JavaWeb

package javax.servlet;

import java.io.IOException;

public interface Servlet {
    void init(ServletConfig var1) throws ServletException;

    ServletConfig getServletConfig();

    void service(ServletRequest var1, ServletResponse var2) throws ServletException, IOException;

    String getServletInfo();

    void destroy();
}

package javax.servlet;

import java.io.IOException;
import java.io.Serializable;
import java.util.Enumeration;
import java.util.ResourceBundle;

public abstract class GenericServlet implements Servlet, ServletConfig, Serializable {
    private static final String LSTRING_FILE = "javax.servlet.LocalStrings";
    private static ResourceBundle lStrings = ResourceBundle.getBundle("javax.servlet.LocalStrings");
    private transient ServletConfig config;

    public GenericServlet() {
    }

    public void destroy() {
    }

    public String getInitParameter(String name) {
        ServletConfig sc = this.getServletConfig();
        if (sc == null) {
            throw new IllegalStateException(lStrings.getString("err.servlet_config_not_initialized"));
        } else {
            return sc.getInitParameter(name);
        }
    }

    public Enumeration<String> getInitParameterNames() {
        ServletConfig sc = this.getServletConfig();
        if (sc == null) {
            throw new IllegalStateException(lStrings.getString("err.servlet_config_not_initialized"));
        } else {
            return sc.getInitParameterNames();
        }
    }

    public ServletConfig getServletConfig() {
        return this.config;
    }

    public ServletContext getServletContext() {
        ServletConfig sc = this.getServletConfig();
        if (sc == null) {
            throw new IllegalStateException(lStrings.getString("err.servlet_config_not_initialized"));
        } else {
            return sc.getServletContext();
        }
    }

    public String getServletInfo() {
        return "";
    }

    public void init(ServletConfig config) throws ServletException {
        this.config = config;
        this.init();
    }

    public void init() throws ServletException {
    }

    public void log(String msg) {
        this.getServletContext().log(this.getServletName() + ": " + msg);
    }

    public void log(String message, Throwable t) {
        this.getServletContext().log(this.getServletName() + ": " + message, t);
    }

    public abstract void service(ServletRequest var1, ServletResponse var2) throws ServletException, IOException;

    public String getServletName() {
        ServletConfig sc = this.getServletConfig();
        if (sc == null) {
            throw new IllegalStateException(lStrings.getString("err.servlet_config_not_initialized"));
        } else {
            return sc.getServletName();
        }
    }
}

package javax.servlet.http;

import java.io.IOException;
import java.lang.reflect.Method;
import java.text.MessageFormat;
import java.util.Enumeration;
import java.util.ResourceBundle;
import javax.servlet.GenericServlet;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public abstract class HttpServlet extends GenericServlet {
    private static final String METHOD_DELETE = "DELETE";
    private static final String METHOD_HEAD = "HEAD";
    private static final String METHOD_GET = "GET";
    private static final String METHOD_OPTIONS = "OPTIONS";
    private static final String METHOD_POST = "POST";
    private static final String METHOD_PUT = "PUT";
    private static final String METHOD_TRACE = "TRACE";
    private static final String HEADER_IFMODSINCE = "If-Modified-Since";
    private static final String HEADER_LASTMOD = "Last-Modified";
    private static final String LSTRING_FILE = "javax.servlet.http.LocalStrings";
    private static ResourceBundle lStrings = ResourceBundle.getBundle("javax.servlet.http.LocalStrings");

    public HttpServlet() {
    }

    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String protocol = req.getProtocol();
        String msg = lStrings.getString("http.method_get_not_supported");
        if (protocol.endsWith("1.1")) {
            resp.sendError(405, msg);
        } else {
            resp.sendError(400, msg);
        }

    }

    protected long getLastModified(HttpServletRequest req) {
        return -1L;
    }

    protected void doHead(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        NoBodyResponse response = new NoBodyResponse(resp);
        this.doGet(req, response);
        response.setContentLength();
    }

    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String protocol = req.getProtocol();
        String msg = lStrings.getString("http.method_post_not_supported");
        if (protocol.endsWith("1.1")) {
            resp.sendError(405, msg);
        } else {
            resp.sendError(400, msg);
        }

    }

    protected void doPut(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String protocol = req.getProtocol();
        String msg = lStrings.getString("http.method_put_not_supported");
        if (protocol.endsWith("1.1")) {
            resp.sendError(405, msg);
        } else {
            resp.sendError(400, msg);
        }

