前言
目的：
网络编程在编程领域随处可见，本文尝试手写一个简单的
HttpServer，了解网络请求后台的大致思路及为学习Tomcat打好基础。
准备知识：
- OOP：面向对象编程思想
- collection：Java常用容器
- IO：网络IO操作
- Thread：多线程
- Socket:网络编程
- XML：配置文件解析
- reflect：框架基石反射
- HTML：HTML基本语法
- HTTP：网络传输协议
思路
先说下大致流程：
- 服务端开启一个服务，进入一个死循环来给前端提供服务。
- 客户端发送一个HTTP请求。
- 服务器端收到请求后，加载一次XML文件解析，主要目的是获得客户的请求网址对应的那个Servlet(服务器端小程序)。
- 找到对应的Servlet后通过反射映射出实例，然后业务处理。
- 最终Socket通信返回结果。
流程图：
代码结构
代码实现
1. XML解析
XML文件解析的方式有多种，本文以SAXException来解析。
xml文件信息
<?xml version="1.0" encoding="UTF-8"?>
<web-app>
<servlet>
<servlet-name>login</servlet-name>
<servlet-class>com.sowhat.user.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>login</servlet-name>
<url-pattern>/login</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>reg</servlet-name>
<servlet-class>com.sowhat.user.RegisterServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>reg</servlet-name>
<url-pattern>/r</url-pattern>
</servlet-mapping>
</web-app>
Servlet类
xml文件中servlet体对应的Java类
package com.sowhat.server.core;
public class Entity {
private String name;
private String clz;
public Entity() {
// TODO Auto-generated constructor stub
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getClz() {
return clz;
}
public void setClz(String clz) {
this.clz = clz;
}
}
Servlet-mapping类
servlet-mapping对应的Java类
package com.sowhat.server.core;
import java.util.HashSet;
import java.util.Set;
public class Mapping {
private String name;
private Set<String> patterns ;
public Mapping() {
patterns = new HashSet<String>();
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Set<String> getPatterns() {
return patterns;
}
public void setPatterns(Set<String> patterns) {
this.patterns = patterns;
}
public void addPattern(String pattern) {
this.patterns.add(pattern);
}
}
WebHandler
解析xml文件代码：WebHandler
package com.sowhat.server.core;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
import java.util.ArrayList;
import java.util.List;
public class WebHandler extends DefaultHandler {
private List<Entity> entitys = new ArrayList<Entity>();
private List<Mapping> mappings = new ArrayList<Mapping>();
private Entity entity;
private Mapping mapping;
private String tag; //存储操作标签
private boolean isMapping = false;
@Override
public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
if (null != qName) {
tag = qName; //存储标签名
if (tag.equals("servlet")) {
entity = new Entity();
isMapping = false;
} else if (tag.equals("servlet-mapping")) {
mapping = new Mapping();
isMapping = true;
}
}
}
@Override
public void characters(char[] ch, int start, int length) throws SAXException {
String contents = new String(ch, start, length).trim();
if (null != tag) { //处理了空
if (isMapping) { //操作servlet-mapping
if (tag.equals("servlet-name")) {
mapping.setName(contents);
} else if (tag.equals("url-pattern")) {
mapping.addPattern(contents);
}
} else { //操作servlet
if (tag.equals("servlet-name")) {
entity.setName(contents);
} else if (tag.equals("servlet-class")) {
entity.setClz(contents);
}
}
}
}
@Override
public void endElement(String uri, String localName, String qName) throws SAXException {
if (null != qName) {
if (qName.equals("servlet")) {
entitys.add(entity);
} else if (qName.equals("servlet-mapping")) {
mappings.add(mapping);
}
}
tag = null; //tag丢弃了
}
public List<Entity> getEntitys() {
return entitys;
}
public List<Mapping> getMappings() {
return mappings;
}
}
WebContext
对解析结果优化映射服务：WebContext
package com.sowhat.server.core;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class WebContext {
private List<Entity> entitys = null;
