自己动手写Tomcat

编程语言 2018-05-12 08:43:23 阅读次数: 2

最近研究一方socket编程，由于想动手写关于socket方面的东西。然而我们知道通过URL去访问某网址，其实其底层用的就是socket，于是我就写了一个很简单的tomcat服务器，主要目地在于学习，在此分享给大家。同时提供下载源工程。

我写的工程用Maven管理的，但是我没有引入其它的JAR包，为此我就不列出pom.xml文件了。

在此简要地说明每个类的作用：

Server.java

该类的作用就是将服务提起来的，并且利用线程池。

package com.cloud.tomcat.server;

import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class Server {
    private static ServerSocket serverSocket;
    private static ExecutorService executorService;
    private final static int POOL_SIZE = 15;

    public static void main(String[] args) throws Exception {
        serverSocket = new ServerSocket(8080);
        Socket socket = null;
        executorService = Executors.newFixedThreadPool(POOL_SIZE);

        while (true) {
            socket = serverSocket.accept();
            PrintWriter writer = new PrintWriter(new OutputStreamWriter(socket.getOutputStream(), "UTF-8"));
            writer.println("HTTP/1.1 200 OK");
            writer.println("Content-Type: text/html;charset=UTF-8");
            writer.println();

            executorService.execute(new Handler(socket, writer));
        }
    }
}

Handler.java

该类的作用是根据浏览器传过来信息做出相应的处理，同时实现Runnable接口。

package com.cloud.tomcat.server;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;

import com.cloud.tomcat.servlet.HttpServlet;

public class Handler implements Runnable {
    private Socket socket;
    private PrintWriter writer;

    public Handler(Socket socket, PrintWriter writer) {
        this.socket = socket;
        this.writer = writer;
    }

    @Override
    public void run() {
        try {
            InputStream inputStream = socket.getInputStream();
            BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
            String path = "";
            String method = "";

            while (true) {
                String msg = reader.readLine();
                if (null == msg || "".equals(msg.trim())) {
                    break;
                }

                String[] msgs = msg.split(" ");
                if (3 == msgs.length && "HTTP/1.1".equalsIgnoreCase(msgs[2])) {
                    method = msgs[0];
                    path = msgs[1];
                    break;
                }
            }

            if (path.endsWith("ico")) {
                return;
            }

            HttpServlet httpServlet = ServletContainer.getHttpServlet(path);
            String html = "";
            if ("GET".equals(method)) {
                html = httpServlet.doGet();
            } else if ("POST".equals(method)) {
                html = httpServlet.doGet();
            }
            writer.write(html);
            writer.flush();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                writer.close();
                socket.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        
    }

}

ServletContainer.java

该类首先会解析web.xml文件，然后根据url的信息，拿到相应的servlet。

package com.cloud.tomcat.server;

import java.util.HashMap;
import java.util.Map;

import com.cloud.tomcat.model.Servlet;
import com.cloud.tomcat.model.ServletMapping;
import com.cloud.tomcat.servlet.HttpServlet;
import com.cloud.tomcat.util.XMLUtil;

public class ServletContainer {
    private static Map<String, Object> servletMaps = new HashMap<String, Object>();
    private static Map<String, Object> servletMappingMaps = new HashMap<String, Object>();
    private static Map<String, HttpServlet> servletContainer = new HashMap<String, HttpServlet>();

    static {
        try {
            Map<Integer, Map<String, Object>> maps = XMLUtil.parseWebXML();
            if (null != maps && 2 == maps.size()) {
                servletMaps = maps.get(0);
                servletMappingMaps = maps.get(1);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static HttpServlet getHttpServlet(String path) {

        if (null == path || "".equals(path.trim()) || "/".equals(path)) {
            path = "/index";
        }
    
        if (servletContainer.containsKey(path)) {
            return servletContainer.get(path);
        }

        if (!servletMappingMaps.containsKey(path)) {
            return null;
        }
        ServletMapping servletMapping = (ServletMapping) servletMappingMaps.get(path);
        String name = servletMapping.getName();

        if (!servletMaps.containsKey(name)) {
            return null;
        }
        Servlet servlet = (Servlet) servletMaps.get(name);
        String clazz = servlet.getClazz();

        if (null == clazz || "".equals(clazz.trim())) {
            return null;
        }

        HttpServlet httpServlet = null;
        try {
            httpServlet = (HttpServlet) Class.forName(clazz).newInstance();
            servletContainer.put(path, httpServlet);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return httpServlet;
    }
}

