BinCat V3 - 實現Servlet3.x API

V1和V2我們完成了一個簡單的文件訪問服務和請求參數解析服務，V3我們繼續添加Servlet API，從而理解Servlet的工作原理。

添加Servlet3.x依賴：

<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
    <version>3.0.1</version>
</dependency>

創建com.anbai.sec.server.servlet.BinCatRequest類并繼承javax.servlet.http.HttpServletRequest，然后需要實現HttpServletRequest接口方法，作為一個非標準的Servlet容器我們自然是沒必要嚴格的是實現里面的所有方法，選擇幾個方法實現一下就行了。

注意：示例以下中省去了解析協議Servlet接口的代碼，完整代碼請參考：com.anbai.sec.server.servlet包下的完整實現代碼。

HttpServletRequest實現

BinCatRequest.java示例代碼片段:

package com.anbai.sec.server.servlet;

import org.javaweb.utils.StringUtils;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.net.Socket;
import java.net.URLDecoder;
import java.security.Principal;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.logging.Logger;

/**
 * BinCat 請求解析實現對象，解析Http請求協議和參數
 */
public class BinCatRequest implements HttpServletRequest {

    // 客戶端Socket連接對象
    private final Socket clientSocket;

    // Socket輸入流對象
    private final InputStream socketInputStream;

    // Http請求頭對象
    private Map<String, String> headerMap;

    // Http請求參數對象
    private Map<String, String[]> parameterMap;

    // Http請求attribute對象
    private final Map<String, Object> attributeMap = new ConcurrentHashMap<String, Object>();

    // Http請求Cookie對象
    private Cookie[] cookie;

    // Http請求Cookie對象
    private final Map<String, String> cookieMap = new ConcurrentHashMap<String, String>();

    // Http請求Session對象
    private final Map<String, BinCatSession> sessionMap = new ConcurrentHashMap<String, BinCatSession>();

    // Http請求方法類型
    private String requestMethod;

    // Http請求URL
    private String requestURL;

    // Http請求QueryString
    private String queryString;

    // Http請求協議版本信息
    private String httpVersion;

    // 是否已經解析過Http請求參數，防止多次解析請求參數
    private volatile boolean parsedParameter = false;

    // Http請求內容長度
    private int contentLength;

    // Http請求內容類型
    private String contentType;

    // 存儲Session的ID名稱
    private static final String SESSION_ID_NAME = "JSESSIONID";

    // Http請求主機名
    private String host;

    // Http請求主機端口
    private int port;

    private static final Logger LOG = Logger.getLogger("info");

    public BinCatRequest(Socket clientSocket) throws IOException {
        this.clientSocket = clientSocket;
        this.socketInputStream = clientSocket.getInputStream();

        // 解析Http協議
        parse();
    }

    /**
     * 解析Http請求協議，不解析Body部分
     *
     * @throws IOException
     */
    private void parse() throws IOException {
        // 此處省略Http請求協議解析、參數解析等內容...
    }

    /**
     * 解析Http請求參數
     *
     * @throws IOException Http協議解析異常
     */
    private synchronized void parseParameter() {
        // 此處省略Http請求協議解析、參數解析等內容...
    }

  // 此處省略HttpServletRequest接口中的大部分方法，僅保留幾個示例方法...

    public String getHeader(String name) {
        return this.headerMap.get(name);
    }

    public ServletInputStream getInputStream() throws IOException {
        return new ServletInputStream() {
            @Override
            public int read() throws IOException {
                return socketInputStream.read();
            }
        };
    }

    public String getParameter(String name) {
        if (!parsedParameter) {
            this.parseParameter();
        }

        if (parameterMap.containsKey(name)) {
            return this.parameterMap.get(name)[0];
        }

        return null;
    }

    public String getRemoteAddr() {
        return clientSocket.getInetAddress().getHostAddress();
    }

    public void setAttribute(String name, Object o) {
        attributeMap.put(name, o);
    }

}

HttpServletResponse實現

BinCatResponse.java示例代碼片段:

package com.anbai.sec.server.servlet;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletResponse;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.URLEncoder;
import java.util.*;

public class BinCatResponse implements HttpServletResponse {

    private final Socket socket;

    private final Map<String, String> header;

    private final ByteArrayOutputStream out;

    private int status = 404;

    private String statusMessage = "Not Found";

    private String charset = "UTF-8";

    private int contentLength = 0;

    private String contentType = "text/html; charset=UTF-8";

    private String location;

    public BinCatResponse(Socket socket, Map<String, String> header, ByteArrayOutputStream out) {
        this.socket = socket;
        this.header = header;
        this.out = out;
    }

