1 项目整体结构的设计
为了让新同学深入的理解tomcat的运行原理，动手实现一个简单的tomcat服务器。
文章比较长，而且需要跟着动手练习，才能有所收获。
思路模型图:
项目结构图:
web.xml映射文件中的内容,用于定义URL请求映射路径和java类之间的对应关系
logincom.bjsxt.servlet.LoginServletlogin/login/login2
2 Entity实体类的处理
/**
* 用于处理别名和对应servlet的实体类
*
* login
* com.bjsxt.servlet.LoginServlet
*
*/
public class Entity {private String name;// servlet-name
private String clazz;// servlet-class3 Mapping映射类的处理
/**
* 用于处理servlet别名和对应映射路径的实体类
*
* login
* /login
* /login2
*
*/
public class Mapping {private String name;//servlet-name
private List<String> urlPattern;//多个url-pattern
public Mapping() {this.urlPattern =new ArrayList<String>();}public Mapping(String name, List<String> urlPattern) {this();this.name = name;this.urlPattern = urlPattern;}4 DOM4j解析xml映射文件
导入DOM4J jar包,帮助我们解析web.xml文件
/*
* 读取web.xml配置文件
* 配置文件中的信息封装进多个 entity对象和多个mapping对象中
*
* */
public class WebDom4j {private List<Entity> entityList;private List<Mapping> mappingList;
public WebDom4j() {entityList=new ArrayList<Entity>();mappingList=new ArrayList<Mapping>();}
public WebDom4j(List<Entity> entityList, List<Mapping> mappingList) {this();this.entityList = entityList;this.mappingList = mappingList;}
public List<Entity> getEntityList() {return entityList;}
public void setEntityList(List<Entity> entityList) {this.entityList = entityList;}
public List<Mapping> getMappingList() {return mappingList;}
public void setMappingList(List<Mapping> mappingList) {this.mappingList = mappingList;}// 读取配置文件,生成一个Document对象的方法
public Document getDocument() {SAXReader reader =new SAXReader();File webXml=new File("myserver/WEB-INF/web.xml");try {return reader.read(webXml);} catch (DocumentException e) {e.printStackTrace();}return null;}// 将Document对象解析成Entity对象和Mapping对象 并放入 entityList 和 mappingList中
public void parseDocument(Document document){// 获取根标签
Element wepApp = document.getRootElement();// 获取多个servlet标签
Iterator<Element> servletElements = wepApp.elementIterator("servlet");while(servletElements.hasNext()){Element servletElement = servletElements.next();Element servletName = servletElement.element("servlet-name");Element servletClass = servletElement.element("servlet-class");Entity entity=new Entity(servletName.getText(),servletClass.getText());entityList.add(entity);}// 获取多个servlet-mapping标签
Iterator<Element> servletMappings = wepApp.elementIterator("servlet-mapping");while(servletMappings.hasNext()){Mapping mapping =new Mapping();Element servletMapping = servletMappings.next();//取出servlet-name
Element servletName = servletMapping.element("servlet-name");mapping.setName(servletName.getText());Iterator<Element> urlPatterns = servletMapping.elementIterator("url-pattern");List<String> patterns=new ArrayList<String>();while(urlPatterns.hasNext()){Element urlPattern = urlPatterns.next();patterns.add(urlPattern.getText());}mapping.setUrlPattern(patterns);mappingList.add(mapping);}}
}5处理ServletContext类
全局容器,目前用于存储映射关系
import java.util.HashMap;
import java.util.Map;
/*
* 全局容器类 存储整个项目的信息
* 暂时我们 需要他存储 全局映射关系信息
* Map mapping 存储映射路径和别名 Map servlet 别名和servlet类的全路径名
* url路径 >>>>> servlet别名 servlet别名 >>>> servlet类的全路径名
* /login login login com.bjsxt.servlet.LoginServlet
* /login2 login
* */
public class ServletContext {/**
* List entityList;
* servlet-name作为键
* servlet-class作为值
*/private Map<String,String> servlet;/*
List mappingList;
* url-pattern 作为键
* servlet-name作为值
* */private Map<String,String> mapping;
public ServletContext() {servlet=new HashMap<String,String>();mapping=new HashMap<String,String>();}
public ServletContext(Map<String, String> servlet, Map<String, String> mapping) {this();this.servlet = servlet;this.mapping = mapping;}6 编写WebApp类
运行时初始化程序
根据不同的url使用反射创建不同的servlet对象
package com.bjsxt.server;
import com.bjsxt.servlet.Servlet;
import org.dom4j.Document;
import java.util.List;
import java.util.Map;
public class WebApp {// 将WebDom4j中的信息转化到ServletContext类中
private static ServletContext context;static{context=new ServletContext();Map<String, String> servlet = context.getServlet();Map<String, String> mapping = context.getMapping();WebDom4j dom4j=new WebDom4j();Document document = dom4j.getDocument();dom4j.parseDocument(document);List<Entity> entityList = dom4j.getEntityList();for(Entity entity:entityList){String name = entity.getName();String clazz = entity.getClazz();servlet.put(name,clazz);}List<Mapping> mappingList = dom4j.getMappingList();for(Mapping mappingx:mappingList){String name = mappingx.getName();List<String> urlPatterns = mappingx.getUrlPattern();for(String urlPattern:urlPatterns){mapping.put(urlPattern,name);}}}