private List<Mapping> mappings = null;
//key-->servlet-name value -->servlet-class
private Map<String, String> entityMap = new HashMap<String, String>();
//key -->url-pattern value -->servlet-name
private Map<String, String> mappingMap = new HashMap<String, String>();
public WebContext(List<Entity> entitys, List<Mapping> mappings) {
this.entitys = entitys;
this.mappings = mappings;
//将entity 的List转成了对应map
for (Entity entity : entitys) {
entityMap.put(entity.getName(), entity.getClz());
}
//将map 的List转成了对应map
for (Mapping mapping : mappings) {
for (String pattern : mapping.getPatterns()) {
mappingMap.put(pattern, mapping.getName());
}
}
}
public String getClz(String pattern) {
String name = mappingMap.get(pattern);
return entityMap.get(name);
}
}
WebApp
package com.sowhat.server.core;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
public class WebApp {
private static WebContext webContext;
static {
try {
//SAX解析
//1、获取解析工厂
SAXParserFactory factory = SAXParserFactory.newInstance();
//2、从解析工厂获取解析器
SAXParser parse = factory.newSAXParser();
//3、编写处理器
//4、加载文档 Document 注册处理器
WebHandler handler = new WebHandler();
//5、解析
parse.parse(Thread.currentThread().getContextClassLoader().getResourceAsStream("web.xml"), handler);
//获取数据
webContext = new WebContext(handler.getEntitys(), handler.getMappings());
} catch (Exception e) {
System.out.println("解析配置文件错误");
}
}
public static Servlet getServletFromUrl(String url) {
//假设你输入了 /login
String className = webContext.getClz("/" + url);
Class clz;
try {
clz = Class.forName(className);
Servlet servlet = (Servlet) clz.getConstructor().newInstance();
return servlet;
} catch (Exception e) {
}
return null;
}
}
2. Request Response
Request 解析
package com.sowhat.server.core;
import org.apache.commons.io.IOUtils;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.net.Socket;
import java.util.*;
public class Request {
//协议信息
private String requestInfo;
//请求方式
private String method;
//请求url
private String url;
//请求参数
private String queryStr;
//存储参数
private Map<String, List<String>> parameterMap;
private final String CRLF = "\r\n";
public Request(Socket client) throws IOException {
this(client.getInputStream());
System.out.println("request 构造函数");
}
public Request(InputStream is) {
parameterMap = new HashMap<String, List<String>>();
byte[] datas = new byte[1024*1024];
int len;
try {
len = is.read(datas);
this.requestInfo = new String(datas,0,len);
} catch (IOException e) {
e.printStackTrace();
return;
}
//分解字符串
parseRequestInfo();
}
//分解字符串
private void parseRequestInfo() {
this.method = this.requestInfo.substring(0, this.requestInfo.indexOf("/")).toLowerCase();
this.method = this.method.trim();
//1)、获取/的位置
int startIdx = this.requestInfo.indexOf("/") + 1;
//2)、获取 HTTP/的位置
int endIdx = this.requestInfo.indexOf("HTTP/");
//3)、分割字符串
this.url = this.requestInfo.substring(startIdx, endIdx).trim();
//4)、获取？的位置
int queryIdx = this.url.indexOf("?");
if (queryIdx >= 0) {//表示存在请求参数
String[] urlArray = this.url.split("\\?");
this.url = urlArray[0];
queryStr = urlArray[1];
}
System.out.println(this.url);
if (method.equals("post")) {
String qStr = this.requestInfo.substring(this.requestInfo.lastIndexOf(CRLF)).trim();
System.out.println(qStr + "-->");
if (null == queryStr) {
queryStr = qStr;
} else {
queryStr += "&" + qStr;
}
}
queryStr = null == queryStr ? "" : queryStr;
System.out.println(method + "-->" + url + "-->" + queryStr);
//转成Map fav=1&fav=2&uname=sowhat&age=18&others=
convertMap();
}
//处理请求参数为Map