  // 此處省略HttpServletResponse接口中的大部分方法，僅保留幾個示例方法...

    public void setHeader(String name, String value) {
        this.header.put(name, value);
    }

    public String getHeader(String name) {
        return header.get(name);
    }

    public PrintWriter getWriter() throws IOException {
        return new PrintWriter(out);
    }

}

HttpSession實現

BinCatSession.java示例代碼片段:

package com.anbai.sec.server.servlet;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionContext;
import java.util.Enumeration;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * BinCat Session實現
 */
public class BinCatSession implements HttpSession {

    private final String sessionID;

    // Http請求Session對象
    private final Map<String, Object> sessionMap = new ConcurrentHashMap<String, Object>();

    public BinCatSession(String sessionID) {
        this.sessionID = sessionID;
    }

  // 此處省略HttpSession接口中的大部分方法，僅保留幾個示例方法...

    public Object getAttribute(String name) {
        return this.sessionMap.get(name);
    }

    public void setAttribute(String name, Object value) {
        this.sessionMap.put(name, value);
    }

}

Servlet類注冊

Servlet3.0支持web.xml和注解兩種方式配置，但不管是通過那種方式都需要知道Servlet的處理類和映射的URL地址，這里為了方法理解我將解析web.xml和掃描@WebServlet注解的步驟省略了，直接改成了手動配置一個Servlet映射類對象。

注冊Servlet類對象代碼片段：

// 初始化Servlet映射類對象
final Set<Class<? extends HttpServlet>> servletList = new HashSet<Class<? extends HttpServlet>>();

// 手動注冊Servlet類
servletList.add(TestServlet.class);
servletList.add(CMDServlet.class);

當接收到瀏覽器請求時候我們需要根據請求的URL地址來動態調用Servlet類相關的代碼。

調用Servlet類處理Http請求代碼片段：

// 處理Http請求URL
for (Class<? extends HttpServlet> clazz : servletList) {
    WebServlet webServlet  = clazz.getAnnotation(WebServlet.class);
    String[]   urlPatterns = webServlet.urlPatterns();

    for (String urlPattern : urlPatterns) {
        try {
          // 檢測請求的URL地址和Servlet的地址是否匹配
          if (Pattern.compile(urlPattern).matcher(uri).find()) {
              // 修改狀態碼
              response.setStatus(200, "OK");

              // 創建Servlet類實例
              HttpServlet httpServlet = clazz.newInstance();

              // 調用Servlet請求處理方法
              httpServlet.service(request, response);
              break;
          }
        } catch (IOException e) {
           // 修改狀態碼
                   response.setStatus(500, "Internal Server Error");
              e.printStackTrace();
        }
    }
}

BinCat V3實現

V3簡單的封裝了BinCatRequest、BinCatResponse、BinCatSession，還是先了部分的Servlet API從而實現了一個最初級的Servlet容器。

V3處理流程:

創建服務端Socket連接(ServerSocket)。
手動注冊Servlet類。
創建用于處理請求的BinCatRequest對象。
BinCatRequest解析請求協議、請求頭、請求參數、Cookie等。
創建用于處理請求的BinCatResponse對象。
解析Servlet類的@WebServlet注解，反射調用Servlet類方法處理Http請求。
輸出響應信息以及Servlet處理結果。
關閉Socket連接。

BinCatServerV3實現代碼:

package com.anbai.sec.server;

import com.anbai.sec.server.servlet.BinCatRequest;
import com.anbai.sec.server.servlet.BinCatResponse;
import com.anbai.sec.server.test.servlet.CMDServlet;
import com.anbai.sec.server.test.servlet.TestServlet;
import org.javaweb.utils.StringUtils;

import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.logging.Logger;
import java.util.regex.Pattern;

/**
 * ServerSocket Http 服務器示例
 */
public class BinCatServerV3 {

    private static final Logger LOG = Logger.getLogger("info");

    public static void main(String[] args) {
        try {
            // 設置服務監聽端口
            int port = 8080;

            // 設置服務名稱
            String serverName = "BinCat-0.0.3";

            // 創建ServerSocket，監聽本地端口
            ServerSocket ss = new ServerSocket(port);

            // 初始化Servlet映射類對象
            final Set<Class<? extends HttpServlet>> servletList = new HashSet<Class<? extends HttpServlet>>();