    }

    protected void doDelete(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String protocol = req.getProtocol();
        String msg = lStrings.getString("http.method_delete_not_supported");
        if (protocol.endsWith("1.1")) {
            resp.sendError(405, msg);
        } else {
            resp.sendError(400, msg);
        }

    }

    private Method[] getAllDeclaredMethods(Class<? extends HttpServlet> c) {
        Class<?> clazz = c;

        Method[] allMethods;
        for(allMethods = null; !clazz.equals(HttpServlet.class); clazz = clazz.getSuperclass()) {
            Method[] thisMethods = clazz.getDeclaredMethods();
            if (allMethods != null && allMethods.length > 0) {
                Method[] subClassMethods = allMethods;
                allMethods = new Method[thisMethods.length + allMethods.length];
                System.arraycopy(thisMethods, 0, allMethods, 0, thisMethods.length);
                System.arraycopy(subClassMethods, 0, allMethods, thisMethods.length, subClassMethods.length);
            } else {
                allMethods = thisMethods;
            }
        }

        return allMethods != null ? allMethods : new Method[0];
    }

    protected void doOptions(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Method[] methods = this.getAllDeclaredMethods(this.getClass());
        boolean ALLOW_GET = false;
        boolean ALLOW_HEAD = false;
        boolean ALLOW_POST = false;
        boolean ALLOW_PUT = false;
        boolean ALLOW_DELETE = false;
        boolean ALLOW_TRACE = true;
        boolean ALLOW_OPTIONS = true;

        for(int i = 0; i < methods.length; ++i) {
            String methodName = methods[i].getName();
            if (methodName.equals("doGet")) {
                ALLOW_GET = true;
                ALLOW_HEAD = true;
            } else if (methodName.equals("doPost")) {
                ALLOW_POST = true;
            } else if (methodName.equals("doPut")) {
                ALLOW_PUT = true;
            } else if (methodName.equals("doDelete")) {
                ALLOW_DELETE = true;
            }
        }

        StringBuilder allow = new StringBuilder();
        if (ALLOW_GET) {
            allow.append("GET");
        }

        if (ALLOW_HEAD) {
            if (allow.length() > 0) {
                allow.append(", ");
            }

            allow.append("HEAD");
        }

        if (ALLOW_POST) {
            if (allow.length() > 0) {
                allow.append(", ");
            }

            allow.append("POST");
        }

        if (ALLOW_PUT) {
            if (allow.length() > 0) {
                allow.append(", ");
            }

            allow.append("PUT");
        }

        if (ALLOW_DELETE) {
            if (allow.length() > 0) {
                allow.append(", ");
            }

            allow.append("DELETE");
        }

        if (ALLOW_TRACE) {
            if (allow.length() > 0) {
                allow.append(", ");
            }

            allow.append("TRACE");
        }

        if (ALLOW_OPTIONS) {
            if (allow.length() > 0) {
                allow.append(", ");
            }

            allow.append("OPTIONS");
        }

        resp.setHeader("Allow", allow.toString());
    }

    protected void doTrace(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String CRLF = "\r\n";
        StringBuilder buffer = (new StringBuilder("TRACE ")).append(req.getRequestURI()).append(" ").append(req.getProtocol());
        Enumeration reqHeaderEnum = req.getHeaderNames();

        while(reqHeaderEnum.hasMoreElements()) {
            String headerName = (String)reqHeaderEnum.nextElement();
            buffer.append(CRLF).append(headerName).append(": ").append(req.getHeader(headerName));
        }

        buffer.append(CRLF);
        int responseLength = buffer.length();
        resp.setContentType("message/http");
        resp.setContentLength(responseLength);
        ServletOutputStream out = resp.getOutputStream();
        out.print(buffer.toString());
    }

    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String method = req.getMethod();
        long lastModified;
        if (method.equals("GET")) {
            lastModified = this.getLastModified(req);
            if (lastModified == -1L) {
                this.doGet(req, resp);
            } else {
                long ifModifiedSince = req.getDateHeader("If-Modified-Since");
                if (ifModifiedSince < lastModified) {
                    this.maybeSetLastModified(resp, lastModified);
                    this.doGet(req, resp);
                } else {
                    resp.setStatus(304);
                }
            }
        } else if (method.equals("HEAD")) {
            lastModified = this.getLastModified(req);
            this.maybeSetLastModified(resp, lastModified);
            this.doHead(req, resp);
        } else if (method.equals("POST")) {
            this.doPost(req, resp);
        } else if (method.equals("PUT")) {
            this.doPut(req, resp);
        } else if (method.equals("DELETE")) {
            this.doDelete(req, resp);
        } else if (method.equals("OPTIONS")) {
            this.doOptions(req, resp);
        } else if (method.equals("TRACE")) {
            this.doTrace(req, resp);
        } else {
            String errMsg = lStrings.getString("http.method_not_implemented");
            Object[] errArgs = new Object[]{method};
            errMsg = MessageFormat.format(errMsg, errArgs);
            resp.sendError(501, errMsg);
        }

