A simple Java Web server implementation

A simple Java Web server implementation

A simple Java web server implementation is relatively simple, based on java.net. Socket and java.net. ServerSocket;

Procedure

1. Create a ServerSocket object;
2. Call the accept method of the ServerSocket object and wait for the connection. If the connection is successful, a Socket object will be returned. Otherwise, the wait will be blocked;
3. Obtain the InputStream and OutputStream byte streams from the Socket object. These two streams correspond to the request and response respectively;
4. Request Processing: Read the InputStream byte stream information, convert it to the string format, and parse it. The parsing here is relatively simple. Only uri (unified resource identifier) information is obtained;
5. Processing response: Find the requested resource file from the WEB_ROOT directory based on the parsed uri information, read the resource file, and write it into the OutputStream byte stream;
6. Disable the Socket object;
7. Go to step 2 and wait for the connection request;

Code Implementation

Server implementation:

Package ex01.pyrmont; import java.net. socket; import java.net. serverSocket; import java.net. inetAddress; import java. io. inputStream; import java. io. outputStream; import java. io. IOException; import java. io. file; public class HttpServer {/*** WEB_ROOT is the directory where HTML and other files are stored. here, WEB_ROOT is the webroot directory under the working directory */public static final String WEB_ROOT = System. getProperty ("user. dir ") + File. separator + "webroot"; // close the service command private static final String SHUTDOWN_COMMAND = "/SHUTDOWN"; public static void main (String [] args) {HttpServer server = new HttpServer (); // wait for the connection request to server. await ();} public void await () {ServerSocket serverSocket = null; int port = 8080; try {// server socket object serverSocket = new ServerSocket (port, 1, InetAddress. getByName ("127.0.0.1");} catch (IOException e) {e. printStackTrace (); System. exit (1);} // wait for a request in a loop while (true) {Socket socket = null; InputStream input = null; OutputStream output = null; try {// wait for the connection, after the connection is successful, a Socket object socket = serverSocket is returned. accept (); input = socket. getInputStream (); output = socket. getOutputStream (); // create a Request object and parse the Request request = new Request (input); request. parse (); // check whether the service command if (request. getUri (). equals (SHUTDOWN_COMMAND) {break;} // create the Response object Response response = new Response (output); response. setRequest (request); response. sendStaticResource (); // closes the socket object socket. close ();} catch (Exception e) {e. printStackTrace (); continue ;}}}}

Request class:

Package ex01.pyrmont; import java. io. inputStream; import java. io. IOException; public class Request {private InputStream input; private String uri; public Request (InputStream input) {this. input = input;} // read the request information from InputStream and obtain the uri value public void parse () {StringBuffer request = new StringBuffer (2048); int I; byte [] buffer = new byte [2048]; try {I = input. read (buffer);} catch (IOExcep Tion e) {e. printStackTrace (); I =-1 ;}for (int j = 0; j <I; j ++) {request. append (char) buffer [j]);} System. out. print (request. toString (); uri = parseUri (request. toString ();}/*** requestString format: * GET/index.html HTTP/1.1 * Host: localhost: 8080 * Connection: keep-alive * Cache-Control: max-age = 0 *... * This function is used to obtain the/index.html String */private String parseUri (String requestString) {int Index1, index2; index1 = requestString. indexOf (''); if (index1! =-1) {index2 = requestString. indexOf ('', index1 + 1); if (index2> index1) return requestString. substring (index1 + 1, index2);} return null;} public String getUri () {return uri ;}}

Response class:

Package ex01.pyrmont; import java. io. outputStream; import java. io. IOException; import java. io. fileInputStream; import java. io. file;/* HTTP Response = Status-Line * (general-header | response-header | entity-header) CRLF) CRLF [message-body] Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase CRLF */public class Response {private static final int BUFFER_SIZE = 1024; Request request; OutputStr Eam output; public Response (OutputStream output) {this. output = output;} public void setRequest (Request request) {this. request = request;} public void sendStaticResource () throws IOException {byte [] bytes = new byte [BUFFER_SIZE]; FileInputStream FCM = null; try {// write the web File to the OutputStream byte stream file = new File (HttpServer. WEB_ROOT, request. getUri (); if (file. exists () {FS = new FileInputSt Ream (file); int ch = Fi. read (bytes, 0, BUFFER_SIZE); while (ch! =-1) {output. write (bytes, 0, ch); ch = FCM. read (bytes, 0, BUFFER_SIZE) ;}} else {// file not found String errorMessage = "HTTP/1.1 404 File Not Found \ r \ n" + "Content-Type: text/html \ r \ n "+" Content-Length: 23 \ r \ n "+" \ r \ n "+" Result Test
Access the existing resource file (note that it is stored in the webroot folder of the project directory ):

Access a nonexistent resource file:

Disable the server:

 
Reference: in-depth analysis of Tomcat PDF download
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