private void convertMap() {
//1、分割字符串 &
String[] keyValues = this.queryStr.split("&");
for (String queryStr : keyValues) {
//2、再次分割字符串 =
String[] kv = queryStr.split("=");
kv = Arrays.copyOf(kv, 2);
//获取key和value
String key = kv[0];
String value = kv[1] == null ? null : decode(kv[1], "utf-8");
//存储到map中
if (!parameterMap.containsKey(key)) { //第一次
parameterMap.put(key, new ArrayList<String>());
}
parameterMap.get(key).add(value);
}
}
private String decode(String value, String enc) {
try {
return java.net.URLDecoder.decode(value, enc);
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
public String[] getParameterValues(String key) {
List<String> values = this.parameterMap.get(key);
if (null == values || values.size() < 1) {
return null;
}
return values.toArray(new String[0]);
}
public String getParameter(String key) {
String[] values = getParameterValues(key);
return values == null ? null : values[0];
}
public String getMethod() {
return method;
}
public String getUrl() {
return url;
}
public String getQueryStr() {
return queryStr;
}
}
Response 解析
package com.sowhat.server.core;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.util.Date;
public class Response {
private BufferedWriter bw;
//正文
private StringBuilder content;
//协议头（状态行与请求头 回车）信息
private StringBuilder headInfo;
private int len; //正文的字节数
private final String BLANK =" ";
private final String CRLF = "\r\n";
private Response() {
content =new StringBuilder();
headInfo=new StringBuilder();
len =0;
}
public Response(Socket client) {
this();
try {
bw=new BufferedWriter(new OutputStreamWriter(client.getOutputStream()));
} catch (IOException e) {
e.printStackTrace();
headInfo = null;
}
}
public Response(OutputStream os) {
this();
bw=new BufferedWriter(new OutputStreamWriter(os));
}
//动态添加内容
public Response print(String info) {
content.append(info);
len+=info.getBytes().length;
return this;
}
public Response println(String info) {
content.append(info).append(CRLF);
len+=(info+CRLF).getBytes().length;
return this;
}
// 推送响应信息
public void pushToBrowser(int code) throws IOException {
if(null ==headInfo) {
code = 505;
}
createHeadInfo(code);
bw.append(headInfo);
bw.append(content);
bw.flush();
}
// 构建头信息
private void createHeadInfo(int code) {
//1、响应行: HTTP/1.1 200 OK
headInfo.append("HTTP/1.1").append(BLANK);
headInfo.append(code).append(BLANK);
switch(code) {
case 200:
headInfo.append("OK").append(CRLF);
break;
case 404:
headInfo.append("NOT FOUND").append(CRLF);
break;
case 505:
headInfo.append("SERVER ERROR").append(CRLF);
break;
}
//2、响应头(最后一行存在空行):
headInfo.append("Date:").append(new Date()).append(CRLF);
headInfo.append("Server:").append("shsxt Server/0.0.1;charset=GBK").append(CRLF);
headInfo.append("Content-type:text/html").append(CRLF);
headInfo.append("Content-length:").append(len).append(CRLF);
headInfo.append(CRLF);
}
}
3. Servlet
Servlet接口
package com.sowhat.server.core;
public interface Servlet {
void service(Request request, Response response);
}
LoginServlet
package com.sowhat.server.user;
import com.sowhat.server.core.Request;
import com.sowhat.server.core.Response;
import com.sowhat.server.core.Servlet;
public class LoginServlet implements Servlet {
@Override
public void service(Request request, Response response) {
response.print("<html>");
response.print("<head>");
response.print("<meta http-equiv=\"content-type\" content=\"text/html;charset=utf-8\">");
response.print("<title>");
response.print("第一个servlet");
response.print("</title>");
response.print("</head>");
