Java's network functions and programming a
Last Update:2017-02-28
Source: Internet
Author: User
Programming | Network function and programming of network Java
Xu Xianxiao
(25#, Shanghai University Computing Center)
Summary: The Java language is the most popular programming language on the Internet, and this article
Java network functions, to Java from the network to obtain images, sound,
The HTML document and the text file and so on the programming method has made the preliminary introduction, with
This paper introduces the method of dynamically acquiring resources on network. In this paper
Provides a wide range of simple and understandable examples.
Key words: Java;internet network
The Java language is a new programming language on the Internet, with Java features and base
This method of programming has been introduced in a number of articles. But the vast majority of Java enthusiasts would prefer
To learn more about Java programming method, this article on the Java network functions and programming methods
To make a preliminary introduction.
In order to facilitate the first contact with Java readers, this article first on Java programming some common sense
For a brief introduction.
Introduction to Java Programming
1. Programming Environment:
For most readers, the following configuration is a more economical option:
Operating system Win95
Compiling software JDK1.01
Browse software Netscape2.0 above (32-bit)
2. Programming Method:
Enter Java programs with a text editor such as edit, Notepad, and so on. Java
FileName suffix disk.
Then execute the command line: "Javac filename" to compile the Java program. Build after compilation
A byte-code file with a. class suffix.
Finally, if it is a Java applitcation, execute the command line: "Java Word
Section code file name to run the Java program.
If it is a Java applet, the Java applet is called with a text editor input
HTML document with. htm for the filename suffix. To execute the command line again:
"Appletviewer HTML filename" to run the Java applet. or with Netscape
Open the HTML document.
3. Notes on the procedure in this article
In order for the program to be the most concise embodiment of the programming method it represents, the process in this article
The order is generally in the simplest form, omitting the thread and other contents. Therefore, the procedure in this article does not
is a "good" program, but easiest for beginners to understand.
After compiling all the programs in this article, the generated bytecode files and corresponding HTML documents
Uploaded to Http://www.shu.edu.cn/~xyx/test/jvnet, all correct
Run. Readers connected to the Internet can open the address in a browser to see how it works.
Readers connected to the Internet can also enter and compile the program on the local hard drive,
Open the HTML document with Netscape's File/open File menu, experience programming methods and
View the run effect. If the reader wants to put Java applets on their host or other
On the FTP server, called in Netscape using the HTTP protocol or FTP protocol, for security
Sexual restrictions should be modified as follows:
If the reader has an account number on a WWW host, you can make a personal homepage (generally
To create a WWW or public_html directory in the user's root directory, the homepage address is
http://HostName/~ personal account), you can use this procedure in the corresponding
The http://www.shu.edu.cn/~xyx/part is modified to the reader's own web node address,
The compiled bytecode file and corresponding HTML document are then uploaded to their node.
If the reader's computer is connected to the Internet, you can also find an uploaded
FTP nodes, such as: Ftp://ftp.shnet.edu.cn/incoming, will be in this program
The corresponding http://www.shu.edu.cn/~xyx/part is modified to the address of the FTP node.
Upload the compiled bytecode file and the corresponding HTML document to the node to check
Look at the running effect.
If the reader's computer is not networked, it can also be run on a stand-alone Web service soft
Pieces such as WebSTAR for Win95, the corresponding HTTP in this program: www. Shu
The. edu.cn/~xyx/section is modified to the form "http://local IP address" to simulate
Network programming.
Java network features and general steps to get resources on the network
Java programs can get nodes on the network image, sound, HTML documents and text
Resources and to deal with the resources available. For example, a Java program can have every
Set time to read the latest data provided by a node and display it as a chart.
In programming, Mr. General becomes an object of a URL type and then uses Java
Gets the resource represented by the object in the corresponding method in the The following are described separately
Several examples of Java network functionality, and thus introduce several different programming methods.
Third, obtain the image from the network
Java applets can get images directly from nodes on the network and display them. For
To understand how the programming method differs from the programming of local display images, let's not consider
Network function to see an example of a simple image display:
Program 1
Import java.applet.*;
Import java.awt.*;
public class Imag0 extends applet{
Image Image;
public void init () {
Image=getimage (Getdocumentbase (), "test.gif");
}
public void Paint (Graphics g) {
G.drawimage (image, 0, 0,this);
}
}
This is one of the simplest examples of capturing and displaying images, in this case, the first
GetImage (Getdocumentbase (), image file name) from the location of the HTML document
The image is test.gif, and this generates an object image of the image type, and then uses the
DrawImage (image, 0, 0,this) shows the image on the screen.
If you want to get images from other nodes on the network, the key is to create the corresponding
Other nodes are objects of the image type, once the object of the image type is obtained,
You can perform any possible image manipulation on it.
Java provides the following ways to create an image that corresponds to another node:
GetImage (new URL (String))
There are two ways to use the format:
String url = "Node url";
Image Image;
try {
Image = GetImage (new URL (URL));
}
catch (Exception e) {
System.out.println ("Can ' t Open the URL");
}
Or
URL Imgur=null;
Image Image;
try {
Imgur=new url ("Node url");
}
catch (Malformedurlexception e) {
System.out.println ("Can ' t Open the URL");
}
Image=getimage (Imgur);
The previous format generates a URL object with a new URL (URL) and acts directly as a
GetImage, the latter format generates a URL using the new URL (URL) first
object, and then passed to GetImage. The two formats are essentially the same. In both formats,
The parts of the generated URL object are included in the
try{
Get URL Object
}
catch (Malformedurlexception e) {
Error prompt
}
In
For example, to invoke a http://www.shu.edu.cn/~xyx/img/shnet.jpg node.
