学完微型服务器（Tomcat）对其工作流程的理解，自己着手写个简单的tomcat

2019-05-09 19:28:42

注：项目(MyEclipse)创建的时候选择：Web Service Project

第一步对Tomcat工作流程进行分析

第二步对其项目进行全局的把关

首先看看Project(FirstTomcat)的目录结构

|-FirstTomcat

|——src

| |-org.mrzhangxd.com

| |-FirstRequest.java

| |-FirstResponse.java

| |-FirstServlet.java

| |-FirstTomcat.java

| |-FirstServletMapping.java

| |_FirstServletMappingConfig.java

| |-JRE System Library[JavaSE-x.y]

| |-JAXB x.y.z Libraries

| |-JavaEE x.y Generic Library

| |-JSTL x.y.z Library

| |-JAX-RS x.y Libraries(Project Jersey x.y)

|___|_WebRoot

第三步代码实现

处理请求：

1. 创建一个request对象并填充那些有可能被所引用的Servlet使用的信息，如参数，头部、cookies、查询字符串等。
2. 创建一个response对象，所引用的servlet使用它来给客户端发送响应。
3. 调用servlet的service方法，并传入request和response对象。这里servlet会从request对象取值，给response写值。
4. 根据servlet返回的response生成相应的HTTP响应报文。

接下来一一实现

请求：FirstRequest.java

package org.mrzhangxd.com;

import java.io.InputStream;

/**

* @author mrzhangxd

public class FirstRequest {

//请求路径

private String url;

//请求方法

private String method;

public FirstRequest(InputStream inputStream)throws Exception{

String httpRequest = "";

byte[] httpRequestBytes = new byte[1024];

int length = 0;

if((length = inputStream.read(httpRequestBytes))>0){

httpRequest = new String(httpRequestBytes,0,length);

}

//HTTP请求协议：首行的内容依次为：请求方法、请求路径以及请求协议及其对应的版本号

//GET /index /HTTP/1.1

String httpHead = httpRequest.split("\n")[0];//取出HTTP协议的首行

System.out.println(httpHead);

method = httpHead.split("\\s")[0];//按照空格进行分割，第一个请求方法

url = httpHead.split("\\s")[1];//按照空格进行分割，第二个是路径

System.out.println(this.toString());

}

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;

}

public String toString(){

return "MyRequest[url = "+url+",method = "+method+"]";

}

回应：FirstResponse.java

package org.mrzhangxd.com;

import java.io.IOException;

import java.io.OutputStream;

/**

* @author mrzhangxd

public class FirstResponse {

private OutputStream outputStream;

public FirstResponse(OutputStream outputStream){

this.outputStream = outputStream;

}

//将文本转换为字节流

public void write(String content)throws IOException{

StringBuffer httpResponse = new StringBuffer();

httpResponse.append("HTTP/1.1 200 OK\n")

.append("Content-Type;text/html\n")

.append("\r\n")

.append("<html><link rel = \"icon\"href = \"data:;base64,=\">")

.append(content)//将页面内容写入

.append("</body></html>")

.append("");

outputStream.write(httpResponse.toString().getBytes());//将文本转换为字节码

outputStream.close();

}

Servlet请求处理基类：FirstServlet.java

package org.mrzhangxd.com;

/**

* @author mrzhangxd

public abstract class FirstServlet {

public void servlet(FirstRequest firstRequest,FirstResponse firstResponse){

if(firstRequest.getMethod().equalsIgnoreCase("POST")){

doPost(firstRequest,firstResponse);

}else if(firstRequest.getMethod().equalsIgnoreCase("GET")){

doGet(firstRequest,firstResponse);

}

private void doGet(FirstRequest firstRequest, FirstResponse firstResponse) {

// TODO Auto-generated method stub

}

private void doPost(FirstRequest firstRequest, FirstResponse firstResponse) {

// TODO Auto-generated method stub

}

public void service(FirstRequest firstRequest, FirstResponse firstResponse) {

// TODO Auto-generated method stub

}

下一步servlet配置：FirstServletMapping.java

package org.mrzhangxd.com;

/**

* @author mrzhangxd

public class FirstServletMapping {

private String servletName;

private String url;

private String clazz;

public FirstServletMapping(String servletName, String url, String clazz) {

super();

this.servletName = servletName;

this.url = url;

this.clazz = clazz;

}

public String getServletName() {

return servletName;

}

public void setServeletName(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;

}

其他配置：FirstServletMappingConfig.java

package org.mrzhangxd.com;

import java.util.ArrayList;

import java.util.List;

/**

* @author mrzhangxd

public class FirstServletMappingConfig {

public static List<FirstServletMapping> servletMappingList = new ArrayList<>();

static {

servletMappingList.add(new FirstServletMapping("index", "/index", "firstTomcat.test.IndexServlet"));

servletMappingList.add(new FirstServletMapping("firstblog", "/firstblog", "firstTomcat.test.MyBlog"));

}

核心处理类：FirstTomcat.java,处理流程如下：

1) 提供Socket服务

2) 封装请求/响应对象

3) 将不同的请求映射到具体的Servlet处理

这里重点说的是，要利用 ServerSocket 通过服务器上的端口通信以及 accpt方法一直等待客户端的请求

package org.mrzhangxd.com;

import java.io.InputStream;

import java.io.OutputStream;

import java.net.ServerSocket;

import java.net.Socket;

import java.util.HashMap;

import java.util.Map;

/**

* @author mrzhangxd

public class FirstTomcat {

private Integer port = 8080; //定义8080端口

private Map<String, String> urlServletMapping = new HashMap<>(); //存储url和对应的类

public FirstTomcat(Integer port) {

super();

this.port = port;

}

@SuppressWarnings("resource")

public void start() {

initServletMapping();

try {

ServerSocket serverSocket = null; //实例化一个 ServerSocket 对象，表示通过服务器上的端口通信

serverSocket = new ServerSocket(port);

System.out.println("MyTomcat is starting...");

while(true) {

Socket socket = serverSocket.accept(); //服务器调用 ServerSocket 类的 accept() 方法，该方法将一直等待，直到客户端连接到服务器上给定的端口

InputStream inputStream = socket.getInputStream();

OutputStream outputStream = socket.getOutputStream();

FirstRequest myRequest = new FirstRequest(inputStream);

FirstResponse myResponse = new FirstResponse (outputStream);

dispatch(myRequest, myResponse);

socket.close();

}

}catch(Exception e) {

e.printStackTrace();

}

//初始化映射

public void initServletMapping() {

for(FirstServletMapping servletMapping : FirstServletMappingConfig.servletMappingList) {

urlServletMapping.put(servletMapping.getUrl(), servletMapping.getClazz());

}

//分发请求

@SuppressWarnings("unchecked")

public void dispatch(FirstRequest firstRequest, FirstResponse firstResponse) {

String clazz = urlServletMapping.get(firstRequest.getUrl());

try {

Class<FirstServlet> firstServletClass = (Class<FirstServlet>)Class.forName(clazz);

FirstServlet firstservlet = firstServletClass.newInstance();

firstservlet.service(firstRequest, firstResponse);

}catch(ClassNotFoundException e) {

e.printStackTrace();

}catch(InstantiationException e) {

e.printStackTrace();

}catch(IllegalAccessException e) {

e.printStackTrace();

}

public static void main(String[] args) {

FirstTomcat myTomcat = new FirstTomcat(8080);

myTomcat.start();

}

测试类按照上面类里的注释自己解决，测试结果略。

注：

编码格式、注释都参考《代码整洁之道》