// 根据映射路径返回对应的servlet对象
public static Servlet getServlet(String urlPattern){// /login >>> com.bjsxt.servlet.LoginServlet
if(null == urlPattern || "".equals(urlPattern)){return null;}Map<String, String> mappging = context.getMapping();String servletName = mappging.get(urlPattern);if(null == servletName){return null;}Map<String, String> servlet = context.getServlet();String servletClassName = servlet.get(servletName);if(null == servletClassName){return null;}try {Class servletClazz = Class.forName(servletClassName);return (Servlet) servletClazz.newInstance();} catch (Exception e) {e.printStackTrace();}return null;}
}7 准备提交信息的HTML页面
="http://127.0.0.1:8888/login" method ="post">
用户名:="text" name="username" />
密码:="password" name="password" />
登录身份:
="checkbox" name="role" value="manager" />管理人员
="checkbox" name="role" value="clerk" />普通员工
="checkbox" name="role" value="visiter" />游客
="submit" />
8 封装请求对象
将请求中的信息放入一个Request对象中,便于我们直接从Request对象上获取信息
package com.bjsxt.server;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.util.*;
public class Request {private InputStream is;private String requestInfo;private String method;// post get
private String url;//
//用于存储参数的Map集合
//username=zhangsan&password=qwer&role=manager&role=clerk
/*
* key value
* username [zhangsan]
* password [qwer]
* role [manager,clerk]
*
* */private Map<String, List<String>> paramaterValues;private static final String CRLF="";private static final String BLANK=" ";
public String getUrl() {return url;}
public Request(){requestInfo="";method="";url="";paramaterValues=new HashMap<String,List<String>>();}
public Request(InputStream is){this();this.is=is;paraseRequeseInfo();}public void paraseRequeseInfo(){// 获取请求信息
byte[] buf=new byte[10240];int index = 0;try {index = is.read(buf);} catch (IOException e) {e.printStackTrace();}requestInfo=new String (buf,0,index);// 取出请求行 请求方式 url地址 请求的协议
String requestLine=requestInfo.substring(0,requestInfo.indexOf(CRLF)).trim();String[] requestLines = requestLine.split(" ");method=requestLines[0];String paramaterLine="";if(method.equalsIgnoreCase("get")){// 请求方式是get
if(requestLines[1].contains("?")){url=requestLines[1].substring(0,requestLines[1].indexOf("?"));String[] urls=requestLines[1].split("?");paramaterLine=urls[1].trim();}else{url=requestLines[1];}}else{//请求方式是Post
url=requestLines[1];paramaterLine=requestInfo.substring(requestInfo.lastIndexOf(CRLF)+1).trim();}parseParamater(paramaterLine);}public void parseParamater(String paramaterLine){//username=asdf&password=qwer&role=manager&role=clerk
System.out.println("paramaterLine:"+paramaterLine);if("".equalsIgnoreCase(paramaterLine)){return;}String[] lines = paramaterLine.split("&");/*
[username,asdf]
[password,qwer]
[role,manager]
[role,clerk]
*//*
* key value
* username [zhangsan]
* password [qwer]
* role [manager,clerk]
*
* */for(String line:lines){String[] keyValue = line.split("=");if(keyValue.length==1){// key=
keyValue=Arrays.copyOf(keyValue,2);keyValue[1]=null;}String key=keyValue[0];String value=keyValue[1]==null?null:decode(keyValue[1],"UTF-8");if(paramaterValues.containsKey(key)){//
List<String> values = paramaterValues.get(key);values.add(value);}else{List<String> values=new ArrayList<String>();values.add(value);paramaterValues.put(key,values);}}System.out.println(paramaterValues);}public String decode(String value,String charset){// %E5%BC%A0%E4%B8%89 UTF-8
try {return URLDecoder.decode(value,charset);} catch (UnsupportedEncodingException e) {e.printStackTrace();}return null;}
// 根据键向外界返回参数的方法
public String getParamater(String name){if(paramaterValues.containsKey(name)){List<String> list = paramaterValues.get(name);if(null == list || list.size()==0){return null;}else{return list.get(0);}}return null;}
public String[] getParamaterValues(String name){if(paramaterValues.containsKey(name)){List<String> list = paramaterValues.get(name);if(null == list || list.size()==0){return null;}else{String[] values = list.toArray(new String[0]);return values;}}return null;}
