筆者也建立的自己的公衆號啦,平時會分享一些編程知識,歡迎各位大佬支持~
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本文公衆號地址:手寫一個基於NIO的迷你版Tomcat
在很久之前看到了一篇文章寫一個迷你版的Tomcat,覺得還是很有意思的,於是也跟着手敲了一遍,果不其然得出了想要的hello world,但是他這個是基於BIO的,正好最近看了併發編程的書,於是嘗試將這位大佬的代碼改一改,於是就有了這個基於NIO的迷你Tomcat。
源代碼已更新至我的Github:https://github.com/tzfun/MyTomcat
BIO和NIO
BIO是同步阻塞IO,在實際場景中大部分時間消耗在了IO等待上了,比較消耗資源,所以這種IO方式逐漸被替代了,具體介紹這裏不再贅述。取而代之的是NIO(New IO),它是一種同步非阻塞式的IO,它通過Selector自旋式或回調式的方式去處理準備好數據的Channel,Channel即通道,相當於BIO中的流,它不存在花費大量時間去IO等待,從而大大提升了吞吐量。Tomcat在老版本也是基於BIO的,後續版本更新也全部替換爲NIO。
項目結構
項目結構和原作者的結構幾乎一樣,只是代碼實現不一樣,具體結構看下圖:
Request和Response
Tomcat主要是Http服務,所以處理的協議是Http協議,那麼Http的頭部信息由請求行、請求頭部、空行、請求數據組成,只需要拆分這些數據即可處理http請求,這裏我只是簡單的處理了一下,其他詳細內容看註釋。
Request
package mytomcat;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.SocketChannel;
import java.util.HashMap;
/**
* @author beifengtz
* <a href='http://www.beifengtz.com'>www.beifengtz.com</a>
* <p>location: mytomcat.javase_learning</p>
* Created in 14:45 2019/4/21
*/
public class MyRequest {
private String url;
private String method;
private HashMap<String,String> param = new HashMap<>();
public MyRequest(SelectionKey selectionKey) throws IOException{
// 從契約獲取通道
SocketChannel channel = (SocketChannel) selectionKey.channel();
String httpRequest = "";
ByteBuffer bb = ByteBuffer.allocate(16*1024); // 從堆內存中獲取內存
int length = 0; // 讀取byte數組的長度
length = channel.read(bb); // 從通道中讀取數據到ByteBuffer容器中
if (length < 0){
selectionKey.cancel(); // 取消該契約
}else {
httpRequest = new String(bb.array()).trim(); // 將ByteBuffer轉爲String
String httpHead = httpRequest.split("\n")[0]; // 獲取請求頭
url = httpHead.split("\\s")[1].split("\\?")[0]; // 獲取請求路徑
String path = httpHead.split("\\s")[1]; // 請求全路徑,包含get的參數數據
method = httpHead.split("\\s")[0];
// 一下是拆分get請求的參數數據
String[] params = path.indexOf("?") > 0 ? path.split("\\?")[1].split("\\&") : null;
if (params != null){
try{
for (String tmp : params){
param.put(tmp.split("\\=")[0],tmp.split("\\=")[1]);
}
}catch (NullPointerException e){
e.printStackTrace();
}
}
System.out.println(this);
}
bb.flip();
}
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
public String getMethod() {
return method;
}
public void setMethod(String method) {
this.method = method;
}
@Override
public String toString() {
return "MyRequest{" +
"url='" + url + '\'' +
", method='" + method + '\'' +
", param=" + param +
'}';
}
}
Response
package mytomcat;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.SocketChannel;
import java.nio.charset.StandardCharsets;
/**
* @author beifengtz
* <a href='http://www.beifengtz.com'>www.beifengtz.com</a>
* <p>location: mytomcat.javase_learning</p>
* Created in 14:49 2019/4/21
*/
public class MyResponse {
private SelectionKey selectionKey;
public MyResponse(SelectionKey selectionKey){
this.selectionKey = selectionKey;
}
public void write(String content) throws IOException{
// 拼接相應數據包
StringBuffer httpResponse = new StringBuffer();
httpResponse.append("HTTP/1.1 200 OK\n")
.append("Content-type:text/html\n")
.append("\r\n")
.append("<html><body>")
.append(content)
.append("</body></html>");
// 轉換爲ByteBuffer
ByteBuffer bb = ByteBuffer.wrap(httpResponse.toString().getBytes(StandardCharsets.UTF_8));
SocketChannel channel = (SocketChannel) selectionKey.channel(); // 從契約獲取通道
long len = channel.write(bb); // 向通道中寫入數據
