基于BIO手写简易Tomcat
# 基于传统的BIO手写一个简易Tomcat
本文主要基于传统的BIO来实现一个简单的Http请求处理过程；
1、Servlet请求无非就是doGet/doPost，所以我们定义抽象Servlet记忆GET/POST方法；
2、基于Socket和ServerSocket实现CS通信；
3、模拟Spring加载配置文件，注册请求以及控制器；
## GlRequest 封装一个请求
> 当然是一个很简单的请求，这里只处理请求的URL和请求方法；
> 获取请求，也就是输入流，解析数据Url和Method，并做相应的处理；
```text
public class GlRequest {
private String url;
private String method;
public GlRequest(InputStream is) {
try {
// 解析http请求的具体内容；
String content = "";
byte[] buff = new byte[1024];
int len = 0;
if ((len = is.read(buff)) > 0) {
content = new String(buff, 0, len);
}
String line = content.split("\\n")[0];
String [] arr = line.split("\\s");
this.method = arr[0];
this.url = arr[1].split("\\?")[0];
} catch (IOException e) {
e.printStackTrace();
}
}
public String getUrl() {
return this.url;
}
public String getMethod() {
return this.method;
}
}
```
## GlResponse 定义返回值response
> 处理请求返回值，将业务处理的结果通过输出流输出；
> 输出大致分为两部分，第一是返回的数据，第二是返回数据的Header;
```text
public class GlResponse {
private OutputStream outputStream;
public GlResponse(OutputStream os) {
this.outputStream = os;
}
public void write(String string) throws Exception {
StringBuffer sb = new StringBuffer();
sb.append("HTTP/1.1 200 OK\n")
.append("Content-Type: text/html;\n")
.append("\r\n")
.append(string);
outputStream.write(sb.toString().getBytes());
}
}
```
## GlServlet 定义抽象servlet，定义GET方法和POST方法
> 定义抽象的Servlet和doGet方法和doPost方法，具体的业务去实现自己的方法和逻辑；
```text
public abstract class GlServlet {
private final static String GET = "GET";
public void service(GlRequest request, GlResponse response) throws Exception {
if (GET.equals(request.getMethod())) {
doGet(request, response);
} else {
doPost(request, response);
}
}
public abstract void doGet(GlRequest request, GlResponse response) throws Exception;
public abstract void doPost(GlRequest request, GlResponse response) throws Exception;
}
```
## FirstServlet 具体的业务Servlet实现抽象Servlet的方法
```text
public class FirstServlet extends GlServlet {
@Override
public void doGet(GlRequest request, GlResponse response) throws Exception {
// 具体的逻辑
this.doPost(request, response);
}
@Override
public void doPost(GlRequest request, GlResponse response) throws Exception {
response.write("This is first servlet from BIO");
}
}
```
## SecondServlet 具体的业务Servlet实现抽象Servlet方法
```text
public class SecondServlet extends GlServlet {
@Override
public void doGet(GlRequest request, GlResponse response) throws Exception {
doPost(request,response);
}
@Override
public void doPost(GlRequest request, GlResponse response) throws Exception {
response.write("This second request form BIO");
}
}
```
## web-bio.properties 配置文件
> 配置请求和处理器，Spring中是通过Controller下的@XXXMapping注解去扫描并加载到工厂的；
```text
servlet.one.className=com.ibli.netty.tomcat.bio.servlet.FirstServlet
servlet.one.url=/firstServlet.do
servlet.two.className=com.ibli.netty.tomcat.bio.servlet.SecondServlet
servlet.two.url=/secondServlet.do
```
## GlTomcat测试类
> 启动服务端，在网页中访问本地8080端口，输入配置文件中定义的url进行测试：
```text
public class GlTomcat {
private ServerSocket server;
private final Integer PORT = 8080;
private Properties webXml = new Properties();
private Map<String, GlServlet> servletMapping = new HashMap<String, GlServlet>();
/**
* 模拟项目main方法，启动加载配置
*
* @param args 启动参数
*/
public static void main(String[] args) {
new GlTomcat().start();
}
/**
* Tomcat的启动入口
*/
private void start() {
//1、加载web配置文件，解析配置
init();
//2、启动服务器socket，等待用户请求
try {
server = new ServerSocket(this.PORT);
System.err.println("Gl tomcat started in port " + this.PORT);
while (true) {
Socket client = server.accept();
// 3、获得请求信息，解析HTTP协议的内容
process(client);
}
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* 加载配置文件
*/
private void init() {
try {
String WEB_INF = this.getClass().getResource("/").getPath();
FileInputStream fis = new FileInputStream(WEB_INF + "web-bio.properties");
webXml.load(fis);
for (Object k : webXml.keySet()) {
String key = k.toString();
if (key.endsWith(".url")) {
//servlet.two.url
String servletName = key.replaceAll("\\.url", "");
String url = webXml.getProperty(key);
//servlet.two.className
String className = webXml.getProperty(servletName + ".className");
//反射创建servlet实例
// load-on-startup >=1 :web启动的时候初始化 0：用户请求的时候才启动
GlServlet obj = (GlServlet) Class.forName(className).newInstance();
// 将url和servlet建立映射关系
servletMapping.put(url, obj);
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* 解析客户端请求
*
* @param client 客户端
*/
private void process(Socket client) throws Exception {
InputStream is = null;
OutputStream os = null;
try {
//请求
is = client.getInputStream();
//封装返回值
os = client.getOutputStream();
GlRequest request = new GlRequest(is);
GlResponse response = new GlResponse(os);
String url = request.getUrl();
if (servletMapping.containsKey(url)) {
servletMapping.get(url).service(request, response);
} else {
response.write("404 Not found!");
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (os != null) {
os.flush();
os.close();
}
if (is != null) {
is.close();
client.close();
}
}
}
}
```
## 打印请求信息
```text
Request content : GET /fitstServlet.do HTTP/1.1
Host: localhost:8080
Connection: keep-alive
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/88.0.4324.150 Safari/537.36 OPR/74.0.3911.160
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Sec-Fetch-Site: none
Sec-Fetch-Mode: navigate
Sec-Fetch-User: ?1
Sec-Fetch-Dest: document
Accept-Encoding: gzip, deflate, br
Accept-Language: zh-CN,zh;q=0.9
```
## 客户端发送请求及结果展示
> 请求： http://localhost:8080/firstServlet.do
