
<pre style="background: #f0f0f0; border: 1px dashed #cccccc; color: black; font-family: "arial"; font-size: 12px; height: auto; line-height: 20px; overflow: auto; padding: 0px; text-align: left; width: 99%;"><code style="color: black; word-wrap: normal;"> <%@ page language="java" contentType="text/html; charset=UTF-8" 
 pageEncoding="UTF-8"%> 
 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" 
 "http://www.w3.org/TR/html4/loose.dtd"> 
 <html> 
 <head> 
 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 
 <title>Upload</title> 
 </head> 
 <body> 
 <center> 
 <h2>${requestScope.message}</h2> 
 </center> 
 </body> 
 </html> 
</code></pre>

<img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgFwd5McdhbLgwD6EK-gkmUoC3jlEb3s7JYhyphenhyphenLDKFxrOrd-PAuFFP1GOM6R0K4NdlRKDv6LqLLJWS8_c1bEfaH-1ZC1i2o539vE2TSYIOvFey5GsHkS3iKj558dd8xouztuIsm94Payjyg/s640/sdasdf_upload_fasd.jpg" width="640" /> <div>
 ជាចុងក្រោយ អ្នកត្រូវកំណត់នៅក្នុង web.xml សំរាប់ធ្វើការ map url ឲ្យត្រូវជាមួយ servlet ដែលយើងបានបង្កើត ដូចខាងក្រោម៖ 
<pre style="background-attachment: initial; background-clip: initial; background-color: #f0f0f0; background-image: initial; background-origin: initial; background-position: initial; background-repeat: initial; background-size: initial; border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 1px dashed rgb(204, 204, 204); color: black; font-family: arial; font-size: 12px; font-weight: bold; height: auto; line-height: 20px; overflow: auto; padding: 0px; text-align: left; width: 99%;"><code style="color: black; word-wrap: normal;"> <?xml version="1.0" encoding="UTF-8"?> 
 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
 xmlns="http://java.sun.com/xml/ns/javaee" 
 xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" 
 xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
 http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" 
 id="WebApp_ID" version="2.5"> 
 <display-name>UploadServletApp</display-name> 
 <servlet> 
 <description></description> 
 <display-name>UploadServlet</display-name> 
 <servlet-name>UploadServlet</servlet-name> 
 <servlet-class>tk.itjonbot.tutorial.java.upload.UploadServlet</servlet-class> 
 </servlet> 
 <servlet-mapping> 
 <servlet-name>UploadServlet</servlet-name> 
 <url-pattern>/upload</url-pattern> 
 </servlet-mapping> 
 </web-app> 
</code></pre>
</div>

ប្រើប្រាស់ Apache Common File Upload APIជាមួយ File Upload Servlet

នៅក្នុងមេរៀននេះ អ្នកនឹងបានសិក្សាអំពីការបង្កើត Java Servlet ដើម្បីអាចឲ្យ client អាចupload fileបាន ហើយនៅក្នុងនេះ យើងនឹងលើកយកចំនុចដូចខា...

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[Java Language] Create App to capture the entire of your screen

<center>
<img alt="Java Capture Screen" src="http://wallpapertube.com/file/9344/600x338/16:9/computer-java-java-programmer-wallpaper.jpg" title=" Java capture screen" />
</center>
 

In this post, I gonna show a Java Code to create an App that can capture the whole screen of your PC . Another quick tutorial on capturing your entire screen with java actually sometimes java makes me mad because sometimes i have to import loads of namespaces than c# or vb.net anyways , as usual to do something in system we import IO thingy yes we are using it here .

 
<pre>
import java.awt.AWTException;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.io.*;
import javax.imageio.*;

public class MainClass {

public static void main(String[] args) throws AWTException, IOException {
  Robot robot=new Robot();
  BufferedImage scr=robot.createScreenCapture(new Rectangle(Toolkit.getDefaultToolkit().getScreenSize()));
  ImageIO.write(scr, "JPEG", new File("img1.jpg"));
 }

}
</pre>

Java.awt.Robot class is used to take the control of mouse and keyboard. Once you get the control, you can do any type of operation related to mouse and keyboard through your java code. This class is used generally for test automation.
 
Java Bufferd Image class is a subclass of Image class. It is used to handle and manipulate the image data. A BufferedImage is made of ColorModel of image data.
 
IMAGEIO class containing static convenience methods for locating ImageReaders and ImageWriters, and performing simple encoding and decoding.
 
Just compile the program and run then you will seen the image in the App root.

[Java Language] Create App to capture the entire of your screen

In this post, I gonna show a Java Code to create an App that can capture the whole screen of your PC . Another quick tutorial on captur...

