Let’s briefly introduce the principle. The browser opens a web page can be simply divided into 3 stages:
1. Send a request string in a certain format to the server through the socket (which contains the URL entered by the user), such as:
| Accept | text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 |
| Accept-Encoding | gzip, deflate |
| Accept-Language | zh-cn,zh;q=0.8,en-us;q=0.5,en;q=0.3 |
| Connection | keep-alive |
| Host | localhost:8001 |
| User-Agent | Mozilla/5.0 (Windows NT 6.1; rv:22.0) Gecko/20100101 Firefox/22.0 |
2. The server receives the request string from the browser and parses out the URL requested by the user. The URL actually corresponds to the file in the server.
For example, http:\\www.demo.com actually corresponds to http:\\www.demo.com\index.html in the server. The server will read the index.html file into the byte array and add the header information (also string), returned to the browser that sent the request.
3. The browser receives the byte stream returned by the server, and judges the original data type of the returned byte array (web page, picture, other) according to the returned header information. For example, the returned header information is as follows:
| Content-Type | text/html |
Note that the returned byte array is originally an html page, and the browser will parse the html page and display the data.
If the header information returned by the server is as follows:
| Content-Type | image/jpeg |
The source code is given below:
Note: 1. To run the program, you need to create a new webapp folder in the same directory, and put the website you want to run into (temporarily only support html, jpg, gif, png)
2. Program running parameters: It can be run without parameters, and it is bound to port 80 by default, which may conflict. You can add a parameter to set the port, for example: java -jar MyHtmlServer.jar 8001
8001 is the bound port number.
3.运行程序后，在浏览器中输入 http://localhost:端口号/资源路径即可。例如绑定的是8001端口，在webapp文件夹下有index.html文件，现在需要访问这个文件，在浏览器中输入：http://localhost:8001/index.html 即可访问。如果绑定的是80端口，可直接写：http://localhost/index.html,浏览器默认使用80作为服务器端口。
源码：
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.InterruptedIOException;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
public class MyHtmlServer {
public static void main(String[] args) throws IOException {
int port=80;
if(args.length>0)
port=Integer.valueOf(args[0]);
new MyHtmlServer().start(port);
}
/**
* 在指定端口启动http服务器
* @param port 指定的端口
* @throws IOException
*/
public void start(int port) throws IOException {
ServerSocket server = new ServerSocket(port);
System.out.println("server start at "+port+"...........");
while (true) {
Socket client = server.accept();
ServerThread serverthread = new ServerThread(client);
serverthread.start();
}
}
/**
* 服务器响应线程，每收到一次浏览器的请求就会启动一个ServerThread线程
* @author
*
*/
class ServerThread extends Thread {
Socket client;
public ServerThread(Socket client) {
this.client = client;
}
/**
* 读取文件内容，转化为byte数组
* @param filename 文件名
* @return
* @throws IOException
*/
public byte[] getFileByte(String filename) throws IOException
{
ByteArrayOutputStream baos=new ByteArrayOutputStream();
File file=new File(filename);
FileInputStream fis=new FileInputStream(file);
byte[] b=new byte[1000];
int read;
while((read=fis.read(b))!=-1)
{
baos.write(b,0,read);
}
fis.close();
baos.close();
return baos.toByteArray();
}
/**
* 分析http请求中的url,分析用户请求的资源，并将请求url规范化
* 例如请求 "/"要规范成"/index.html","/index"要规范成"/index.html"
* @param queryurl 用户原始的url
* @return 规范化的url，即为用户请求资源的路径
*/
private String getQueryResource(String queryurl)
{
String queryresource=null;
int index=queryurl.indexOf('?');
if(index!=-1)
{
queryresource=queryurl.substring(0,queryurl.indexOf('?'));
}
else
queryresource=queryurl;
index=queryresource.lastIndexOf("/");
if(index+1==queryresource.length())
{
queryresource=queryresource+"index.html";
}
else
{
String filename=queryresource.substring(index+1);
if(!filename.contains("."))
queryresource=queryresource+".html";
}
return queryresource;
}
/**
* 根据用户请求的资源类型，设定http响应头的信息，主要是判断用户请求的文件类型（html、jpg...）
* @param queryresource
* @return
*/
private String getHead(String queryresource)
{
String filename="";
int index=queryresource.lastIndexOf("/");
filename=queryresource.substring(index+1);
String[] filetypes=filename.split("\\.");
String filetype=filetypes[filetypes.length-1];
if(filetype.equals("html"))
{
return "HTTP/1.0200OK\n"+"Content-Type:text/html\n" + "Server:myserver\n" + "\n";
}
else if(filetype.equals("jpg")||filetype.equals("gif")||filetype.equals("png"))
{
return "HTTP/1.0200OK\n"+"Content-Type:image/jpeg\n" + "Server:myserver\n" + "\n";
}
else return null;
}
@Override
public void run() {
InputStream is;
try {
is = client.getInputStream();
BufferedReader br = new BufferedReader(
new InputStreamReader(is));
int readint;
char c;
byte[] buf = new byte[1000];
OutputStream os = client.getOutputStream();
client.setSoTimeout(50);
byte[] data = null;
String cmd = "";
String queryurl = "";
int state = 0;
String queryresource;
String head;
while (true) {
readint = is.read();
c = (char) readint;
boolean space=Character.isWhitespace(readint);
switch (state) {
case 0:
if (space)
continue;
state = 1;
case 1:
if (space) {
state=2;
continue;
}
cmd+=c;
continue;
case 2:
if(space)
continue;
state=3;
case 3:
if(space)
break;
queryurl+=c;
continue;
}
break;
}
queryresource=getQueryResource(queryurl);
head=getHead(queryresource);
while (true) {
try {
if ((readint = is.read(buf)) > 0) {
// System.out.write(buf);
} else if (readint < 0)
break;
} catch (InterruptedIOException e) {
data = getFileByte("webapp"+queryresource);
}
if (data != null) {
os.write(head.getBytes("utf-8"));
os.write(data);
os.close();
break;
}
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}