新建一个java普通工程
工程目录结构如下:
新建webroot目录用于存放要访问的servlet以及静态资源
各个类的关系说明
主类(含main方法)HttpServer1主要功能
- 通过socket进行服务器(main方法启动服务)端监听,等待远程客户端(浏览器)连接
- 与客户端建立连接
- 通过socket获取到输入inputstrem以及输出流outputstream
- 用输入流实例化request对象,输出流实例化response对象
- 关联(实例化)两个处理器ServletProcessor(处理servlet的处理器)和StaticResourceProcessor(处理静态资源的处理器)
- 将request对象及response对象传给两个处理器进行处理,处理后分别返回结果给客户端
HttpServer1 完整代码
package com.xl.test;
import java.net.Socket;
import java.net.ServerSocket;
import java.net.InetAddress;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.IOException;
public class HttpServer1 {
/** WEB_ROOT is the directory where our HTML and other files reside.
* For this package, WEB_ROOT is the "webroot" directory under the working
* directory.
* The working directory is the location in the file system
* from where the java command was invoked.
*/
// shutdown command
private static final String SHUTDOWN_COMMAND = "/SHUTDOWN";
// the shutdown command received
private boolean shutdown = false;
public static void main(String[] args) {
HttpServer1 server = new HttpServer1();
server.await();
}
public void await() {
ServerSocket serverSocket = null;
int port = 8080;
try {
serverSocket = new ServerSocket(port, 1, InetAddress.getByName("127.0.0.1"));
}
catch (IOException e) {
e.printStackTrace();
System.exit(1);
}
// Loop waiting for a request
while (!shutdown) {
Socket socket = null;
InputStream input = null;
OutputStream output = null;
try {
socket = serverSocket.accept();
input = socket.getInputStream();
output = socket.getOutputStream();
String responseHeader = "HTTP/1.1 200 success\r\n" + "\r\n";
output.write(responseHeader.getBytes());
// create Request object and parse
Request request = new Request(input);
request.parse();
// create Response object
Response response = new Response(output);
response.setRequest(request);
// check if this is a request for a servlet or a static resource
// a request for a servlet begins with "/servlet/"
if (request.getUri().startsWith("/servlet/")) {
ServletProcessor1 processor = new ServletProcessor1();
processor.process(request, response);
}
else {
StaticResourceProcessor processor = new StaticResourceProcessor();
processor.process(request, response);
}
// Close the socket
socket.close();
//check if the previous URI is a shutdown command
shutdown = request.getUri().equals(SHUTDOWN_COMMAND);
}
catch (Exception e) {
e.printStackTrace();
System.exit(1);
}
}
}
}
注意:一定要设置协议头,否则客户端无法正常接收到数据
String responseHeader = "HTTP/1.1 200 success\r\n" + "\r\n";
output.write(responseHeader.getBytes());
Request完整代码
package com.xl.test;
import java.io.InputStream;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.UnsupportedEncodingException;
import java.util.Enumeration;
import java.util.Locale;
import java.util.Map;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletInputStream;
import javax.servlet.ServletRequest;
public class Request implements ServletRequest {
private InputStream input;
private String uri;
public Request(InputStream input) {
this.input = input;
}
public String getUri() {
return uri;
}
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 void parse() {
// Read a set of characters from the socket
StringBuffer request = new StringBuffer(2048);
int i;
byte[] buffer = new byte[2048];
try {
i = input.read(buffer);
}
catch (IOException 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());
}
/* implementation of the ServletRequest*/
public Object getAttribute(String attribute) {
return null;
}
public Enumeration getAttributeNames() {
return null;
}
public String getRealPath(String path) {
return null;
}
public RequestDispatcher getRequestDispatcher(String path) {
return null;
}
public boolean isSecure() {
return false;
}
public String getCharacterEncoding() {
return null;
}
public int getContentLength() {
return 0;
}
public String getContentType() {
return null;
}
public ServletInputStream getInputStream() throws IOException {
return null;
}
public Locale getLocale() {
return null;
}
public Enumeration getLocales() {
return null;
}
public String getParameter(String name) {
return null;
}
public Map getParameterMap() {
return null;
}
public Enumeration getParameterNames() {
return null;
}
public String[] getParameterValues(String parameter) {
return null;
}
public String getProtocol() {
return null;
}
public BufferedReader getReader() throws IOException {
return null;
}
public String getRemoteAddr() {
return null;
}
public String getRemoteHost() {
return null;
}
public String getScheme() {
return null;
}
public String getServerName() {
return null;
}
public int getServerPort() {
return 0;
}
public void removeAttribute(String attribute) {
}
public void setAttribute(String key, Object value) {
}
public void setCharacterEncoding(String encoding)
throws UnsupportedEncodingException {
}
}
Response完整代码
package com.xl.test;
import java.io.OutputStream;
import java.io.IOException;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.File;
import java.io.PrintWriter;
import java.util.Locale;
import javax.servlet.ServletResponse;
import javax.servlet.ServletOutputStream;
public class Response implements ServletResponse {
private static final int BUFFER_SIZE = 1024;
Request request;
OutputStream output;
PrintWriter writer;
public Response(OutputStream output) {
this.output = output;
}
public void setRequest(Request request) {
this.request = request;
}
/* This method is used to serve a static page */
public void sendStaticResource() throws IOException {
byte[] bytes = new byte[BUFFER_SIZE];
FileInputStream fis = null;
try {
// String responseHeader = "HTTP/1.1 200 success\r\n" + "\r\n";
// output.write(responseHeader.getBytes());
/* request.getUri has been replaced by request.getRequestURI */
File file = new File(Constants.WEB_ROOT, request.getUri());
fis = new FileInputStream(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
*/
int ch = fis.read(bytes, 0, BUFFER_SIZE);
while (ch!=-1) {
output.write(bytes, 0, ch);
ch = fis.read(bytes, 0, BUFFER_SIZE);
}
}
catch (FileNotFoundException e) {
String errorMessage = "HTTP/1.1 404 File Not Found\r\n" +
"Content-Type: text/html\r\n" +
"Content-Length: 23\r\n" +
"\r\n" +
"<h1>File Not Found</h1>";
output.write(errorMessage.getBytes());
}
finally {
if (fis!=null)
fis.close();
}
}
/** implementation of ServletResponse */
public void flushBuffer() throws IOException {
}
public int getBufferSize() {
return 0;
}
public String getCharacterEncoding() {
return null;
}
public Locale getLocale() {
return null;
}
public ServletOutputStream getOutputStream() throws IOException {
return null;
}
public PrintWriter getWriter() throws IOException {
// autoflush is true, println() will flush,
// but print() will not.