    }

    private void maybeSetLastModified(HttpServletResponse resp, long lastModified) {
        if (!resp.containsHeader("Last-Modified")) {
            if (lastModified >= 0L) {
                resp.setDateHeader("Last-Modified", lastModified);
            }

        }
    }

    public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
        if (req instanceof HttpServletRequest && res instanceof HttpServletResponse) {
            HttpServletRequest request = (HttpServletRequest)req;
            HttpServletResponse response = (HttpServletResponse)res;
            this.service(request, response);
        } else {
            throw new ServletException("non-HTTP request or response");
        }
    }
}

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    // 获取要下载文件的路径
    String realPath = "C:/Users/Administrator/Desktop/test.png";
    // 获取文件名
    String fileName = realPath.substring(realPath.lastIndexOf("\\") + 1);
    // 设置响应头，让浏览器实施下载、URLEncoder
    resp.setHeader("Content-Disposition", "attachment;filename" + URLEncoder.encode(fileName, "UTF-8"));
    // 创建下载文件的输入流
    FileInputStream inputStream = new FileInputStream(realPath);
    // 创建缓冲区
    int len = 0;
    byte[] buffer = new byte[1024];
    // 创建OutputStream对象
    ServletOutputStream outputStream = resp.getOutputStream();
    // 将FileOutputStream流写入到buffer缓冲区，使用OutputStream将缓冲区中的数据输出到客户端
    while ((len= inputStream.read()) > 0){
        outputStream.write(buffer, 0, len);
    }

    inputStream.close();
    outputStream.close();
}

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    // 使浏览器3秒刷新一次
    resp.setHeader("refresh", "3");

    // 创建一张图片
    BufferedImage image = new BufferedImage(80, 20, BufferedImage.TYPE_INT_RGB);
    Graphics2D graphics = (Graphics2D) image.getGraphics();
    graphics.setColor(Color.white);
    graphics.fillRect(0 ,0 ,80, 20);

    // 在图片上写东西
    graphics.setColor(Color.blue);
    graphics.setFont(new Font(null, Font.BOLD, 20));
    graphics.drawString(makeNum(), 0 ,20);

    // 设置响应
    resp.setContentType("image/jpeg");
    resp.setDateHeader("expires", -1);
    resp.setHeader("Cache-Control", "no-cache");
    resp.setHeader("Pragma", "no-cache");

    JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(resp.getOutputStream());
    encoder.encode(image);
}

//生成7位随机数
private String makeNum(){
    Random random = new Random();
    String num = random.nextInt(9999999) + "";
    StringBuffer sb = new StringBuffer();
    for(int i = 0; i < 7 - num.length(); i++){
        sb.append("0");
    }
    num = sb.toString() + num;
    return num;
}

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    // 重定向
    resp.sendRedirect("/waston/code");
}

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    resp.setHeader("Location", "/waston/code");
    resp.setStatus(302);
}

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    String username = req.getParameter("username");
    String password = req.getParameter("password");

    System.out.println(username + password);
    resp.sendRedirect("/waston/success.jsp");
}

// 移除session的属性
session.removeAttribute("name");
// session注销
session.invalidate();

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    req.setCharacterEncoding("utf-8");
    resp.setHeader("content-type", "text/html;charset=UTF-8");
    resp.setCharacterEncoding("utf-8");

    PrintWriter out = resp.getWriter();
    // 通过request对象获得cookie，cookie可以是多个
    Cookie[] cookies = req.getCookies();
    if(cookies != null){
        for(Cookie cookie : cookies){
            if(cookie.getName().equals("lastLoginTime")){
                long lastLoginTime = Long.parseLong(cookie.getValue());
                Date date = new Date(lastLoginTime);
                out.write("您上次的访问时间是：" + date.toLocaleString());
            }
        }
    }else {
        out.write("这是您第一次访问");
    }

    //给客户端一个cookie
    Cookie cookie = new Cookie("lastLoginTime", System.currentTimeMillis() + "");
    resp.addCookie(cookie);
}

//设置cookie有效期为1天 关闭浏览器后cookie还在
cookie.setMaxAge(24*60*60);