if (len == -1){
selectionKey.cancel();
}
bb.flip();
channel.close();
selectionKey.cancel();
}
}
Servlet和Mapping映射類及其配置類
在Java web開發中都會遇到Servlet和Mapping的配置,這些是必備的元素,Servlet負責定義處理請求和響應的方法,它是一個抽象類。
Servlet
package mytomcat;
/**
* @author beifengtz
* <a href='http://www.beifengtz.com'>www.beifengtz.com</a>
* <p>location: mytomcat.javase_learning</p>
* Created in 14:53 2019/4/21
*/
public abstract class MyServlet {
public abstract void doGet(MyRequest myRequest,MyResponse myResponse);
public abstract void doPost(MyRequest myRequest,MyResponse myResponse);
public void service(MyRequest myRequest,MyResponse myResponse){
if (myRequest.getMethod().equalsIgnoreCase("POST")){
doPost(myRequest,myResponse);
}else if (myRequest.getMethod().equalsIgnoreCase("GET")){
doGet(myRequest,myResponse);
}
}
}
Mapping映射是負責將某些請求路徑分發到各自處理類進行處理,那麼就需要一個配置類,以下是ServletMapping類的定義和Config類。
ServletMapping
package mytomcat;
/**
* @author beifengtz
* <a href='http://www.beifengtz.com'>www.beifengtz.com</a>
* <p>location: mytomcat.javase_learning</p>
* Created in 14:59 2019/4/21
*/
public class ServletMapping {
private String servletName;
private String url;
private String clazz;
public ServletMapping(String servletName, String url, String clazz) {
this.servletName = servletName;
this.url = url;
this.clazz = clazz;
}
public String getServletName() {
return servletName;
}
public void setServletName(String servletName) {
this.servletName = servletName;
}
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
public String getClazz() {
return clazz;
}
public void setClazz(String clazz) {
this.clazz = clazz;
}
}
ServletMappingConfig
package mytomcat;
import java.util.ArrayList;
import java.util.List;
/**
* @author beifengtz
* <a href='http://www.beifengtz.com'>www.beifengtz.com</a>
* <p>location: mytomcat.javase_learning</p>
* Created in 15:01 2019/4/21
*/
public class ServletMappingConfig {
public static List<ServletMapping> servletMappingList = new ArrayList<>();
static {
servletMappingList.add(new ServletMapping("helloWorld","/world","mytomcat.HelloWorldServlet"));
}
}
當然一般這個配置是通過xml文件去配置的。
下面是處理/world請求的處理類
package mytomcat;
import java.io.IOException;
/**
* @author beifengtz
* <a href='http://www.beifengtz.com'>www.beifengtz.com</a>
* <p>location: mytomcat.javase_learning</p>
* Created in 14:57 2019/4/21
*/
public class HelloWorldServlet extends MyServlet {
@Override
public void doGet(MyRequest myRequest, MyResponse myResponse) {
try{
myResponse.write("get hello world");
}catch (IOException e){
e.printStackTrace();
}
}
@Override
public void doPost(MyRequest myRequest, MyResponse myResponse) {
try{
myResponse.write("post hello world");
}catch (IOException e){
e.printStackTrace();
}
}
}
Tomcat核心啓動類
Tomcat的啓動類是它的核心,其中包含初始化Mapping、監聽端口、處理請求和響應等,我與原作者的主要區別也就是在這一部分,用NIO替換了BIO的接收數據模式,採用線程池處理數據。
MyTomcat
package mytomcat;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.channels.spi.SelectorProvider;
import java.util.*;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/**
* @author beifengtz
* <a href='http://www.beifengtz.com'>www.beifengtz.com</a>
* <p>location: mytomcat.javase_learning</p>
* Created in 15:03 2019/4/21
*/
public class MyTomcat {
private int port = 8080;
private Map<String, String> urlServletMap = new HashMap<>();
private Selector selector;