            // 手動注冊Servlet類
            servletList.add(TestServlet.class);
            servletList.add(CMDServlet.class);

            LOG.info(serverName + " 啟動成功，監聽端口: " + port);

            while (true) {
                // 等待客戶端連接
                Socket socket = ss.accept();

                try {
                    // 獲取Socket輸入流對象
                    InputStream in = socket.getInputStream();

                    // 獲取Socket輸出流對象
                    OutputStream out = socket.getOutputStream();

                    // 創建BinCat請求處理對象
                    BinCatRequest request = new BinCatRequest(socket);

                    // 創建BinCat請求處理結果輸出流
                    ByteArrayOutputStream baos = new ByteArrayOutputStream();

                    // 創建BinCat請求處理結果Header對象
                    Map<String, String> responseHeader = new ConcurrentHashMap<String, String>();

                    // 創建BinCat響應處理對象
                    BinCatResponse response = new BinCatResponse(socket, responseHeader, baos);

                    // 請求URI地址
                    String uri = request.getRequestURI();

                    // 處理Http請求URL
                    for (Class<? extends HttpServlet> clazz : servletList) {
                        WebServlet webServlet  = clazz.getAnnotation(WebServlet.class);
                        String[]   urlPatterns = webServlet.urlPatterns();

                        for (String urlPattern : urlPatterns) {
                            try {
                                // 檢測請求的URL地址和Servlet的地址是否匹配
                                if (Pattern.compile(urlPattern).matcher(uri).find()) {
                                    // 修改狀態碼
                                    response.setStatus(200, "OK");

                                    // 創建Servlet類實例
                                    HttpServlet httpServlet = clazz.newInstance();

                                    // 調用Servlet請求處理方法
                                    httpServlet.service(request, response);
                                    break;
                                }
                            } catch (Exception e) {
                                // 修改狀態碼
                                response.setStatus(500, "Internal Server Error");
                                e.printStackTrace();

                                baos.write(("<pre>" + StringUtils.exceptionToString(e) + "</pre>").getBytes());
                            }
                        }
                    }

                    // 處理Http響應內容
                    out.write(("HTTP/1.1 " + response.getStatus() + " " + response.getMessage() + "\n").getBytes());
                    // 輸出Web服務器信息
                    out.write(("Server: " + serverName + "\n").getBytes());
                    // 輸出返回的消息類型
                    out.write(("Content-Type: " + response.getContentType() + "\n").getBytes());
                    // 輸出返回字節數
                    out.write(("Content-Length: " + baos.size() + "\n").getBytes());

                    // 輸出用戶自定義的Header
                    for (String key : responseHeader.keySet()) {
                        out.write((key + ": " + responseHeader.get(key) + "\n").getBytes());
                    }

                    // 寫入換行
                    out.write("\n".getBytes());
                    // 將讀取到的數據寫入到客戶端Socket
                    out.write(baos.toByteArray());

                    in.close();
                    out.close();
                } catch (Exception e) {
                    LOG.info("處理客戶端請求異常:" + e);
                } finally {
                    socket.close();
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

Servlet功能測試

為了驗證BinCat是否真的具備了Servlet處理能力，我們寫兩個測試用例：TestServlet和CMDServlet。

TestServlet示例代碼：

package com.anbai.sec.server.test.servlet;

import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.OutputStream;

@WebServlet(name = "TestServlet", urlPatterns = "/TestServlet/")
public class TestServlet extends HttpServlet {

   @Override
   public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
      doPost(request, response);
   }

   @Override
   public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
      OutputStream out = response.getOutputStream();
      out.write(("Hello....<br/>Request Method:" + request.getMethod() + "<br/>Class:" + this.getClass()).getBytes());
   }

}

瀏覽器請求http://localhost:8080/TestServlet/:

CMDServlet示例代碼：

package com.anbai.sec.server.test.servlet;

import org.javaweb.utils.IOUtils;

import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.OutputStream;

@WebServlet(name = "CMDServlet", urlPatterns = "/CMD/")
public class CMDServlet extends HttpServlet {

   @Override
   public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
      doPost(request, response);
   }

   @Override
   public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
      String cmd   = request.getParameter("cmd");
      byte[] bytes = IOUtils.toByteArray(Runtime.getRuntime().exec(cmd).getInputStream());

      OutputStream out = response.getOutputStream();
      out.write(bytes);
      out.flush();
      out.close();
   }

}