HttpServlet.java

为了实现起来简单方便，我自己定义了一个HttpServlet。

package com.cloud.tomcat.servlet;

public interface HttpServlet {
    public String doGet();
    public String doPost();
}

CloudServlet.java

HttpServlet的具体实现类。

package com.cloud.tomcat.servlet;

public class CloudServlet implements HttpServlet {

    @Override
    public String doGet() {
        return this.doPost();
    }

    @Override
    public String doPost() {
        return "<h1>Chicago at Cloud!!!</h1>";
    }

}

下面一一列出解析web.xml用到的类，由于我没有引入第三JAR包，可能这部分有点麻烦。

Servlet.java

package com.cloud.tomcat.model;

public class Servlet {
    private String name;
    private String clazz;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getClazz() {
        return clazz;
    }

    public void setClazz(String clazz) {
        this.clazz = clazz;
    }
}

ServletMapping.java

package com.cloud.tomcat.model;

public class ServletMapping {
    private String name;
    private String url;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }
}

XMLUtil.java

package com.cloud.tomcat.util;

import java.io.InputStream;
import java.util.HashMap;
import java.util.Map;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

import com.cloud.tomcat.model.Servlet;
import com.cloud.tomcat.model.ServletMapping;

public class XMLUtil {

    public static Map<Integer, Map<String, Object>> parseWebXML() throws Exception {
        Map<Integer, Map<String, Object>> result = new HashMap<Integer, Map<String,Object>>();
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        DocumentBuilder db = dbf.newDocumentBuilder();

        InputStream in = XMLUtil.class.getClassLoader().getResourceAsStream("web.xml");
        Document document = db.parse(in);
        Element root = document.getDocumentElement();
        NodeList xmlNodes = root.getChildNodes();
        for (int i = 0; i < xmlNodes.getLength(); i++) {
            Node config = xmlNodes.item(i);
            if (null != config && config.getNodeType() == Node.ELEMENT_NODE) {
                String nodeName1 = config.getNodeName();
                if ("servlet".equals(nodeName1)) {
                    Map<String, Object> servletMaps = null;
                    if (result.containsKey(0)) {
                        servletMaps = result.get(0);
                    } else {
                        servletMaps = new HashMap<String, Object>();
                    }

                    NodeList childNodes = config.getChildNodes();
                    Servlet servlet = new Servlet();
                    for (int j = 0; j < childNodes.getLength(); j++) {
                        Node node = childNodes.item(j);
                        if (null != node && node.getNodeType() == Node.ELEMENT_NODE) {
                            String nodeName2 = node.getNodeName();
                            String textContent = node.getTextContent();
                            if ("servlet-name".equals(nodeName2)) {
                                servlet.setName(textContent);
                            } else if ("servlet-class".equals(nodeName2)) {
                                servlet.setClazz(textContent);
                            }
                        }
                    }
                    servletMaps.put(servlet.getName(), servlet);

                    result.put(0, servletMaps);
                } else if ("servlet-mapping".equals(nodeName1)) {
                    Map<String, Object> servletMappingMaps = null;
                    if (result.containsKey(1)) {
                        servletMappingMaps = result.get(1);
                    } else {
                        servletMappingMaps = new HashMap<String, Object>();
                    }

                    NodeList childNodes = config.getChildNodes();
                    ServletMapping servletMapping = new ServletMapping();
                    for (int j = 0; j < childNodes.getLength(); j++) {
                        Node node = childNodes.item(j);
                        if (null != node && node.getNodeType() == Node.ELEMENT_NODE) {
                            String nodeName2 = node.getNodeName();
                            String textContent = node.getTextContent();
                            if ("servlet-name".equals(nodeName2)) {
                                servletMapping.setName(textContent);
                            } else if ("url-pattern".equals(nodeName2)) {
                                servletMapping.setUrl(textContent);
                            }
                        }
                    }
                    servletMappingMaps.put(servletMapping.getUrl(), servletMapping);

                    result.put(1, servletMappingMaps);
                }
            }
        }
        return result;
    }

    public static void main(String[] args) throws Exception {
        System.out.println(parseWebXML());
    }
}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
   version="2.5"> 

    <servlet>
        <servlet-name>cloud</servlet-name>
        <servlet-class>com.cloud.tomcat.servlet.CloudServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>cloud</servlet-name>
        <url-pattern>/index</url-pattern>
    </servlet-mapping>
</web-app>

运行结果：

将Server类运行起来，然后用浏览器输入：

http://localhost:8080/index或http://localhost:8080

得到如下结果：


 



 

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转载自09094224.iteye.com/blog/2023841
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