Image, the first form of the complete program is as follows:
Program 2
Import java.applet.*;
Import java.net.*;
Import java.awt.*;
public class Imag extends applet{
Image Image;
public void init () {
String url = "Http://www.shu.edu.cn/~xyx/img/shnet.jpg";
try {
Image = GetImage (new URL (URL));
catch (Exception e) {}
}
public void Paint (Graphics g) {
G.drawimage (image, 0, 0,this);
}
}
The second form is complete as follows:
Program 3
Import java.applet.*;
Import java.net.*;
Import java.awt.*;
public class Imag2 extends applet{
Image Image;
URL Imgur=null;
public void init () {
try {
Imgur=new URL ("http://www.shu.edu.cn/~xyx/img/shnet.jpg");
}
catch (Malformedurlexception e) {
System.out.println ("Can ' t Open the URL");
}
Image=getimage (Imgur);
}
public void Paint (Graphics g) {
G.drawimage (image, 0, 0,this);
}
}
Save the above two programs in Imag.java and Imag2. Java, and execute
Javac Imag.java and Javac Imag2.java will be compiled and generated imag
. class and Imag2.class, and finally create the HTML that calls the two Java applets
Files, such as the imag.class corresponding HTML document can be as follows:
< HTML >
< head >
< title >example </title >
< Center >
< applet Code=imag.class width=550 height=250 >
</applet >
Save the HTML document in test.html file, open with Netscape, if you
Computer is connected to the Internet, you can see what the Java Applet displays from the Web
The image obtained on the envelope. (for the other different Java applets in this article, the corresponding
HTML document as long as the corresponding "Code=imag.class" can be modified. )
Iv. getting sound from the Internet
Java has two types of programming methods for getting sound files from a network and playing sounds.
Is the use of Java provided play (URL) and plays (url,string) direct Playback Network
The sound file on the other is via getAudioClip (URL) or getAudioClip
(url,string) Get the sound file from the network first and generate the AudioClip type
object, and then manipulate the object.
The use of the former format is:
String Audur = "Node url";
try {
Play (New URL (Audur));
catch (Exception e) {}
Or
String Audur = "Node url";
try {
Play (New URL (Audur), sound filename);
catch (Exception e) {}
The format used by the latter is:
String Audur = "Node url";
AudioClip Loopclip;
try {
Loopclip = getAudioClip (new URL (Audur));
}
catch (Exception e) {
System.out.println ("Can ' t Open the URL");
}
Or
String Audur = "Node url";
AudioClip Loopclip;
try {
Loopclip = getAudioClip (new URL (Audur), sound filename);
}
catch (Exception e) {
System.out.println ("Can ' t Open the URL");
}
All four of the above formats are to generate the URL object part--"New URL (URL)"
As a direct parameter to play or getaudioclip; As with the previous image processing example,
You can also use the new URL (URL) to get a URL object, and then pass to play or
getAudioClip. For the first play (URL) format, you can also use the following series
Process format:
URL Audur =null;
try {
Audur=new url ("Node url");
catch (Exception e) {
System.out.println ("Can ' t Open the URL");
}
Play (Audur);
The following is a simple example of the above four formats for getting and playing sound files from the network.
For programming purposes:
Program 4 Format One
Import java.applet.*;
Import java.awt.*;
Import java.net.*;
public class Sound1 extends Applet
{AudioClip loopclip;
public void Paint (Graphics g) {
String Audur = "http://www.shu.edu.cn/~xyx/java/Animator/audio/bark.au";
try {
Play (New URL (Audur));
catch (Exception e) {}
}
}
Program 5 Format Two
Import java.applet.*;
Import java.awt.*;
Import java.net.*;
public class Sound2 extends Applet
{AudioClip loopclip;
public void Paint (Graphics g) {
String Audur = "http://www.shu.edu.cn/~xyx/java/Animator/audio/";
try {
Play (New URL (Audur), "bark.au");
catch (Exception e) {}
}
}
Program 6 Format Three
Import java.applet.*;
Import java.awt.*;
Import java.net.*;
public class Sound extends applet{
AudioClip Loopclip;
public void init () {
String Audur = "http://www.shu.edu.cn/~xyx/java/Animator/audio/bark.au";
try {
Loopclip = getAudioClip (new URL (Audur));
catch (Exception e) {}
}
public void Paint (Graphics g) {
Loopclip.loop ();
}
}
Program 7 format Four
Import java.applet.*;
Import java.awt.*;
Import java.net.*;
public class Sound0 extends applet{
AudioClip Loopclip;
URL Auur;
public void init () {
try {
Auur=new URL ("http://www.shu.edu.cn/~xyx/java/Animator/audio/");
}
catch (Malformedurlexception e) {
System.out.println ("Can ' t Open the URL");
}
Loopclip = getAudioClip (Auur, "bark.au");
}
public void Paint (Graphics g) {
Loopclip.loop ();
}
}