response.print("<body>");
response.print("欢迎回来:" + request.getParameter("uname"));
response.print("</body>");
response.print("</html>");
}
}
RegisterServlet
package com.sowhat.server.user;
import com.sowhat.server.core.Request;
import com.sowhat.server.core.Response;
import com.sowhat.server.core.Servlet;
public class RegisterServlet implements Servlet {
@Override
public void service(Request request, Response response) {
//关注业务逻辑
String uname = request.getParameter("uname");
String[] favs = request.getParameterValues("fav");
response.print("<html>");
response.print("<head>");
response.print("<meta http-equiv=\"content-type\" content=\"text/html;charset=utf-8\">");
response.print("<title>");
response.print("注册成功");
response.print("</title>");
response.print("</head>");
response.print("<body>");
response.println("你注册的信息为:" + uname);
response.println("你喜欢的类型为:");
for (String v : favs) {
if (v.equals("0")) {
response.print("萝莉型");
} else if (v.equals("1")) {
response.print("豪放型");
} else if (v.equals("2")) {
response.print("经济节约型");
}
}
response.print("</body>");
response.print("</html>");
}
}
package com.sowhat.server.core;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
public class WebApp {
private static WebContext webContext;
static {
try {
//SAX解析
//1、获取解析工厂
SAXParserFactory factory = SAXParserFactory.newInstance();
//2、从解析工厂获取解析器
SAXParser parse = factory.newSAXParser();
//3、编写处理器
//4、加载文档 Document 注册处理器
WebHandler handler = new WebHandler();
//5、解析
parse.parse(Thread.currentThread().getContextClassLoader().getResourceAsStream("web.xml"), handler);
//获取数据
webContext = new WebContext(handler.getEntitys(), handler.getMappings());
} catch (Exception e) {
System.out.println("解析配置文件错误");
}
}
public static Servlet getServletFromUrl(String url) {
//假设你输入了 /login
String className = webContext.getClz("/" + url);
Class clz;
try {
System.out.println(url + "-->" + className + "-->");
clz = Class.forName(className);
Servlet servlet = (Servlet) clz.getConstructor().newInstance();
return servlet;
} catch (Exception e) {
}
return null;
}
}
开启服务
package com.sowhat.server.core;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
public class Server {
private ServerSocket serverSocket;
private boolean isRunning;
public static void main(String[] args) {
Server server = new Server();
server.start();
}
//启动服务
public void start() {
try {
serverSocket = new ServerSocket(8888);
isRunning = true;
receive();
} catch (IOException e) {
e.printStackTrace();
System.out.println("服务器启动失败....");
stop();
}
}
//接受连接处理
public void receive() {
while (isRunning) {
try {
Socket client = serverSocket.accept();
System.out.println("一个客户端建立了连接....");
//多线程处理
new Thread(new Dispatcher(client)).start(); // 此处是 一个服务入口 重点
} catch (IOException e) {
e.printStackTrace();
System.out.println("客户端错误");
}
}
}
//停止服务
public void stop() {
isRunning = false;
try {
this.serverSocket.close();
System.out.println("服务器已停止");
} catch (IOException e) {
e.printStackTrace();
}
}
}
HTML
Error.HTML
<html>
<head>
<meta http-equiv="content-type" content="text/html;charset=utf-8">
<title>404页面</title>
</head>
<body>
<h1>404错误</h1>
</body>
</html>
index.html
<html>
<head>
<meta http-equiv="content-type" content="text/html;charset=utf-8">
<title>首页</title>
</head>
<body>
<h1>欢迎使用服务器简易版哈哈</h1>
</body>
</html>
demo
延伸
上面只是个简易版的Tomcat雏型，可大致了解到Tomcat的流程，Tomcat无非就是 在基础版本上添加了各种Servlet,Request,Response,Session,Cookie,ServletContext,ServletConfig,EL,JSTL,Filter,Listener,JSP等这些东西，有空再写两章Tomcat源码底层的东西。
参考
源码密码:afnd
Tomcat入门