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Write and Append Object to binary file with ObjectOutputStream [Java Programming]

An ObjectOutputStream writes primitive data types and graphs of Java objects to an OutputStream. The objects can be read (reconstituted) using an ObjectInputStream. Only objects that support the java.io.Serializable interface can be written to streams. The class of each serializable object is encoded including the class name and signature of the class, the values of the object's fields and arrays, and the closure of any other objects referenced from the initial objects.

 
<center>
<img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhB_80ZOgVykhYTmAPAe9fIfU85sBhZBvOkNxRbLqmfa4yIl56OjK_1i_KaPldUiykwpV9MI71TkgR01YhC5SrqPdbr1gQeCgiLk2qvdEe5N6Ierev0mPuqLBK6AyO2idO89i44Ox_GWJc/s320/java.jpg" />
</center>

As the API says, the ObjectOutputStream constructor writes the serialization stream header to the underlying stream. And this header is expected to be only once, in the beginning of the file. So calling
 
new ObjectOutputStream(fos); 
 
multiple times on the FileOutputStream that refers to the same file will write the header multiple times and corrupt the file.
 
So in order to append the Object to the file, you can code like this: 

<pre>
public class AppendingObjectOutputStream extends ObjectOutputStream {

public AppendingObjectOutputStream(OutputStream out) {
    super(out);
  }
  @Override
  protected void writeStreamHeader() throws IOException {
    // do not write a header, but reset:

reset();
 }
}
</pre>
 

Any time you want to append, just simply create new Object from this class and call its writeObject() method.

Write and Append Object to binary file with ObjectOutputStream [Java Programming]

An ObjectOutputStream writes primitive data types and graphs of Java objects to an OutputStream. The objects can be read (reconstituted) ...

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បង្កើតWindows Form-GUIជាមួយភាសាJava

<img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjLmvEfFMrHLOGfjdVa1eJe6flo7B6i-tEIzDpvj-hT_YAQqr_prvGFcAqw0IwsnJR7zt-IJ_UFMtn56hRZhI_INNOv1tD2Vlx4GSseMqywYl4XykUuy4GsUlAIYNzMvDPuUJLmyc8YISQ/s320/01.PNG" style="float: left;" />តោះយើងចាប់ផ្តើមបង្កើតGraphic User Interface ជាមួយ <a href="http://www.blogger.com/blogger.g?blogID=5930098683428569143#">អាយធីជនបទ</a> ដែលនេះជាមេរៀនក្នុងការបង្កើតនូវFormមួយសំរាប់បង្ហាញថា "This is Java Programming. I Love JAVA. And you?"
 
ចាប់ផ្តើមការសរសេររបស់អ្នកដោយការបង្កើតនូវFileថ្មី ដែលទីនេះយើងបានប្រើកម្មវិធីJCreator។ បន្ទាប់មករើសយក Java Classes ►► Main Class ហើយដាក់ឈ្មោះClassរបស់អ្នក HelloWorld.java។ឥឡូវចាប់ផ្តើមអនុវត្តការសរសេរកូដដូចខាងក្រោម៖
 
 
<ol type="1">
<li>import java.awt.*;</li>
<li>import java.awt.event.*;</li>
<li>public class HelloWorld {</li>
<li>private Frame myFrame;</li>
<li>private Label lblInfo;</li>
<li>public HelloWorld() {</li>
<li>myFrame=new Frame("HELLO WORLD");// Create New Frame and settitle="HELLO WORLD"</li>
<li>myFrame.setVisible(true);//to Show Frame for User;</li>
<li>myFrame.setSize(280,130);//to set Size of Frame width=280 and height=130;</li>
<li>myFrame.addWindowListener(new WindowAdapter(){</li>
<li>public void windowClosing(WindowEvent e){</li>
<li>System.exit(0);</li>
<li>}</li>
<li>});// to Close Exit Program when Frame is closed;</li>
<li>myFrame.setResizable(false);//Not Allow User to Resize Form -FixedToolDialogBox;</li>
<li>lblInfo=new Label("This is Java Programming. I Love JAVA. And You?");//Create new label</li>
<li>// and show text "This is Java Programming. I Love JAVA. And You?";</li>
<li>myFrame.add(lblInfo);//add above label to Frame;</li>
<li>}</li>
<li>public static void main(String[] args) {</li>
<li>new HelloWorld();</li>
<li>}</li>
<li>}</li>
</ol>
 
ជាការស្រេច! ឥឡូវសាកល្បងRunនិងមើលលទ្ធផលរបស់អ្នក! <a href="https://app.box.com/s/a2yaracctsek540be748" target="new">ទាញយកSoucre Code</a>

បង្កើតWindows Form-GUIជាមួយភាសាJava

តោះយើងចាប់ផ្តើមបង្កើតGraphic User Interface ជាមួយ អាយធីជនបទ ដែលនេះជាមេរៀនក្នុងការបង្កើតនូវFormមួយសំរាប់បង្ហាញថា "This is Java Programm...

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