}9封装响应对象
package com.bjsxt.server;
import java.io.*;
public class Response {// 字符输出流
private BufferedWriter bw;// 响应行
private StringBuilder responseLine;// 响应头
private StringBuilder responseHeaders;// 响应数据实体
private StringBuilder content;// 响应数据的长度
private int length;private static final String CRLF="";private static final String BLANK=" ";
public Response() {responseLine=new StringBuilder();responseHeaders=new StringBuilder();content=new StringBuilder();length=0;}public Response(OutputStream os){this();bw =new BufferedWriter(new OutputStreamWriter(os));}
// 处理响应行的方法
public void createResponseLine(int code){//HTTP/1.1 200 OK
responseLine.append("HTTP/1.1").append(BLANK).append(code).append(BLANK);switch (code){case 200:responseLine.append("OK");break;case 404:responseLine.append("NOTFOUND");break;case 500:responseLine.append("SERVEREXCEPTION");break;
default:responseLine.append("Other");break;}responseLine.append(CRLF);}
// 生成响应头的方法
public void createResponseHeaders(){responseHeaders.append("Content-Type: text/html;charset=UTF-8").append(CRLF);responseHeaders.append("Content-Length: ").append(length).append(CRLF).append(CRLF);}
// 生成响应内容的方法
public void write(String info){content.append(info);try {length+=info.getBytes("UTF-8").length;} catch (UnsupportedEncodingException e) {e.printStackTrace();}}
// 将内容响应给浏览器的方法
public void responseToBrowser(int code){createResponseLine(code);createResponseHeaders();StringBuilder info=new StringBuilder();info.append(responseLine).append(responseHeaders).append(content);try {bw.write(info.toString());bw.flush();} catch (IOException e) {e.printStackTrace();}}
}创建server类,用于启动服务,接受请求
package com.bjsxt.server;
import com.bjsxt.servlet.Servlet;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
public class Server {public static void main(String[] args) {new Server().start();}
private ServerSocket serverSocket;// 启动服务,接受请求
public void start(){try {
serverSocket=new ServerSocket(8888);System.out.println("服务已经启动,准备接受请求");Socket socket = serverSocket.accept();InputStream inputStream = socket.getInputStream();OutputStream outputStream = socket.getOutputStream();// 将请求信息封装进一个Request对象
Request request =new Request(inputStream);// 封装一个Response响应对象
Response response=new Response(outputStream);// 根据请求的url 实例化一个Servlet对象
String url = request.getUrl();Servlet servlet = WebApp.getServlet(url);int code =200;if(null == servlet){code=404;response.write("未找到您要访问的资源");}else {// 调用servlet的service方法去处理请求
try {servlet.service(request,response);} catch (Exception e) {code=500;response.write(e.getMessage());}}response.responseToBrowser(code);} catch (IOException e) {e.printStackTrace();}}
}10多线程处理
定义请求分发线程任务
import com.bjsxt.servlet.Servlet;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
public class RequestDispacher implements Runnable{private Socket socket;public RequestDispacher(Socket socket){this.socket=socket;}@Overridepublic void run() {InputStream inputStream = null;OutputStream outputStream = null;try {inputStream = socket.getInputStream();outputStream = socket.getOutputStream();} catch (IOException e) {e.printStackTrace();}// 将请求信息封装进一个Request对象
Request request =new Request(inputStream);// 封装一个Response响应对象
Response response=new Response(outputStream);// 根据请求的url 实例化一个Servlet对象
String url = request.getUrl();Servlet servlet = WebApp.getServlet(url);int code =200;if(null == servlet){code=404;response.write("未找到您要访问的资源");}else {// 调用servlet的service方法去处理请求
try {servlet.service(request,response);} catch (Exception e) {code=500;response.write(e.getMessage());}}response.responseToBrowser(code);// 释放资源
try {inputStream.close();} catch (IOException e) {e.printStackTrace();}try {socket.close();} catch (IOException e) {e.printStackTrace();}}
}在Server中使用多线程处理
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
public class Server {public static void main(String[] args) {new Server().start();}
private ServerSocket serverSocket;// 启动服务,接受请求
public void start(){try {
serverSocket=new ServerSocket(8888);System.out.println("服务已经启动,准备接受请求");while(true){Socket socket = serverSocket.accept();new Thread(new RequestDispacher(socket)).start();}
} catch (IOException e) {e.printStackTrace();}}
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