private ExecutorService es = Executors.newCachedThreadPool();
public MyTomcat() {
}
public MyTomcat(int port) {
this.port = port;
}
public void start() throws IOException {
// 初始化映射關係
initServletMapping();
// 啓動Selector
selector = SelectorProvider.provider().openSelector();
// 啓動Channel
ServerSocketChannel ssc = ServerSocketChannel.open();
// 配置非阻塞選擇
ssc.configureBlocking(false);
// 監聽端口
InetSocketAddress isa = new InetSocketAddress(port);
ssc.socket().bind(isa);
// 將Channel綁定到Selector上,並選擇準備模式爲Accept,此處可能會失敗,後續可再次開啓
SelectionKey acceptKey = ssc.register(selector, SelectionKey.OP_ACCEPT);
System.out.println("MyTomcat is started...");
ConcurrentLinkedQueue<MyRequest> requestList = new ConcurrentLinkedQueue<>();
ConcurrentLinkedQueue<MyResponse> responseList = new ConcurrentLinkedQueue<>();
while (true) {
selector.select(); // 等待Channel準備數據
Set readyKeys = selector.selectedKeys();
Iterator i = readyKeys.iterator();
while (i.hasNext()) {
SelectionKey sk = (SelectionKey) i.next();
i.remove(); // 從集合中移除,防止重複處理
if (sk.isAcceptable()) { // 如果鍵的接收狀態未正常打開,再次嘗試打開
doAccept(sk);
} else if (sk.isValid() && sk.isReadable()) { // 可讀
requestList.add(getRequest(sk));
// 切換準備狀態
sk.interestOps(SelectionKey.OP_WRITE);
} else if (sk.isValid() && sk.isWritable()) { // 可寫
responseList.add(getResponse(sk));
// 切換準備狀態
sk.interestOps(SelectionKey.OP_READ);
}
// 等待一對請求和響應均準備好時處理
if (!requestList.isEmpty() && !responseList.isEmpty()) {
dispatch(requestList.poll(), responseList.poll());
}
}
}
}
/**
* 如果沒有正常開啓接收模式
* 嘗試開啓接收模式
* @param selectionKey
*/
private void doAccept(SelectionKey selectionKey) {
ServerSocketChannel server = (ServerSocketChannel) selectionKey.channel();
SocketChannel clientChannel;
try {
clientChannel = server.accept();
clientChannel.configureBlocking(false);
SelectionKey clientKey = clientChannel.register(selector, SelectionKey.OP_READ);
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* 從通道中獲取請求並進行包裝
*
* @param selectionKey
* @return
* @throws IOException
*/
private MyRequest getRequest(SelectionKey selectionKey) throws IOException {
return new MyRequest(selectionKey); // 包裝request
}
/**
* 從通道中獲取響應並進行包裝
*
* @param selectionKey
* @return
*/
private MyResponse getResponse(SelectionKey selectionKey) {
return new MyResponse(selectionKey); // 包裝response
}
/**
* 初始化Servlet的映射對象
*/
private void initServletMapping() {
for (ServletMapping servletMapping : ServletMappingConfig.servletMappingList) {
urlServletMap.put(servletMapping.getUrl(), servletMapping.getClazz());
}
}
/**
* 請求調度
*
* @param myRequest
* @param myResponse
*/
private void dispatch(MyRequest myRequest, MyResponse myResponse) {
if (myRequest == null) return;
if (myResponse == null) return;
String clazz = urlServletMap.get(myRequest.getUrl());
try {
if (clazz == null) {
myResponse.write("404");
return;
}
es.execute(new Runnable() {
@Override
public void run() {
try {
Class<MyServlet> myServletClass = (Class<MyServlet>) Class.forName(clazz);
MyServlet myServlet = myServletClass.newInstance();
myServlet.service(myRequest, myResponse);
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
}
}
});
} catch (IOException e) {
e.printStackTrace();
}
}
public static void main(String[] args) throws IOException {
new MyTomcat().start();
}
}
測試
當我們在瀏覽器中輸入http://localhost:8080/world?data=yes時,成功得到了預期的結果
控制檯輸出: