1. servlet容器是如何工作的？
- 创建一个Request对象，填充一些信息比如参数、headers、cookies、查询字符串、URI等。一个Request对象是javax.servlet.ServletRequest或javax.servlet.http.ServletRequest接口的实例。
- 创建一个Response对象，用于调用的servlet向客户端传递响应信息。其是javax.servlet.ServletResponse或javax.servlet.http.ServletResponse的实例。
- 调用servlet的service方法，传递request和response对象。servlet从request对象中读取值，向response对象中写入值。
2.Catalina主要模块
- Connector，连接器主要是连接请求到容器。它的工作是为每一个接收到http请求构建一个request和response对象，接下来传递给待处理的容器。
- Container，容器从连接器接收到request和response对象，负责调用servlet的service方法。
连接器和容器是多对1的关系（*对1）
3.tomcat4和5对比
- tomcat5支持servlet2.4和jsp2.0规范，tomcat4支持servlet2.3和jsp1.2
- tomcat5拥有比tomcat4更高效的默认连接器
- tomcat5使用更少的资源。因为tomcat5共享一个后台处理的线程，而tomcat4的每个模块都有自己的后台处理线程。
- tomcat5代码更简洁。因为不需要一个mapper组件来找到一个子组件。
一个简单的HttpServer代码示例：
流程图：
package com.flyer.tomcat.first;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
/**
* 一个简单的http服务器
* <p />
*
* @author Administrator
*/
public class HttpServer {
private final static String SHUTDOWN_COMMAND = "/shutdown";
public final static String WEB_ROOT = System.getProperty("user.dir") + File.separator + "webroot";
private boolean shutdown = false;
public static void main(String[] args) {
System.out.println("server start");
System.out.println(WEB_ROOT);
HttpServer server = new HttpServer();
try {
server.await();
} catch (IOException e) {
System.out.println(e.getMessage());
}
}
private void await() throws IOException {
ServerSocket serverSocket = new ServerSocket(9090,1,InetAddress.getByName("127.0.0.1"));
InputStream input = null;
OutputStream output = null;
while (!shutdown) {
Socket socket = null;
try {
socket = serverSocket.accept();
input = socket.getInputStream();
output = socket.getOutputStream();
Request request = new Request(input);
request.parse();
Response response = new Response(output);
response.setRequest(request);
response.sendStaticResource();
shutdown = request.getUri().equals(SHUTDOWN_COMMAND);
} catch (Exception e) {
e.printStackTrace();
} finally {
socket.close();
input.close();
output.close();
}
}
}
}
Request类
package com.flyer.tomcat.first;
import java.io.IOException;
import java.io.InputStream;
public class Request {
private byte[] buffer = new byte[1024];
private InputStream input;
private String uri;
public Request(InputStream input) {
this.setInput(input);
}
/**
* @return
*/
public InputStream getInput() {
return input;
}
/**
* @param
*/
public void setInput(InputStream input) {
this.input = input;
}
public void parse() {
int count = 0;
StringBuilder sb = new StringBuilder();
try {
count = input.read(buffer);
} catch (IOException e) {
count = -1;
}
if (count != -1) {
for (int i = 0; i < count; i++) {
sb.append((char) buffer[i]);
}
}
uri = parseUri(sb.toString());
}
private String parseUri(String requestString) {
int index1, index2;
String uri = requestString;
index1 = uri.indexOf(" ");
if (index1 != -1) {
index2 = uri.indexOf(" ", index1 + 1);
if (index1 < index2) {
uri = uri.substring(index1 + 1, index2);
return uri;
}
}
return "";
}
/**
* @return
*/
public String getUri() {
return uri;
}
// public static void main(String[] args) {
// Request request = new Request(new InputStream() {
//
// @Override
// public int read() throws IOException {
// // TODO Auto-generated method stub
// return 0;
// }
//
// });
// String test = "GET /index.jsp HTTP/1.1";
// System.out.println(request.parseUri(test));
// }
}
Response类
package com.flyer.tomcat.first;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
public class Response {
public final static int BUFFER_SIZE = 1024;
private Request request;
private OutputStream output;
public Response(OutputStream output) {
this.setOutput(output);
}
/**
* @return
*/
public Request getRequest() {
return request;
}
/**
* @param
*/
public void setRequest(Request request) {
this.request = request;
}
public void sendStaticResource() {
byte[] buffer = new byte[BUFFER_SIZE];
InputStream inputStream = null;
try {
File file = new File(HttpServer.WEB_ROOT + request.getUri());
if (file.exists()) {
inputStream = new FileInputStream(file);
int count = 0;
while ((count = inputStream.read(buffer)) != -1) {
output.write(buffer, 0, count);
}
} else {
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());
}
} catch (Exception e) {
// TODO: handle exception
} finally {
try {
if (inputStream != null) {
inputStream.close();
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
/**
* @return
*/
public OutputStream getOutput() {
return output;
}
/**
* @param
*/
public void setOutput(OutputStream output) {
this.output = output;
}
}