writer = new PrintWriter(output, true);
return writer;
}
public boolean isCommitted() {
return false;
}
public void reset() {
}
public void resetBuffer() {
}
public void setBufferSize(int size) {
}
public void setContentLength(int length) {
}
public void setContentType(String type) {
}
public void setLocale(Locale locale) {
}
}
ServletPorcessor1完整代码
package com.xl.test;
import java.net.URL;
import java.net.URLClassLoader;
import java.net.URLStreamHandler;
import java.io.File;
import java.io.IOException;
import javax.servlet.Servlet;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
public class ServletProcessor1 {
public void process(Request request, Response response) {
String uri = request.getUri();
String servletName = uri.substring(uri.lastIndexOf("/") + 1);
URLClassLoader loader = null;
try {
// create a URLClassLoader
URL[] urls = new URL[1];
URLStreamHandler streamHandler = null;
File classPath = new File(Constants.WEB_ROOT);
// the forming of repository is taken from the createClassLoader method in
// org.apache.catalina.startup.ClassLoaderFactory
String repository = (new URL("file", null, classPath.getCanonicalPath() + File.separator)).toString() ;
// the code for forming the URL is taken from the addRepository method in
// org.apache.catalina.loader.StandardClassLoader class.
urls[0] = new URL(null, repository, streamHandler);
loader = new URLClassLoader(urls);
}
catch (IOException e) {
System.out.println(e.toString() );
}
Class myClass = null;
try {
myClass = loader.loadClass(servletName);
}
catch (ClassNotFoundException e) {
System.out.println(e.toString());
}
Servlet servlet = null;
try {
servlet = (Servlet) myClass.newInstance();
servlet.service((ServletRequest) request, (ServletResponse) response);
}
catch (Exception e) {
System.out.println(e.toString());
}
catch (Throwable e) {
System.out.println(e.toString());
}
}
}
StaticResourceProcessor完整代码
package com.xl.test;
import java.io.IOException;
public class StaticResourceProcessor {
public void process(Request request, Response response) {
try {
response.sendStaticResource();
}
catch (IOException e) {
e.printStackTrace();
}
}
}
Constants完整代码
package com.xl.test;
import java.io.File;
public class Constants {
public static final String WEB_ROOT =
System.getProperty("user.dir") + File.separator + "webroot";
}
PrimitiveServlet完整代码
import javax.servlet.*;
import java.io.IOException;
import java.io.PrintWriter;
public class PrimitiveServlet implements Servlet {
public void init(ServletConfig config) throws ServletException {
System.out.println("init");
}
public void service(ServletRequest request, ServletResponse response)
throws ServletException, IOException {
System.out.println("from service");
PrintWriter out = response.getWriter();
out.println("Hello. Roses are red.");
out.print("Violets are blue.");
}
public void destroy() {
System.out.println("destroy");
}
public String getServletInfo() {
return null;
}
public ServletConfig getServletConfig() {
return null;
}
}
index.html完整代码
<html>
<head>
<title>Welcome to BrainySoftware</title>
</head>
<body>
<br>
Welcome to BrainySoftware.
</body>
</html>
test.html完整代码
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>测试文件</title>
</head>
<body>
<table border="1">
<tr style="color:#00FF00">
<th>Header 1</th>
<th>Header 2</th>
</tr>
<tr style="color:#00FFFF">
<td>row 1, cell 1</td>
<td>row 1, cell 2</td>
</tr>
<tr style="color:#FF00FF">
<td>row 2, cell 1</td>
<td>row 2, cell 2</td>
</tr>
</table>
</body>
</html>
测试
启动HttpServer1中的main方法
浏览器中输入http://localhost:8080/servlet/PrimitiveServlet,测试访问servlet
如果浏览器收到 Hello. Roses are red,则说明访问servlet成功
结果
测试访问静态资源
浏览器中分别输入http://localhost:8080/index.html测试index.html文件以及http://localhost:8080/test.html测试 test.html文件
结果显示访问静态资源成功。
参考:《how tomcat works》