手写tomcat系列2-第一个Servlet容器
插曲：加班回家写博客花了两个小时，中间网页挂了好几次，浪费了一个小时，完成时已经十一点多了，计划写两篇，只能完成一篇，累，但有收获，明天继续，本实现有安全问题，将在系列3中优化。
从大局开始先上UML图：
1.HttpServer1：负责处理接受请求，依赖（dependency）Request类和Response类；关联（association）ServletProcessor1和StaticResourceProcessor；
2.ServletProcessor1：处理servlet请求，依赖（dependency）Request类和Response类。有点小干货，有兴趣下面有总结。
3.StaticResourceProcessor：处理静态文件请求，依赖（dependency）Request类和Response类。
4.request：不解释，直接去看源码。
5.Response：不解释，直接去看源码。
6.Constants：常量类。
HttpServer1 类代码：
public class HttpServer1 {
// 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();
// create Request object and parse 获取请求中的uri
Request request = new Request(input);
request.parse();
// create Response object
Response response = new Response(output);
response.setRequest(request);
// a request for a servlet begins with "/servlet/"
if (request.getUri().startsWith("/servlet/")) {
// 动态servlet处理组件 设计
ServletProcessor1 processor = new ServletProcessor1();
processor.process(request, response);
} else {
// 静态文件处理组件 设计
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);
}
}
}
}
StaticResourceProcessor
public class StaticResourceProcessor {
public void process(Request request, Response response) {
try {
response.sendStaticResource();
}
catch (IOException e) {
e.printStackTrace();
}
}
}
ServletProcessor1
功能总结：
1.初始化ClassLoader，用于加载servlet类。
2.通过ClassLoader加载Class，并实例化对象。
3.执行servlet的service方法。
4.下面两行代码干货小技巧
URLStreamHandler streamHandler = null;
/**streamHandler参数的作用只是告诉构造函数传参类型，以避免构造函数混淆。*/
urls[0] = new URL(null, repository, streamHandler);
public class ServletProcessor1 {
public void process(Request request, Response response) {
String uri = request.getUri();//URI格式： /servlet/servletName
String servletName = uri.substring(uri.lastIndexOf("/") + 1);
URLClassLoader loader = null;
/**
* create a URLClassLoader
* process 方法加载 servlet。
* 要完成这个，你需要创建一个类加载器并告诉这个类加载器要加载的类的位置。
* 对于这个 servlet 容器，类加载器直接在 Constants 指向的目录里边查找。
* WEB_ROOT 就是指向工作目录下面的 webroot 目录(repository)。
*/
try {
URL[] urls = new URL[1];
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.
URLStreamHandler streamHandler = null;
/**
* streamHandler参数的作用只是告诉构造函数传参类型，以避免构造函数混淆。
*/
urls[0] = new URL(null, repository, streamHandler);
/**
* 要加载 servlet，你可以使用 java.net.URLClassLoader 类，它是 java.lang.ClassLoader类的一个直接子类。
* 这里 urls 是一个 java.net.URL 的对象数组，这些对象指向了加载类时候查找的位置。任何以/结尾的 URL 都假设是一个目录。
* 否则，URL 会 Otherwise the URL 假定是一个将被下载并在需要的时候打开的 JAR 文件。
**/
loader = new URLClassLoader(urls);
} catch (IOException e) {
System.out.println(e.toString());
}
Class myClass = null;
try {
// 加载servlet
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());
}
}
}
Constants
public class Constants {
public static final String WEB_ROOT =
System.getProperty("user.dir") + File.separator + "webroot";
}
Request
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; jResponse
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 {
/* 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) {
// 返回静态文件内容
output.write(bytes, 0, ch);
ch = fis.read(bytes, 0, BUFFER_SIZE);
}
} catch (FileNotFoundException e) {
// 如果找不到，返回404
String errorMessage = "HTTP/1.1 404 File Not Found\r\n" + "Content-Type: text/html\r\n"
+ "Content-Length: 23\r\n" + "\r\n" + "File Not Found
";
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) {
}
}